<
 draft-ietf-avt-rtp-rfc3984bis-05.txt   draft-ietf-avt-rtp-rfc3984bis-06.txt 
Obsoletes RFC 3984
Audio/Video Transport WG Y.-K. Wang Audio/Video Transport WG Y.-K. Wang
Internet Draft Huawei Technologies Internet Draft Huawei Technologies
Intended status: Standards track R. Even Intended status: Standards track R. Even
Expires: October 2009 Self-employed Expires: October 2009 Self-employed
T. Kristensen T. Kristensen
Tandberg Tandberg
April 22, 2009 April 30, 2009
RTP Payload Format for H.264 Video RTP Payload Format for H.264 Video
draft-ietf-avt-rtp-rfc3984bis-05.txt draft-ietf-avt-rtp-rfc3984bis-06.txt
Status of this Memo Status of this Memo
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Abstract Abstract
This memo describes an RTP Payload format for the ITU-T This memo describes an RTP Payload format for the ITU-T
Recommendation H.264 video codec and the technically identical Recommendation H.264 video codec and the technically identical
ISO/IEC International Standard 14496-10 video codec, excluding the ISO/IEC International Standard 14496-10 video codec, excluding the
Scalable Video Coding (SVC) extension and the Multivew Video Coding Scalable Video Coding (SVC) extension and the Multivew Video Coding
extension, for which the RTP payload formats are defined elsewhere. extension, for which the RTP payload formats are defined elsewhere.
The RTP payload format allows for packetization of one or more The RTP payload format allows for packetization of one or more
Network Abstraction Layer Units (NALUs), produced by an H.264 video Network Abstraction Layer Units (NALUs), produced by an H.264 video
skipping to change at page 2, line 36 skipping to change at page 2, line 38
applicability, as it supports applications from simple low bit-rate applicability, as it supports applications from simple low bit-rate
conversational usage, to Internet video streaming with interleaved conversational usage, to Internet video streaming with interleaved
transmission, to high bit-rate video-on-demand. transmission, to high bit-rate video-on-demand.
This memo obsoletes RFC 3984. Changes from RFC 3984 are summarized This memo obsoletes RFC 3984. Changes from RFC 3984 are summarized
in section 18. Issues on backward compatibility to RFC 3984 are in section 18. Issues on backward compatibility to RFC 3984 are
discussed in section 17. discussed in section 17.
Table of Contents Table of Contents
1. Introduction...................................................4 1. Introduction..................................................4
1.1. The H.264 Codec...........................................4 1.1. The H.264 Codec..........................................4
1.2. Parameter Set Concept.....................................5 1.2. Parameter Set Concept....................................6
1.3. Network Abstraction Layer Unit Types......................6 1.3. Network Abstraction Layer Unit Types.....................6
2. Conventions....................................................7 2. Conventions...................................................7
3. Scope..........................................................7 3. Scope.........................................................8
4. Definitions and Abbreviations..................................8 4. Definitions and Abbreviations.................................8
4.1. Definitions...............................................8 4.1. Definitions..............................................8
4.2. Abbreviations............................................10 4.2. Abbreviations...........................................10
5. RTP Payload Format............................................10 5. RTP Payload Format...........................................11
5.1. RTP Header Usage.........................................10 5.1. RTP Header Usage........................................11
5.2. Payload Structures.......................................13 5.2. Payload Structures......................................13
5.3. NAL Unit Header Usage....................................14 5.3. NAL Unit Header Usage...................................15
5.4. Packetization Modes......................................17 5.4. Packetization Modes.....................................17
5.5. Decoding Order Number (DON)..............................18 5.5. Decoding Order Number (DON).............................18
5.6. Single NAL Unit Packet...................................20 5.6. Single NAL Unit Packet..................................21
5.7. Aggregation Packets......................................21 5.7. Aggregation Packets.....................................22
5.7.1. Single-Time Aggregation Packet......................23 5.7.1. Single-Time Aggregation Packet.....................24
5.7.2. Multi-Time Aggregation Packets (MTAPs)..............25 5.7.2. Multi-Time Aggregation Packets (MTAPs).............26
5.7.3. Fragmentation Units (FUs)...........................29 5.7.3. Fragmentation Units (FUs)..........................30
6. Packetization Rules...........................................33 6. Packetization Rules..........................................34
6.1. Common Packetization Rules...............................33 6.1. Common Packetization Rules..............................34
6.2. Single NAL Unit Mode.....................................34 6.2. Single NAL Unit Mode....................................35
6.3. Non-Interleaved Mode.....................................34 6.3. Non-Interleaved Mode....................................35
6.4. Interleaved Mode.........................................34 6.4. Interleaved Mode........................................36
7. De-Packetization Process......................................35 7. De-Packetization Process.....................................36
7.1. Single NAL Unit and Non-Interleaved Mode.................35 7.1. Single NAL Unit and Non-Interleaved Mode................36
7.2. Interleaved Mode.........................................35 7.2. Interleaved Mode........................................37
7.2.1. Size of the De-interleaving Buffer..................36 7.2.1. Size of the De-interleaving Buffer.................37
7.2.2. De-interleaving Process.............................36 7.2.2. De-interleaving Process............................38
7.3. Additional De-Packetization Guidelines...................38 7.3. Additional De-Packetization Guidelines..................39
8. Payload Format Parameters.....................................39 8. Payload Format Parameters....................................40
8.1. Media Type Registration..................................39 8.1. Media Type Registration.................................40
8.2. SDP Parameters...........................................56 8.2. SDP Parameters..........................................58
8.2.1. Mapping of Payload Type Parameters to SDP...........56 8.2.1. Mapping of Payload Type Parameters to SDP..........58
8.2.2. Usage with the SDP Offer/Answer Model...............57 8.2.2. Usage with the SDP Offer/Answer Model..............59
8.2.3. Usage in Declarative Session Descriptions...........64 8.2.3. Usage in Declarative Session Descriptions..........66
8.3. Examples.................................................65 8.3. Examples................................................67
8.4. Parameter Set Considerations.............................72 8.4. Parameter Set Considerations............................74
8.5. Decoder Refresh Point Procedure using In-Band Transport of 8.5. Decoder Refresh Point Procedure using In-Band Transport of
Parameter Sets (Informative)..................................74 Parameter Sets (Informative).................................76
8.5.1. IDR Procedure to Respond to a Request for a Decoder 8.5.1. IDR Procedure to Respond to a Request for a Decoder
Refresh Point..............................................75 Refresh Point.............................................77
8.5.2. Gradual Recovery Procedure to Respond to a Request for a 8.5.2. Gradual Recovery Procedure to Respond to a Request for
Decoder Refresh Point......................................75 a Decoder Refresh Point...................................77
9. Security Considerations.......................................76 9. Security Considerations......................................78
10. Congestion Control...........................................77 10. Congestion Control..........................................79
11. IANA Consideration...........................................77 11. IANA Consideration..........................................80
12. Informative Appendix: Application Examples...................78 12. Informative Appendix: Application Examples..................80
12.1. Video Telephony according to ITU-T Recommendation H.241 12.1. Video Telephony according to ITU-T Recommendation H.241
Annex A.......................................................78 Annex A......................................................80
12.2. Video Telephony, No Slice Data Partitioning, No NAL Unit 12.2. Video Telephony, No Slice Data Partitioning, No NAL Unit
Aggregation...................................................78 Aggregation..................................................80
12.3. Video Telephony, Interleaved Packetization Using NAL Unit 12.3. Video Telephony, Interleaved Packetization Using NAL Unit
Aggregation...................................................79 Aggregation..................................................81
12.4. Video Telephony with Data Partitioning..................79 12.4. Video Telephony with Data Partitioning.................82
12.5. Video Telephony or Streaming with FUs and Forward Error 12.5. Video Telephony or Streaming with FUs and Forward Error
Correction....................................................80 Correction...................................................82
12.6. Low Bit-Rate Streaming..................................82 12.6. Low Bit-Rate Streaming.................................85
12.7. Robust Packet Scheduling in Video Streaming.............83 12.7. Robust Packet Scheduling in Video Streaming............85
13. Informative Appendix: Rationale for Decoding Order Number....84 13. Informative Appendix: Rationale for Decoding Order Number...86
13.1. Introduction............................................84 13.1. Introduction...........................................86
13.2. Example of Multi-Picture Slice Interleaving.............84 13.2. Example of Multi-Picture Slice Interleaving............86
13.3. Example of Robust Packet Scheduling.....................86 13.3. Example of Robust Packet Scheduling....................88
13.4. Robust Transmission Scheduling of Redundant Coded Slices89 13.4. Robust Transmission Scheduling of Redundant Coded Slices92
13.5. Remarks on Other Design Possibilities...................90 13.5. Remarks on Other Design Possibilities..................93
14. Acknowledgements.............................................91 14. Acknowledgements............................................93
15. References...................................................91 15. References..................................................94
15.1. Normative References....................................91 15.1. Normative References...................................94
15.2. Informative References..................................92 15.2. Informative References.................................94
16. Authors' Addresses...........................................94 16. Authors' Addresses..........................................96
17. Backward Compatibility to RFC 3984...........................94 17. Backward Compatibility to RFC 3984..........................97
18. Changes from RFC 3984........................................96 18. Changes from RFC 3984.......................................98
1. Introduction 1. Introduction
This memo specifies an RTP payload specification for the video coding This memo specifies an RTP payload specification for the video
standard known as ITU-T Recommendation H.264 [1] and ISO/IEC coding standard known as ITU-T Recommendation H.264 [1] and ISO/IEC
International Standard 14496 Part 10 [2] (both also known as Advanced International Standard 14496 Part 10 [2] (both also known as
Video Coding, or AVC). In this memo the name H.264 is used for the Advanced Video Coding, or AVC). In this memo the name H.264 is
codec and the standard, but the memo is equally applicable to the used for the codec and the standard, but the memo is equally
ISO/IEC counterpart of the coding standard. applicable to the ISO/IEC counterpart of the coding standard.
This memo obsoletes RFC 3984. Changes from RFC 3984 are summarized This memo obsoletes RFC 3984. Changes from RFC 3984 are summarized
in section 18. Issues on backward compatibility to RFC 3984 are in section 18. Issues on backward compatibility to RFC 3984 are
discussed in section 17. discussed in section 17.
1.1. The H.264 Codec 1.1. The H.264 Codec
The H.264 video codec has a very broad application range that covers The H.264 video codec has a very broad application range that
all forms of digital compressed video, from low bit-rate Internet covers all forms of digital compressed video, from low bit-rate
streaming applications to HDTV broadcast and Digital Cinema Internet streaming applications to HDTV broadcast and Digital
applications with nearly lossless coding. Compared to the current Cinema applications with nearly lossless coding. Compared to the
state of technology, the overall performance of H.264 is such that current state of technology, the overall performance of H.264 is
bit rate savings of 50% or more are reported. Digital Satellite TV such that bit rate savings of 50% or more are reported. Digital
quality, for example, was reported to be achievable at 1.5 Mbit/s, Satellite TV quality, for example, was reported to be achievable at
compared to the current operation point of MPEG 2 video at around 3.5 1.5 Mbit/s, compared to the current operation point of MPEG 2 video
Mbit/s [10]. at around 3.5 Mbit/s [10].
The codec specification [1] itself distinguishes conceptually between The codec specification [1] itself distinguishes conceptually
a video coding layer (VCL) and a network abstraction layer (NAL). between a video coding layer (VCL) and a network abstraction layer
The VCL contains the signal processing functionality of the codec; (NAL). The VCL contains the signal processing functionality of the
mechanisms such as transform, quantization, and motion compensated codec; mechanisms such as transform, quantization, and motion
prediction; and a loop filter. It follows the general concept of compensated prediction; and a loop filter. It follows the general
most of today's video codecs, a macroblock-based coder that uses concept of most of today's video codecs, a macroblock-based coder
inter picture prediction with motion compensation and transform that uses inter picture prediction with motion compensation and
coding of the residual signal. The VCL encoder outputs slices: a bit transform coding of the residual signal. The VCL encoder outputs
string that contains the macroblock data of an integer number of slices: a bit string that contains the macroblock data of an
macroblocks, and the information of the slice header (containing the integer number of macroblocks, and the information of the slice
spatial address of the first macroblock in the slice, the initial header (containing the spatial address of the first macroblock in
quantization parameter, and similar information). Macroblocks in the slice, the initial quantization parameter, and similar
slices are arranged in scan order unless a different macroblock information). Macroblocks in slices are arranged in scan order
allocation is specified, by using the so-called Flexible Macroblock unless a different macroblock allocation is specified, by using the
Ordering syntax. In-picture prediction is used only within a slice. so-called Flexible Macroblock Ordering syntax. In-picture
More information is provided in [10]. prediction is used only within a slice. More information is
provided in [10].
The Network Abstraction Layer (NAL) encoder encapsulates the slice The Network Abstraction Layer (NAL) encoder encapsulates the slice
output of the VCL encoder into Network Abstraction Layer Units (NAL output of the VCL encoder into Network Abstraction Layer Units (NAL
units), which are suitable for transmission over packet networks or units), which are suitable for transmission over packet networks or
use in packet oriented multiplex environments. Annex B of H.264 use in packet oriented multiplex environments. Annex B of H.264
defines an encapsulation process to transmit such NAL units over defines an encapsulation process to transmit such NAL units over
byte-stream oriented networks. In the scope of this memo, Annex B is byte-stream oriented networks. In the scope of this memo, Annex B
not relevant. is not relevant.
Internally, the NAL uses NAL units. A NAL unit consists of a one- Internally, the NAL uses NAL units. A NAL unit consists of a one-
byte header and the payload byte string. The header indicates the byte header and the payload byte string. The header indicates the
type of the NAL unit, the (potential) presence of bit errors or type of the NAL unit, the (potential) presence of bit errors or
syntax violations in the NAL unit payload, and information regarding syntax violations in the NAL unit payload, and information
the relative importance of the NAL unit for the decoding process. regarding the relative importance of the NAL unit for the decoding
This RTP payload specification is designed to be unaware of the bit process. This RTP payload specification is designed to be unaware
string in the NAL unit payload. of the bit string in the NAL unit payload.
One of the main properties of H.264 is the complete decoupling of the One of the main properties of H.264 is the complete decoupling of
transmission time, the decoding time, and the sampling or the transmission time, the decoding time, and the sampling or
presentation time of slices and pictures. The decoding process presentation time of slices and pictures. The decoding process
specified in H.264 is unaware of time, and the H.264 syntax does not specified in H.264 is unaware of time, and the H.264 syntax does
carry information such as the number of skipped frames (as is common not carry information such as the number of skipped frames (as is
in the form of the Temporal Reference in earlier video compression common in the form of the Temporal Reference in earlier video
standards). Also, there are NAL units that affect many pictures and compression standards). Also, there are NAL units that affect many
that are, therefore, inherently timeless. For this reason, the pictures and that are, therefore, inherently timeless. For this
handling of the RTP timestamp requires some special considerations reason, the handling of the RTP timestamp requires some special
for NAL units for which the sampling or presentation time is not considerations for NAL units for which the sampling or presentation
defined or, at transmission time, unknown. time is not defined or, at transmission time, unknown.
1.2. Parameter Set Concept 1.2. Parameter Set Concept
One very fundamental design concept of H.264 is to generate self- One very fundamental design concept of H.264 is to generate self-
contained packets, to make mechanisms such as the header duplication contained packets, to make mechanisms such as the header
of RFC 2429 [11] or MPEG-4 Visual's Header Extension Code (HEC) [12] duplication of RFC 4629 [11] or MPEG-4 Visual's Header Extension
unnecessary. This was achieved by decoupling information relevant to Code (HEC) [12] unnecessary. This was achieved by decoupling
more than one slice from the media stream. This higher layer meta information relevant to more than one slice from the media stream.
information should be sent reliably, asynchronously, and in advance This higher layer meta information should be sent reliably,
from the RTP packet stream that contains the slice packets. asynchronously, and in advance from the RTP packet stream that
(Provisions for sending this information in-band are also available contains the slice packets. (Provisions for sending this
for applications that do not have an out-of-band transport channel information in-band are also available for applications that do not
appropriate for the purpose.) The combination of the higher-level have an out-of-band transport channel appropriate for the purpose.)
parameters is called a parameter set. The H.264 specification The combination of the higher-level parameters is called a
includes two types of parameter sets: sequence parameter set and parameter set. The H.264 specification includes two types of
picture parameter set. An active sequence parameter set remains parameter sets: sequence parameter set and picture parameter set.
unchanged throughout a coded video sequence, and an active picture An active sequence parameter set remains unchanged throughout a
parameter set remains unchanged within a coded picture. The sequence coded video sequence, and an active picture parameter set remains
and picture parameter set structures contain information such as unchanged within a coded picture. The sequence and picture
picture size, optional coding modes employed, and macroblock to slice parameter set structures contain information such as picture size,
group map. optional coding modes employed, and macroblock to slice group map.
To be able to change picture parameters (such as the picture size) To be able to change picture parameters (such as the picture size)
without having to transmit parameter set updates synchronously to the without having to transmit parameter set updates synchronously to
slice packet stream, the encoder and decoder can maintain a list of the slice packet stream, the encoder and decoder can maintain a
more than one sequence and picture parameter set. Each slice header list of more than one sequence and picture parameter set. Each
contains a codeword that indicates the sequence and picture parameter slice header contains a codeword that indicates the sequence and
set to be used. picture parameter set to be used.
This mechanism allows the decoupling of the transmission of parameter This mechanism allows the decoupling of the transmission of
sets from the packet stream, and the transmission of them by external parameter sets from the packet stream, and the transmission of them
means (e.g., as a side effect of the capability exchange), or through by external means (e.g., as a side effect of the capability
a (reliable or unreliable) control protocol. It may even be possible exchange), or through a (reliable or unreliable) control protocol.
that they are never transmitted but are fixed by an application It may even be possible that they are never transmitted but are
design specification. fixed by an application design specification.
1.3. Network Abstraction Layer Unit Types 1.3. Network Abstraction Layer Unit Types
Tutorial information on the NAL design can be found in [13], [14], Tutorial information on the NAL design can be found in [13], [14],
and [15]. and [15].
All NAL units consist of a single NAL unit type octet, which also co- All NAL units consist of a single NAL unit type octet, which also
serves as the payload header of this RTP payload format. The payload co-serves as the payload header of this RTP payload format. The
of a NAL unit follows immediately. payload of a NAL unit follows immediately.
The syntax and semantics of the NAL unit type octet are specified in The syntax and semantics of the NAL unit type octet are specified
[1], but the essential properties of the NAL unit type octet are in [1], but the essential properties of the NAL unit type octet are
summarized below. The NAL unit type octet has the following format: summarized below. The NAL unit type octet has the following format:
+---------------+ +---------------+
|0|1|2|3|4|5|6|7| |0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|F|NRI| Type | |F|NRI| Type |
+---------------+ +---------------+
The semantics of the components of the NAL unit type octet, as The semantics of the components of the NAL unit type octet, as
specified in the H.264 specification, are described briefly below. specified in the H.264 specification, are described briefly below.
F: 1 bit F: 1 bit
forbidden_zero_bit. The H.264 specification declares a value of forbidden_zero_bit. The H.264 specification declares a value of
1 as a syntax violation. 1 as a syntax violation.
NRI: 2 bits NRI: 2 bits
nal_ref_idc. A value of 00 indicates that the content of the NAL nal_ref_idc. A value of 00 indicates that the content of the
unit is not used to reconstruct reference pictures for inter NAL unit is not used to reconstruct reference pictures for inter
picture prediction. Such NAL units can be discarded without picture prediction. Such NAL units can be discarded without
risking the integrity of the reference pictures. Values greater risking the integrity of the reference pictures. Values greater
than 00 indicate that the decoding of the NAL unit is required to than 00 indicate that the decoding of the NAL unit is required
maintain the integrity of the reference pictures. to maintain the integrity of the reference pictures.
Type: 5 bits Type: 5 bits
nal_unit_type. This component specifies the NAL unit payload nal_unit_type. This component specifies the NAL unit payload
type as defined in Table 7-1 of [1], and later within this memo. type as defined in Table 7-1 of [1], and later within this memo.
For a reference of all currently defined NAL unit types and their For a reference of all currently defined NAL unit types and
semantics, please refer to section 7.4.1 in [1]. their semantics, please refer to section 7.4.1 in [1].
This memo introduces new NAL unit types, which are presented in This memo introduces new NAL unit types, which are presented in
section 5.2. The NAL unit types defined in this memo are marked as section 5.2. The NAL unit types defined in this memo are marked as
unspecified in [1]. Moreover, this specification extends the unspecified in [1]. Moreover, this specification extends the
semantics of F and NRI as described in section 5.3. semantics of F and NRI as described in section 5.3.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
document are to be interpreted as described in RFC-2119 [3]. this document are to be interpreted as described in RFC 2119 [4].
This specification uses the notion of setting and clearing a bit when This specification uses the notion of setting and clearing a bit
bit fields are handled. Setting a bit is the same as assigning that when bit fields are handled. Setting a bit is the same as
bit the value of 1 (On). Clearing a bit is the same as assigning assigning that bit the value of 1 (On). Clearing a bit is the same
that bit the value of 0 (Off). as assigning that bit the value of 0 (Off).
3. Scope 3. Scope
This payload specification can only be used to carry the "naked" This payload specification can only be used to carry the "naked"
H.264 NAL unit stream over RTP, and not the bitstream format H.264 NAL unit stream over RTP, and not the bitstream format
discussed in Annex B of H.264. Likely, the first applications of discussed in Annex B of H.264. Likely, the first applications of
this specification will be in the conversational multimedia field, this specification will be in the conversational multimedia field,
video telephony or video conferencing, but the payload format also video telephony or video conferencing, but the payload format also
covers other applications, such as Internet streaming and TV over IP. covers other applications, such as Internet streaming and TV over
IP.
4. Definitions and Abbreviations 4. Definitions and Abbreviations
4.1. Definitions 4.1. Definitions
This document uses the definitions of [1]. The following terms, This document uses the definitions of [1]. The following terms,
defined in [1], are summed up for convenience: defined in [1], are summed up for convenience:
access unit: A set of NAL units always containing a primary coded access unit: A set of NAL units always containing a primary
picture. In addition to the primary coded picture, an access coded picture. In addition to the primary coded picture, an
unit may also contain one or more redundant coded pictures or access unit may also contain one or more redundant coded
other NAL units not containing slices or slice data partitions of pictures or other NAL units not containing slices or slice data
a coded picture. The decoding of an access unit always results partitions of a coded picture. The decoding of an access unit
in a decoded picture. always results in a decoded picture.
coded video sequence: A sequence of access units that consists, coded video sequence: A sequence of access units that consists,
in decoding order, of an instantaneous decoding refresh (IDR) in decoding order, of an instantaneous decoding refresh (IDR)
access unit followed by zero or more non-IDR access units access unit followed by zero or more non-IDR access units
including all subsequent access units up to but not including any including all subsequent access units up to but not including
subsequent IDR access unit. any subsequent IDR access unit.
IDR access unit: An access unit in which the primary coded IDR access unit: An access unit in which the primary coded
picture is an IDR picture. picture is an IDR picture.
IDR picture: A coded picture containing only slices with I or SI IDR picture: A coded picture containing only slices with I or SI
slice types that causes a "reset" in the decoding process. After slice types that causes a "reset" in the decoding process.
the decoding of an IDR picture, all following coded pictures in After the decoding of an IDR picture, all following coded
decoding order can be decoded without inter prediction from any pictures in decoding order can be decoded without inter
picture decoded prior to the IDR picture. prediction from any picture decoded prior to the IDR picture.
primary coded picture: The coded representation of a picture to primary coded picture: The coded representation of a picture to
be used by the decoding process for a bitstream conforming to be used by the decoding process for a bitstream conforming to
H.264. The primary coded picture contains all macroblocks of the H.264. The primary coded picture contains all macroblocks of
picture. the picture.
redundant coded picture: A coded representation of a picture or a redundant coded picture: A coded representation of a picture or
part of a picture. The content of a redundant coded picture a part of a picture. The content of a redundant coded picture
shall not be used by the decoding process for a bitstream shall not be used by the decoding process for a bitstream
conforming to H.264. The content of a redundant coded picture conforming to H.264. The content of a redundant coded picture
may be used by the decoding process for a bitstream that contains may be used by the decoding process for a bitstream that
errors or losses. contains errors or losses.
VCL NAL unit: A collective term used to refer to coded slice and VCL NAL unit: A collective term used to refer to coded slice and
coded data partition NAL units. coded data partition NAL units.
In addition, the following definitions apply: In addition, the following definitions apply:
decoding order number (DON): A field in the payload structure or decoding order number (DON): A field in the payload structure or
a derived variable indicating NAL unit decoding order. Values of a derived variable indicating NAL unit decoding order. Values
DON are in the range of 0 to 65535, inclusive. After reaching of DON are in the range of 0 to 65535, inclusive. After
the maximum value, the value of DON wraps around to 0. reaching the maximum value, the value of DON wraps around to 0.
NAL unit decoding order: A NAL unit order that conforms to the NAL unit decoding order: A NAL unit order that conforms to the
constraints on NAL unit order given in section 7.4.1.2 in [1]. constraints on NAL unit order given in section 7.4.1.2 in [1].
NALU-time: The value that the RTP timestamp would have if the NAL NALU-time: The value that the RTP timestamp would have if the
unit would be transported in its own RTP packet. NAL unit would be transported in its own RTP packet.
transmission order: The order of packets in ascending RTP transmission order: The order of packets in ascending RTP
sequence number order (in modulo arithmetic). Within an sequence number order (in modulo arithmetic). Within an
aggregation packet, the NAL unit transmission order is the same aggregation packet, the NAL unit transmission order is the same
as the order of appearance of NAL units in the packet. as the order of appearance of NAL units in the packet.
media aware network element (MANE): A network element, such as a media aware network element (MANE): A network element, such as a
middlebox or application layer gateway that is capable of parsing middlebox or application layer gateway that is capable of
certain aspects of the RTP payload headers or the RTP payload and parsing certain aspects of the RTP payload headers or the RTP
reacting to the contents. payload and reacting to the contents.
Informative note: The concept of a MANE goes beyond normal Informative note: The concept of a MANE goes beyond normal
routers or gateways in that a MANE has to be aware of the routers or gateways in that a MANE has to be aware of the
signaling (e.g., to learn about the payload type mappings of signaling (e.g., to learn about the payload type mappings of
the media streams), and in that it has to be trusted when the media streams), and in that it has to be trusted when
working with SRTP. The advantage of using MANEs is that they working with SRTP. The advantage of using MANEs is that they
allow packets to be dropped according to the needs of the allow packets to be dropped according to the needs of the
media coding. For example, if a MANE has to drop packets due media coding. For example, if a MANE has to drop packets due
to congestion on a certain link, it can identify and remove to congestion on a certain link, it can identify and remove
those packets whose elimination produces the least adverse those packets whose elimination produces the least adverse
effect on the user experience. effect on the user experience.
static macroblock: A certain amount of macroblocks in the video static macroblock: A certain amount of macroblocks in the video
stream can be defined as static, as defined in section 8.3.2.8 in stream can be defined as static, as defined in section 8.3.2.8
[3]. Static macroblocks free up additional processing cycles for in [3]. Static macroblocks free up additional processing
the handling of non-static macroblocks. Based on a given amount cycles for the handling of non-static macroblocks. Based on a
of video processing resources and a given resolution, a higher given amount of video processing resources and a given
number of static macroblocks enables a correspondingly higher resolution, a higher number of static macroblocks enables a
frame rate. correspondingly higher frame rate.
default sub-profile: The subset of coding tools, which may be all default sub-profile: The subset of coding tools, which may be
coding tools of one profile or the common subset of coding tools all coding tools of one profile or the common subset of coding
of more than one profile, indicated by the profile-level-id tools of more than one profile, indicated by the profile-level-
parameter. id parameter.
default level: The level indicated by the profile-level-id default level: The level indicated by the profile-level-id
parameter, which consists of three octets, profile_idc, profile- parameter, which consists of three octets, profile_idc, profile-
iop, and level_idc. The default level is indicated by level_idc iop, and level_idc. The default level is indicated by level_idc
in most cases, and, in some cases, additionally by profile-iop. in most cases, and, in some cases, additionally by profile-iop.
4.2. Abbreviations 4.2. Abbreviations
DON: Decoding Order Number DON: Decoding Order Number
DONB: Decoding Order Number Base DONB: Decoding Order Number Base
skipping to change at page 10, line 44 skipping to change at page 11, line 10
STAP-B: STAP type B STAP-B: STAP type B
TS: Timestamp TS: Timestamp
VCL: Video Coding Layer VCL: Video Coding Layer
VUI: Video Usability Information VUI: Video Usability Information
5. RTP Payload Format 5. RTP Payload Format
5.1. RTP Header Usage 5.1. RTP Header Usage
The format of the RTP header is specified in RFC 3550 [5] and The format of the RTP header is specified in RFC 3550 [5] and
reprinted in Figure 1 for convenience. This payload format uses the reprinted in Figure 1 for convenience. This payload format uses
fields of the header in a manner consistent with that specification. the fields of the header in a manner consistent with that
specification.
When one NAL unit is encapsulated per RTP packet, the RECOMMENDED RTP When one NAL unit is encapsulated per RTP packet, the RECOMMENDED
payload format is specified in section 5.6. The RTP payload (and the RTP payload format is specified in section 5.6. The RTP payload
settings for some RTP header bits) for aggregation packets and (and the settings for some RTP header bits) for aggregation packets
fragmentation units are specified in sections 5.7 and 5.8, and fragmentation units are specified in sections 5.7 and 5.8,
respectively. respectively.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X| CC |M| PT | sequence number | |V=2|P|X| CC |M| PT | sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timestamp | | timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| synchronization source (SSRC) identifier | | synchronization source (SSRC) identifier |
skipping to change at page 12, line 6 skipping to change at page 12, line 19
is outside the scope of this document and will not be specified is outside the scope of this document and will not be specified
here. The assignment of a payload type has to be performed here. The assignment of a payload type has to be performed
either through the profile used or in a dynamic way. either through the profile used or in a dynamic way.
Sequence number (SN): 16 bits Sequence number (SN): 16 bits
Set and used in accordance with RFC 3550. For the single NALU Set and used in accordance with RFC 3550. For the single NALU
and non-interleaved packetization mode, the sequence number is and non-interleaved packetization mode, the sequence number is
used to determine decoding order for the NALU. used to determine decoding order for the NALU.
Timestamp: 32 bits Timestamp: 32 bits
The RTP timestamp is set to the sampling timestamp of the content. The RTP timestamp is set to the sampling timestamp of the
A 90 kHz clock rate MUST be used. content. A 90 kHz clock rate MUST be used.
If the NAL unit has no timing properties of its own (e.g., If the NAL unit has no timing properties of its own (e.g.,
parameter set and SEI NAL units), the RTP timestamp is set to the parameter set and SEI NAL units), the RTP timestamp is set to
RTP timestamp of the primary coded picture of the access unit in the RTP timestamp of the primary coded picture of the access
which the NAL unit is included, according to section 7.4.1.2 of unit in which the NAL unit is included, according to section
[1]. 7.4.1.2 of [1].
The setting of the RTP Timestamp for MTAPs is defined in section The setting of the RTP Timestamp for MTAPs is defined in section
5.7.2. 5.7.2.
Receivers SHOULD ignore any picture timing SEI messages included Receivers SHOULD ignore any picture timing SEI messages included
in access units that have only one display timestamp. Instead, in access units that have only one display timestamp. Instead,
receivers SHOULD use the RTP timestamp for synchronizing the receivers SHOULD use the RTP timestamp for synchronizing the
display process. display process.
RTP senders SHOULD NOT transmit picture timing SEI messages for RTP senders SHOULD NOT transmit picture timing SEI messages for
pictures that are not supposed to be displayed as multiple fields. pictures that are not supposed to be displayed as multiple
fields.
If one access unit has more than one display timestamp carried in If one access unit has more than one display timestamp carried
a picture timing SEI message, then the information in the SEI in a picture timing SEI message, then the information in the SEI
message SHOULD be treated as relative to the RTP timestamp, with message SHOULD be treated as relative to the RTP timestamp, with
the earliest event occurring at the time given by the RTP the earliest event occurring at the time given by the RTP
timestamp, and subsequent events later, as given by the timestamp, and subsequent events later, as given by the
difference in SEI message picture timing values. Let tSEI1, difference in SEI message picture timing values. Let tSEI1,
tSEI2, ..., tSEIn be the display timestamps carried in the SEI tSEI2, ..., tSEIn be the display timestamps carried in the SEI
message of an access unit, where tSEI1 is the earliest of all message of an access unit, where tSEI1 is the earliest of all
such timestamps. Let tmadjst() be a function that adjusts the such timestamps. Let tmadjst() be a function that adjusts the
SEI messages time scale to a 90-kHz time scale. Let TS be the SEI messages time scale to a 90-kHz time scale. Let TS be the
RTP timestamp. Then, the display time for the event associated RTP timestamp. Then, the display time for the event associated
with tSEI1 is TS. The display time for the event with tSEIx, with tSEI1 is TS. The display time for the event with tSEIx,
skipping to change at page 13, line 16 skipping to change at page 13, line 32
jitter reported in the RTCP reports may not be a trustworthy jitter reported in the RTCP reports may not be a trustworthy
indication of the network performance, as the calculation indication of the network performance, as the calculation
rules for inter-arrival jitter (section 6.4.1 of RFC 3550) rules for inter-arrival jitter (section 6.4.1 of RFC 3550)
assume that the RTP timestamp of a packet is directly assume that the RTP timestamp of a packet is directly
proportional to its transmission time. proportional to its transmission time.
5.2. Payload Structures 5.2. Payload Structures
The payload format defines three different basic payload structures. The payload format defines three different basic payload structures.
A receiver can identify the payload structure by the first byte of A receiver can identify the payload structure by the first byte of
the RTP packet payload, which co-serves as the RTP payload header and, the RTP packet payload, which co-serves as the RTP payload header
in some cases, as the first byte of the payload. This byte is always and, in some cases, as the first byte of the payload. This byte is
structured as a NAL unit header. The NAL unit type field indicates always structured as a NAL unit header. The NAL unit type field
which structure is present. The possible structures are as follows: indicates which structure is present. The possible structures are
as follows:
Single NAL Unit Packet: Contains only a single NAL unit in the Single NAL Unit Packet: Contains only a single NAL unit in the
payload. The NAL header type field will be equal to the original NAL payload. The NAL header type field will be equal to the original
unit type; i.e., in the range of 1 to 23, inclusive. Specified in NAL unit type; i.e., in the range of 1 to 23, inclusive. Specified
section 5.6. in section 5.6.
Aggregation Packet: Packet type used to aggregate multiple NAL units Aggregation Packet: Packet type used to aggregate multiple NAL
into a single RTP payload. This packet exists in four versions, the units into a single RTP payload. This packet exists in four
Single-Time Aggregation Packet type A (STAP-A), the Single-Time versions, the Single-Time Aggregation Packet type A (STAP-A), the
Aggregation Packet type B (STAP-B), Multi-Time Aggregation Packet Single-Time Aggregation Packet type B (STAP-B), Multi-Time
(MTAP) with 16-bit offset (MTAP16), and Multi-Time Aggregation Packet Aggregation Packet (MTAP) with 16-bit offset (MTAP16), and Multi-
(MTAP) with 24-bit offset (MTAP24). The NAL unit type numbers Time Aggregation Packet (MTAP) with 24-bit offset (MTAP24). The
assigned for STAP-A, STAP-B, MTAP16, and MTAP24 are 24, 25, 26, and NAL unit type numbers assigned for STAP-A, STAP-B, MTAP16, and
27, respectively. Specified in section 5.7. MTAP24 are 24, 25, 26, and 27, respectively. Specified in section
5.7.
Fragmentation Unit: Used to fragment a single NAL unit over multiple Fragmentation Unit: Used to fragment a single NAL unit over
RTP packets. Exists with two versions, FU-A and FU-B, identified multiple RTP packets. Exists with two versions, FU-A and FU-B,
with the NAL unit type numbers 28 and 29, respectively. Specified in identified with the NAL unit type numbers 28 and 29, respectively.
section 5.8. Specified in section 5.8.
Informative note: This specification does not limit the size of Informative note: This specification does not limit the size of
NAL units encapsulated in single NAL unit packets and NAL units encapsulated in single NAL unit packets and
fragmentation units. The maximum size of a NAL unit encapsulated fragmentation units. The maximum size of a NAL unit
in any aggregation packet is 65535 bytes. encapsulated in any aggregation packet is 65535 bytes.
Table 1 summarizes NAL unit types and the corresponding RTP packet Table 1 summarizes NAL unit types and the corresponding RTP packet
types when each of these NAL units is directly used as a packet types when each of these NAL units is directly used as a packet
payload, and where the types are described in this memo. payload, and where the types are described in this memo.
Table 1. Summary of NAL unit types and the corresponding packet Table 1. Summary of NAL unit types and the corresponding packet
types types
NAL Unit Packet Packet Type Name Section NAL Unit Packet Packet Type Name Section
Type Type Type Type
--------------------------------------------------------- ---------------------------------------------------------
0 reserved - 0 reserved -
1-23 NAL unit Single NAL unit packet 5.6 1-23 NAL unit Single NAL unit packet 5.6
24 STAP-A Single-time aggregation packet 5.7.1 24 STAP-A Single-time aggregation packet 5.7.1
25 STAP-B Single-time aggregation packet 5.7.1 25 STAP-B Single-time aggregation packet 5.7.1
26 MTAP16 Multi-time aggregation packet 5.7.2 26 MTAP16 Multi-time aggregation packet 5.7.2
27 MTAP24 Multi-time aggregation packet 5.7.2 27 MTAP24 Multi-time aggregation packet 5.7.2
28 FU-A Fragmentation unit 5.8 28 FU-A Fragmentation unit 5.8
skipping to change at page 14, line 23 skipping to change at page 15, line 19
24 STAP-A Single-time aggregation packet 5.7.1 24 STAP-A Single-time aggregation packet 5.7.1
25 STAP-B Single-time aggregation packet 5.7.1 25 STAP-B Single-time aggregation packet 5.7.1
26 MTAP16 Multi-time aggregation packet 5.7.2 26 MTAP16 Multi-time aggregation packet 5.7.2
27 MTAP24 Multi-time aggregation packet 5.7.2 27 MTAP24 Multi-time aggregation packet 5.7.2
28 FU-A Fragmentation unit 5.8 28 FU-A Fragmentation unit 5.8
29 FU-B Fragmentation unit 5.8 29 FU-B Fragmentation unit 5.8
30-31 reserved - 30-31 reserved -
5.3. NAL Unit Header Usage 5.3. NAL Unit Header Usage
The structure and semantics of the NAL unit header were introduced in The structure and semantics of the NAL unit header were introduced
section 1.3. For convenience, the format of the NAL unit header is in section 1.3. For convenience, the format of the NAL unit header
reprinted below: is reprinted below:
+---------------+ +---------------+
|0|1|2|3|4|5|6|7| |0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|F|NRI| Type | |F|NRI| Type |
+---------------+ +---------------+
This section specifies the semantics of F and NRI according to this This section specifies the semantics of F and NRI according to this
specification. specification.
F: 1 bit F: 1 bit
forbidden_zero_bit. A value of 0 indicates that the NAL unit forbidden_zero_bit. A value of 0 indicates that the NAL unit
type octet and payload should not contain bit errors or other type octet and payload should not contain bit errors or other
syntax violations. A value of 1 indicates that the NAL unit type syntax violations. A value of 1 indicates that the NAL unit
octet and payload may contain bit errors or other syntax type octet and payload may contain bit errors or other syntax
violations. violations.
MANEs SHOULD set the F bit to indicate detected bit errors in the MANEs SHOULD set the F bit to indicate detected bit errors in
NAL unit. The H.264 specification requires that the F bit is the NAL unit. The H.264 specification requires that the F bit
equal to 0. When the F bit is set, the decoder is advised that is equal to 0. When the F bit is set, the decoder is advised
bit errors or any other syntax violations may be present in the that bit errors or any other syntax violations may be present in
payload or in the NAL unit type octet. The simplest decoder the payload or in the NAL unit type octet. The simplest decoder
reaction to a NAL unit in which the F bit is equal to 1 is to reaction to a NAL unit in which the F bit is equal to 1 is to
discard such a NAL unit and to conceal the lost data in the discard such a NAL unit and to conceal the lost data in the
discarded NAL unit. discarded NAL unit.
NRI: 2 bits NRI: 2 bits
nal_ref_idc. The semantics of value 00 and a non-zero value nal_ref_idc. The semantics of value 00 and a non-zero value
remain unchanged from the H.264 specification. In other words, a remain unchanged from the H.264 specification. In other words,
value of 00 indicates that the content of the NAL unit is not a value of 00 indicates that the content of the NAL unit is not
used to reconstruct reference pictures for inter picture used to reconstruct reference pictures for inter picture
prediction. Such NAL units can be discarded without risking the prediction. Such NAL units can be discarded without risking the
integrity of the reference pictures. Values greater than 00 integrity of the reference pictures. Values greater than 00
indicate that the decoding of the NAL unit is required to indicate that the decoding of the NAL unit is required to
maintain the integrity of the reference pictures. maintain the integrity of the reference pictures.
In addition to the specification above, according to this RTP In addition to the specification above, according to this RTP
payload specification, values of NRI indicate the relative payload specification, values of NRI indicate the relative
transport priority, as determined by the encoder. MANEs can use transport priority, as determined by the encoder. MANEs can use
this information to protect more important NAL units better than this information to protect more important NAL units better than
they do less important NAL units. The highest transport priority they do less important NAL units. The highest transport
is 11, followed by 10, and then by 01; finally, 00 is the lowest. priority is 11, followed by 10, and then by 01; finally, 00 is
the lowest.
Informative note: Any non-zero value of NRI is handled Informative note: Any non-zero value of NRI is handled
identically in H.264 decoders. Therefore, receivers need not identically in H.264 decoders. Therefore, receivers need not
manipulate the value of NRI when passing NAL units to the manipulate the value of NRI when passing NAL units to the
decoder. decoder.
An H.264 encoder MUST set the value of NRI according to the H.264 An H.264 encoder MUST set the value of NRI according to the
specification (subclause 7.4.1) when the value of nal_unit_type H.264 specification (subclause 7.4.1) when the value of
is in the range of 1 to 12, inclusive. In particular, the H.264 nal_unit_type is in the range of 1 to 12, inclusive. In
specification requires that the value of NRI SHALL be equal to 0 particular, the H.264 specification requires that the value of
for all NAL units having nal_unit_type equal to 6, 9, 10, 11, or NRI SHALL be equal to 0 for all NAL units having nal_unit_type
12. equal to 6, 9, 10, 11, or 12.
For NAL units having nal_unit_type equal to 7 or 8 (indicating a For NAL units having nal_unit_type equal to 7 or 8 (indicating a
sequence parameter set or a picture parameter set, respectively), sequence parameter set or a picture parameter set, respectively),
an H.264 encoder SHOULD set the value of NRI to 11 (in binary an H.264 encoder SHOULD set the value of NRI to 11 (in binary
format). For coded slice NAL units of a primary coded picture format). For coded slice NAL units of a primary coded picture
having nal_unit_type equal to 5 (indicating a coded slice having nal_unit_type equal to 5 (indicating a coded slice
belonging to an IDR picture), an H.264 encoder SHOULD set the belonging to an IDR picture), an H.264 encoder SHOULD set the
value of NRI to 11 (in binary format). value of NRI to 11 (in binary format).
For a mapping of the remaining nal_unit_types to NRI values, the For a mapping of the remaining nal_unit_types to NRI values, the
following example MAY be used and has been shown to be efficient following example MAY be used and has been shown to be efficient
in a certain environment [14]. Other mappings MAY also be in a certain environment [14]. Other mappings MAY also be
desirable, depending on the application and the H.264/AVC Annex A desirable, depending on the application and the H.264/AVC Annex
profile in use. A profile in use.
Informative note: Data Partitioning is not available in Informative note: Data Partitioning is not available in
certain profiles; e.g., in the Main or Baseline profiles. certain profiles; e.g., in the Main or Baseline profiles.
Consequently, the NAL unit types 2, 3, and 4 can occur only if Consequently, the NAL unit types 2, 3, and 4 can occur only
the video bitstream conforms to a profile in which data if the video bitstream conforms to a profile in which data
partitioning is allowed and not in streams that conform to the partitioning is allowed and not in streams that conform to
Main or Baseline profiles. the Main or Baseline profiles.
Table 2. Example of NRI values for coded slices and coded slice data Table 2. Example of NRI values for coded slices and coded slice
partitions of primary coded reference pictures data partitions of primary coded reference pictures
NAL Unit Type Content of NAL unit NRI (binary) NAL Unit Type Content of NAL unit NRI (binary)
---------------------------------------------------------------- ----------------------------------------------------------------
1 non-IDR coded slice 10 1 non-IDR coded slice 10
2 Coded slice data partition A 10 2 Coded slice data partition A 10
3 Coded slice data partition B 01 3 Coded slice data partition B 01
4 Coded slice data partition C 01 4 Coded slice data partition C 01
Informative note: As mentioned before, the NRI value of non- Informative note: As mentioned before, the NRI value of non-
reference pictures is 00 as mandated by H.264/AVC. reference pictures is 00 as mandated by H.264/AVC.
An H.264 encoder SHOULD set the value of NRI for coded slice and An H.264 encoder SHOULD set the value of NRI for coded slice and
coded slice data partition NAL units of redundant coded reference coded slice data partition NAL units of redundant coded
pictures equal to 01 (in binary format). reference pictures equal to 01 (in binary format).
Definitions of the values for NRI for NAL unit types 24 to 29, Definitions of the values for NRI for NAL unit types 24 to 29,
inclusive, are given in sections 5.7 and 5.8 of this memo. inclusive, are given in sections 5.7 and 5.8 of this memo.
No recommendation for the value of NRI is given for NAL units No recommendation for the value of NRI is given for NAL units
having nal_unit_type in the range of 13 to 23, inclusive, because having nal_unit_type in the range of 13 to 23, inclusive,
these values are reserved for ITU-T and ISO/IEC. No because these values are reserved for ITU-T and ISO/IEC. No
recommendation for the value of NRI is given for NAL units having recommendation for the value of NRI is given for NAL units
nal_unit_type equal to 0 or in the range of 30 to 31, inclusive, having nal_unit_type equal to 0 or in the range of 30 to 31,
as the semantics of these values are not specified in this memo. inclusive, as the semantics of these values are not specified in
this memo.
5.4. Packetization Modes 5.4. Packetization Modes
This memo specifies three cases of packetization modes: This memo specifies three cases of packetization modes:
o Single NAL unit mode o Single NAL unit mode
o Non-interleaved mode o Non-interleaved mode
o Interleaved mode o Interleaved mode
The single NAL unit mode is targeted for conversational systems that The single NAL unit mode is targeted for conversational systems
comply with ITU-T Recommendation H.241 [3] (see section 12.1). The that comply with ITU-T Recommendation H.241 [3] (see section 12.1).
non-interleaved mode is targeted for conversational systems that may The non-interleaved mode is targeted for conversational systems
not comply with ITU-T Recommendation H.241. In the non-interleaved that may not comply with ITU-T Recommendation H.241. In the non-
mode, NAL units are transmitted in NAL unit decoding order. The interleaved mode, NAL units are transmitted in NAL unit decoding
interleaved mode is targeted for systems that do not require very low order. The interleaved mode is targeted for systems that do not
end-to-end latency. The interleaved mode allows transmission of NAL require very low end-to-end latency. The interleaved mode allows
units out of NAL unit decoding order. transmission of NAL units out of NAL unit decoding order.
The packetization mode in use MAY be signaled by the value of the The packetization mode in use MAY be signaled by the value of the
OPTIONAL packetization-mode media type parameter. The used OPTIONAL packetization-mode media type parameter. The used
packetization mode governs which NAL unit types are allowed in RTP packetization mode governs which NAL unit types are allowed in RTP
payloads. Table 3 summarizes the allowed packet payload types for payloads. Table 3 summarizes the allowed packet payload types for
each packetization mode. Packetization modes are explained in more each packetization mode. Packetization modes are explained in more
detail in section 6. detail in section 6.
Table 3. Summary of allowed NAL unit types for each packetization Table 3. Summary of allowed NAL unit types for each packetization
mode (yes = allowed, no = disallowed, ig = ignore) mode (yes = allowed, no = disallowed, ig = ignore)
skipping to change at page 18, line 5 skipping to change at page 18, line 37
28 FU-A no yes yes 28 FU-A no yes yes
29 FU-B no no yes 29 FU-B no no yes
30-31 reserved ig ig ig 30-31 reserved ig ig ig
Some NAL unit or payload type values (indicated as reserved in Some NAL unit or payload type values (indicated as reserved in
Table 3) are reserved for future extensions. NAL units of those Table 3) are reserved for future extensions. NAL units of those
types SHOULD NOT be sent by a sender (direct as packet payloads, or types SHOULD NOT be sent by a sender (direct as packet payloads, or
as aggregation units in aggregation packets, or as fragmented units as aggregation units in aggregation packets, or as fragmented units
in FU packets) and MUST be ignored by a receiver. For example, the in FU packets) and MUST be ignored by a receiver. For example, the
payload types 1-23, with the associated packet type "NAL unit", are payload types 1-23, with the associated packet type "NAL unit", are
allowed in "Single NAL Unit Mode" and in "Non-Interleaved Mode", but allowed in "Single NAL Unit Mode" and in "Non-Interleaved Mode",
disallowed in "Interleaved Mode". However, NAL units of NAL unit but disallowed in "Interleaved Mode". However, NAL units of NAL
types 1-23 can be used in ''Interleaved Mode'' as aggregation units in unit types 1-23 can be used in ''Interleaved Mode'' as aggregation
STAP-B, MTAP16 and MTAP14 packets as well as fragmented units in FU-A units in STAP-B, MTAP16 and MTAP14 packets as well as fragmented
and FU-B packets. Similarly, NAL units of NAL unit types 1-23 can units in FU-A and FU-B packets. Similarly, NAL units of NAL unit
also be used in the "Non-Interleaved Mode" as aggregation units in types 1-23 can also be used in the "Non-Interleaved Mode" as
STAP-A packets or fragmented units in FU-A packets, in addition to aggregation units in STAP-A packets or fragmented units in FU-A
being directly used as packet payloads. packets, in addition to being directly used as packet payloads.
5.5. Decoding Order Number (DON) 5.5. Decoding Order Number (DON)
In the interleaved packetization mode, the transmission order of NAL In the interleaved packetization mode, the transmission order of
units is allowed to differ from the decoding order of the NAL units. NAL units is allowed to differ from the decoding order of the NAL
Decoding order number (DON) is a field in the payload structure or a units. Decoding order number (DON) is a field in the payload
derived variable that indicates the NAL unit decoding order. structure or a derived variable that indicates the NAL unit
Rationale and examples of use cases for transmission out of decoding decoding order. Rationale and examples of use cases for
order and for the use of DON are given in section 13. transmission out of decoding order and for the use of DON are given
in section 13.
The coupling of transmission and decoding order is controlled by the The coupling of transmission and decoding order is controlled by
OPTIONAL sprop-interleaving-depth media type parameter as follows. the OPTIONAL sprop-interleaving-depth media type parameter as
When the value of the OPTIONAL sprop-interleaving-depth media type follows. When the value of the OPTIONAL sprop-interleaving-depth
parameter is equal to 0 (explicitly or per default), the transmission media type parameter is equal to 0 (explicitly or per default), the
order of NAL units MUST conform to the NAL unit decoding order. When transmission order of NAL units MUST conform to the NAL unit
the value of the OPTIONAL sprop-interleaving-depth media type decoding order. When the value of the OPTIONAL sprop-interleaving-
parameter is greater than 0, depth media type parameter is greater than 0,
o the order of NAL units in an MTAP16 and an MTAP24 is NOT REQUIRED o the order of NAL units in an MTAP16 and an MTAP24 is not
to be the NAL unit decoding order, and required to be the NAL unit decoding order, and
o the order of NAL units generated by de-packetizing STAP-Bs, MTAPs, o the order of NAL units generated by de-packetizing STAP-Bs,
and FUs in two consecutive packets is NOT REQUIRED to be the NAL MTAPs, and FUs in two consecutive packets is not required to be
unit decoding order. the NAL unit decoding order.
The RTP payload structures for a single NAL unit packet, an STAP-A, The RTP payload structures for a single NAL unit packet, an STAP-A,
and an FU-A do not include DON. STAP-B and FU-B structures include and an FU-A do not include DON. STAP-B and FU-B structures include
DON, and the structure of MTAPs enables derivation of DON as DON, and the structure of MTAPs enables derivation of DON as
specified in section 5.7.2. specified in section 5.7.2.
Informative note: When an FU-A occurs in interleaved mode, it Informative note: When an FU-A occurs in interleaved mode, it
always follows an FU-B, which sets its DON. always follows an FU-B, which sets its DON.
Informative note: If a transmitter wants to encapsulate a single Informative note: If a transmitter wants to encapsulate a single
NAL unit per packet and transmit packets out of their decoding NAL unit per packet and transmit packets out of their decoding
order, STAP-B packet type can be used. order, STAP-B packet type can be used.
In the single NAL unit packetization mode, the transmission order of In the single NAL unit packetization mode, the transmission order
NAL units, determined by the RTP sequence number, MUST be the same as of NAL units, determined by the RTP sequence number, MUST be the
their NAL unit decoding order. In the non-interleaved packetization same as their NAL unit decoding order. In the non-interleaved
mode, the transmission order of NAL units in single NAL unit packets, packetization mode, the transmission order of NAL units in single
STAP-As, and FU-As MUST be the same as their NAL unit decoding order. NAL unit packets, STAP-As, and FU-As MUST be the same as their NAL
The NAL units within an STAP MUST appear in the NAL unit decoding unit decoding order. The NAL units within an STAP MUST appear in
order. Thus, the decoding order is first provided through the the NAL unit decoding order. Thus, the decoding order is first
implicit order within a STAP, and second provided through the RTP provided through the implicit order within a STAP, and second
sequence number for the order between STAPs, FUs, and single NAL unit provided through the RTP sequence number for the order between
packets. STAPs, FUs, and single NAL unit packets.
Signaling of the value of DON for NAL units carried in STAP-B, MTAP, Signaling of the value of DON for NAL units carried in STAP-B, MTAP,
and a series of fragmentation units starting with an FU-B is and a series of fragmentation units starting with an FU-B is
specified in sections 5.7.1, 5.7.2, and 5.8, respectively. The DON specified in sections 5.7.1, 5.7.2, and 5.8, respectively. The DON
value of the first NAL unit in transmission order MAY be set to any value of the first NAL unit in transmission order MAY be set to any
value. Values of DON are in the range of 0 to 65535, inclusive. value. Values of DON are in the range of 0 to 65535, inclusive.
After reaching the maximum value, the value of DON wraps around to 0. After reaching the maximum value, the value of DON wraps around to
0.
The decoding order of two NAL units contained in any STAP-B, MTAP, or The decoding order of two NAL units contained in any STAP-B, MTAP,
a series of fragmentation units starting with an FU-B is determined or a series of fragmentation units starting with an FU-B is
as follows. Let DON(i) be the decoding order number of the NAL unit determined as follows. Let DON(i) be the decoding order number of
having index i in the transmission order. Function don_diff(m,n) is the NAL unit having index i in the transmission order. Function
specified as follows: don_diff(m,n) is specified as follows:
If DON(m) == DON(n), don_diff(m,n) = 0 If DON(m) == DON(n), don_diff(m,n) = 0
If (DON(m) < DON(n) and DON(n) - DON(m) < 32768), If (DON(m) < DON(n) and DON(n) - DON(m) < 32768),
don_diff(m,n) = DON(n) - DON(m) don_diff(m,n) = DON(n) - DON(m)
If (DON(m) > DON(n) and DON(m) - DON(n) >= 32768), If (DON(m) > DON(n) and DON(m) - DON(n) >= 32768),
don_diff(m,n) = 65536 - DON(m) + DON(n) don_diff(m,n) = 65536 - DON(m) + DON(n)
If (DON(m) < DON(n) and DON(n) - DON(m) >= 32768), If (DON(m) < DON(n) and DON(n) - DON(m) >= 32768),
don_diff(m,n) = - (DON(m) + 65536 - DON(n)) don_diff(m,n) = - (DON(m) + 65536 - DON(n))
If (DON(m) > DON(n) and DON(m) - DON(n) < 32768), If (DON(m) > DON(n) and DON(m) - DON(n) < 32768),
don_diff(m,n) = - (DON(m) - DON(n)) don_diff(m,n) = - (DON(m) - DON(n))
A positive value of don_diff(m,n) indicates that the NAL unit having A positive value of don_diff(m,n) indicates that the NAL unit
transmission order index n follows, in decoding order, the NAL unit having transmission order index n follows, in decoding order, the
having transmission order index m. When don_diff(m,n) is equal to 0, NAL unit having transmission order index m. When don_diff(m,n) is
then the NAL unit decoding order of the two NAL units can be in equal to 0, then the NAL unit decoding order of the two NAL units
either order. A negative value of don_diff(m,n) indicates that the can be in either order. A negative value of don_diff(m,n)
NAL unit having transmission order index n precedes, in decoding indicates that the NAL unit having transmission order index n
order, the NAL unit having transmission order index m. precedes, in decoding order, the NAL unit having transmission order
index m.
Values of DON related fields (DON, DONB, and DOND; see section 5.7) Values of DON related fields (DON, DONB, and DOND; see section 5.7)
MUST be such that the decoding order determined by the values of DON, MUST be such that the decoding order determined by the values of
as specified above, conforms to the NAL unit decoding order. If the DON, as specified above, conforms to the NAL unit decoding order.
order of two NAL units in NAL unit decoding order is switched and the If the order of two NAL units in NAL unit decoding order is
new order does not conform to the NAL unit decoding order, the NAL switched and the new order does not conform to the NAL unit
units MUST NOT have the same value of DON. If the order of two decoding order, the NAL units MUST NOT have the same value of DON.
consecutive NAL units in the NAL unit stream is switched and the new If the order of two consecutive NAL units in the NAL unit stream is
order still conforms to the NAL unit decoding order, the NAL units switched and the new order still conforms to the NAL unit decoding
MAY have the same value of DON. For example, when arbitrary slice order, the NAL units MAY have the same value of DON. For example,
order is allowed by the video coding profile in use, all the coded when arbitrary slice order is allowed by the video coding profile
slice NAL units of a coded picture are allowed to have the same value in use, all the coded slice NAL units of a coded picture are
of DON. Consequently, NAL units having the same value of DON can be allowed to have the same value of DON. Consequently, NAL units
decoded in any order, and two NAL units having a different value of having the same value of DON can be decoded in any order, and two
DON should be passed to the decoder in the order specified above. NAL units having a different value of DON should be passed to the
When two consecutive NAL units in the NAL unit decoding order have a decoder in the order specified above. When two consecutive NAL
different value of DON, the value of DON for the second NAL unit in units in the NAL unit decoding order have a different value of DON,
decoding order SHOULD be the value of DON for the first, incremented the value of DON for the second NAL unit in decoding order SHOULD
by one. be the value of DON for the first, incremented by one.
An example of the de-packetization process to recover the NAL unit An example of the de-packetization process to recover the NAL unit
decoding order is given in section 7. decoding order is given in section 7.
Informative note: Receivers should not expect that the absolute Informative note: Receivers should not expect that the absolute
difference of values of DON for two consecutive NAL units in the difference of values of DON for two consecutive NAL units in the
NAL unit decoding order will be equal to one, even in error-free NAL unit decoding order will be equal to one, even in error-free
transmission. An increment by one is not required, as at the transmission. An increment by one is not required, as at the
time of associating values of DON to NAL units, it may not be time of associating values of DON to NAL units, it may not be
known whether all NAL units are delivered to the receiver. For known whether all NAL units are delivered to the receiver. For
example, a gateway may not forward coded slice NAL units of non- example, a gateway may not forward coded slice NAL units of non-
reference pictures or SEI NAL units when there is a shortage of reference pictures or SEI NAL units when there is a shortage of
bit rate in the network to which the packets are forwarded. In bit rate in the network to which the packets are forwarded. In
another example, a live broadcast is interrupted by pre-encoded another example, a live broadcast is interrupted by pre-encoded
content, such as commercials, from time to time. The first intra content, such as commercials, from time to time. The first
picture of a pre-encoded clip is transmitted in advance to ensure intra picture of a pre-encoded clip is transmitted in advance to
that it is readily available in the receiver. When transmitting ensure that it is readily available in the receiver. When
the first intra picture, the originator does not exactly know how transmitting the first intra picture, the originator does not
many NAL units will be encoded before the first intra picture of exactly know how many NAL units will be encoded before the first
the pre-encoded clip follows in decoding order. Thus, the values intra picture of the pre-encoded clip follows in decoding order.
of DON for the NAL units of the first intra picture of the pre- Thus, the values of DON for the NAL units of the first intra
encoded clip have to be estimated when they are transmitted, and picture of the pre-encoded clip have to be estimated when they
gaps in values of DON may occur. are transmitted, and gaps in values of DON may occur.
5.6. Single NAL Unit Packet 5.6. Single NAL Unit Packet
The single NAL unit packet defined here MUST contain only one NAL The single NAL unit packet defined here MUST contain only one NAL
unit, of the types defined in [1]. This means that neither an unit, of the types defined in [1]. This means that neither an
aggregation packet nor a fragmentation unit can be used within a aggregation packet nor a fragmentation unit can be used within a
single NAL unit packet. A NAL unit stream composed by de-packetizing single NAL unit packet. A NAL unit stream composed by de-
single NAL unit packets in RTP sequence number order MUST conform to packetizing single NAL unit packets in RTP sequence number order
the NAL unit decoding order. The structure of the single NAL unit MUST conform to the NAL unit decoding order. The structure of the
packet is shown in Figure 2. single NAL unit packet is shown in Figure 2.
Informative note: The first byte of a NAL unit co-serves as the Informative note: The first byte of a NAL unit co-serves as the
RTP payload header. RTP payload header.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|NRI| Type | | |F|NRI| Type | |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
skipping to change at page 21, line 30 skipping to change at page 22, line 23
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 RTP payload format for single NAL unit packet Figure 2 RTP payload format for single NAL unit packet
5.7. Aggregation Packets 5.7. Aggregation Packets
Aggregation packets are the NAL unit aggregation scheme of this Aggregation packets are the NAL unit aggregation scheme of this
payload specification. The scheme is introduced to reflect the payload specification. The scheme is introduced to reflect the
dramatically different MTU sizes of two key target networks: wireline dramatically different MTU sizes of two key target networks:
IP networks (with an MTU size that is often limited by the Ethernet wireline IP networks (with an MTU size that is often limited by the
MTU size; roughly 1500 bytes), and IP or non-IP (e.g., ITU-T H.324/M) Ethernet MTU size; roughly 1500 bytes), and IP or non-IP (e.g.,
based wireless communication systems with preferred transmission unit ITU-T H.324/M) based wireless communication systems with preferred
sizes of 254 bytes or less. To prevent media transcoding between the transmission unit sizes of 254 bytes or less. To prevent media
two worlds, and to avoid undesirable packetization overhead, a NAL transcoding between the two worlds, and to avoid undesirable
unit aggregation scheme is introduced. packetization overhead, a NAL unit aggregation scheme is introduced.
Two types of aggregation packets are defined by this specification: Two types of aggregation packets are defined by this specification:
o Single-time aggregation packet (STAP): aggregates NAL units with o Single-time aggregation packet (STAP): aggregates NAL units with
identical NALU-time. Two types of STAPs are defined, one without identical NALU-time. Two types of STAPs are defined, one
DON (STAP-A) and another including DON (STAP-B). without DON (STAP-A) and another including DON (STAP-B).
o Multi-time aggregation packet (MTAP): aggregates NAL units with o Multi-time aggregation packet (MTAP): aggregates NAL units with
potentially differing NALU-time. Two different MTAPs are defined, potentially differing NALU-time. Two different MTAPs are
differing in the length of the NAL unit timestamp offset. defined, differing in the length of the NAL unit timestamp
offset.
Each NAL unit to be carried in an aggregation packet is encapsulated Each NAL unit to be carried in an aggregation packet is
in an aggregation unit. Please see below for the four different encapsulated in an aggregation unit. Please see below for the four
aggregation units and their characteristics. different aggregation units and their characteristics.
The structure of the RTP payload format for aggregation packets is The structure of the RTP payload format for aggregation packets is
presented in Figure 3. presented in Figure 3.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|NRI| Type | | |F|NRI| Type | |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
skipping to change at page 22, line 41 skipping to change at page 23, line 38
Type Packet Timestamp offset DON related fields Type Packet Timestamp offset DON related fields
field length (DON, DONB, DOND) field length (DON, DONB, DOND)
(in bits) present (in bits) present
-------------------------------------------------------- --------------------------------------------------------
24 STAP-A 0 no 24 STAP-A 0 no
25 STAP-B 0 yes 25 STAP-B 0 yes
26 MTAP16 16 yes 26 MTAP16 16 yes
27 MTAP24 24 yes 27 MTAP24 24 yes
The marker bit in the RTP header is set to the value that the marker The marker bit in the RTP header is set to the value that the
bit of the last NAL unit of the aggregated packet would have if it marker bit of the last NAL unit of the aggregated packet would have
were transported in its own RTP packet. if it were transported in its own RTP packet.
The payload of an aggregation packet consists of one or more The payload of an aggregation packet consists of one or more
aggregation units. See sections 5.7.1 and 5.7.2 for the four aggregation units. See sections 5.7.1 and 5.7.2 for the four
different types of aggregation units. An aggregation packet can different types of aggregation units. An aggregation packet can
carry as many aggregation units as necessary; however, the total carry as many aggregation units as necessary; however, the total
amount of data in an aggregation packet obviously MUST fit into an IP amount of data in an aggregation packet obviously MUST fit into an
packet, and the size SHOULD be chosen so that the resulting IP packet IP packet, and the size SHOULD be chosen so that the resulting IP
is smaller than the MTU size. An aggregation packet MUST NOT contain packet is smaller than the MTU size. An aggregation packet MUST
fragmentation units specified in section 5.8. Aggregation packets NOT contain fragmentation units specified in section 5.8.
MUST NOT be nested; i.e., an aggregation packet MUST NOT contain
another aggregation packet. Aggregation packets MUST NOT be nested; i.e., an aggregation packet
MUST NOT contain another aggregation packet.
5.7.1. Single-Time Aggregation Packet 5.7.1. Single-Time Aggregation Packet
Single-time aggregation packet (STAP) SHOULD be used whenever NAL Single-time aggregation packet (STAP) SHOULD be used whenever NAL
units are aggregated that all share the same NALU-time. The payload units are aggregated that all share the same NALU-time. The
of an STAP-A does not include DON and consists of at least one payload of an STAP-A does not include DON and consists of at least
single-time aggregation unit, as presented in Figure 4. The payload one single-time aggregation unit, as presented in Figure 4. The
of an STAP-B consists of a 16-bit unsigned decoding order number (DON) payload of an STAP-B consists of a 16-bit unsigned decoding order
(in network byte order) followed by at least one single-time number (DON) (in network byte order) followed by at least one
aggregation unit, as presented in Figure 5. single-time aggregation unit, as presented in Figure 5.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: | : |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
| single-time aggregation units | | single-time aggregation units |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 23, line 46 skipping to change at page 24, line 46
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
| single-time aggregation units | | single-time aggregation units |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5 Payload format for STAP-B Figure 5 Payload format for STAP-B
The DON field specifies the value of DON for the first NAL unit in an The DON field specifies the value of DON for the first NAL unit in
STAP-B in transmission order. For each successive NAL unit in an STAP-B in transmission order. For each successive NAL unit in
appearance order in an STAP-B, the value of DON is equal to (the appearance order in an STAP-B, the value of DON is equal to (the
value of DON of the previous NAL unit in the STAP-B + 1) % 65536, in value of DON of the previous NAL unit in the STAP-B + 1) % 65536,
which '%' stands for the modulo operation. in which '%' stands for the modulo operation.
A single-time aggregation unit consists of 16-bit unsigned size A single-time aggregation unit consists of 16-bit unsigned size
information (in network byte order) that indicates the size of the information (in network byte order) that indicates the size of the
following NAL unit in bytes (excluding these two octets, but following NAL unit in bytes (excluding these two octets, but
including the NAL unit type octet of the NAL unit), followed by the including the NAL unit type octet of the NAL unit), followed by the
NAL unit itself, including its NAL unit type byte. A single-time NAL unit itself, including its NAL unit type byte. A single-time
aggregation unit is byte aligned within the RTP payload, but it may aggregation unit is byte aligned within the RTP payload, but it may
not be aligned on a 32-bit word boundary. Figure 6 presents the not be aligned on a 32-bit word boundary. Figure 6 presents the
structure of the single-time aggregation unit. structure of the single-time aggregation unit.
skipping to change at page 24, line 28 skipping to change at page 25, line 28
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
| NAL unit | | NAL unit |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6 Structure for single-time aggregation unit Figure 6 Structure for single-time aggregation unit
Figure 7 presents an example of an RTP packet that contains an STAP-A. Figure 7 presents an example of an RTP packet that contains an
The STAP contains two single-time aggregation units, labeled as 1 and STAP-A. The STAP contains two single-time aggregation units,
2 in the figure. labeled as 1 and 2 in the figure.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP Header | | RTP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAP-A NAL HDR | NALU 1 Size | NALU 1 HDR | |STAP-A NAL HDR | NALU 1 Size | NALU 1 HDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 1 Data | | NALU 1 Data |
: : : :
skipping to change at page 25, line 4 skipping to change at page 26, line 4
| | NALU 2 Size | NALU 2 HDR | | | NALU 2 Size | NALU 2 HDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 2 Data | | NALU 2 Data |
: : : :
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7 An example of an RTP packet including an STAP-A containing Figure 7 An example of an RTP packet including an STAP-A containing
two single-time aggregation units two single-time aggregation units
Figure 8 presents an example of an RTP packet that contains an STAP-B. Figure 8 presents an example of an RTP packet that contains an
The STAP contains two single-time aggregation units, labeled as 1 and STAP-B. The STAP contains two single-time aggregation units,
2 in the figure. labeled as 1 and 2 in the figure.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP Header | | RTP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAP-B NAL HDR | DON | NALU 1 Size | |STAP-B NAL HDR | DON | NALU 1 Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 1 Size | NALU 1 HDR | NALU 1 Data | | NALU 1 Size | NALU 1 HDR | NALU 1 Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
skipping to change at page 25, line 32 skipping to change at page 26, line 32
: : : :
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8 An example of an RTP packet including an STAP-B containing Figure 8 An example of an RTP packet including an STAP-B containing
two single-time aggregation units two single-time aggregation units
5.7.2. Multi-Time Aggregation Packets (MTAPs) 5.7.2. Multi-Time Aggregation Packets (MTAPs)
The NAL unit payload of MTAPs consists of a 16-bit unsigned decoding The NAL unit payload of MTAPs consists of a 16-bit unsigned
order number base (DONB) (in network byte order) and one or more decoding order number base (DONB) (in network byte order) and one
multi-time aggregation units, as presented in Figure 9. DONB MUST or more multi-time aggregation units, as presented in Figure 9.
contain the value of DON for the first NAL unit in the NAL unit DONB MUST contain the value of DON for the first NAL unit in the
decoding order among the NAL units of the MTAP. NAL unit decoding order among the NAL units of the MTAP.
Informative note: The first NAL unit in the NAL unit decoding Informative note: The first NAL unit in the NAL unit decoding
order is not necessarily the first NAL unit in the order in which order is not necessarily the first NAL unit in the order in
the NAL units are encapsulated in an MTAP. which the NAL units are encapsulated in an MTAP.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: decoding order number base | | : decoding order number base | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
| multi-time aggregation units | | multi-time aggregation units |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9 NAL unit payload format for MTAPs Figure 9 NAL unit payload format for MTAPs
Two different multi-time aggregation units are defined in this Two different multi-time aggregation units are defined in this
specification. Both of them consist of 16 bits unsigned size specification. Both of them consist of 16 bits unsigned size
information of the following NAL unit (in network byte order), an 8- information of the following NAL unit (in network byte order), an
bit unsigned decoding order number difference (DOND), and n bits (in 8-bit unsigned decoding order number difference (DOND), and n bits
network byte order) of timestamp offset (TS offset) for this NAL unit, (in network byte order) of timestamp offset (TS offset) for this
whereby n can be 16 or 24. The choice between the different MTAP NAL unit, whereby n can be 16 or 24. The choice between the
types (MTAP16 and MTAP24) is application dependent: the larger the different MTAP types (MTAP16 and MTAP24) is application dependent:
timestamp offset is, the higher the flexibility of the MTAP, but the the larger the timestamp offset is, the higher the flexibility of
overhead is also higher. the MTAP, but the overhead is also higher.
The structure of the multi-time aggregation units for MTAP16 and The structure of the multi-time aggregation units for MTAP16 and
MTAP24 are presented in Figures 10 and 11, respectively. The MTAP24 are presented in Figures 10 and 11, respectively. The
starting or ending position of an aggregation unit within a packet is starting or ending position of an aggregation unit within a packet
NOT REQUIRED to be on a 32-bit word boundary. The DON of the NAL is not required to be on a 32-bit word boundary. The DON of the
unit contained in a multi-time aggregation unit is equal to (DONB + NAL unit contained in a multi-time aggregation unit is equal to
DOND) % 65536, in which % denotes the modulo operation. This memo (DONB + DOND) % 65536, in which % denotes the modulo operation.
does not specify how the NAL units within an MTAP are ordered, but, This memo does not specify how the NAL units within an MTAP are
in most cases, NAL unit decoding order SHOULD be used. ordered, but, in most cases, NAL unit decoding order SHOULD be used.
The timestamp offset field MUST be set to a value equal to the value The timestamp offset field MUST be set to a value equal to the
of the following formula: If the NALU-time is larger than or equal to value of the following formula: If the NALU-time is larger than or
the RTP timestamp of the packet, then the timestamp offset equals equal to the RTP timestamp of the packet, then the timestamp offset
(the NALU-time of the NAL unit - the RTP timestamp of the packet). equals (the NALU-time of the NAL unit - the RTP timestamp of the
If the NALU-time is smaller than the RTP timestamp of the packet, packet). If the NALU-time is smaller than the RTP timestamp of the
then the timestamp offset is equal to the NALU-time + (2^32 - the RTP packet, then the timestamp offset is equal to the NALU-time + (2^32
timestamp of the packet). - the RTP timestamp of the packet).
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: NAL unit size | DOND | TS offset | : NAL unit size | DOND | TS offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TS offset | | | TS offset | |
+-+-+-+-+-+-+-+-+ NAL unit | +-+-+-+-+-+-+-+-+ NAL unit |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 27, line 34 skipping to change at page 28, line 34
| TS offset | | | TS offset | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| NAL unit | | NAL unit |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11 Multi-time aggregation unit for MTAP24 Figure 11 Multi-time aggregation unit for MTAP24
For the "earliest" multi-time aggregation unit in an MTAP the For the "earliest" multi-time aggregation unit in an MTAP the
timestamp offset MUST be zero. Hence, the RTP timestamp of the MTAP timestamp offset MUST be zero. Hence, the RTP timestamp of the
itself is identical to the earliest NALU-time. MTAP itself is identical to the earliest NALU-time.
Informative note: The "earliest" multi-time aggregation unit is Informative note: The "earliest" multi-time aggregation unit is
the one that would have the smallest extended RTP timestamp among the one that would have the smallest extended RTP timestamp
all the aggregation units of an MTAP if the NAL units contained among all the aggregation units of an MTAP if the NAL units
in the aggregation units were encapsulated in single NAL unit contained in the aggregation units were encapsulated in single
packets. An extended timestamp is a timestamp that has more than NAL unit packets. An extended timestamp is a timestamp that has
32 bits and is capable of counting the wraparound of the more than 32 bits and is capable of counting the wraparound of
timestamp field, thus enabling one to determine the smallest the timestamp field, thus enabling one to determine the smallest
value if the timestamp wraps. Such an "earliest" aggregation value if the timestamp wraps. Such an "earliest" aggregation
unit may not be the first one in the order in which the unit may not be the first one in the order in which the
aggregation units are encapsulated in an MTAP. The "earliest" aggregation units are encapsulated in an MTAP. The "earliest"
NAL unit need not be the same as the first NAL unit in the NAL NAL unit need not be the same as the first NAL unit in the NAL
unit decoding order either. unit decoding order either.
Figure 12 presents an example of an RTP packet that contains a multi- Figure 12 presents an example of an RTP packet that contains a
time aggregation packet of type MTAP16 that contains two multi-time multi-time aggregation packet of type MTAP16 that contains two
aggregation units, labeled as 1 and 2 in the figure. multi-time aggregation units, labeled as 1 and 2 in the figure.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP Header | | RTP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MTAP16 NAL HDR | decoding order number base | NALU 1 Size | |MTAP16 NAL HDR | decoding order number base | NALU 1 Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 1 Size | NALU 1 DOND | NALU 1 TS offset | | NALU 1 Size | NALU 1 DOND | NALU 1 TS offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 28, line 31 skipping to change at page 29, line 31
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | NALU 2 SIZE | NALU 2 DOND | | | NALU 2 SIZE | NALU 2 DOND |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 2 TS offset | NALU 2 HDR | NALU 2 DATA | | NALU 2 TS offset | NALU 2 HDR | NALU 2 DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
: : : :
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12 An RTP packet including a multi-time aggregation packet of Figure 12 An RTP packet including a multi-time aggregation packet
type MTAP16 containing two multi-time aggregation units of type MTAP16 containing two multi-time aggregation units
Figure 13 presents an example of an RTP packet that contains a multi- Figure 13 presents an example of an RTP packet that contains a
time aggregation packet of type MTAP24 that contains two multi-time multi-time aggregation packet of type MTAP24 that contains two
aggregation units, labeled as 1 and 2 in the figure. multi-time aggregation units, labeled as 1 and 2 in the figure.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP Header | | RTP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MTAP24 NAL HDR | decoding order number base | NALU 1 Size | |MTAP24 NAL HDR | decoding order number base | NALU 1 Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 1 Size | NALU 1 DOND | NALU 1 TS offs | | NALU 1 Size | NALU 1 DOND | NALU 1 TS offs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 29, line 28 skipping to change at page 30, line 28
| | NALU 2 SIZE | NALU 2 DOND | | | NALU 2 SIZE | NALU 2 DOND |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 2 TS offset | NALU 2 HDR | | NALU 2 TS offset | NALU 2 HDR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NALU 2 DATA | | NALU 2 DATA |
: : : :
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13 An RTP packet including a multi-time aggregation packet of Figure 13 An RTP packet including a multi-time aggregation packet
type MTAP24 containing two multi-time aggregation units of type MTAP24 containing two multi-time aggregation units
5.7.3. Fragmentation Units (FUs) 5.7.3. Fragmentation Units (FUs)
This payload type allows fragmenting a NAL unit into several RTP This payload type allows fragmenting a NAL unit into several RTP
packets. Doing so on the application layer instead of relying on packets. Doing so on the application layer instead of relying on
lower layer fragmentation (e.g., by IP) has the following advantages: lower layer fragmentation (e.g., by IP) has the following
advantages:
o The payload format is capable of transporting NAL units bigger o The payload format is capable of transporting NAL units bigger
than 64 kbytes over an IPv4 network that may be present in pre- than 64 kbytes over an IPv4 network that may be present in pre-
recorded video, particularly in High Definition formats (there is recorded video, particularly in High Definition formats (there
a limit of the number of slices per picture, which results in a is a limit of the number of slices per picture, which results in
limit of NAL units per picture, which may result in big NAL units). a limit of NAL units per picture, which may result in big NAL
units).
o The fragmentation mechanism allows fragmenting a single NAL unit o The fragmentation mechanism allows fragmenting a single NAL unit
and applying generic forward error correction as described in and applying generic forward error correction as described in
section 12.5. section 12.5.
Fragmentation is defined only for a single NAL unit and not for any Fragmentation is defined only for a single NAL unit and not for any
aggregation packets. A fragment of a NAL unit consists of an integer aggregation packets. A fragment of a NAL unit consists of an
number of consecutive octets of that NAL unit. Each octet of the NAL integer number of consecutive octets of that NAL unit. Each octet
unit MUST be part of exactly one fragment of that NAL unit. of the NAL unit MUST be part of exactly one fragment of that NAL
Fragments of the same NAL unit MUST be sent in consecutive order with unit. Fragments of the same NAL unit MUST be sent in consecutive
ascending RTP sequence numbers (with no other RTP packets within the order with ascending RTP sequence numbers (with no other RTP
same RTP packet stream being sent between the first and last packets within the same RTP packet stream being sent between the
fragment). Similarly, a NAL unit MUST be reassembled in RTP sequence first and last fragment). Similarly, a NAL unit MUST be
number order. reassembled in RTP sequence number order.
When a NAL unit is fragmented and conveyed within fragmentation units When a NAL unit is fragmented and conveyed within fragmentation
(FUs), it is referred to as a fragmented NAL unit. STAPs and MTAPs units (FUs), it is referred to as a fragmented NAL unit. STAPs and
MUST NOT be fragmented. FUs MUST NOT be nested; i.e., an FU MUST NOT MTAPs MUST NOT be fragmented. FUs MUST NOT be nested; i.e., an FU
contain another FU. MUST NOT contain another FU.
The RTP timestamp of an RTP packet carrying an FU is set to the NALU- The RTP timestamp of an RTP packet carrying an FU is set to the
time of the fragmented NAL unit. NALU-time of the fragmented NAL unit.
Figure 14 presents the RTP payload format for FU-As. An FU-A Figure 14 presents the RTP payload format for FU-As. An FU-A
consists of a fragmentation unit indicator of one octet, a consists of a fragmentation unit indicator of one octet, a
fragmentation unit header of one octet, and a fragmentation unit fragmentation unit header of one octet, and a fragmentation unit
payload. payload.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FU indicator | FU header | | | FU indicator | FU header | |
skipping to change at page 30, line 38 skipping to change at page 31, line 41
| FU payload | | FU payload |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14 RTP payload format for FU-A Figure 14 RTP payload format for FU-A
Figure 15 presents the RTP payload format for FU-Bs. An FU-B Figure 15 presents the RTP payload format for FU-Bs. An FU-B
consists of a fragmentation unit indicator of one octet, a consists of a fragmentation unit indicator of one octet, a
fragmentation unit header of one octet, a decoding order number (DON) fragmentation unit header of one octet, a decoding order number
(in network byte order), and a fragmentation unit payload. In other (DON) (in network byte order), and a fragmentation unit payload.
words, the structure of FU-B is the same as the structure of FU-A, In other words, the structure of FU-B is the same as the structure
except for the additional DON field. of FU-A, except for the additional DON field.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FU indicator | FU header | DON | | FU indicator | FU header | DON |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
| | | |
| FU payload | | FU payload |
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding | | :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15 RTP payload format for FU-B Figure 15 RTP payload format for FU-B
NAL unit type FU-B MUST be used in the interleaved packetization mode NAL unit type FU-B MUST be used in the interleaved packetization
for the first fragmentation unit of a fragmented NAL unit. NAL unit mode for the first fragmentation unit of a fragmented NAL unit.
type FU-B MUST NOT be used in any other case. In other words, in the NAL unit type FU-B MUST NOT be used in any other case. In other
interleaved packetization mode, each NALU that is fragmented has an words, in the interleaved packetization mode, each NALU that is
FU-B as the first fragment, followed by one or more FU-A fragments. fragmented has an FU-B as the first fragment, followed by one or
more FU-A fragments.
The FU indicator octet has the following format: The FU indicator octet has the following format:
+---------------+ +---------------+
|0|1|2|3|4|5|6|7| |0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|F|NRI| Type | |F|NRI| Type |
+---------------+ +---------------+
Values equal to 28 and 29 in the Type field of the FU indicator octet Values equal to 28 and 29 in the Type field of the FU indicator
identify an FU-A and an FU-B, respectively. The use of the F bit is octet identify an FU-A and an FU-B, respectively. The use of the F
described in section 5.3. The value of the NRI field MUST be set bit is described in section 5.3. The value of the NRI field MUST
according to the value of the NRI field in the fragmented NAL unit. be set according to the value of the NRI field in the fragmented
NAL unit.
The FU header has the following format: The FU header has the following format:
+---------------+ +---------------+
|0|1|2|3|4|5|6|7| |0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|S|E|R| Type | |S|E|R| Type |
+---------------+ +---------------+
S: 1 bit S: 1 bit
When set to one, the Start bit indicates the start of a When set to one, the Start bit indicates the start of a
fragmented NAL unit. When the following FU payload is not the fragmented NAL unit. When the following FU payload is not the
start of a fragmented NAL unit payload, the Start bit is set to start of a fragmented NAL unit payload, the Start bit is set to
zero. zero.
E: 1 bit E: 1 bit
When set to one, the End bit indicates the end of a fragmented When set to one, the End bit indicates the end of a fragmented
NAL unit, i.e., the last byte of the payload is also the last NAL unit, i.e., the last byte of the payload is also the last
byte of the fragmented NAL unit. When the following FU payload byte of the fragmented NAL unit. When the following FU payload
is not the last fragment of a fragmented NAL unit, the End bit is is not the last fragment of a fragmented NAL unit, the End bit
set to zero. is set to zero.
R: 1 bit R: 1 bit
The Reserved bit MUST be equal to 0 and MUST be ignored by the The Reserved bit MUST be equal to 0 and MUST be ignored by the
receiver. receiver.
Type: 5 bits Type: 5 bits
The NAL unit payload type as defined in Table 7-1 of [1]. The NAL unit payload type as defined in Table 7-1 of [1].
The value of DON in FU-Bs is selected as described in section 5.5. The value of DON in FU-Bs is selected as described in section 5.5.
Informative note: The DON field in FU-Bs allows gateways to Informative note: The DON field in FU-Bs allows gateways to
fragment NAL units to FU-Bs without organizing the incoming NAL fragment NAL units to FU-Bs without organizing the incoming NAL
units to the NAL unit decoding order. units to the NAL unit decoding order.
A fragmented NAL unit MUST NOT be transmitted in one FU; i.e., the A fragmented NAL unit MUST NOT be transmitted in one FU; i.e., the
Start bit and End bit MUST NOT both be set to one in the same FU Start bit and End bit MUST NOT both be set to one in the same FU
header. header.
The FU payload consists of fragments of the payload of the fragmented The FU payload consists of fragments of the payload of the
NAL unit so that if the fragmentation unit payloads of consecutive fragmented NAL unit so that if the fragmentation unit payloads of
FUs are sequentially concatenated, the payload of the fragmented NAL consecutive FUs are sequentially concatenated, the payload of the
unit can be reconstructed. The NAL unit type octet of the fragmented fragmented NAL unit can be reconstructed. The NAL unit type octet
NAL unit is not included as such in the fragmentation unit payload, of the fragmented NAL unit is not included as such in the
but rather the information of the NAL unit type octet of the fragmentation unit payload, but rather the information of the NAL
fragmented NAL unit is conveyed in F and NRI fields of the FU unit type octet of the fragmented NAL unit is conveyed in F and NRI
indicator octet of the fragmentation unit and in the type field of fields of the FU indicator octet of the fragmentation unit and in
the FU header. An FU payload MAY have any number of octets and MAY the type field of the FU header. An FU payload MAY have any number
be empty. of octets and MAY be empty.
Informative note: Empty FUs are allowed to reduce the latency of Informative note: Empty FUs are allowed to reduce the latency of
a certain class of senders in nearly lossless environments. a certain class of senders in nearly lossless environments.
These senders can be characterized in that they packetize NALU These senders can be characterized in that they packetize NALU
fragments before the NALU is completely generated and, hence, fragments before the NALU is completely generated and, hence,
before the NALU size is known. If zero-length NALU fragments before the NALU size is known. If zero-length NALU fragments
were not allowed, the sender would have to generate at least one were not allowed, the sender would have to generate at least one
bit of data of the following fragment before the current fragment bit of data of the following fragment before the current
could be sent. Due to the characteristics of H.264, where fragment could be sent. Due to the characteristics of H.264,
sometimes several macroblocks occupy zero bits, this is where sometimes several macroblocks occupy zero bits, this is
undesirable and can add delay. However, the (potential) use of undesirable and can add delay. However, the (potential) use of
zero-length NALU fragments should be carefully weighed against zero-length NALU fragments should be carefully weighed against
the increased risk of the loss of at least a part of the NALU the increased risk of the loss of at least a part of the NALU
because of the additional packets employed for its transmission. because of the additional packets employed for its transmission.
If a fragmentation unit is lost, the receiver SHOULD discard all If a fragmentation unit is lost, the receiver SHOULD discard all
following fragmentation units in transmission order corresponding to following fragmentation units in transmission order corresponding
the same fragmented NAL unit. to the same fragmented NAL unit.
A receiver in an endpoint or in a MANE MAY aggregate the first n-1 A receiver in an endpoint or in a MANE MAY aggregate the first n-1
fragments of a NAL unit to an (incomplete) NAL unit, even if fragment fragments of a NAL unit to an (incomplete) NAL unit, even if
n of that NAL unit is not received. In this case, the fragment n of that NAL unit is not received. In this case, the
forbidden_zero_bit of the NAL unit MUST be set to one to indicate a forbidden_zero_bit of the NAL unit MUST be set to one to indicate a
syntax violation. syntax violation.
6. Packetization Rules 6. Packetization Rules
The packetization modes are introduced in section 5.2. The The packetization modes are introduced in section 5.2. The
packetization rules common to more than one of the packetization packetization rules common to more than one of the packetization
modes are specified in section 6.1. The packetization rules for the modes are specified in section 6.1. The packetization rules for
single NAL unit mode, the non-interleaved mode, and the interleaved the single NAL unit mode, the non-interleaved mode, and the
mode are specified in sections 6.2, 6.3, and 6.4, respectively. interleaved mode are specified in sections 6.2, 6.3, and 6.4,
respectively.
6.1. Common Packetization Rules 6.1. Common Packetization Rules
All senders MUST enforce the following packetization rules regardless All senders MUST enforce the following packetization rules
of the packetization mode in use: regardless of the packetization mode in use:
o Coded slice NAL units or coded slice data partition NAL units o Coded slice NAL units or coded slice data partition NAL units
belonging to the same coded picture (and thus sharing the same RTP belonging to the same coded picture (and thus sharing the same
timestamp value) MAY be sent in any order; however, for delay- RTP timestamp value) MAY be sent in any order; however, for
critical systems, they SHOULD be sent in their original decoding delay-critical systems, they SHOULD be sent in their original
order to minimize the delay. Note that the decoding order is the decoding order to minimize the delay. Note that the decoding
order of the NAL units in the bitstream. order is the order of the NAL units in the bitstream.
o Parameter sets are handled in accordance with the rules and o Parameter sets are handled in accordance with the rules and
recommendations given in section 8.4. recommendations given in section 8.4.
o MANEs MUST NOT duplicate any NAL unit except for sequence or o MANEs MUST NOT duplicate any NAL unit except for sequence or
picture parameter set NAL units, as neither this memo nor the picture parameter set NAL units, as neither this memo nor the
H.264 specification provides means to identify duplicated NAL H.264 specification provides means to identify duplicated NAL
units. Sequence and picture parameter set NAL units MAY be units. Sequence and picture parameter set NAL units MAY be
duplicated to make their correct reception more probable, but any duplicated to make their correct reception more probable, but
such duplication MUST NOT affect the contents of any active any such duplication MUST NOT affect the contents of any active
sequence or picture parameter set. Duplication SHOULD be sequence or picture parameter set. Duplication SHOULD be
performed on the application layer and not by duplicating RTP performed on the application layer and not by duplicating RTP
packets (with identical sequence numbers). packets (with identical sequence numbers).
Senders using the non-interleaved mode and the interleaved mode MUST Senders using the non-interleaved mode and the interleaved mode
enforce the following packetization rule: MUST enforce the following packetization rule:
o MANEs MAY convert single NAL unit packets into one aggregation o MANEs MAY convert single NAL unit packets into one aggregation
packet, convert an aggregation packet into several single NAL unit packet, convert an aggregation packet into several single NAL
packets, or mix both concepts, in an RTP translator. The RTP unit packets, or mix both concepts, in an RTP translator. The
translator SHOULD take into account at least the following RTP translator SHOULD take into account at least the following
parameters: path MTU size, unequal protection mechanisms (e.g., parameters: path MTU size, unequal protection mechanisms (e.g.,
through packet-based FEC according to RFC 2733 [18], especially through packet-based FEC according to RFC 2733 [18], especially
for sequence and picture parameter set NAL units and coded slice for sequence and picture parameter set NAL units and coded slice
data partition A NAL units), bearable latency of the system, and data partition A NAL units), bearable latency of the system, and
buffering capabilities of the receiver. buffering capabilities of the receiver.
Informative note: An RTP translator is required to handle RTCP Informative note: An RTP translator is required to handle
as per RFC 3550. RTCP as per RFC 3550.
6.2. Single NAL Unit Mode 6.2. Single NAL Unit Mode
This mode is in use when the value of the OPTIONAL packetization-mode This mode is in use when the value of the OPTIONAL packetization-
media type parameter is equal to 0 or the packetization-mode is not mode media type parameter is equal to 0 or the packetization-mode
present. All receivers MUST support this mode. It is primarily is not present. All receivers MUST support this mode. It is
intended for low-delay applications that are compatible with systems primarily intended for low-delay applications that are compatible
using ITU-T Recommendation H.241 [3] (see section 12.1). Only single with systems using ITU-T Recommendation H.241 [3] (see section
NAL unit packets MAY be used in this mode. STAPs, MTAPs, and FUs 12.1). Only single NAL unit packets MAY be used in this mode.
MUST NOT be used. The transmission order of single NAL unit packets STAPs, MTAPs, and FUs MUST NOT be used. The transmission order of
MUST comply with the NAL unit decoding order. single NAL unit packets MUST comply with the NAL unit decoding
order.
6.3. Non-Interleaved Mode 6.3. Non-Interleaved Mode
This mode is in use when the value of the OPTIONAL packetization-mode This mode is in use when the value of the OPTIONAL packetization-
media type parameter is equal to 1. This mode SHOULD be supported. mode media type parameter is equal to 1. This mode SHOULD be
It is primarily intended for low-delay applications. Only single NAL supported. It is primarily intended for low-delay applications.
unit packets, STAP-As, and FU-As MAY be used in this mode. STAP-Bs, Only single NAL unit packets, STAP-As, and FU-As MAY be used in
MTAPs, and FU-Bs MUST NOT be used. The transmission order of NAL this mode. STAP-Bs, MTAPs, and FU-Bs MUST NOT be used. The
units MUST comply with the NAL unit decoding order. transmission order of NAL units MUST comply with the NAL unit
decoding order.
6.4. Interleaved Mode 6.4. Interleaved Mode
This mode is in use when the value of the OPTIONAL packetization-mode This mode is in use when the value of the OPTIONAL packetization-
media type parameter is equal to 2. Some receivers MAY support this mode media type parameter is equal to 2. Some receivers MAY
mode. STAP-Bs, MTAPs, FU-As, and FU-Bs MAY be used. STAP-As and support this mode. STAP-Bs, MTAPs, FU-As, and FU-Bs MAY be used.
single NAL unit packets MUST NOT be used. The transmission order of STAP-As and single NAL unit packets MUST NOT be used. The
packets and NAL units is constrained as specified in section 5.5. transmission order of packets and NAL units is constrained as
specified in section 5.5.
7. De-Packetization Process 7. De-Packetization Process
The de-packetization process is implementation dependent. Therefore, The de-packetization process is implementation dependent.
the following description should be seen as an example of a suitable Therefore, the following description should be seen as an example
implementation. Other schemes may be used as well as long as the of a suitable implementation. Other schemes may be used as well as
output for the same input is the same as the process described below. long as the output for the same input is the same as the process
The same output means that the resulting NAL units, and their order, described below. The same output means that the resulting NAL
are identical. Optimizations relative to the described algorithms units, and their order, are identical. Optimizations relative to
are likely possible. Section 7.1 presents the de-packetization the described algorithms are likely possible. Section 7.1 presents
process for the single NAL unit and non-interleaved packetization the de-packetization process for the single NAL unit and non-
modes, whereas section 7.2 describes the process for the interleaved interleaved packetization modes, whereas section 7.2 describes the
mode. Section 7.3 includes additional de-packetization guidelines process for the interleaved mode. Section 7.3 includes additional
for intelligent receivers. de-packetization guidelines for intelligent receivers.
All normal RTP mechanisms related to buffer management apply. In All normal RTP mechanisms related to buffer management apply. In
particular, duplicated or outdated RTP packets (as indicated by the particular, duplicated or outdated RTP packets (as indicated by the
RTP sequence number and the RTP timestamp) are removed. To determine RTP sequence number and the RTP timestamp) are removed. To
the exact time for decoding, factors such as a possible intentional determine the exact time for decoding, factors such as a possible
delay to allow for proper inter-stream synchronization must be intentional delay to allow for proper inter-stream synchronization
factored in. must be factored in.
7.1. Single NAL Unit and Non-Interleaved Mode 7.1. Single NAL Unit and Non-Interleaved Mode
The receiver includes a receiver buffer to compensate for The receiver includes a receiver buffer to compensate for
transmission delay jitter. The receiver stores incoming packets in transmission delay jitter. The receiver stores incoming packets in
reception order into the receiver buffer. Packets are de-packetized reception order into the receiver buffer. Packets are de-
in RTP sequence number order. If a de-packetized packet is a single packetized in RTP sequence number order. If a de-packetized packet
NAL unit packet, the NAL unit contained in the packet is passed is a single NAL unit packet, the NAL unit contained in the packet
directly to the decoder. If a de-packetized packet is an STAP-A, the is passed directly to the decoder. If a de-packetized packet is an
NAL units contained in the packet are passed to the decoder in the STAP-A, the NAL units contained in the packet are passed to the
order in which they are encapsulated in the packet. For all the FU-A decoder in the order in which they are encapsulated in the packet.
packets containing fragments of a single NAL unit, the de-packetized For all the FU-A packets containing fragments of a single NAL unit,
fragments are concatenated in their sending order to recover the NAL the de-packetized fragments are concatenated in their sending order
unit, which is then passed to the decoder. to recover the NAL unit, which is then passed to the decoder.
Informative note: If the decoder supports Arbitrary Slice Order, Informative note: If the decoder supports Arbitrary Slice Order,
coded slices of a picture can be passed to the decoder in any coded slices of a picture can be passed to the decoder in any
order regardless of their reception and transmission order. order regardless of their reception and transmission order.
7.2. Interleaved Mode 7.2. Interleaved Mode
The general concept behind these de-packetization rules is to reorder The general concept behind these de-packetization rules is to
NAL units from transmission order to the NAL unit decoding order. reorder NAL units from transmission order to the NAL unit decoding
order.
The receiver includes a receiver buffer, which is used to compensate The receiver includes a receiver buffer, which is used to
for transmission delay jitter and to reorder NAL units from compensate for transmission delay jitter and to reorder NAL units
transmission order to the NAL unit decoding order. In this section, from transmission order to the NAL unit decoding order. In this
the receiver operation is described under the assumption that there section, the receiver operation is described under the assumption
is no transmission delay jitter. To make a difference from a that there is no transmission delay jitter. To make a difference
practical receiver buffer that is also used for compensation of from a practical receiver buffer that is also used for compensation
transmission delay jitter, the receiver buffer is here after called of transmission delay jitter, the receiver buffer is here after
the de-interleaving buffer in this section. Receivers SHOULD also called the de-interleaving buffer in this section. Receivers
prepare for transmission delay jitter; i.e., either reserve separate SHOULD also prepare for transmission delay jitter; i.e., either
buffers for transmission delay jitter buffering and de-interleaving reserve separate buffers for transmission delay jitter buffering
buffering or use a receiver buffer for both transmission delay jitter and de-interleaving buffering or use a receiver buffer for both
and de-interleaving. Moreover, receivers SHOULD take transmission transmission delay jitter and de-interleaving. Moreover, receivers
delay jitter into account in the buffering operation; e.g., by SHOULD take transmission delay jitter into account in the buffering
additional initial buffering before starting of decoding and playback. operation; e.g., by additional initial buffering before starting of
decoding and playback.
This section is organized as follows: subsection 7.2.1 presents how This section is organized as follows: subsection 7.2.1 presents how
to calculate the size of the de-interleaving buffer. Subsection to calculate the size of the de-interleaving buffer. Subsection
7.2.2 specifies the receiver process on how to organize received NAL 7.2.2 specifies the receiver process on how to organize received
units to the NAL unit decoding order. NAL units to the NAL unit decoding order.
7.2.1. Size of the De-interleaving Buffer 7.2.1. Size of the De-interleaving Buffer
In either Offer/Answer or declarative SDP usage, the sprop-deint-buf- In either Offer/Answer or declarative SDP usage, the sprop-deint-
req media type parameter signals the requirement for the de- buf-req media type parameter signals the requirement for the de-
interleaving buffer size. It is therefore RECOMMENDED to set the de- interleaving buffer size. It is therefore RECOMMENDED to set the
interleaving buffer size, in terms of number of bytes, equal to or de-interleaving buffer size, in terms of number of bytes, equal to
greater than the value of sprop-deint-buf-req media type parameter. or greater than the value of sprop-deint-buf-req media type
parameter.
When the SDP Offer/Answer model or any other capability exchange When the SDP Offer/Answer model or any other capability exchange
procedure is used in session setup, the properties of the received procedure is used in session setup, the properties of the received
stream SHOULD be such that the receiver capabilities are not exceeded. stream SHOULD be such that the receiver capabilities are not
In the SDP Offer/Answer model, the receiver can indicate its exceeded. In the SDP Offer/Answer model, the receiver can indicate
capabilities to allocate a de-interleaving buffer with the deint-buf- its capabilities to allocate a de-interleaving buffer with the
cap media type parameter. See section 8.1 for further information on deint-buf-cap media type parameter. See section 8.1 for further
deint-buf-cap and sprop-deint-buf-req media type parameters and information on deint-buf-cap and sprop-deint-buf-req media type
section 8.2.2 for further information on their use in the SDP parameters and section 8.2.2 for further information on their use
Offer/Answer model. in the SDP Offer/Answer model.
7.2.2. De-interleaving Process 7.2.2. De-interleaving Process
There are two buffering states in the receiver: initial buffering and There are two buffering states in the receiver: initial buffering
buffering while playing. Initial buffering occurs when the RTP and buffering while playing. Initial buffering occurs when the RTP
session is initialized. After initial buffering, decoding and session is initialized. After initial buffering, decoding and
playback are started, and the buffering-while-playing mode is used. playback are started, and the buffering-while-playing mode is used.
Regardless of the buffering state, the receiver stores incoming NAL Regardless of the buffering state, the receiver stores incoming NAL
units, in reception order, in the de-interleaving buffer as follows. units, in reception order, in the de-interleaving buffer as follows.
NAL units of aggregation packets are stored in the de-interleaving NAL units of aggregation packets are stored in the de-interleaving
buffer individually. The value of DON is calculated and stored for buffer individually. The value of DON is calculated and stored for
each NAL unit. each NAL unit.
The receiver operation is described below with the help of the The receiver operation is described below with the help of the
skipping to change at page 37, line 21 skipping to change at page 38, line 37
o Constant N is the value of the OPTIONAL sprop-interleaving-depth o Constant N is the value of the OPTIONAL sprop-interleaving-depth
media type parameter (see section 8.1) incremented by 1. media type parameter (see section 8.1) incremented by 1.
Initial buffering lasts until one of the following conditions is Initial buffering lasts until one of the following conditions is
fulfilled: fulfilled:
o There are N or more VCL NAL units in the de-interleaving buffer. o There are N or more VCL NAL units in the de-interleaving buffer.
o If sprop-max-don-diff is present, don_diff(m,n) is greater than o If sprop-max-don-diff is present, don_diff(m,n) is greater than
the value of sprop-max-don-diff, in which n corresponds to the NAL the value of sprop-max-don-diff, in which n corresponds to the
unit having the greatest value of AbsDON among the received NAL NAL unit having the greatest value of AbsDON among the received
units and m corresponds to the NAL unit having the smallest value NAL units and m corresponds to the NAL unit having the smallest
of AbsDON among the received NAL units. value of AbsDON among the received NAL units.
o Initial buffering has lasted for the duration equal to or greater o Initial buffering has lasted for the duration equal to or
than the value of the OPTIONAL sprop-init-buf-time media type greater than the value of the OPTIONAL sprop-init-buf-time media
parameter. type parameter.
The NAL units to be removed from the de-interleaving buffer are The NAL units to be removed from the de-interleaving buffer are
determined as follows: determined as follows:
o If the de-interleaving buffer contains at least N VCL NAL units, o If the de-interleaving buffer contains at least N VCL NAL units,
NAL units are removed from the de-interleaving buffer and passed NAL units are removed from the de-interleaving buffer and passed
to the decoder in the order specified below until the buffer to the decoder in the order specified below until the buffer
contains N-1 VCL NAL units. contains N-1 VCL NAL units.
o If sprop-max-don-diff is present, all NAL units m for which o If sprop-max-don-diff is present, all NAL units m for which
don_diff(m,n) is greater than sprop-max-don-diff are removed from don_diff(m,n) is greater than sprop-max-don-diff are removed
the de-interleaving buffer and passed to the decoder in the order from the de-interleaving buffer and passed to the decoder in the
specified below. Herein, n corresponds to the NAL unit having the order specified below. Herein, n corresponds to the NAL unit
greatest value of AbsDON among the NAL units in the de- having the greatest value of AbsDON among the NAL units in the
interleaving buffer. de-interleaving buffer.
The order in which NAL units are passed to the decoder is specified The order in which NAL units are passed to the decoder is specified
as follows: as follows:
o Let PDON be a variable that is initialized to 0 at the beginning o Let PDON be a variable that is initialized to 0 at the beginning
of the RTP session. of the RTP session.
o For each NAL unit associated with a value of DON, a DON distance o For each NAL unit associated with a value of DON, a DON distance
is calculated as follows. If the value of DON of the NAL unit is is calculated as follows. If the value of DON of the NAL unit
larger than the value of PDON, the DON distance is equal to DON - is larger than the value of PDON, the DON distance is equal to
PDON. Otherwise, the DON distance is equal to 65535 - PDON + DON DON - PDON. Otherwise, the DON distance is equal to 65535 -
+ 1. PDON + DON + 1.
o NAL units are delivered to the decoder in ascending order of DON o NAL units are delivered to the decoder in ascending order of DON
distance. If several NAL units share the same value of DON distance. If several NAL units share the same value of DON
distance, they can be passed to the decoder in any order. distance, they can be passed to the decoder in any order.
o When a desired number of NAL units have been passed to the decoder, o When a desired number of NAL units have been passed to the
the value of PDON is set to the value of DON for the last NAL unit decoder, the value of PDON is set to the value of DON for the
passed to the decoder. last NAL unit passed to the decoder.
7.3. Additional De-Packetization Guidelines 7.3. Additional De-Packetization Guidelines
The following additional de-packetization rules may be used to The following additional de-packetization rules may be used to
implement an operational H.264 de-packetizer: implement an operational H.264 de-packetizer:
o Intelligent RTP receivers (e.g., in gateways) may identify lost o Intelligent RTP receivers (e.g., in gateways) may identify lost
coded slice data partitions A (DPAs). If a lost DPA is detected, coded slice data partitions A (DPAs). If a lost DPA is detected,
after taking into account possible retransmission and FEC, a after taking into account possible retransmission and FEC, a
gateway may decide not to send the corresponding coded slice data gateway may decide not to send the corresponding coded slice
partitions B and C, as their information is meaningless for H.264 data partitions B and C, as their information is meaningless for
decoders. In this way a MANE can reduce network load by H.264 decoders. In this way a MANE can reduce network load by
discarding useless packets without parsing a complex bitstream. discarding useless packets without parsing a complex bitstream.
o Intelligent RTP receivers (e.g., in gateways) may identify lost o Intelligent RTP receivers (e.g., in gateways) may identify lost
FUs. If a lost FU is found, a gateway may decide not to send the FUs. If a lost FU is found, a gateway may decide not to send
following FUs of the same fragmented NAL unit, as their the following FUs of the same fragmented NAL unit, as their
information is meaningless for H.264 decoders. In this way a MANE information is meaningless for H.264 decoders. In this way a
can reduce network load by discarding useless packets without MANE can reduce network load by discarding useless packets
parsing a complex bitstream. without parsing a complex bitstream.
o Intelligent receivers having to discard packets or NALUs should o Intelligent receivers having to discard packets or NALUs should
first discard all packets/NALUs in which the value of the NRI first discard all packets/NALUs in which the value of the NRI
field of the NAL unit type octet is equal to 0. This will field of the NAL unit type octet is equal to 0. This will
minimize the impact on user experience and keep the reference minimize the impact on user experience and keep the reference
pictures intact. If more packets have to be discarded, then pictures intact. If more packets have to be discarded, then
packets with a numerically lower NRI value should be discarded packets with a numerically lower NRI value should be discarded
before packets with a numerically higher NRI value. However, before packets with a numerically higher NRI value. However,
discarding any packets with an NRI bigger than 0 very likely leads discarding any packets with an NRI bigger than 0 very likely
to decoder drift and SHOULD be avoided. leads to decoder drift and SHOULD be avoided.
8. Payload Format Parameters 8. Payload Format Parameters
This section specifies the parameters that MAY be used to select This section specifies the parameters that MAY be used to select
optional features of the payload format and certain features of the optional features of the payload format and certain features of the
bitstream. The parameters are specified here as part of the media bitstream. The parameters are specified here as part of the media
subtype registration for the ITU-T H.264 | ISO/IEC 14496-10 codec. A subtype registration for the ITU-T H.264 | ISO/IEC 14496-10 codec.
mapping of the parameters into the Session Description Protocol (SDP) A mapping of the parameters into the Session Description Protocol
[6] is also provided for applications that use SDP. Equivalent (SDP) [6] is also provided for applications that use SDP.
parameters could be defined elsewhere for use with control protocols Equivalent parameters could be defined elsewhere for use with
that do not use SDP. control protocols that do not use SDP.
Some parameters provide a receiver with the properties of the stream Some parameters provide a receiver with the properties of the
that will be sent. The names of all these parameters start with stream that will be sent. The names of all these parameters start
"sprop" for stream properties. Some of these "sprop" parameters are with "sprop" for stream properties. Some of these "sprop"
limited by other payload or codec configuration parameters. For parameters are limited by other payload or codec configuration
example, the sprop-parameter-sets parameter is constrained by the parameters. For example, the sprop-parameter-sets parameter is
profile-level-id parameter. The media sender selects all "sprop" constrained by the profile-level-id parameter. The media sender
parameters rather than the receiver. This uncommon characteristic of selects all "sprop" parameters rather than the receiver. This
the "sprop" parameters may not be compatible with some signaling uncommon characteristic of the "sprop" parameters may not be
protocol concepts, in which case the use of these parameters SHOULD compatible with some signaling protocol concepts, in which case the
be avoided. use of these parameters SHOULD be avoided.
8.1. Media Type Registration 8.1. Media Type Registration
The media subtype for the ITU-T H.264 | ISO/IEC 14496-10 codec is The media subtype for the ITU-T H.264 | ISO/IEC 14496-10 codec is
allocated from the IETF tree. allocated from the IETF tree.
The receiver MUST ignore any unspecified parameter. The receiver MUST ignore any unspecified parameter.
Media Type name: video Media Type name: video
skipping to change at page 40, line 9 skipping to change at page 41, line 27
profile-iop, composed of the values of constraint_set0_flag, profile-iop, composed of the values of constraint_set0_flag,
constraint_set1_flag,constraint_set2_flag, constraint_set1_flag,constraint_set2_flag,
constraint_set3_flag, and reserved_zero_4bits in bit- constraint_set3_flag, and reserved_zero_4bits in bit-
significance order, starting from the most significant bit, significance order, starting from the most significant bit,
and 3) level_idc. Note that reserved_zero_4bits is required and 3) level_idc. Note that reserved_zero_4bits is required
to be equal to 0 in [1], but other values for it may be to be equal to 0 in [1], but other values for it may be
specified in the future by ITU-T or ISO/IEC. specified in the future by ITU-T or ISO/IEC.
The profile-level-id parameter indicates the default sub- The profile-level-id parameter indicates the default sub-
profile, i.e. the subset of coding tools that may have been profile, i.e. the subset of coding tools that may have been
used to generate the stream or that the receiver supports, and used to generate the stream or that the receiver supports,
the default level of the stream or the receiver supports. and the default level of the stream or the receiver supports.
The default sub-profile is indicated collectively by the The default sub-profile is indicated collectively by the
profile_idc byte and some fields in the profile-iop byte. profile_idc byte and some fields in the profile-iop byte.
Depending on the values of the fields in the profile-iop byte, Depending on the values of the fields in the profile-iop byte,
the default sub-profile may be the set of coding tools the default sub-profile may be the set of coding tools
supported by one profile, or a common subset of coding tools supported by one profile, or a common subset of coding tools
of multiple profiles, as specified in subsection 7.4.2.1.1 of of multiple profiles, as specified in subsection 7.4.2.1.1 of
[1]. The default level is indicated by the level_idc byte, [1]. The default level is indicated by the level_idc byte,
and, when profile_idc is equal to 66, 77 or 88 (the Baseline, and, when profile_idc is equal to 66, 77 or 88 (the Baseline,
Main, or Extended profile) and level_idc is equal to 11, Main, or Extended profile) and level_idc is equal to 11,
additionally by bit 4 (constraint_set3_flag) of the profile- additionally by bit 4 (constraint_set3_flag) of the profile-
iop byte. When profile_idc is equal to 66, 77 or 88 (the iop byte. When profile_idc is equal to 66, 77 or 88 (the
Baseline, Main, or Extended profile) and level_idc is equal to Baseline, Main, or Extended profile) and level_idc is equal
11, and bit 4 (constraint_set3_flag) of the profile-iop byte to 11, and bit 4 (constraint_set3_flag) of the profile-iop
is equal to 1, the default level is level 1b. byte is equal to 1, the default level is level 1b.
Table 5 lists all profiles defined in Annex A of [1] and, for Table 5 lists all profiles defined in Annex A of [1] and, for
each of the profiles, the possible combinations of profile_idc each of the profiles, the possible combinations of
and profile-iop that represent the same sub-profile. profile_idc and profile-iop that represent the same sub-
profile.
Table 5. Combinations of profile_idc and profile-iop Table 5. Combinations of profile_idc and profile-iop
representing the same sub-profile corresponding to the full representing the same sub-profile corresponding to the
set of coding tools supported by one profile. In the full set of coding tools supported by one profile. In
following, x may be either 0 or 1, while the profile names the following, x may be either 0 or 1, while the profile
are indicated as follows. CB: Constrained Baseline profile, names are indicated as follows. CB: Constrained Baseline
B: Baseline profile, M: Main profile, E: Extended profile, profile, B: Baseline profile, M: Main profile, E:
H: High profile, H10: High 10 profile, H42: High 4:2:2 Extended profile, H: High profile, H10: High 10 profile,
profile, H44: High 4:4:4 Predictive profile, H10I: High 10 H42: High 4:2:2 profile, H44: High 4:4:4 Predictive
Intra profile, H42I: High 4:2:2 Intra profile, H44I: High profile, H10I: High 10 Intra profile, H42I: High 4:2:2
4:4:4 Intra profile, and C44I: CAVLC 4:4:4 Intra profile. Intra profile, H44I: High 4:4:4 Intra profile, and C44I:
CAVLC 4:4:4 Intra profile.
Profile profile_idc profile-iop Profile profile_idc profile-iop
(hexadecimal) (binary) (hexadecimal) (binary)
CB 42 (B) x1xx0000 CB 42 (B) x1xx0000
same as: 4D (M) 1xxx0000 same as: 4D (M) 1xxx0000
same as: 58 (E) 11xx0000 same as: 58 (E) 11xx0000
same as: 64 (H), 6E (H10), 1xx00000 same as: 64 (H), 6E (H10), 1xx00000
7A (H42), or F4 (H44) 7A (H42), or F4 (H44)
B 42 (B) x0xx0000 B 42 (B) x0xx0000
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H42I 7A 00010000 H42I 7A 00010000
H44I F4 00010000 H44I F4 00010000
C44I 2C 00010000 C44I 2C 00010000
For example, in the table above, profile_idc equal to 58 For example, in the table above, profile_idc equal to 58
(Extended) with profile-iop equal to 11xx0000 indicates the (Extended) with profile-iop equal to 11xx0000 indicates the
same sub-profile corresponding to profile_idc equal to 42 same sub-profile corresponding to profile_idc equal to 42
(Baseline) with profile-iop equal to x1xx0000. Note that (Baseline) with profile-iop equal to x1xx0000. Note that
other combinations of profile_idc and profile-iop (not listed other combinations of profile_idc and profile-iop (not listed
in Table 5) may represent a sub-profile equivalent to the in Table 5) may represent a sub-profile equivalent to the
common subset of coding tools for more than one profile. Note common subset of coding tools for more than one profile.
also that a decoder conforming to a certain profile may be Note also that a decoder conforming to a certain profile may
able to decode bitstreams conforming to other profiles. For be able to decode bitstreams conforming to other profiles.
example, a decoder conforming to the High 4:4:4 profile at For example, a decoder conforming to the High 4:4:4 profile
certain level must be able to decode bitstreams confirming to at certain level must be able to decode bitstreams confirming
the Constrained Baseline, Main, High, High 10 or High 4:2:2 to the Constrained Baseline, Main, High, High 10 or High
profile at the same or a lower level. 4:2:2 profile at the same or a lower level.
If the profile-level-id parameter is used to indicate If the profile-level-id parameter is used to indicate
properties of a NAL unit stream, it indicates that, to decode properties of a NAL unit stream, it indicates that, to decode
the stream, the minimum subset of coding tools a decoder has the stream, the minimum subset of coding tools a decoder has
to support is the default sub-profile, and the lowest level to support is the default sub-profile, and the lowest level
the decoder has to support is the default level. the decoder has to support is the default level.
If the profile-level-id parameter is used for capability If the profile-level-id parameter is used for capability
exchange or session setup procedure, it indicates the subset exchange or session setup procedure, it indicates the subset
of coding tools, which is equal to the default sub-profile, of coding tools, which is equal to the default sub-profile,
and the highest level, which is equal to the default level, and the highest level, which is equal to the default level,
that the codec supports. All levels lower than the default that the codec supports. All levels lower than the default
level are also supported by the codec. level are also supported by the codec.
Informative note: Capability exchange and session setup Informative note: Capability exchange and session setup
procedures should provide means to list the capabilities procedures should provide means to list the capabilities
for each supported sub-profile separately. For example, for each supported sub-profile separately. For example,
the one-of-N codec selection procedure of the SDP the one-of-N codec selection procedure of the SDP
Offer/Answer model can be used (section 10.2 of [8]). The Offer/Answer model can be used (section 10.2 of [8]).
one-of-N codec selection procedure may also be used to The one-of-N codec selection procedure may also be used
provide different combinations of profile_idc and profile- to provide different combinations of profile_idc and
iop that represent the same sub-profile. When there are profile-iop that represent the same sub-profile. When
many different combinations of profile_idc and profile-iop there are many different combinations of profile_idc and
that represent the same sub-profile, using the one-of-N profile-iop that represent the same sub-profile, using
codec selection procedure may result into a fairly large the one-of-N codec selection procedure may result into a
SDP message. Therefore, a receiver should understand the fairly large SDP message. Therefore, a receiver should
different equivalent combinations of profile_idc and understand the different equivalent combinations of
profile-iop that represent the same sub-profile, and be profile_idc and profile-iop that represent the same sub-
ready to accept an offer using any of the equivalent profile, and be ready to accept an offer using any of the
combinations. equivalent combinations.
If no profile-level-id is present, the Baseline Profile If no profile-level-id is present, the Baseline Profile
without additional constraints at Level 1 MUST be inferred. without additional constraints at Level 1 MUST be inferred.
max-mbps, max-smbps, max-fs, max-cpb, max-dpb, and max-br: max-mbps, max-smbps, max-fs, max-cpb, max-dpb, and max-br:
These parameters MAY be used to signal the capabilities of a These parameters MAY be used to signal the capabilities of a
receiver implementation. These parameters MUST NOT be used for receiver implementation. These parameters MUST NOT be used
any other purpose. The profile-level-id parameter MUST be for any other purpose. The profile-level-id parameter MUST
present in the same receiver capability description that be present in the same receiver capability description that
contains any of these parameters. The level conveyed in the contains any of these parameters. The level conveyed in the
value of the profile-level-id parameter MUST be such that the value of the profile-level-id parameter MUST be such that the
receiver is fully capable of supporting. max-mbps, max-smbps, receiver is fully capable of supporting. max-mbps, max-smbps,
max-fs, max-cpb, max-dpb, and max-br MAY be used to indicate max-fs, max-cpb, max-dpb, and max-br MAY be used to indicate
capabilities of the receiver that extend the required capabilities of the receiver that extend the required
capabilities of the signaled level, as specified below. capabilities of the signaled level, as specified below.
When more than one parameter from the set (max-mbps, max- When more than one parameter from the set (max-mbps, max-
smbps , max-fs, max-cpb, max-dpb, max-br) is present, the smbps , max-fs, max-cpb, max-dpb, max-br) is present, the
receiver MUST support all signaled capabilities simultaneously. receiver MUST support all signaled capabilities
For example, if both max-mbps and max-br are present, the simultaneously. For example, if both max-mbps and max-br are
signaled level with the extension of both the frame rate and present, the signaled level with the extension of both the
bit rate is supported. That is, the receiver is able to frame rate and bit rate is supported. That is, the receiver
decode NAL unit streams in which the macroblock processing is able to decode NAL unit streams in which the macroblock
rate is up to max-mbps (inclusive), the bit rate is up to max- processing rate is up to max-mbps (inclusive), the bit rate
br (inclusive), the coded picture buffer size is derived as is up to max-br (inclusive), the coded picture buffer size is
specified in the semantics of the max-br parameter below, and derived as specified in the semantics of the max-br parameter
other properties comply with the level specified in the value below, and other properties comply with the level specified
of the profile-level-id parameter. in the value of the profile-level-id parameter.
If a receiver can support all the properties of level A, the If a receiver can support all the properties of level A, the
level specified in the value of the profile-level-id MUST be level specified in the value of the profile-level-id MUST be
level A (i.e. MUST NOT be lower than level A). In other words, level A (i.e. MUST NOT be lower than level A). In other
a sender or receiver MUST NOT signal values of max-mbps, max- words, a sender or receiver MUST NOT signal values of max-
fs, max-cpb, max-dpb, and max-br that taken together meet the mbps, max-fs, max-cpb, max-dpb, and max-br that taken
requirements of a higher level compared to the level specified together meet the requirements of a higher level compared to
in the value of the profile-level-id parameter. the level specified in the value of the profile-level-id
parameter.
Informative note: When the OPTIONAL media type parameters Informative note: When the OPTIONAL media type parameters
are used to signal the properties of a NAL unit stream, are used to signal the properties of a NAL unit stream,
max-mbps, max-smbps, max-fs, max-cpb, max-dpb, and max-br max-mbps, max-smbps, max-fs, max-cpb, max-dpb, and max-br
are not present, and the value of profile-level-id must are not present, and the value of profile-level-id must
always be such that the NAL unit stream complies fully with always be such that the NAL unit stream complies fully
the specified profile and level. with the specified profile and level.
max-mbps: The value of max-mbps is an integer indicating the max-mbps: The value of max-mbps is an integer indicating the
maximum macroblock processing rate in units of macroblocks per maximum macroblock processing rate in units of macroblocks
second. The max-mbps parameter signals that the receiver is per second. The max-mbps parameter signals that the receiver
capable of decoding video at a higher rate than is required by is capable of decoding video at a higher rate than is
the signaled level conveyed in the value of the profile-level- required by the signaled level conveyed in the value of the
id parameter. When max-mbps is signaled, the receiver MUST be profile-level-id parameter. When max-mbps is signaled, the
able to decode NAL unit streams that conform to the signaled receiver MUST be able to decode NAL unit streams that conform
level, with the exception that the MaxMBPS value in Table A-1 to the signaled level, with the exception that the MaxMBPS
of [1] for the signaled level is replaced with the value of value in Table A-1 of [1] for the signaled level is replaced
max-mbps. The value of max-mbps MUST be greater than or equal with the value of max-mbps. The value of max-mbps MUST be
to the value of MaxMBPS for the level given in Table A-1 of greater than or equal to the value of MaxMBPS for the level
[1]. Senders MAY use this knowledge to send pictures of a given in Table A-1 of [1]. Senders MAY use this knowledge to
given size at a higher picture rate than is indicated in the send pictures of a given size at a higher picture rate than
signaled level. is indicated in the signaled level.
max-smbps: The value of max-smbps is an integer indicating the max-smbps: The value of max-smbps is an integer indicating the
maximum static macroblock processing rate in units of static maximum static macroblock processing rate in units of static
macroblocks per second, under the hypothetical assumption that macroblocks per second, under the hypothetical assumption
all macroblocks are static macroblocks. When max-smbps is that all macroblocks are static macroblocks. When max-smbps
signalled the MaxMBPS value in Table A-1 of [1] should be is signalled the MaxMBPS value in Table A-1 of [1] should be
replaced with the result of the following computation: replaced with the result of the following computation:
o If the parameter max-mbps is signalled, set a variable o If the parameter max-mbps is signalled, set a variable
MaxMacroblocksPerSecond to the value of max-mbps. MaxMacroblocksPerSecond to the value of max-mbps.
Otherwise, set MaxMacroblocksPerSecond equal to the value Otherwise, set MaxMacroblocksPerSecond equal to the value
of MaxMBPS for the level in Table A-1 [1]. of MaxMBPS for the level in Table A-1 [1].
o Set a variable P_non-static to the proportion of non-static o Set a variable P_non-static to the proportion of non-
macroblocks in picture n. static macroblocks in picture n.
o Set a variable P_static to the proportion of static o Set a variable P_static to the proportion of static
macroblocks in picture n. macroblocks in picture n.
o The value of MaxMBPS in Table A-1 of [1] should be o The value of MaxMBPS in Table A-1 of [1] should be
considered by the encoder to be equal to: considered by the encoder to be equal to:
MaxMacroblocksPerSecond * max-smbps / ( P_non-static * max- MaxMacroblocksPerSecond * max-smbps / ( P_non-static *
smbps + P_static * MaxMacroblocksPerSecond) max-smbps + P_static * MaxMacroblocksPerSecond)
The encoder should recompute this value for each picture. The The encoder should recompute this value for each picture. The
value of max-smbps MUST be greater than the value of MaxMBPS value of max-smbps MUST be greater than the value of MaxMBPS
for the level given in Table A-1 of [1]. Senders MAY use this for the level given in Table A-1 of [1]. Senders MAY use
knowledge to send pictures of a given size at a higher picture this knowledge to send pictures of a given size at a higher
rate than is indicated in the signalled level. picture rate than is indicated in the signalled level.
max-fs: The value of max-fs is an integer indicating the maximum max-fs: The value of max-fs is an integer indicating the maximum
frame size in units of macroblocks. The max-fs parameter frame size in units of macroblocks. The max-fs parameter
signals that the receiver is capable of decoding larger signals that the receiver is capable of decoding larger
picture sizes than are required by the signaled level conveyed picture sizes than are required by the signaled level
in the value of the profile-level-id parameter. When max-fs conveyed in the value of the profile-level-id parameter.
is signaled, the receiver MUST be able to decode NAL unit When max-fs is signaled, the receiver MUST be able to decode
streams that conform to the signaled level, with the exception NAL unit streams that conform to the signaled level, with the
that the MaxFS value in Table A-1 of [1] for the signaled exception that the MaxFS value in Table A-1 of [1] for the
level is replaced with the value of max-fs. The value of max- signaled level is replaced with the value of max-fs. The
fs MUST be greater than or equal to the value of MaxFS for the value of max-fs MUST be greater than or equal to the value of
level given in Table A-1 of [1]. Senders MAY use this MaxFS for the level given in Table A-1 of [1]. Senders MAY
knowledge to send larger pictures at a proportionally lower use this knowledge to send larger pictures at a
frame rate than is indicated in the signaled level. proportionally lower frame rate than is indicated in the
signaled level.
max-cpb: The value of max-cpb is an integer indicating the max-cpb: The value of max-cpb is an integer indicating the
maximum coded picture buffer size in units of 1000 bits for maximum coded picture buffer size in units of 1000 bits for
the VCL HRD parameters (see A.3.1 item i of [1]) and in units the VCL HRD parameters (see A.3.1 item i of [1]) and in units
of 1200 bits for the NAL HRD parameters (see A.3.1 item j of of 1200 bits for the NAL HRD parameters (see A.3.1 item j of
[1]). The max-cpb parameter signals that the receiver has [1]). The max-cpb parameter signals that the receiver has
more memory than the minimum amount of coded picture buffer more memory than the minimum amount of coded picture buffer
memory required by the signaled level conveyed in the value of memory required by the signaled level conveyed in the value
the profile-level-id parameter. When max-cpb is signaled, the of the profile-level-id parameter. When max-cpb is signaled,
receiver MUST be able to decode NAL unit streams that conform the receiver MUST be able to decode NAL unit streams that
to the signaled level, with the exception that the MaxCPB conform to the signaled level, with the exception that the
value in Table A-1 of [1] for the signaled level is replaced MaxCPB value in Table A-1 of [1] for the signaled level is
with the value of max-cpb. The value of max-cpb MUST be replaced with the value of max-cpb. The value of max-cpb
greater than or equal to the value of MaxCPB for the level MUST be greater than or equal to the value of MaxCPB for the
given in Table A-1 of [1]. Senders MAY use this knowledge to level given in Table A-1 of [1]. Senders MAY use this
construct coded video streams with greater variation of bit knowledge to construct coded video streams with greater
rate than can be achieved with the MaxCPB value in Table A-1 variation of bit rate than can be achieved with the MaxCPB
of [1]. value in Table A-1 of [1].
Informative note: The coded picture buffer is used in the Informative note: The coded picture buffer is used in the
hypothetical reference decoder (Annex C) of H.264. The use hypothetical reference decoder (Annex C) of H.264. The
of the hypothetical reference decoder is recommended in use of the hypothetical reference decoder is recommended
H.264 encoders to verify that the produced bitstream in H.264 encoders to verify that the produced bitstream
conforms to the standard and to control the output bitrate. conforms to the standard and to control the output
Thus, the coded picture buffer is conceptually independent bitrate. Thus, the coded picture buffer is conceptually
of any other potential buffers in the receiver, including independent of any other potential buffers in the
de-interleaving and de-jitter buffers. The coded picture receiver, including de-interleaving and de-jitter buffers.
buffer need not be implemented in decoders as specified in The coded picture buffer need not be implemented in
Annex C of H.264, but rather standard-compliant decoders decoders as specified in Annex C of H.264, but rather
can have any buffering arrangements provided that they can standard-compliant decoders can have any buffering
decode standard-compliant bitstreams. Thus, in practice, arrangements provided that they can decode standard-
the input buffer for video decoder can be integrated with compliant bitstreams. Thus, in practice, the input
de-interleaving and de-jitter buffers of the receiver. buffer for video decoder can be integrated with de-
interleaving and de-jitter buffers of the receiver.
max-dpb: The value of max-dpb is an integer indicating the max-dpb: The value of max-dpb is an integer indicating the
maximum decoded picture buffer size in units of 1024 bytes. maximum decoded picture buffer size in units of 1024 bytes.
The max-dpb parameter signals that the receiver has more The max-dpb parameter signals that the receiver has more
memory than the minimum amount of decoded picture buffer memory than the minimum amount of decoded picture buffer
memory required by the signaled level conveyed in the value of memory required by the signaled level conveyed in the value
the profile-level-id parameter. When max-dpb is signaled, the of the profile-level-id parameter. When max-dpb is signaled,
receiver MUST be able to decode NAL unit streams that conform the receiver MUST be able to decode NAL unit streams that
to the signaled level, with the exception that the MaxDPB conform to the signaled level, with the exception that the
value in Table A-1 of [1] for the signaled level is replaced MaxDPB value in Table A-1 of [1] for the signaled level is
with the value of max-dpb. Consequently, a receiver that replaced with the value of max-dpb. Consequently, a receiver
signals max-dpb MUST be capable of storing the following that signals max-dpb MUST be capable of storing the following
number of decoded frames, complementary field pairs, and non- number of decoded frames, complementary field pairs, and non-
paired fields in its decoded picture buffer: paired fields in its decoded picture buffer:
Min(1024 * max-dpb / ( PicWidthInMbs * FrameHeightInMbs * Min(1024 * max-dpb / ( PicWidthInMbs * FrameHeightInMbs *
256 * ChromaFormatFactor ), 16) 256 * ChromaFormatFactor ), 16)
PicWidthInMbs, FrameHeightInMbs, and ChromaFormatFactor are PicWidthInMbs, FrameHeightInMbs, and ChromaFormatFactor are
defined in [1]. defined in [1].
The value of max-dpb MUST be greater than or equal to the The value of max-dpb MUST be greater than or equal to the
value of MaxDPB for the level given in Table A-1 of [1]. value of MaxDPB for the level given in Table A-1 of [1].
Senders MAY use this knowledge to construct coded video Senders MAY use this knowledge to construct coded video
streams with improved compression. streams with improved compression.
Informative note: This parameter was added primarily to Informative note: This parameter was added primarily to
complement a similar codepoint in the ITU-T Recommendation complement a similar codepoint in the ITU-T
H.245, so as to facilitate signaling gateway designs. The Recommendation H.245, so as to facilitate signaling
decoded picture buffer stores reconstructed samples. There gateway designs. The decoded picture buffer stores
is no relationship between the size of the decoded picture reconstructed samples. There is no relationship between
buffer and the buffers used in RTP, especially de- the size of the decoded picture buffer and the buffers
interleaving and de-jitter buffers. used in RTP, especially de-interleaving and de-jitter
buffers.
max-br: The value of max-br is an integer indicating the maximum max-br: The value of max-br is an integer indicating the maximum
video bit rate in units of 1000 bits per second for the VCL video bit rate in units of 1000 bits per second for the VCL
HRD parameters (see A.3.1 item i of [1]) and in units of 1200 HRD parameters (see A.3.1 item i of [1]) and in units of 1200
bits per second for the NAL HRD parameters (see A.3.1 item j bits per second for the NAL HRD parameters (see A.3.1 item j
of [1]). of [1]).
The max-br parameter signals that the video decoder of the The max-br parameter signals that the video decoder of the
receiver is capable of decoding video at a higher bit rate receiver is capable of decoding video at a higher bit rate
than is required by the signaled level conveyed in the value than is required by the signaled level conveyed in the value
of the profile-level-id parameter. of the profile-level-id parameter.
When max-br is signaled, the video codec of the receiver MUST When max-br is signaled, the video codec of the receiver MUST
be able to decode NAL unit streams that conform to the be able to decode NAL unit streams that conform to the
signaled level, conveyed in the profile-level-id parameter, signaled level, conveyed in the profile-level-id parameter,
with the following exceptions in the limits specified by the with the following exceptions in the limits specified by the
level: level:
o The value of max-br replaces the MaxBR value of the signaled o The value of max-br replaces the MaxBR value of the
level (in Table A-1 of [1]). signaled level (in Table A-1 of [1]).
o When the max-cpb parameter is not present, the result of the o When the max-cpb parameter is not present, the result of
following formula replaces the value of MaxCPB in Table A-1 the following formula replaces the value of MaxCPB in
of [1]: (MaxCPB of the signaled level) * max-br / (MaxBR of Table A-1 of [1]: (MaxCPB of the signaled level) * max-br
the signaled level). / (MaxBR of the signaled level).
For example, if a receiver signals capability for Level 1.2 For example, if a receiver signals capability for Level 1.2
with max-br equal to 1550, this indicates a maximum video with max-br equal to 1550, this indicates a maximum video
bitrate of 1550 kbits/sec for VCL HRD parameters, a maximum bitrate of 1550 kbits/sec for VCL HRD parameters, a maximum
video bitrate of 1860 kbits/sec for NAL HRD parameters, and a video bitrate of 1860 kbits/sec for NAL HRD parameters, and a
CPB size of 4036458 bits (1550000 / 384000 * 1000 * 1000). CPB size of 4036458 bits (1550000 / 384000 * 1000 * 1000).
The value of max-br MUST be greater than or equal to the value The value of max-br MUST be greater than or equal to the
MaxBR for the signaled level given in Table A-1 of [1]. value MaxBR for the signaled level given in Table A-1 of [1].
Senders MAY use this knowledge to send higher bitrate video as Senders MAY use this knowledge to send higher bitrate video
allowed in the level definition of Annex A of H.264, to as allowed in the level definition of Annex A of H.264, to
achieve improved video quality. achieve improved video quality.
Informative note: This parameter was added primarily to Informative note: This parameter was added primarily to
complement a similar codepoint in the ITU-T Recommendation complement a similar codepoint in the ITU-T
H.245, so as to facilitate signaling gateway designs. No Recommendation H.245, so as to facilitate signaling
assumption can be made from the value of this parameter gateway designs. No assumption can be made from the
that the network is capable of handling such bit rates at value of this parameter that the network is capable of
any given time. In particular, no conclusion can be drawn handling such bit rates at any given time. In particular,
that the signaled bit rate is possible under congestion no conclusion can be drawn that the signaled bit rate is
control constraints. possible under congestion control constraints.
redundant-pic-cap: redundant-pic-cap:
This parameter signals the capabilities of a receiver This parameter signals the capabilities of a receiver
implementation. When equal to 0, the parameter indicates that implementation. When equal to 0, the parameter indicates
the receiver makes no attempt to use redundant coded pictures that the receiver makes no attempt to use redundant coded
to correct incorrectly decoded primary coded pictures. When pictures to correct incorrectly decoded primary coded
equal to 0, the receiver is not capable of using redundant pictures. When equal to 0, the receiver is not capable of
slices; therefore, a sender SHOULD avoid sending redundant using redundant slices; therefore, a sender SHOULD avoid
slices to save bandwidth. When equal to 1, the receiver is sending redundant slices to save bandwidth. When equal to 1,
capable of decoding any such redundant slice that covers a the receiver is capable of decoding any such redundant slice
corrupted area in a primary decoded picture (at least partly), that covers a corrupted area in a primary decoded picture (at
and therefore a sender MAY send redundant slices. When the least partly), and therefore a sender MAY send redundant
parameter is not present, then a value of 0 MUST be used for slices. When the parameter is not present, then a value of 0
redundant-pic-cap. When present, the value of redundant-pic- MUST be used for redundant-pic-cap. When present, the value
cap MUST be either 0 or 1. of redundant-pic-cap MUST be either 0 or 1.
When the profile-level-id parameter is present in the same When the profile-level-id parameter is present in the same
signaling as the redundant-pic-cap parameter, and the profile signaling as the redundant-pic-cap parameter, and the profile
indicated in profile-level-id is such that it disallows the indicated in profile-level-id is such that it disallows the
use of redundant coded pictures (e.g., Main Profile), the use of redundant coded pictures (e.g., Main Profile), the
value of redundant-pic-cap MUST be equal to 0. When a value of redundant-pic-cap MUST be equal to 0. When a
receiver indicates redundant-pic-cap equal to 0, the received receiver indicates redundant-pic-cap equal to 0, the received
stream SHOULD NOT contain redundant coded pictures. stream SHOULD NOT contain redundant coded pictures.
Informative note: Even if redundant-pic-cap is equal to 0, Informative note: Even if redundant-pic-cap is equal to 0,
the decoder is able to ignore redundant codec pictures the decoder is able to ignore redundant codec pictures
provided that the decoder supports such a profile (Baseline, provided that the decoder supports such a profile
Extended) in which redundant coded pictures are allowed. (Baseline, Extended) in which redundant coded pictures
are allowed.
Informative note: Even if redundant-pic-cap is equal to 1, Informative note: Even if redundant-pic-cap is equal to 1,
the receiver may also choose other error concealment the receiver may also choose other error concealment
strategies to replace or complement decoding of redundant strategies to replace or complement decoding of redundant
slices. slices.
sprop-parameter-sets: sprop-parameter-sets:
This parameter MAY be used to convey any sequence and picture This parameter MAY be used to convey any sequence and picture
parameter set NAL units (herein referred to as the initial parameter set NAL units (herein referred to as the initial
parameter set NAL units) that can be placed in the NAL unit parameter set NAL units) that can be placed in the NAL unit
stream to precede any other NAL units in decoding order. The stream to precede any other NAL units in decoding order. The
parameter MUST NOT be used to indicate codec capability in any parameter MUST NOT be used to indicate codec capability in
capability exchange procedure. The value of the parameter is any capability exchange procedure. The value of the
a comma (',') separated list of base64 [7] representations of parameter is a comma (',') separated list of base64 [7]
parameter set NAL units as specified in sections 7.3.2.1 and representations of parameter set NAL units as specified in
7.3.2.2 of [1]. Note that the number of bytes in a parameter sections 7.3.2.1 and 7.3.2.2 of [1]. Note that the number of
set NAL unit is typically less than 10, but a picture bytes in a parameter set NAL unit is typically less than 10,
parameter set NAL unit can contain several hundreds of bytes. but a picture parameter set NAL unit can contain several
hundreds of bytes.
Informative note: When several payload types are offered in Informative note: When several payload types are offered
the SDP Offer/Answer model, each with its own sprop- in the SDP Offer/Answer model, each with its own sprop-
parameter-sets parameter, then the receiver cannot assume parameter-sets parameter, then the receiver cannot assume
that those parameter sets do not use conflicting storage that those parameter sets do not use conflicting storage
locations (i.e., identical values of parameter set locations (i.e., identical values of parameter set
identifiers). Therefore, a receiver should buffer all identifiers). Therefore, a receiver should buffer all
sprop-parameter-sets and make them available to the decoder sprop-parameter-sets and make them available to the
instance that decodes a certain payload type. decoder instance that decodes a certain payload type.
The "sprop-parameter-sets" parameter MUST only contain The "sprop-parameter-sets" parameter MUST only contain
parameter sets that are conforming to the profile-level-id, parameter sets that are conforming to the profile-level-id,
i.e., the subset of coding tools indicated by any of the i.e., the subset of coding tools indicated by any of the
parameter sets MUST be equal to the default sub-profile, and parameter sets MUST be equal to the default sub-profile, and
the level indicated by any of the parameter sets MUST be equal the level indicated by any of the parameter sets MUST be
to the default level. equal to the default level.
sprop-level-parameter-sets: sprop-level-parameter-sets:
This parameter MAY be used to convey any sequence and picture This parameter MAY be used to convey any sequence and picture
parameter set NAL units (herein referred to as the initial parameter set NAL units (herein referred to as the initial
parameter set NAL units) that can be placed in the NAL unit parameter set NAL units) that can be placed in the NAL unit
stream to precede any other NAL units in decoding order and stream to precede any other NAL units in decoding order and
that are associated with one or more levels lower than the that are associated with one or more levels lower than the
default level. The parameter MUST NOT be used to indicate default level. The parameter MUST NOT be used to indicate
codec capability in any capability exchange procedure. codec capability in any capability exchange procedure.
The sprop-level-parameter-sets parameter contains parameter The sprop-level-parameter-sets parameter contains parameter
sets for one or more levels which are lower than the default sets for one or more levels which are lower than the default
level. All parameter sets associated with one level are level. All parameter sets associated with one level are
clustered and prefixed with a three-byte field which has the clustered and prefixed with a three-byte field which has the
same syntax as profile-level-id. This enables the receiver to same syntax as profile-level-id. This enables the receiver
install the parameter sets for one level and discard the rest. to install the parameter sets for one level and discard the
The three-byte field is named PLId, and all parameter sets rest. The three-byte field is named PLId, and all parameter
associated with one level are named PSL, which has the same sets associated with one level are named PSL, which has the
syntax as sprop-parameter-sets. Parameter sets for each level same syntax as sprop-parameter-sets. Parameter sets for each
are represented in the form of PLId:PSL, i.e., PLId followed level are represented in the form of PLId:PSL, i.e., PLId
by a colon (':') and the base64 [7] representation of the followed by a colon (':') and the base64 [7] representation
initial parameter set NAL units for the level. Each pair of of the initial parameter set NAL units for the level. Each
PLId:PSL is also separated by a colon. Note that a PSL can pair of PLId:PSL is also separated by a colon. Note that a
contain multiple parameter sets for that level, separated with PSL can contain multiple parameter sets for that level,
commas (','). separated with commas (',').
The subset of coding tools indicated by each PLId field MUST The subset of coding tools indicated by each PLId field MUST
be equal to the default sub-profile, and the level indicated be equal to the default sub-profile, and the level indicated
by each PLId field MUST be lower than the default level. All by each PLId field MUST be lower than the default level. All
sequence parameter sets contained in each PSL MUST have the sequence parameter sets contained in each PSL MUST have the
three bytes from profile_idc to level_idc, inclusive, equal to three bytes from profile_idc to level_idc, inclusive, equal
the preceding PLId. to the preceding PLId.
Informative note: This parameter allows for efficient level Informative note: This parameter allows for efficient
downgrade in SDP Offer/Answer and out-of-band transport of level downgrade in SDP Offer/Answer and out-of-band
parameter sets, simultaneously. transport of parameter sets, simultaneously.
use-level-src-parameter-sets: use-level-src-parameter-sets:
This parameter MAY be used to indicate a receiver capability. This parameter MAY be used to indicate a receiver capability.
The value MAY be equal to either 0 or 1. When the parameter The value MAY be equal to either 0 or 1. When the parameter
is not present, the value MUST be inferred to be equal to 0. is not present, the value MUST be inferred to be equal to 0.
The value 0 indicates that the receiver does not understand The value 0 indicates that the receiver does not understand
the sprop-level-parameter-sets parameter, and does not the sprop-level-parameter-sets parameter, and does not
understand the "fmtp" source attribute as specified in section understand the "fmtp" source attribute as specified in
6.3 of [9], and will ignore sprop-level-parameter-sets when section 6.3 of [9], and will ignore sprop-level-parameter-
present, and will ignore sprop-parameter-sets when conveyed sets when present, and will ignore sprop-parameter-sets when
using the "fmtp" source attribute. The value 1 indicates that conveyed using the "fmtp" source attribute. The value 1
the receiver understands the sprop-level-parameter-sets indicates that the receiver understands the sprop-level-
parameter, and understands the "fmtp" source attribute as parameter-sets parameter, and understands the "fmtp" source
specified in section 6.3 of [9], and is capable of using attribute as specified in section 6.3 of [9], and is capable
parameter sets contained in the sprop-level-parameter-sets or of using parameter sets contained in the sprop-level-
contained in the sprop-parameter-sets that is conveyed using parameter-sets or contained in the sprop-parameter-sets that
the "fmtp" source attribute. is conveyed using the "fmtp" source attribute.
Informative note: An RFC 3984 receiver does not understand Informative note: An RFC 3984 receiver does not
sprop-level-parameter-sets, use-level-src-parameter-sets, understand sprop-level-parameter-sets, use-level-src-
or the "fmtp" source attribute as specified in section 6.3 parameter-sets, or the "fmtp" source attribute as
of [9]. Therefore, during SDP Offer/Answer, an RFC 3984 specified in section 6.3 of [9]. Therefore, during SDP
receiver as the answerer will simply ignore sprop-level- Offer/Answer, an RFC 3984 receiver as the answerer will
parameter-sets, when present in an offer, and sprop- simply ignore sprop-level-parameter-sets, when present in
parameter-sets, when conveyed using the "fmtp" source an offer, and sprop-parameter-sets, when conveyed using
attribute as specified in section 6.3 of [9]. Assume that the "fmtp" source attribute as specified in section 6.3
the offered payload type was accepted at a level lower than of [9]. Assume that the offered payload type was
the default level. If the offered payload type included accepted at a level lower than the default level. If the
sprop-level-parameter-sets or included sprop-parameter-sets offered payload type included sprop-level-parameter-sets
conveyed using the "fmtp" source attribute, and the offerer or included sprop-parameter-sets conveyed using the
sees that the answerer has not included use-level-src- "fmtp" source attribute, and the offerer sees that the
parameter-sets equal to 1 in the answer, the offerer gets answerer has not included use-level-src-parameter-sets
to know that in-band transport of parameter sets is needed. equal to 1 in the answer, the offerer gets to know that
in-band transport of parameter sets is needed.
in-band-parameter-sets: in-band-parameter-sets:
This parameter MAY be used to indicate a receiver capability. This parameter MAY be used to indicate a receiver capability.
The value MAY be equal to either 0 or 1. The value 1 The value MAY be equal to either 0 or 1. The value 1
indicates that receiver discards out-of-band parameter sets in indicates that receiver discards out-of-band parameter sets
sprop-parameter-sets and sprop-level-parameter-sets, therefore in sprop-parameter-sets and sprop-level-parameter-sets,
the sender MUST transmit all parameter sets in-band. The therefore the sender MUST transmit all parameter sets in-band.
value 0 indicates that the receiver utilizes out-of-band The value 0 indicates that the receiver utilizes out-of-band
parameter sets included in sprop-parameter-sets and sprop- parameter sets included in sprop-parameter-sets and sprop-
level-parameter-sets. However, in this case, the sender MAY level-parameter-sets. However, in this case, the sender MAY
still choose to send parameter sets in-band. When in-band- still choose to send parameter sets in-band. When in-band-
parameter-sets is equal to 1, use-level-src-parameter-sets parameter-sets is equal to 1, use-level-src-parameter-sets
MUST NOT be present or MUST be equal to 0. When the parameter MUST NOT be present or MUST be equal to 0. When the
is not present, this receiver capability is not specified, and parameter is not present, this receiver capability is not
therefore the sender MAY send out-of-band parameter sets only, specified, and therefore the sender MAY send out-of-band
or it MAY send in-band-parameter-sets only, or it MAY send parameter sets only, or it MAY send in-band-parameter-sets
both. only, or it MAY send both.
packetization-mode: packetization-mode:
This parameter signals the properties of an RTP payload type This parameter signals the properties of an RTP payload type
or the capabilities of a receiver implementation. Only a or the capabilities of a receiver implementation. Only a
single configuration point can be indicated; thus, when single configuration point can be indicated; thus, when
capabilities to support more than one packetization-mode are capabilities to support more than one packetization-mode are
declared, multiple configuration points (RTP payload types) declared, multiple configuration points (RTP payload types)
must be used. must be used.
When the value of packetization-mode is equal to 0 or When the value of packetization-mode is equal to 0 or
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NAL unit decoding order when the buffer size for NAL unit NAL unit decoding order when the buffer size for NAL unit
decoding order recovery is at least the value of sprop- decoding order recovery is at least the value of sprop-
interleaving-depth + 1 in terms of VCL NAL units. interleaving-depth + 1 in terms of VCL NAL units.
The value of sprop-interleaving-depth MUST be an integer in The value of sprop-interleaving-depth MUST be an integer in
the range of 0 to 32767, inclusive. the range of 0 to 32767, inclusive.
sprop-deint-buf-req: sprop-deint-buf-req:
This parameter MUST NOT be present when packetization-mode is This parameter MUST NOT be present when packetization-mode is
not present or the value of packetization-mode is equal to 0 not present or the value of packetization-mode is equal to 0
or 1. It MUST be present when the value of packetization-mode or 1. It MUST be present when the value of packetization-
is equal to 2. mode is equal to 2.
sprop-deint-buf-req signals the required size of the de- sprop-deint-buf-req signals the required size of the de-
interleaving buffer for the RTP packet stream. The value of interleaving buffer for the RTP packet stream. The value of
the parameter MUST be greater than or equal to the maximum the parameter MUST be greater than or equal to the maximum
buffer occupancy (in units of bytes) required in such a de- buffer occupancy (in units of bytes) required in such a de-
interleaving buffer that is specified in section 7.2 of RFC interleaving buffer that is specified in section 7.2 of RFC
3984. It is guaranteed that receivers can perform the de- 3984. It is guaranteed that receivers can perform the de-
interleaving of interleaved NAL units into NAL unit decoding interleaving of interleaved NAL units into NAL unit decoding
order, when the de-interleaving buffer size is at least the order, when the de-interleaving buffer size is at least the
value of sprop-deint-buf-req in terms of bytes. value of sprop-deint-buf-req in terms of bytes.
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range of 0 to 4294967295, inclusive. range of 0 to 4294967295, inclusive.
Informative note: sprop-deint-buf-req indicates the Informative note: sprop-deint-buf-req indicates the
required size of the de-interleaving buffer only. When required size of the de-interleaving buffer only. When
network jitter can occur, an appropriately sized jitter network jitter can occur, an appropriately sized jitter
buffer has to be provisioned for as well. buffer has to be provisioned for as well.
deint-buf-cap: deint-buf-cap:
This parameter signals the capabilities of a receiver This parameter signals the capabilities of a receiver
implementation and indicates the amount of de-interleaving implementation and indicates the amount of de-interleaving
buffer space in units of bytes that the receiver has available buffer space in units of bytes that the receiver has
for reconstructing the NAL unit decoding order. A receiver is available for reconstructing the NAL unit decoding order. A
able to handle any stream for which the value of the sprop- receiver is able to handle any stream for which the value of
deint-buf-req parameter is smaller than or equal to this the sprop-deint-buf-req parameter is smaller than or equal to
parameter. this parameter.
If the parameter is not present, then a value of 0 MUST be If the parameter is not present, then a value of 0 MUST be
used for deint-buf-cap. The value of deint-buf-cap MUST be an used for deint-buf-cap. The value of deint-buf-cap MUST be
integer in the range of 0 to 4294967295, inclusive. an integer in the range of 0 to 4294967295, inclusive.
Informative note: deint-buf-cap indicates the maximum Informative note: deint-buf-cap indicates the maximum
possible size of the de-interleaving buffer of the receiver possible size of the de-interleaving buffer of the
only. When network jitter can occur, an appropriately receiver only. When network jitter can occur, an
sized jitter buffer has to be provisioned for as well. appropriately sized jitter buffer has to be provisioned
for as well.
sprop-init-buf-time: sprop-init-buf-time:
This parameter MAY be used to signal the properties of an RTP This parameter MAY be used to signal the properties of an RTP
packet stream. The parameter MUST NOT be present, if the packet stream. The parameter MUST NOT be present, if the
value of packetization-mode is equal to 0 or 1. value of packetization-mode is equal to 0 or 1.
The parameter signals the initial buffering time that a The parameter signals the initial buffering time that a
receiver MUST wait before starting decoding to recover the NAL receiver MUST wait before starting decoding to recover the
unit decoding order from the transmission order. The NAL unit decoding order from the transmission order. The
parameter is the maximum value of (decoding time of the NAL parameter is the maximum value of (decoding time of the NAL
unit - transmission time of a NAL unit), assuming reliable and unit - transmission time of a NAL unit), assuming reliable
instantaneous transmission, the same timeline for transmission and instantaneous transmission, the same timeline for
and decoding, and that decoding starts when the first packet transmission and decoding, and that decoding starts when the
arrives. first packet arrives.
An example of specifying the value of sprop-init-buf-time An example of specifying the value of sprop-init-buf-time
follows. A NAL unit stream is sent in the following follows. A NAL unit stream is sent in the following
interleaved order, in which the value corresponds to the interleaved order, in which the value corresponds to the
decoding time and the transmission order is from left to right: decoding time and the transmission order is from left to
right:
0 2 1 3 5 4 6 8 7 ... 0 2 1 3 5 4 6 8 7 ...
Assuming a steady transmission rate of NAL units, the Assuming a steady transmission rate of NAL units, the
transmission times are: transmission times are:
0 1 2 3 4 5 6 7 8 ... 0 1 2 3 4 5 6 7 8 ...
Subtracting the decoding time from the transmission time Subtracting the decoding time from the transmission time
column-wise results in the following series: column-wise results in the following series:
0 -1 1 0 -1 1 0 -1 1 ... 0 -1 1 0 -1 1 0 -1 1 ...
Thus, in terms of intervals of NAL unit transmission times, Thus, in terms of intervals of NAL unit transmission times,
the value of sprop-init-buf-time in this example is 1. The the value of sprop-init-buf-time in this example is 1. The
parameter is coded as a non-negative base10 integer parameter is coded as a non-negative base10 integer
representation in clock ticks of a 90-kHz clock. If the representation in clock ticks of a 90-kHz clock. If the
parameter is not present, then no initial buffering time value parameter is not present, then no initial buffering time
is defined. Otherwise the value of sprop-init-buf-time MUST value is defined. Otherwise the value of sprop-init-buf-time
be an integer in the range of 0 to 4294967295, inclusive. MUST be an integer in the range of 0 to 4294967295, inclusive.
In addition to the signaled sprop-init-buf-time, receivers In addition to the signaled sprop-init-buf-time, receivers
SHOULD take into account the transmission delay jitter SHOULD take into account the transmission delay jitter
buffering, including buffering for the delay jitter caused by buffering, including buffering for the delay jitter caused by
mixers, translators, gateways, proxies, traffic-shapers, and mixers, translators, gateways, proxies, traffic-shapers, and
other network elements. other network elements.
sprop-max-don-diff: sprop-max-don-diff:
This parameter MAY be used to signal the properties of an RTP This parameter MAY be used to signal the properties of an RTP
packet stream. It MUST NOT be used to signal transmitter or packet stream. It MUST NOT be used to signal transmitter or
receiver or codec capabilities. The parameter MUST NOT be receiver or codec capabilities. The parameter MUST NOT be
present if the value of packetization-mode is equal to 0 or 1. present if the value of packetization-mode is equal to 0 or 1.
sprop-max-don-diff is an integer in the range of 0 to 32767, sprop-max-don-diff is an integer in the range of 0 to 32767,
inclusive. If sprop-max-don-diff is not present, the value of inclusive. If sprop-max-don-diff is not present, the value
the parameter is unspecified. sprop-max-don-diff is of the parameter is unspecified. sprop-max-don-diff is
calculated as follows: calculated as follows:
sprop-max-don-diff = max{AbsDON(i) - AbsDON(j)}, sprop-max-don-diff = max{AbsDON(i) - AbsDON(j)},
for any i and any j>i, for any i and any j>i,
where i and j indicate the index of the NAL unit in the where i and j indicate the index of the NAL unit in the
transmission order and AbsDON denotes a decoding order number transmission order and AbsDON denotes a decoding order number
of the NAL unit that does not wrap around to 0 after 65535. of the NAL unit that does not wrap around to 0 after 65535.
In other words, AbsDON is calculated as follows: Let m and n In other words, AbsDON is calculated as follows: Let m and n
be consecutive NAL units in transmission order. For the very be consecutive NAL units in transmission order. For the very
first NAL unit in transmission order (whose index is 0), first NAL unit in transmission order (whose index is 0),
AbsDON(0) = DON(0). For other NAL units, AbsDON is calculated AbsDON(0) = DON(0). For other NAL units, AbsDON is
as follows: calculated as follows:
If DON(m) == DON(n), AbsDON(n) = AbsDON(m) If DON(m) == DON(n), AbsDON(n) = AbsDON(m)
If (DON(m) < DON(n) and DON(n) - DON(m) < 32768), If (DON(m) < DON(n) and DON(n) - DON(m) < 32768),
AbsDON(n) = AbsDON(m) + DON(n) - DON(m) AbsDON(n) = AbsDON(m) + DON(n) - DON(m)
If (DON(m) > DON(n) and DON(m) - DON(n) >= 32768), If (DON(m) > DON(n) and DON(m) - DON(n) >= 32768),
AbsDON(n) = AbsDON(m) + 65536 - DON(m) + DON(n) AbsDON(n) = AbsDON(m) + 65536 - DON(m) + DON(n)
If (DON(m) < DON(n) and DON(n) - DON(m) >= 32768), If (DON(m) < DON(n) and DON(n) - DON(m) >= 32768),
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This parameter MAY be used to signal the capabilities of a This parameter MAY be used to signal the capabilities of a
receiver. The parameter MUST NOT be used for any other receiver. The parameter MUST NOT be used for any other
purposes. The value of the parameter indicates the largest purposes. The value of the parameter indicates the largest
NALU size in bytes that the receiver can handle efficiently. NALU size in bytes that the receiver can handle efficiently.
The parameter value is a recommendation, not a strict upper The parameter value is a recommendation, not a strict upper
boundary. The sender MAY create larger NALUs but must be boundary. The sender MAY create larger NALUs but must be
aware that the handling of these may come at a higher cost aware that the handling of these may come at a higher cost
than NALUs conforming to the limitation. than NALUs conforming to the limitation.
The value of max-rcmd-nalu-size MUST be an integer in the The value of max-rcmd-nalu-size MUST be an integer in the
range of 0 to 4294967295, inclusive. If this parameter is not range of 0 to 4294967295, inclusive. If this parameter is
specified, no known limitation to the NALU size exists. not specified, no known limitation to the NALU size exists.
Senders still have to consider the MTU size available between Senders still have to consider the MTU size available between
the sender and the receiver and SHOULD run MTU discovery for the sender and the receiver and SHOULD run MTU discovery for
this purpose. this purpose.
This parameter is motivated by, for example, an IP to H.223 This parameter is motivated by, for example, an IP to H.223
video telephony gateway, where NALUs smaller than the H.223 video telephony gateway, where NALUs smaller than the H.223
transport data unit will be more efficient. A gateway may transport data unit will be more efficient. A gateway may
terminate IP; thus, MTU discovery will normally not work terminate IP; thus, MTU discovery will normally not work
beyond the gateway. beyond the gateway.
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This parameter MAY be used to indicate a receiver capability This parameter MAY be used to indicate a receiver capability
and not anything else. The parameter indicates the maximum and not anything else. The parameter indicates the maximum
value of aspect_ratio_idc (specified in [1]) smaller than 255 value of aspect_ratio_idc (specified in [1]) smaller than 255
that the receiver understands. Table E-1 of [1] specifies that the receiver understands. Table E-1 of [1] specifies
aspect_ratio_idc equal to 0 as "unspecified", 1 to 16, aspect_ratio_idc equal to 0 as "unspecified", 1 to 16,
inclusive, as specific Sample Aspect Ratios (SARs), 17 to 254, inclusive, as specific Sample Aspect Ratios (SARs), 17 to 254,
inclusive, as "reserved", and 255 as the Extended SAR, for inclusive, as "reserved", and 255 as the Extended SAR, for
which SAR width and SAR height are explicitly signaled. which SAR width and SAR height are explicitly signaled.
Therefore, a receiver with a decoder according to [1] Therefore, a receiver with a decoder according to [1]
understands aspect_ratio_idc in the range of 1 to 16, understands aspect_ratio_idc in the range of 1 to 16,
inclusive and aspect_ratio_idc equal to 255, in the sense that inclusive and aspect_ratio_idc equal to 255, in the sense
the receiver knows what exactly the SAR is. For such a that the receiver knows what exactly the SAR is. For such a
receiver, the value of sar-understood is 16. If in the future receiver, the value of sar-understood is 16. If in the
Table E-1 of [1] is extended, e.g., such that the SAR for future Table E-1 of [1] is extended, e.g., such that the SAR
aspect_ratio_idc equal to 17 is specified, then for a receiver for aspect_ratio_idc equal to 17 is specified, then for a
with a decoder that understands the extension, the value of receiver with a decoder that understands the extension, the
sar-understood is 17. For a receiver with a decoder according value of sar-understood is 17. For a receiver with a decoder
to the 2003 version of [1], the value of sar-understood is 13, according to the 2003 version of [1], the value of sar-
as the minimum reserved aspect_ratio_idc therein is 14. understood is 13, as the minimum reserved aspect_ratio_idc
therein is 14.
When sar-understood is not present, the value MUST be inferred When sar-understood is not present, the value MUST be
to be equal to 13. inferred to be equal to 13.
sar-supported: sar-supported:
This parameter MAY be used to indicate a receiver capability This parameter MAY be used to indicate a receiver capability
and not anything else. The value of this parameter is an and not anything else. The value of this parameter is an
integer in the range of 1 to sar-understood, inclusive, equal integer in the range of 1 to sar-understood, inclusive, equal
to 255. The value of sar-supported equal to N smaller than to 255. The value of sar-supported equal to N smaller than
255 indicates that the reciever supports all the SARs 255 indicates that the reciever supports all the SARs
corresponding to H.264 aspect_ratio_idc values (see Table E-1 corresponding to H.264 aspect_ratio_idc values (see Table E-1
of [1]) in the range from 1 to N, inclusive, without geometric of [1]) in the range from 1 to N, inclusive, without
distortion. The value of sar-supported equal to 255 indicates geometric distortion. The value of sar-supported equal to
that the receiver supports all sample aspect ratios which are 255 indicates that the receiver supports all sample aspect
expressible using two 16-bit integer values as the numerator ratios which are expressible using two 16-bit integer values
and denominator, i.e., those that are expressible using the as the numerator and denominator, i.e., those that are
H.264 aspect_ratio_idc value of 255 (Extended_SAR, see Table expressible using the H.264 aspect_ratio_idc value of 255
E-1 of [1]), without geometric distortion. (Extended_SAR, see Table E-1 of [1]), without geometric
distortion.
H.264 compliant encoders SHOULD NOT send an aspect_ratio_idc H.264 compliant encoders SHOULD NOT send an aspect_ratio_idc
equal to 0, or an aspect_ratio_idc larger than sar-understood equal to 0, or an aspect_ratio_idc larger than sar-understood
and smaller than 255. H.264 compliant encoders SHOULD send an and smaller than 255. H.264 compliant encoders SHOULD send
aspect_ratio_idc that the receiver is able to display without an aspect_ratio_idc that the receiver is able to display
geometrical distortion. However, H.264 compliant encoders MAY without geometrical distortion. However, H.264 compliant
choose to send pictures using any SAR. encoders MAY choose to send pictures using any SAR.
Note that the actual sample aspect ratio or extended sample Note that the actual sample aspect ratio or extended sample
aspect ratio, when present, of the stream is conveyed in the aspect ratio, when present, of the stream is conveyed in the
Video Usability Information (VUI) part of the sequence Video Usability Information (VUI) part of the sequence
parameter set. parameter set.
Encoding considerations: Encoding considerations:
This type is only defined for transfer via RTP (RFC 3550). This type is only defined for transfer via RTP (RFC 3550).
Security considerations: Security considerations:
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8.2. SDP Parameters 8.2. SDP Parameters
8.2.1. Mapping of Payload Type Parameters to SDP 8.2.1. Mapping of Payload Type Parameters to SDP
The media type video/H264 string is mapped to fields in the Session The media type video/H264 string is mapped to fields in the Session
Description Protocol (SDP) [6] as follows: Description Protocol (SDP) [6] as follows:
o The media name in the "m=" line of SDP MUST be video. o The media name in the "m=" line of SDP MUST be video.
o The encoding name in the "a=rtpmap" line of SDP MUST be H264 (the o The encoding name in the "a=rtpmap" line of SDP MUST be H264
media subtype). (the media subtype).
o The clock rate in the "a=rtpmap" line MUST be 90000. o The clock rate in the "a=rtpmap" line MUST be 90000.
o The OPTIONAL parameters "profile-level-id", "max-mbps", "max- o The OPTIONAL parameters "profile-level-id", "max-mbps", "max-
smbps", "max-fs", "max-cpb", "max-dpb", "max-br", "redundant-pic- smbps", "max-fs", "max-cpb", "max-dpb", "max-br", "redundant-
cap", "use-level-src-parameter-sets", "in-band-parameter-sets", pic-cap", "use-level-src-parameter-sets", "in-band-parameter-
"packetization-mode", "sprop-interleaving-depth", "sprop-deint- sets", "packetization-mode", "sprop-interleaving-depth", "sprop-
buf-req", "deint-buf-cap", "sprop-init-buf-time", "sprop-max-don- deint-buf-req", "deint-buf-cap", "sprop-init-buf-time", "sprop-
diff", "max-rcmd-nalu-size", "sar-understood", and "sar-supported", max-don-diff", "max-rcmd-nalu-size", "sar-understood", and "sar-
when present, MUST be included in the "a=fmtp" line of SDP. These supported", when present, MUST be included in the "a=fmtp" line
parameters are expressed as a media type string, in the form of a of SDP. These parameters are expressed as a media type string,
semicolon separated list of parameter=value pairs. in the form of a semicolon separated list of parameter=value
pairs.
o The OPTIONAL parameters "sprop-parameter-sets" and "sprop-level- o The OPTIONAL parameters "sprop-parameter-sets" and "sprop-level-
parameter-sets", when present, MUST be included in the "a=fmtp" parameter-sets", when present, MUST be included in the "a=fmtp"
line of SDP or conveyed using the "fmtp" source attribute as line of SDP or conveyed using the "fmtp" source attribute as
specified in section 6.3 of [9]. For a particular media format specified in section 6.3 of [9]. For a particular media format
(i.e., RTP payload type), a "sprop-parameter-sets" or "sprop- (i.e., RTP payload type), a "sprop-parameter-sets" or "sprop-
level-parameter-sets" MUST NOT be both included in the "a=fmtp" level-parameter-sets" MUST NOT be both included in the "a=fmtp"
line of SDP and conveyed using the "fmtp" source attribute. When line of SDP and conveyed using the "fmtp" source attribute.
included in the "a=fmtp" line of SDP, these parameters are When included in the "a=fmtp" line of SDP, these parameters are
expressed as a media type string, in the form of a semicolon expressed as a media type string, in the form of a semicolon
separated list of parameter=value pairs. When conveyed using the separated list of parameter=value pairs. When conveyed using
"fmtp" source attribute, these parameters are only associated with the "fmtp" source attribute, these parameters are only
the given source and payload type as parts of the "fmtp" source associated with the given source and payload type as parts of
attribute. the "fmtp" source attribute.
Informative note: Conveyance of "sprop-parameter-sets" and Informative note: Conveyance of "sprop-parameter-sets" and
"sprop-level-parameter-sets" using the "fmtp" source attribute "sprop-level-parameter-sets" using the "fmtp" source
allows for out-of-band transport of parameter sets in attribute allows for out-of-band transport of parameter sets
topologies like Topo-Video-switch-MCU [29]. in topologies like Topo-Video-switch-MCU [29].
An example of media representation in SDP is as follows (Baseline An example of media representation in SDP is as follows (Baseline
Profile, Level 3.0, some of the constraints of the Main profile may Profile, Level 3.0, some of the constraints of the Main profile may
not be obeyed): not be obeyed):
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; a=fmtp:98 profile-level-id=42A01E;
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data> sprop-parameter-sets=<parameter sets data>
8.2.2. Usage with the SDP Offer/Answer Model 8.2.2. Usage with the SDP Offer/Answer Model
When H.264 is offered over RTP using SDP in an Offer/Answer model [8] When H.264 is offered over RTP using SDP in an Offer/Answer model
for negotiation for unicast usage, the following limitations and [8] for negotiation for unicast usage, the following limitations
rules apply: and rules apply:
o The parameters identifying a media format configuration for H.264 o The parameters identifying a media format configuration for
are "profile-level-id" and "packetization-mode", when present. H.264 are "profile-level-id" and "packetization-mode", when
These media format configuration parameters (except for the level present. These media format configuration parameters (except
part of "profile-level-id") MUST be used symmetrically; i.e., the for the level part of "profile-level-id") MUST be used
answerer MUST either maintain all configuration parameters or symmetrically; i.e., the answerer MUST either maintain all
remove the media format (payload type) completely, if one or more configuration parameters or remove the media format (payload
of the parameter values are not supported. Note that the level type) completely, if one or more of the parameter values are not
part of "profile-level-id" includes level_idc, and, for indication supported. Note that the level part of "profile-level-id"
of level 1b when profile_idc is equal to 66, 77 or 88, bit 4 includes level_idc, and, for indication of level 1b when
profile_idc is equal to 66, 77 or 88, bit 4
(constraint_set3_flag) of profile-iop. The level part of (constraint_set3_flag) of profile-iop. The level part of
"profile-level-id" is downgradable, i.e. the answerer MUST "profile-level-id" is downgradable, i.e. the answerer MUST
maintain the same or a lower level or remove the media format maintain the same or a lower level or remove the media format
(payload type) completely. (payload type) completely.
Informative note: The requirement for symmetric use applies Informative note: The requirement for symmetric use applies
only for the above media format configuration parameters only for the above media format configuration parameters
excluding the level part of "profile-level-id", and not for excluding the level part of "profile-level-id", and not for
the other stream properties and capability parameters. the other stream properties and capability parameters.
Informative note: In H.264 [1], all the levels except for Informative note: In H.264 [1], all the levels except for
level 1b are equal to the value of level_idc divided by 10. level 1b are equal to the value of level_idc divided by 10.
Level 1b is a level higher than level 1.0 but lower than level Level 1b is a level higher than level 1.0 but lower than
1.1, and is signaled in an ad-hoc manner, due to that the level 1.1, and is signaled in an ad-hoc manner, due to that
level was specified after level 1.0 and level 1.1. For the the level was specified after level 1.0 and level 1.1. For
Baseline, Main and Extended profiles (with profile_idc equal the Baseline, Main and Extended profiles (with profile_idc
to 66, 77 and 88, respectively), level 1b is indicated by equal to 66, 77 and 88, respectively), level 1b is indicated
level_idc equal to 11 (i.e. same as level 1.1) and by level_idc equal to 11 (i.e. same as level 1.1) and
constraint_set3_flag equal to 1. For other profiles, level 1b constraint_set3_flag equal to 1. For other profiles, level
is indicated by level_idc equal to 9 (but note that level 1b 1b is indicated by level_idc equal to 9 (but note that level
for these profiles are still higher than level 1, which has 1b for these profiles are still higher than level 1, which
level_idc equal to 10, and lower than level 1.1). In SDP has level_idc equal to 10, and lower than level 1.1). In SDP
Offer/Answer, an answer to an offer may indicate a level equal Offer/Answer, an answer to an offer may indicate a level
to or lower than the level indicated in the offer. Due to the equal to or lower than the level indicated in the offer. Due
ad-hoc indication of level 1b, offerers and answerers must to the ad-hoc indication of level 1b, offerers and answerers
check the value of bit 4 (constraint_set3_flag) of the middle must check the value of bit 4 (constraint_set3_flag) of the
octet of the parameter "profile-level-id", when profile_idc is middle octet of the parameter "profile-level-id", when
equal to 66, 77 or 88 and level_idc is equal to 11. profile_idc is equal to 66, 77 or 88 and level_idc is equal
to 11.
To simplify handling and matching of these configurations, the To simplify handling and matching of these configurations, the
same RTP payload type number used in the offer SHOULD also be same RTP payload type number used in the offer SHOULD also be
used in the answer, as specified in [8]. An answer MUST NOT used in the answer, as specified in [8]. An answer MUST NOT
contain a payload type number used in the offer unless the contain a payload type number used in the offer unless the
configuration is exactly the same as in the offer or the configuration is exactly the same as in the offer or the
configuration in the answer only differs from that in the offer configuration in the answer only differs from that in the offer
with a level lower than the default level offered. with a level lower than the default level offered.
Informative note: When an offerer receives an answer, it has Informative note: When an offerer receives an answer, it has
to compare payload types not declared in the offer based on to compare payload types not declared in the offer based on
the media type (i.e., video/H264) and the above media the media type (i.e., video/H264) and the above media
configuration parameters with any payload types it has already configuration parameters with any payload types it has
declared. This will enable it to determine whether the already declared. This will enable it to determine whether
configuration in question is new or if it is equivalent to the configuration in question is new or if it is equivalent
configuration already offered, since a different payload type to configuration already offered, since a different payload
number may be used in the answer. type number may be used in the answer.
o The parameters "sprop-deint-buf-req", "sprop-interleaving-depth", o The parameters "sprop-deint-buf-req", "sprop-interleaving-depth",
"sprop-max-don-diff", and "sprop-init-buf-time" describe the "sprop-max-don-diff", and "sprop-init-buf-time" describe the
properties of the RTP packet stream that the offerer or answerer properties of the RTP packet stream that the offerer or answerer
is sending for the media format configuration. This differs from is sending for the media format configuration. This differs
the normal usage of the Offer/Answer parameters: normally such from the normal usage of the Offer/Answer parameters: normally
parameters declare the properties of the stream that the offerer such parameters declare the properties of the stream that the
or the answerer is able to receive. When dealing with H.264, the offerer or the answerer is able to receive. When dealing with
offerer assumes that the answerer will be able to receive media H.264, the offerer assumes that the answerer will be able to
encoded using the configuration being offered. receive media encoded using the configuration being offered.
Informative note: The above parameters apply for any stream Informative note: The above parameters apply for any stream
sent by the declaring entity with the same configuration; i.e., sent by the declaring entity with the same configuration;
they are dependent on their source. Rather than being bound i.e., they are dependent on their source. Rather than being
to the payload type, the values may have to be applied to bound to the payload type, the values may have to be applied
another payload type when being sent, as they apply for the to another payload type when being sent, as they apply for
configuration. the configuration.
o The capability parameters ("max-mbps", "max-smbps", "max-fs", o The capability parameters ("max-mbps", "max-smbps", "max-fs",
"max-cpb", "max-dpb", "max-br", ,"redundant-pic-cap", "max-rcmd- "max-cpb", "max-dpb", "max-br", ,"redundant-pic-cap", "max-rcmd-
nalu-size", "sar-understood", "sar-supported") MAY be used to nalu-size", "sar-understood", "sar-supported") MAY be used to
declare further capabilities of the offerer or answerer for declare further capabilities of the offerer or answerer for
receiving. These parameters can only be present when the receiving. These parameters can only be present when the
direction attribute is sendrecv or recvonly, and the parameters direction attribute is sendrecv or recvonly, and the parameters
describe the limitations of what the offerer or answerer accepts describe the limitations of what the offerer or answerer accepts
for receiving streams. for receiving streams.
o An offerer has to include the size of the de-interleaving buffer, o An offerer has to include the size of the de-interleaving buffer,
"sprop-deint-buf-req", in the offer for an interleaved H.264 "sprop-deint-buf-req", in the offer for an interleaved H.264
stream. To enable the offerer and answerer to inform each other stream. To enable the offerer and answerer to inform each other
about their capabilities for de-interleaving buffering in about their capabilities for de-interleaving buffering in
receiving streams, both parties are RECOMMENDED to include "deint- receiving streams, both parties are RECOMMENDED to include
buf-cap". For interleaved streams, it is also RECOMMENDED to "deint-buf-cap". For interleaved streams, it is also
consider offering multiple payload types with different buffering RECOMMENDED to consider offering multiple payload types with
requirements when the capabilities of the receiver are unknown. different buffering requirements when the capabilities of the
receiver are unknown.
o The "sprop-parameter-sets" or "sprop-level-parameter-sets" o The "sprop-parameter-sets" or "sprop-level-parameter-sets"
parameter, when present (included in the "a=fmtp" line of SDP or parameter, when present (included in the "a=fmtp" line of SDP or
conveyed using the "fmtp" source attribute as specified in section conveyed using the "fmtp" source attribute as specified in
6.3 of [9]), is used for out-of-band transport of parameter sets. section 6.3 of [9]), is used for out-of-band transport of
However, when out-of-band transport of parameter sets is used, parameter sets. However, when out-of-band transport of
parameter sets MAY still be additionally transported in-band. If parameter sets is used, parameter sets MAY still be additionally
neither "sprop-parameter-sets" nor "sprop-level-parameter-sets" is transported in-band. If neither "sprop-parameter-sets" nor
present, then only in-band transport of parameter sets is used. "sprop-level-parameter-sets" is present, then only in-band
transport of parameter sets is used.
An offer MAY include either or both of "sprop-parameter-sets" and An offer MAY include either or both of "sprop-parameter-sets"
"sprop-level-parameter-sets". An answer MAY include "sprop- and "sprop-level-parameter-sets". An answer MAY include "sprop-
parameter-sets", and MUST NOT include "sprop-level-parameter- parameter-sets", and MUST NOT include "sprop-level-parameter-
sets". sets".
If the answer includes "in-band-parameter-sets" equal to 1, then If the answer includes "in-band-parameter-sets" equal to 1, then
the sender MUST transmit parameter sets in-band. the sender MUST transmit parameter sets in-band.
Otherwise, the following applies. Otherwise, the following applies.
o When an offered payload type is accepted without level o When an offered payload type is accepted without level
downgrade, i.e. the default level is accepted, the following downgrade, i.e. the default level is accepted, the
applies. following applies.
o When there is a "sprop-parameter-sets" included in the o When there is a "sprop-parameter-sets" included in the
"a=fmtp" line of SDP, the answerer MUST be prepared to "a=fmtp" line of SDP, the answerer MUST be prepared to
use the parameter sets included in "sprop-parameter- use the parameter sets included in "sprop-parameter-
sets" for decoding the incoming NAL unit stream. sets" for decoding the incoming NAL unit stream.
o When there is a "sprop-parameter-sets" conveyed using o When there is a "sprop-parameter-sets" conveyed using
the "fmtp" source attribute as specified in section 6.3 the "fmtp" source attribute as specified in section
of [9], and the answerer understands the "fmtp" source 6.3 of [9], and the answerer understands the "fmtp"
attribute, it MUST be prepared to use the parameter source attribute, it MUST be prepared to use the
sets included in "sprop-parameter-sets" for decoding parameter sets included in "sprop-parameter-sets" for
the incoming NAL unit stream, and it MUST include decoding the incoming NAL unit stream, and it MUST
either "use-level-src-parameter-sets" equal to 1 or the include either "use-level-src-parameter-sets" equal to
"fmtp" source attribute in the answer. 1 or the "fmtp" source attribute in the answer.
o When there is a "sprop-parameter-sets" conveyed using o When there is a "sprop-parameter-sets" conveyed using
the "fmtp" source attribute as specified in section 6.3 the "fmtp" source attribute as specified in section
of [9], and the answerer does not understand the "fmtp" 6.3 of [9], and the answerer does not understand the
source attribute, the sender MUST transmit parameter "fmtp" source attribute, the sender MUST transmit
sets in-band, and the answerer MUST NOT include "use- parameter sets in-band, and the answerer MUST NOT
level-src-parameter-sets" equal to 1 or the "fmtp" include "use-level-src-parameter-sets" equal to 1 or
source attribute in the answer. the "fmtp" source attribute in the answer.
o When "sprop-parameter-sets" is not present, the sender o When "sprop-parameter-sets" is not present, the sender
MUST transmit parameter sets in-band. MUST transmit parameter sets in-band.
o The answerer MUST ignore "sprop-level-parameter-sets", o The answerer MUST ignore "sprop-level-parameter-sets",
when present (either included in the "a=fmtp" line of when present (either included in the "a=fmtp" line of
SDP or conveyed using the "fmtp" source attribute). SDP or conveyed using the "fmtp" source attribute).
o When level downgrade is in use, i.e., a level lower than the o When level downgrade is in use, i.e., a level lower than
default level offered is accepted, the following applies. the default level offered is accepted, the following
applies.
o The answerer MUST ignore "sprop-parameter-sets", when o The answerer MUST ignore "sprop-parameter-sets", when
present (either included in the "a=fmtp" line of SDP or present (either included in the "a=fmtp" line of SDP
conveyed using the "fmtp" source attribute). or conveyed using the "fmtp" source attribute).
o When "use-level-src-parameter-sets" equal to 1 and the o When "use-level-src-parameter-sets" equal to 1 and the
"fmtp" source attribute are not present in the answer "fmtp" source attribute are not present in the answer
for the accepted payload type, the answerer MUST ignore for the accepted payload type, the answerer MUST
"sprop-level-parameter-sets", when present, and the ignore "sprop-level-parameter-sets", when present, and
sender MUST transmit parameter sets in-band. the sender MUST transmit parameter sets in-band.
o When "use-level-src-parameter-sets" equal to 1 or the o When "use-level-src-parameter-sets" equal to 1 or the
"fmtp" source attribute is present in the answer for "fmtp" source attribute is present in the answer for
the accepted payload type, the answerer MUST be the accepted payload type, the answerer MUST be
prepared to use the parameter sets that are included in prepared to use the parameter sets that are included
"sprop-level-parameter-sets" for the accepted level, in "sprop-level-parameter-sets" for the accepted level,
when present, for decoding the incoming NAL unit stream, when present, for decoding the incoming NAL unit
and ignore all other parameter sets included in "sprop- stream, and ignore all other parameter sets included
level-parameter-sets". in "sprop-level-parameter-sets".
o When no parameter sets for the accepted level are o When no parameter sets for the accepted level are
present in the "sprop-level-parameter-sets", the sender present in the "sprop-level-parameter-sets", the
MUST transmit parameter sets in-band. sender MUST transmit parameter sets in-band.
The answerer MAY or MAY not include "sprop-parameter-sets", i.e., The answerer MAY or MAY not include "sprop-parameter-sets", i.e.,
the answerer MAY use either out-of-band or in-band transport of the answerer MAY use either out-of-band or in-band transport of
parameter sets for the stream it is sending, regardless of parameter sets for the stream it is sending, regardless of
whether out-of-band parameter sets transport has been used in the whether out-of-band parameter sets transport has been used in
offerer-to-answerer direction. When the offer includes "in-band- the offerer-to-answerer direction. When the offer includes "in-
parameter-sets" equal to 1, the answerer MUST not include "sprop- band-parameter-sets" equal to 1, the answerer MUST NOT include
parameter-sets" and MUST transmit parameter sets in-band. All "sprop-parameter-sets" and MUST transmit parameter sets in-band.
parameter sets included in the "sprop-parameter-sets", when All parameter sets included in the "sprop-parameter-sets", when
present, for the accepted payload type in an answer MUST be present, for the accepted payload type in an answer MUST be
associated with the accepted level, as indicated by the profile- associated with the accepted level, as indicated by the profile-
level-id in the answer for the accepted payload type. level-id in the answer for the accepted payload type.
Parameter sets included in "sprop-parameter-sets" in an answer Parameter sets included in "sprop-parameter-sets" in an answer
are independent of those parameter sets included in the offer, as are independent of those parameter sets included in the offer,
they are used for decoding two different video streams, one from as they are used for decoding two different video streams, one
the answerer to the offerer, and the other in the opposite from the answerer to the offerer, and the other in the opposite
direction. The offerer MUST be prepared to use the parameter direction. The offerer MUST be prepared to use the parameter
sets included in the answer's "sprop-parameter-sets", when sets included in the answer's "sprop-parameter-sets", when
present, for decoding the incoming NAL unit stream. present, for decoding the incoming NAL unit stream.
When "sprop-parameter-sets" or "sprop-level-parameter-sets" is When "sprop-parameter-sets" or "sprop-level-parameter-sets" is
conveyed using the "fmtp" source attribute in as specified in conveyed using the "fmtp" source attribute in as specified in
section 6.3 of [9], the receiver of the parameters MUST store the section 6.3 of [9], the receiver of the parameters MUST store
parameter sets included in the "sprop-parameter-sets" or "sprop- the parameter sets included in the "sprop-parameter-sets" or
level-parameter-sets" for the accepted level and associate them "sprop-level-parameter-sets" for the accepted level and
to the source given as a part of the "fmtp" source attribute. associate them to the source given as a part of the "fmtp"
Parameter sets associated with one source MUST only be used to source attribute. Parameter sets associated with one source
decode NAL units conveyed in RTP packets from the same source. MUST only be used to decode NAL units conveyed in RTP packets
When this mechanism is in use, SSRC collision detection and from the same source. When this mechanism is in use, SSRC
resolution MUST be performed as specified in [9]. collision detection and resolution MUST be performed as
specified in [9].
Informative note: Conveyance of "sprop-parameter-sets" and Informative note: Conveyance of "sprop-parameter-sets" and
"sprop-level-parameter-sets" using the "fmtp" source attribute "sprop-level-parameter-sets" using the "fmtp" source
may be used in topologies like Topo-Video-switch-MCU [29] to attribute may be used in topologies like Topo-Video-switch-
enable out-of-band transport of parameter sets. MCU [29] to enable out-of-band transport of parameter sets.
For streams being delivered over multicast, the following rules apply: For streams being delivered over multicast, the following rules
apply:
o The media format configuration is identified by the same o The media format configuration is identified by the same
parameters as above for unicast (i.e. "profile-level-id" and parameters as above for unicast (i.e. "profile-level-id" and
"packetization-mode", when present). These media format "packetization-mode", when present). These media format
configuration parameters (including the level part of "profile- configuration parameters (including the level part of "profile-
level-id") MUST be used symmetrically; i.e., the answerer MUST level-id") MUST be used symmetrically; i.e., the answerer MUST
either maintain all configuration parameters or remove the media either maintain all configuration parameters or remove the media
format (payload type) completely. Note that this implies that the format (payload type) completely. Note that this implies that
level part of "profile-level-id" for Offer/Answer in multicast is the level part of "profile-level-id" for Offer/Answer in
not downgradable. multicast is not downgradable.
To simplify handling and matching of these configurations, the To simplify handling and matching of these configurations, the
same RTP payload type number used in the offer SHOULD also be same RTP payload type number used in the offer SHOULD also be
used in the answer, as specified in [8]. An answer MUST NOT used in the answer, as specified in [8]. An answer MUST NOT
contain a payload type number used in the offer unless the contain a payload type number used in the offer unless the
configuration is the same as in the offer. configuration is the same as in the offer.
o Parameter sets received MUST be associated with the originating o Parameter sets received MUST be associated with the originating
source, and MUST be only used in decoding the incoming NAL unit source, and MUST be only used in decoding the incoming NAL unit
stream from the same source. stream from the same source.
o The rules for other parameters are the same as above for unicast. o The rules for other parameters are the same as above for unicast.
Table 6 lists the interpretation of all the 20 media type parameters Table 6 lists the interpretation of all the 20 media type
that MUST be used for the different direction attributes. parameters that MUST be used for the different direction attributes.
Table 6. Interpretation of parameters for different direction Table 6. Interpretation of parameters for different direction
attributes. attributes.
sendonly --+ sendonly --+
recvonly --+ | recvonly --+ |
sendrecv --+ | | sendrecv --+ | |
| | | | | |
profile-level-id C C P profile-level-id C C P
packetization-mode C C P packetization-mode C C P
skipping to change at page 63, line 44 skipping to change at page 65, line 27
Legend: Legend:
C: configuration for sending and receiving streams C: configuration for sending and receiving streams
P: properties of the stream to be sent P: properties of the stream to be sent
R: receiver capabilities R: receiver capabilities
S: out-of-band parameter sets S: out-of-band parameter sets
-: not usable, when present SHOULD be ignored -: not usable, when present SHOULD be ignored
Parameters used for declaring receiver capabilities are in general Parameters used for declaring receiver capabilities are in general
downgradable; i.e., they express the upper limit for a sender's downgradable; i.e., they express the upper limit for a sender's
possible behavior. Thus a sender MAY select to set its encoder using possible behavior. Thus a sender MAY select to set its encoder
only lower/less or equal values of these parameters. using only lower/less or equal values of these parameters.
Parameters declaring a configuration point are not downgradable, with Parameters declaring a configuration point are not downgradable,
the exception of the level part of the "profile-level-id" parameter with the exception of the level part of the "profile-level-id"
for unicast usage. This expresses values a receiver expects to be parameter for unicast usage. This expresses values a receiver
used and must be used verbatim on the sender side. expects to be used and must be used verbatim on the sender side.
When a sender's capabilities are declared, and non-downgradable When a sender's capabilities are declared, and non-downgradable
parameters are used in this declaration, then these parameters parameters are used in this declaration, then these parameters
express a configuration that is acceptable for the sender to receive express a configuration that is acceptable for the sender to
streams. In order to achieve high interoperability levels, it is receive streams. In order to achieve high interoperability levels,
often advisable to offer multiple alternative configurations; e.g., it is often advisable to offer multiple alternative configurations;
for the packetization mode. It is impossible to offer multiple e.g., for the packetization mode. It is impossible to offer
configurations in a single payload type. Thus, when multiple multiple configurations in a single payload type. Thus, when
configuration offers are made, each offer requires its own RTP multiple configuration offers are made, each offer requires its own
payload type associated with the offer. RTP payload type associated with the offer.
A receiver SHOULD understand all media type parameters, even if it A receiver SHOULD understand all media type parameters, even if it
only supports a subset of the payload format's functionality. This only supports a subset of the payload format's functionality. This
ensures that a receiver is capable of understanding when an offer to ensures that a receiver is capable of understanding when an offer
receive media can be downgraded to what is supported by the receiver to receive media can be downgraded to what is supported by the
of the offer. receiver of the offer.
An answerer MAY extend the offer with additional media format An answerer MAY extend the offer with additional media format
configurations. However, to enable their usage, in most cases a configurations. However, to enable their usage, in most cases a
second offer is required from the offerer to provide the stream second offer is required from the offerer to provide the stream
property parameters that the media sender will use. This also has property parameters that the media sender will use. This also has
the effect that the offerer has to be able to receive this media the effect that the offerer has to be able to receive this media
format configuration, not only to send it. format configuration, not only to send it.
If an offerer wishes to have non-symmetric capabilities between If an offerer wishes to have non-symmetric capabilities between
sending and receiving, the offerer should offer different RTP sending and receiving, the offerer should offer different RTP
sessions; i.e., different media lines declared as "recvonly" and sessions; i.e., different media lines declared as "recvonly" and
"sendonly", respectively. This may have further implications on the "sendonly", respectively. This may have further implications on
system. the system.
8.2.3. Usage in Declarative Session Descriptions 8.2.3. Usage in Declarative Session Descriptions
When H.264 over RTP is offered with SDP in a declarative style, as in When H.264 over RTP is offered with SDP in a declarative style, as
RTSP [27] or SAP [28], the following considerations are necessary. in RTSP [27] or SAP [28], the following considerations are
necessary.
o All parameters capable of indicating both stream properties and o All parameters capable of indicating both stream properties and
receiver capabilities are used to indicate only stream properties. receiver capabilities are used to indicate only stream
For example, in this case, the parameter "profile-level-id" properties. For example, in this case, the parameter "profile-
declares only the values used by the stream, not the capabilities level-id" declares only the values used by the stream, not the
for receiving streams. This results in that the following capabilities for receiving streams. This results in that the
interpretation of the parameters MUST be used: following interpretation of the parameters MUST be used:
Declaring actual configuration or stream properties: Declaring actual configuration or stream properties:
- profile-level-id - profile-level-id
- packetization-mode - packetization-mode
- sprop-interleaving-depth - sprop-interleaving-depth
- sprop-deint-buf-req - sprop-deint-buf-req
- sprop-max-don-diff - sprop-max-don-diff
- sprop-init-buf-time - sprop-init-buf-time
skipping to change at page 65, line 37 skipping to change at page 67, line 23
o A receiver of the SDP is required to support all parameters and o A receiver of the SDP is required to support all parameters and
values of the parameters provided; otherwise, the receiver MUST values of the parameters provided; otherwise, the receiver MUST
reject (RTSP) or not participate in (SAP) the session. It falls reject (RTSP) or not participate in (SAP) the session. It falls
on the creator of the session to use values that are expected to on the creator of the session to use values that are expected to
be supported by the receiving application. be supported by the receiving application.
8.3. Examples 8.3. Examples
An SDP Offer/Answer exchange wherein both parties are expected to An SDP Offer/Answer exchange wherein both parties are expected to
both send and receive could look like the following. Only the media both send and receive could look like the following. Only the
codec specific parts of the SDP are shown. Some lines are wrapped media codec specific parts of the SDP are shown. Some lines are
due to text constraints. wrapped due to text constraints.
Offerer -> Answerer SDP message: Offerer -> Answerer SDP message:
m=video 49170 RTP/AVP 100 99 98 m=video 49170 RTP/AVP 100 99 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; packetization-mode=0; a=fmtp:98 profile-level-id=42A01E; packetization-mode=0;
sprop-parameter-sets=<parameter sets data#0> sprop-parameter-sets=<parameter sets data#0>
a=rtpmap:99 H264/90000 a=rtpmap:99 H264/90000
a=fmtp:99 profile-level-id=42A01E; packetization-mode=1; a=fmtp:99 profile-level-id=42A01E; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#1> sprop-parameter-sets=<parameter sets data#1>
a=rtpmap:100 H264/90000 a=rtpmap:100 H264/90000
a=fmtp:100 profile-level-id=42A01E; packetization-mode=2; a=fmtp:100 profile-level-id=42A01E; packetization-mode=2;
sprop-parameter-sets=<parameter sets data#2>; sprop-parameter-sets=<parameter sets data#2>;
sprop-interleaving-depth=45; sprop-deint-buf-req=64000; sprop-interleaving-depth=45; sprop-deint-buf-req=64000;
sprop-init-buf-time=102478; deint-buf-cap=128000 sprop-init-buf-time=102478; deint-buf-cap=128000
The above offer presents the same codec configuration in three The above offer presents the same codec configuration in three
different packetization formats. PT 98 represents single NALU mode, different packetization formats. PT 98 represents single NALU mode,
PT 99 represents non-interleaved mode, and PT 100 indicates the PT 99 represents non-interleaved mode, and PT 100 indicates the
interleaved mode. In the interleaved mode case, the interleaving interleaved mode. In the interleaved mode case, the interleaving
parameters that the offerer would use if the answer indicates support parameters that the offerer would use if the answer indicates
for PT 100 are also included. In all three cases the parameter support for PT 100 are also included. In all three cases the
"sprop-parameter-sets" conveys the initial parameter sets that are parameter "sprop-parameter-sets" conveys the initial parameter sets
required by the answerer when receiving a stream from the offerer that are required by the answerer when receiving a stream from the
when this configuration is accepted. Note that the value for "sprop- offerer when this configuration is accepted. Note that the value
parameter-sets" could be different for each payload type. for "sprop-parameter-sets" could be different for each payload type.
Answerer -> Offerer SDP message: Answerer -> Offerer SDP message:
m=video 49170 RTP/AVP 100 99 97 m=video 49170 RTP/AVP 100 99 97
a=rtpmap:97 H264/90000 a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=42A01E; packetization-mode=0; a=fmtp:97 profile-level-id=42A01E; packetization-mode=0;
sprop-parameter-sets=<parameter sets data#3> sprop-parameter-sets=<parameter sets data#3>
a=rtpmap:99 H264/90000 a=rtpmap:99 H264/90000
a=fmtp:99 profile-level-id=42A01E; packetization-mode=1; a=fmtp:99 profile-level-id=42A01E; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#4>; sprop-parameter-sets=<parameter sets data#4>;
max-rcmd-nalu-size=3980 max-rcmd-nalu-size=3980
a=rtpmap:100 H264/90000 a=rtpmap:100 H264/90000
a=fmtp:100 profile-level-id=42A01E; packetization-mode=2; a=fmtp:100 profile-level-id=42A01E; packetization-mode=2;
sprop-parameter-sets=<parameter sets data#5>; sprop-parameter-sets=<parameter sets data#5>;
sprop-interleaving-depth=60; sprop-interleaving-depth=60;
sprop-deint-buf-req=86000; sprop-init-buf-time=156320; sprop-deint-buf-req=86000; sprop-init-buf-time=156320;
deint-buf-cap=128000; max-rcmd-nalu-size=3980 deint-buf-cap=128000; max-rcmd-nalu-size=3980
As the Offer/Answer negotiation covers both sending and receiving As the Offer/Answer negotiation covers both sending and receiving
streams, an offer indicates the exact parameters for what the offerer streams, an offer indicates the exact parameters for what the
is willing to receive, whereas the answer indicates the same for what offerer is willing to receive, whereas the answer indicates the
the answerer accepts to receive. In this case the offerer declared same for what the answerer accepts to receive. In this case the
that it is willing to receive payload type 98. The answerer accepts offerer declared that it is willing to receive payload type 98.
this by declaring an equivalent payload type 97; i.e., it has The answerer accepts this by declaring an equivalent payload type
identical values for the two parameters "profile-level-id" and 97; i.e., it has identical values for the two parameters "profile-
"packetization-mode" (since "packetization-mode" is equal to 0, level-id" and "packetization-mode" (since "packetization-mode" is
"sprop-deint-buf-req" is not present). As the offered payload type equal to 0, "sprop-deint-buf-req" is not present). As the offered
98 is accepted, the answerer needs to store parameter sets included payload type 98 is accepted, the answerer needs to store parameter
in sprop-parameter-sets=<parameter sets data#0> in case the offer sets included in sprop-parameter-sets=<parameter sets data#0> in
finally decides to use this configuration. In the answer, the case the offer finally decides to use this configuration. In the
answerer includes the parameter sets in sprop-parameter- answer, the answerer includes the parameter sets in sprop-
sets=<parameter sets data#3> that the answerer would use in the parameter-sets=<parameter sets data#3> that the answerer would use
stream sent from the answerer if this configuration is finally used. in the stream sent from the answerer if this configuration is
finally used.
The answerer also accepts the reception of the two configurations The answerer also accepts the reception of the two configurations
that payload types 99 and 100 represent. Again, the answerer needs that payload types 99 and 100 represent. Again, the answerer needs
to store parameter sets included in sprop-parameter-sets=<parameter to store parameter sets included in sprop-parameter-sets=<parameter
sets data#1> and sprop-parameter-sets=<parameter sets data#2> in case sets data#1> and sprop-parameter-sets=<parameter sets data#2> in
the offer finally decides to use either of these two configurations. case the offer finally decides to use either of these two
The answerer provides the initial parameter sets for the answerer-to- configurations. The answerer provides the initial parameter sets
offerer direction, i.e. the parameter sets in sprop-parameter- for the answerer-to-offerer direction, i.e. the parameter sets in
sets=<parameter sets data#4> and sprop-parameter-sets=<parameter sets sprop-parameter-sets=<parameter sets data#4> and sprop-parameter-
data#5>, for payload types 99 and 100, respectively, that it will use sets=<parameter sets data#5>, for payload types 99 and 100,
to send the payload types. The answerer also provides the offerer respectively, that it will use to send the payload types. The
with its memory limit for de-interleaving operations by providing a answerer also provides the offerer with its memory limit for de-
"deint-buf-cap" parameter. This is only useful if the offerer interleaving operations by providing a "deint-buf-cap" parameter.
decides on making a second offer, where it can take the new value This is only useful if the offerer decides on making a second offer,
into account. The "max-rcmd-nalu-size" indicates that the answerer where it can take the new value into account. The "max-rcmd-nalu-
can efficiently process NALUs up to the size of 3980 bytes. However, size" indicates that the answerer can efficiently process NALUs up
there is no guarantee that the network supports this size. to the size of 3980 bytes. However, there is no guarantee that the
network supports this size.
In the following example, the offer is accepted without level In the following example, the offer is accepted without level
downgrading (i.e. the default level, 3.0, is accepted), and both downgrading (i.e. the default level, 3.0, is accepted), and both
"sprop-parameter-sets" and "sprop-level-parameter-sets" are present "sprop-parameter-sets" and "sprop-level-parameter-sets" are present
in the offer. The answerer must ignore sprop-level-parameter- in the offer. The answerer must ignore sprop-level-parameter-
sets=<parameter sets data#1> and store parameter sets in sprop- sets=<parameter sets data#1> and store parameter sets in sprop-
parameter-sets=<parameter sets data#0> for decoding the incoming NAL parameter-sets=<parameter sets data#0> for decoding the incoming
unit stream. The offerer must store the parameter sets in sprop- NAL unit stream. The offerer must store the parameter sets in
parameter-sets=<parameter sets data#2> in the answer for decoding the sprop-parameter-sets=<parameter sets data#2> in the answer for
incoming NAL unit stream. Note that in this example, parameter sets decoding the incoming NAL unit stream. Note that in this example,
in sprop-parameter-sets=<parameter sets data#2> must be associated parameter sets in sprop-parameter-sets=<parameter sets data#2> must
with level 3.0. be associated with level 3.0.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#0>; sprop-parameter-sets=<parameter sets data#0>;
sprop-level-parameter-sets=<parameter sets data#1> sprop-level-parameter-sets=<parameter sets data#1>
Answer SDP: Answer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#2> sprop-parameter-sets=<parameter sets data#2>
In the following example, the offer (Baseline profile, level 1.1) is In the following example, the offer (Baseline profile, level 1.1)
accepted with level downgrading (the accepted level is 1b), and both is accepted with level downgrading (the accepted level is 1b), and
"sprop-parameter-sets" and "sprop-level-parameter-sets" are present both "sprop-parameter-sets" and "sprop-level-parameter-sets" are
in the offer. The answerer must ignore sprop-parameter- present in the offer. The answerer must ignore sprop-parameter-
sets=<parameter sets data#0> and all parameter sets not for the sets=<parameter sets data#0> and all parameter sets not for the
accepted level (level 1b) in sprop-level-parameter-sets=<parameter accepted level (level 1b) in sprop-level-parameter-sets=<parameter
sets data#1>, and must store parameter sets for the accepted level sets data#1>, and must store parameter sets for the accepted level
(level 1b) in sprop-level-parameter-sets=<parameter sets data#1> for (level 1b) in sprop-level-parameter-sets=<parameter sets data#1>
decoding the incoming NAL unit stream. The offerer must store the for decoding the incoming NAL unit stream. The offerer must store
parameter sets in sprop-parameter-sets=<parameter sets data#2> in the the parameter sets in sprop-parameter-sets=<parameter sets data#2>
answer for decoding the incoming NAL unit stream. Note that in this in the answer for decoding the incoming NAL unit stream. Note that
example, parameter sets in sprop-parameter-sets=<parameter sets in this example, parameter sets in sprop-parameter-sets=<parameter
data#2> must be associated with level 1b. sets data#2> must be associated with level 1b.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A00B; //Baseline profile, Level 1.1 a=fmtp:98 profile-level-id=42A00B; //Baseline profile, Level 1.1
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#0>; sprop-parameter-sets=<parameter sets data#0>;
sprop-level-parameter-sets=<parameter sets data#1> sprop-level-parameter-sets=<parameter sets data#1>
Answer SDP: Answer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42B00B; //Baseline profile, Level 1b a=fmtp:98 profile-level-id=42B00B; //Baseline profile, Level 1b
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#2>; sprop-parameter-sets=<parameter sets data#2>;
use-level-src-parameter-sets=1 use-level-src-parameter-sets=1
In the following example, the offer (Baseline profile, level 1.1) is In the following example, the offer (Baseline profile, level 1.1)
accepted with level downgrading (the accepted level is 1b), and both is accepted with level downgrading (the accepted level is 1b), and
"sprop-parameter-sets" and "sprop-level-parameter-sets" are present both "sprop-parameter-sets" and "sprop-level-parameter-sets" are
in the offer. However, the answerer is a legacy RFC 3984 present in the offer. However, the answerer is a legacy RFC 3984
implementation and does not understand "sprop-level-parameter-sets", implementation and does not understand "sprop-level-parameter-sets",
hence it does not include "use-level-src-parameter-sets" (which the hence it does not include "use-level-src-parameter-sets" (which the
answerer does not understand, either) in the answer. Therefore, the answerer does not understand, either) in the answer. Therefore,
answerer must ignore both sprop-parameter-sets=<parameter sets the answerer must ignore both sprop-parameter-sets=<parameter sets
data#0> and sprop-level-parameter-sets=<parameter sets data#1>, and data#0> and sprop-level-parameter-sets=<parameter sets data#1>, and
the offerer must transport parameter sets in-band. the offerer must transport parameter sets in-band.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A00B; //Baseline profile, Level 1.1 a=fmtp:98 profile-level-id=42A00B; //Baseline profile, Level 1.1
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#0>; sprop-parameter-sets=<parameter sets data#0>;
skipping to change at page 69, line 22 skipping to change at page 71, line 13
Answer SDP: Answer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42B00B; //Baseline profile, Level 1b a=fmtp:98 profile-level-id=42B00B; //Baseline profile, Level 1b
packetization-mode=1 packetization-mode=1
In the following example, the offer is accepted without level In the following example, the offer is accepted without level
downgrading, and "sprop-parameter-sets" is present in the offer. downgrading, and "sprop-parameter-sets" is present in the offer.
Parameter sets in sprop-parameter-sets=<parameter sets data#0> must Parameter sets in sprop-parameter-sets=<parameter sets data#0> must
be stored and used used by the encoder of the offerer and the decoder be stored and used used by the encoder of the offerer and the
of the answerer, and parameter sets in sprop-parameter- decoder of the answerer, and parameter sets in sprop-parameter-
sets=<parameter sets data#1>must be used by the encoder of the sets=<parameter sets data#1>must be used by the encoder of the
answerer and the decoder of the offerer. Note that sprop-parameter- answerer and the decoder of the offerer. Note that sprop-
sets=<parameter sets data#0> is basically independent of sprop- parameter-sets=<parameter sets data#0> is basically independent of
parameter-sets=<parameter sets data#1>. sprop-parameter-sets=<parameter sets data#1>.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#0> sprop-parameter-sets=<parameter sets data#0>
Answer SDP: Answer SDP:
skipping to change at page 70, line 22 skipping to change at page 72, line 13
Answer SDP: Answer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1 packetization-mode=1
In the following example, the offer is accepted with level In the following example, the offer is accepted with level
downgrading and "sprop-parameter-sets" is present in the offer. As downgrading and "sprop-parameter-sets" is present in the offer. As
sprop-parameter-sets=<parameter sets data#0> contains level_idc sprop-parameter-sets=<parameter sets data#0> contains level_idc
indicating Level 3.0, therefore cannot be used as the answerer wants indicating Level 3.0, therefore cannot be used as the answerer
Level 2.0 and must be ignored by the answerer, and in-band parameter wants Level 2.0 and must be ignored by the answerer, and in-band
sets must be used. parameter sets must be used.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1; packetization-mode=1;
sprop-parameter-sets=<parameter sets data#0> sprop-parameter-sets=<parameter sets data#0>
Answer SDP: Answer SDP:
skipping to change at page 71, line 13 skipping to change at page 73, line 4
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1 packetization-mode=1
Answer SDP: Answer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A014; //Baseline profile, Level 2.0 a=fmtp:98 profile-level-id=42A014; //Baseline profile, Level 2.0
packetization-mode=1 packetization-mode=1
In the following example, the offerer is a Multipoint Control Unit In the following example, the offerer is a Multipoint Control Unit
(MCU) in a Topo-Video-switch-MCU like topology [29], offering (MCU) in a Topo-Video-switch-MCU like topology [29], offering
parameter sets received (using out-of-band transport) from three parameter sets received (using out-of-band transport) from three
other participants B, C, and D, and receiving parameter sets from the other participants B, C, and D, and receiving parameter sets from
participant A, which is the answerer. The participants are the participant A, which is the answerer. The participants are
identified by their values of CNAME, which are mapped to different identified by their values of CNAME, which are mapped to different
SSRC values. The same codec configuration is used by all the four SSRC values. The same codec configuration is used by all the four
participants. The participant A stores and associates the parameter participants. The participant A stores and associates the
sets included in <parameter sets data#B>, <parameter sets data#C>, parameter sets included in <parameter sets data#B>, <parameter sets
and <parameter sets data#D> to participants B, C, and D, respectively, data#C>, and <parameter sets data#D> to participants B, C, and D,
and uses <parameter sets data#B> for decoding NAL units carried in respectively, and uses <parameter sets data#B> for decoding NAL
RTP packets originated from participant B only, uses <parameter sets units carried in RTP packets originated from participant B only,
data#C> for decoding NAL units carried in RTP packets originated from uses <parameter sets data#C> for decoding NAL units carried in RTP
participant C only, and uses <parameter sets data#D> for decoding NAL packets originated from participant C only, and uses <parameter
units carried in RTP packets originated from participant D only. sets data#D> for decoding NAL units carried in RTP packets
originated from participant D only.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
a=ssrc:SSRC-B cname:CNAME-B a=ssrc:SSRC-B cname:CNAME-B
a=ssrc:SSRC-C cname:CNAME-C a=ssrc:SSRC-C cname:CNAME-C
a=ssrc:SSRC-D cname:CNAME-D a=ssrc:SSRC-D cname:CNAME-D
a=ssrc:SSRC-B fmtp:98 a=ssrc:SSRC-B fmtp:98
sprop-parameter-sets=<parameter sets data#B> sprop-parameter-sets=<parameter sets data#B>
a=ssrc:SSRC-C fmtp:98 a=ssrc:SSRC-C fmtp:98
skipping to change at page 72, line 15 skipping to change at page 74, line 11
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0 a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1 packetization-mode=1
8.4. Parameter Set Considerations 8.4. Parameter Set Considerations
The H.264 parameter sets are a fundamental part of the video codec The H.264 parameter sets are a fundamental part of the video codec
and vital to its operation; see section 1.2. Due to their and vital to its operation; see section 1.2. Due to their
characteristics and their importance for the decoding process, lost characteristics and their importance for the decoding process, lost
or erroneously transmitted parameter sets can hardly be concealed or erroneously transmitted parameter sets can hardly be concealed
locally at the receiver. A reference to a corrupt parameter set has locally at the receiver. A reference to a corrupt parameter set
normally fatal results to the decoding process. Corruption could has normally fatal results to the decoding process. Corruption
occur, for example, due to the erroneous transmission or loss of a could occur, for example, due to the erroneous transmission or loss
parameter set NAL unit, but also due to the untimely transmission of of a parameter set NAL unit, but also due to the untimely
a parameter set update. A parameter set update refers to a change of transmission of a parameter set update. A parameter set update
at least one parameter in a picture parameter set or sequence refers to a change of at least one parameter in a picture parameter
parameter set for which the picture parameter set or sequence set or sequence parameter set for which the picture parameter set
parameter set identifier remains unchanged. Therefore, the following or sequence parameter set identifier remains unchanged. Therefore,
recommendations are provided as a guideline for the implementer of the following recommendations are provided as a guideline for the
the RTP sender. implementer of the RTP sender.
Parameter set NALUs can be transported using three different Parameter set NALUs can be transported using three different
principles: principles:
A. Using a session control protocol (out-of-band) prior to the actual A. Using a session control protocol (out-of-band) prior to the
RTP session. actual RTP session.
B. Using a session control protocol (out-of-band) during an ongoing B. Using a session control protocol (out-of-band) during an ongoing
RTP session. RTP session.
C. Within the RTP packet stream in the payload (in-band) during an C. Within the RTP packet stream in the payload (in-band) during an
ongoing RTP session. ongoing RTP session.
It is recommended to implement principles A and B within a session It is recommended to implement principles A and B within a session
control protocol. SIP and SDP can be used as described in the SDP control protocol. SIP and SDP can be used as described in the SDP
Offer/Answer model and in the previous sections of this memo. Offer/Answer model and in the previous sections of this memo.
Section 8.2.2 includes a detailed discussion on transport of Section 8.2.2 includes a detailed discussion on transport of
parameter sets in-band or out-of-band in SDP Offer/Answer using media parameter sets in-band or out-of-band in SDP Offer/Answer using
type parameters "sprop-parameter-sets", "sprop-level-parameter-sets", media type parameters "sprop-parameter-sets", "sprop-level-
"use-level-src-parameter-sets" and "in-band-parameter-sets". This parameter-sets", "use-level-src-parameter-sets" and "in-band-
section contains guidelines on how principles A and B should be parameter-sets". This section contains guidelines on how
implemented within session control protocols. It is independent of principles A and B should be implemented within session control
the particular protocol used. Principle C is supported by the RTP protocols. It is independent of the particular protocol used.
payload format defined in this specification. There are topologies Principle C is supported by the RTP payload format defined in this
like Topo-Video-switch-MCU [29] for which the use of principle C may specification. There are topologies like Topo-Video-switch-MCU [29]
be desirable. for which the use of principle C may be desirable.
If in-band signaling of parameter sets is used, the picture and If in-band signaling of parameter sets is used, the picture and
sequence parameter set NALUs SHOULD be transmitted in the RTP payload sequence parameter set NALUs SHOULD be transmitted in the RTP
using a reliable method of delivering of RTP (see below), as a loss payload using a reliable method of delivering of RTP (see below),
of a parameter set of either type will likely prevent decoding of a as a loss of a parameter set of either type will likely prevent
considerable portion of the corresponding RTP packet stream. decoding of a considerable portion of the corresponding RTP packet
stream.
If in-band signaling of parameter sets is used, the sender SHOULD If in-band signaling of parameter sets is used, the sender SHOULD
take the error characteristics into account and use mechanisms to take the error characteristics into account and use mechanisms to
provide a high probability for delivering the parameter sets provide a high probability for delivering the parameter sets
correctly. Mechanisms that increase the probability for a correct correctly. Mechanisms that increase the probability for a correct
reception include packet repetition, FEC, and retransmission. The reception include packet repetition, FEC, and retransmission. The
use of an unreliable, out-of-band control protocol has similar use of an unreliable, out-of-band control protocol has similar
disadvantages as the in-band signaling (possible loss) and, in disadvantages as the in-band signaling (possible loss) and, in
addition, may also lead to difficulties in the synchronization (see addition, may also lead to difficulties in the synchronization (see
below). Therefore, it is NOT RECOMMENDED. below). Therefore, it is NOT RECOMMENDED.
Parameter sets MAY be added or updated during the lifetime of a Parameter sets MAY be added or updated during the lifetime of a
session using principles B and C. It is required that parameter sets session using principles B and C. It is required that parameter
are present at the decoder prior to the NAL units that refer to them. sets are present at the decoder prior to the NAL units that refer
Updating or adding of parameter sets can result in further problems, to them. Updating or adding of parameter sets can result in
and therefore the following recommendations should be considered. further problems, and therefore the following recommendations
should be considered.
- When parameter sets are added or updated, care SHOULD be taken to - When parameter sets are added or updated, care SHOULD be taken
ensure that any parameter set is delivered prior to its usage. to ensure that any parameter set is delivered prior to its usage.
When new parameter sets are added, previously unused parameter set When new parameter sets are added, previously unused parameter
identifiers are used. It is common that no synchronization is set identifiers are used. It is common that no synchronization
present between out-of-band signaling and in-band traffic. If is present between out-of-band signaling and in-band traffic.
out-of-band signaling is used, it is RECOMMENDED that a sender If out-of-band signaling is used, it is RECOMMENDED that a
does not start sending NALUs requiring the added or updated sender does not start sending NALUs requiring the added or
parameter sets prior to acknowledgement of delivery from the updated parameter sets prior to acknowledgement of delivery from
signaling protocol. the signaling protocol.
- When parameter sets are updated, the following synchronization - When parameter sets are updated, the following synchronization
issue should be taken into account. When overwriting a parameter issue should be taken into account. When overwriting a
set at the receiver, the sender has to ensure that the parameter parameter set at the receiver, the sender has to ensure that the
set in question is not needed by any NALU present in the network parameter set in question is not needed by any NALU present in
or receiver buffers. Otherwise, decoding with a wrong parameter the network or receiver buffers. Otherwise, decoding with a
set may occur. To lessen this problem, it is RECOMMENDED either wrong parameter set may occur. To lessen this problem, it is
to overwrite only those parameter sets that have not been used for RECOMMENDED either to overwrite only those parameter sets that
a sufficiently long time (to ensure that all related NALUs have have not been used for a sufficiently long time (to ensure that
been consumed), or to add a new parameter set instead (which may all related NALUs have been consumed), or to add a new parameter
have negative consequences for the efficiency of the video coding). set instead (which may have negative consequences for the
efficiency of the video coding).
Informative note: In some topologies like Topo-Video-switch- Informative note: In some topologies like Topo-Video-switch-
MCU [29] the origin of the whole set of parameter sets may MCU [29] the origin of the whole set of parameter sets may
come from multiple sources that may use non-unique parameter come from multiple sources that may use non-unique parameter
sets identifiers. In this case an offer may overwrite an sets identifiers. In this case an offer may overwrite an
existing parameter set if no other mechanism that enables existing parameter set if no other mechanism that enables
uniqueness of the parameter sets in the out-of-band channel uniqueness of the parameter sets in the out-of-band channel
exists. exists.
- In a multiparty session, one participant MUST associate parameter - In a multiparty session, one participant MUST associate
sets coming from different sources with the source identification parameter sets coming from different sources with the source
whenever possible, e.g. by conveying out-of-band transported identification whenever possible, e.g. by conveying out-of-band
parameter sets, as different sources typically use independent transported parameter sets, as different sources typically use
parameter set identifier value spaces. independent parameter set identifier value spaces.
- Adding or modifying parameter sets by using both principles B and - Adding or modifying parameter sets by using both principles B
C in the same RTP session may lead to inconsistencies of the and C in the same RTP session may lead to inconsistencies of the
parameter sets because of the lack of synchronization between the parameter sets because of the lack of synchronization between
control and the RTP channel. Therefore, principles B and C MUST the control and the RTP channel. Therefore, principles B and C
NOT both be used in the same session unless sufficient MUST NOT both be used in the same session unless sufficient
synchronization can be provided. synchronization can be provided.
In some scenarios (e.g., when only the subset of this payload format In some scenarios (e.g., when only the subset of this payload
specification corresponding to H.241 is used) or topologies, it is format specification corresponding to H.241 is used) or topologies,
not possible to employ out-of-band parameter set transmission. In it is not possible to employ out-of-band parameter set transmission.
this case, parameter sets have to be transmitted in-band. Here, the In this case, parameter sets have to be transmitted in-band. Here,
synchronization with the non-parameter-set-data in the bitstream is the synchronization with the non-parameter-set-data in the
implicit, but the possibility of a loss has to be taken into account. bitstream is implicit, but the possibility of a loss has to be
The loss probability should be reduced using the mechanisms discussed taken into account. The loss probability should be reduced using
above. In case a loss of a parameter set is detected, recovery may the mechanisms discussed above. In case a loss of a parameter set
be achieved by using a Decoder Refresh Point procedure, for example, is detected, recovery may be achieved by using a Decoder Refresh
using RTCP feedback Full Intra Request (FIR) [30]. Two example Point procedure, for example, using RTCP feedback Full Intra
Decoder Refresh Point procedures are provided in the informative Request (FIR) [30]. Two example Decoder Refresh Point procedures
Section 8.5. are provided in the informative Section 8.5.
- When parameter sets are initially provided using principle A and - When parameter sets are initially provided using principle A and
then later added or updated in-band (principle C), there is a risk then later added or updated in-band (principle C), there is a
associated with updating the parameter sets delivered out-of-band. risk associated with updating the parameter sets delivered out-
If receivers miss some in-band updates (for example, because of a of-band. If receivers miss some in-band updates (for example,
loss or a late tune-in), those receivers attempt to decode the because of a loss or a late tune-in), those receivers attempt to
bitstream using out-dated parameters. It is therefore RECOMMENDED decode the bitstream using out-dated parameters. It is
that parameter set IDs be partitioned between the out-of-band and therefore RECOMMENDED that parameter set IDs be partitioned
in-band parameter sets. between the out-of-band and in-band parameter sets.
8.5. Decoder Refresh Point Procedure using In-Band Transport of 8.5. Decoder Refresh Point Procedure using In-Band Transport of
Parameter Sets (Informative) Parameter Sets (Informative)
When a sender with a video encoder according to [1] receives a When a sender with a video encoder according to [1] receives a
request for a decoder refresh point, the encoder shall enter the fast request for a decoder refresh point, the encoder shall enter the
update mode by using one of the procedures specified in Section 8.5.1 fast update mode by using one of the procedures specified
or 8.5.2 below. The procedure in 8.5.1 is the preferred response in in Section 8.5.1 or 8.5.2 below. The procedure in 8.5.1 is the
a lossless transmission environment. Both procedures satisfy the preferred response in a lossless transmission environment. Both
requirement to enter the fast update mode for H.264 video encoding. procedures satisfy the requirement to enter the fast update mode
for H.264 video encoding.
8.5.1. IDR Procedure to Respond to a Request for a Decoder Refresh Point 8.5.1. IDR Procedure to Respond to a Request for a Decoder Refresh
Point
This section gives one possible way to respond to a request for a This section gives one possible way to respond to a request for a
decoder refresh point. decoder refresh point.
The encoder shall, in the order presented here: The encoder shall, in the order presented here:
1) Immediately prepare to send an IDR picture. 1) Immediately prepare to send an IDR picture.
2) Send a sequence parameter set to be used by the IDR picture to be 2) Send a sequence parameter set to be used by the IDR picture to
sent. The encoder may optionally also send other sequence be sent. The encoder may optionally also send other sequence
parameter sets. parameter sets.
3) Send a picture parameter set to be used by the IDR picture to be 3) Send a picture parameter set to be used by the IDR picture to be
sent. The encoder may optionally also send other picture parameter sent. The encoder may optionally also send other picture
sets. parameter sets.
4) Send the IDR picture. 4) Send the IDR picture.
5) From this point forward in time, send any other sequence or 5) From this point forward in time, send any other sequence or
picture parameter sets that have not yet been sent in this picture parameter sets that have not yet been sent in this
procedure, prior to their reference by any NAL unit, regardless of procedure, prior to their reference by any NAL unit, regardless
whether such parameter sets were previously sent prior to of whether such parameter sets were previously sent prior to
receiving the request for a decoder refresh point. As needed, receiving the request for a decoder refresh point. As needed,
such parameter sets may be sent in a batch, one at a time, or in such parameter sets may be sent in a batch, one at a time, or in
any combination of these two methods. Parameter sets may be re- any combination of these two methods. Parameter sets may be re-
sent at any time for redundancy. Caution should be taken when sent at any time for redundancy. Caution should be taken when
parameter set updates are present, as described above in Section parameter set updates are present, as described above in Section
8.4. 8.4.
8.5.2. Gradual Recovery Procedure to Respond to a Request for a Decoder 8.5.2. Gradual Recovery Procedure to Respond to a Request for a
Refresh Point Decoder Refresh Point
This section gives another possible way to respond to a request for a This section gives another possible way to respond to a request for
decoder refresh point. a decoder refresh point.
The encoder shall, in the order presented here: The encoder shall, in the order presented here:
1) Send a recovery point SEI message (see Sections D.1.7 and D.2.7 of 1) Send a recovery point SEI message (see Sections D.1.7 and D.2.7
[1]). of [1]).
2) Repeat any sequence and picture parameter sets that were sent 2) Repeat any sequence and picture parameter sets that were sent
before the recovery point SEI message, prior to their reference by before the recovery point SEI message, prior to their reference
a NAL unit. by a NAL unit.
The encoder shall ensure that the decoder has access to all reference The encoder shall ensure that the decoder has access to all
pictures for inter prediction of pictures at or after the recovery reference pictures for inter prediction of pictures at or after the
point, which is indicated by the recovery point SEI message, in recovery point, which is indicated by the recovery point SEI
output order, assuming that the transmission from now on is error- message, in output order, assuming that the transmission from now
free. on is error-free.
The value of the recovery_frame_cnt syntax element in the recovery The value of the recovery_frame_cnt syntax element in the recovery
point SEI message should be small enough to ensure a fast recovery. point SEI message should be small enough to ensure a fast recovery.
As needed, such parameter sets may be re-sent in a batch, one at a As needed, such parameter sets may be re-sent in a batch, one at a
time, or in any combination of these two methods. Parameter sets may time, or in any combination of these two methods. Parameter sets
be re-sent at any time for redundancy. Caution should be taken when may be re-sent at any time for redundancy. Caution should be taken
parameter set updates are present, as described above in Section 8.4. when parameter set updates are present, as described above in
Section 8.4.
9. Security Considerations 9. Security Considerations
RTP packets using the payload format defined in this specification RTP packets using the payload format defined in this specification
are subject to the security considerations discussed in the RTP are subject to the security considerations discussed in the RTP
specification [5], and in any appropriate RTP profile (for example, specification [5], and in any appropriate RTP profile (for example,
[16]). This implies that confidentiality of the media streams is [16]). This implies that confidentiality of the media streams is
achieved by encryption; for example, through the application of SRTP achieved by encryption; for example, through the application of
[26]. Because the data compression used with this payload format is SRTP [26]. Because the data compression used with this payload
applied end-to-end, any encryption needs to be performed after format is applied end-to-end, any encryption needs to be performed
compression. A potential denial-of-service threat exists for data after compression. A potential denial-of-service threat exists for
encodings using compression techniques that have non-uniform data encodings using compression techniques that have non-uniform
receiver-end computational load. The attacker can inject receiver-end computational load. The attacker can inject
pathological datagrams into the stream that are complex to decode and pathological datagrams into the stream that are complex to decode
that cause the receiver to be overloaded. H.264 is particularly and that cause the receiver to be overloaded. H.264 is
vulnerable to such attacks, as it is extremely simple to generate particularly vulnerable to such attacks, as it is extremely simple
datagrams containing NAL units that affect the decoding process of to generate datagrams containing NAL units that affect the decoding
many future NAL units. Therefore, the usage of data origin process of many future NAL units. Therefore, the usage of data
authentication and data integrity protection of at least the RTP origin authentication and data integrity protection of at least the
packet is RECOMMENDED; for example, with SRTP [26]. RTP packet is RECOMMENDED; for example, with SRTP [26].
Note that the appropriate mechanism to ensure confidentiality and Note that the appropriate mechanism to ensure confidentiality and
integrity of RTP packets and their payloads is very dependent on the integrity of RTP packets and their payloads is very dependent on
application and on the transport and signaling protocols employed. the application and on the transport and signaling protocols
Thus, although SRTP is given as an example above, other possible employed. Thus, although SRTP is given as an example above, other
choices exist. possible choices exist.
Decoders MUST exercise caution with respect to the handling of user Decoders MUST exercise caution with respect to the handling of user
data SEI messages, particularly if they contain active elements, and data SEI messages, particularly if they contain active elements,
MUST restrict their domain of applicability to the presentation and MUST restrict their domain of applicability to the presentation
containing the stream. containing the stream.
End-to-End security with either authentication, integrity or End-to-End security with either authentication, integrity or
confidentiality protection will prevent a MANE from performing media- confidentiality protection will prevent a MANE from performing
aware operations other than discarding complete packets. And in the media-aware operations other than discarding complete packets. And
case of confidentiality protection it will even be prevented from in the case of confidentiality protection it will even be prevented
performing discarding of packets in a media aware way. To allow any from performing discarding of packets in a media aware way. To
MANE to perform its operations, it will be required to be a trusted allow any MANE to perform its operations, it will be required to be
entity which is included in the security context establishment. a trusted entity which is included in the security context
establishment.
10. Congestion Control 10. Congestion Control
Congestion control for RTP SHALL be used in accordance with RFC 3550 Congestion control for RTP SHALL be used in accordance with RFC
[5], and with any applicable RTP profile; e.g., RFC 3551 [16]. An 3550 [5], and with any applicable RTP profile; e.g., RFC 3551 [16].
additional requirement if best-effort service is being used is: users An additional requirement if best-effort service is being used is:
of this payload format MUST monitor packet loss to ensure that the users of this payload format MUST monitor packet loss to ensure
packet loss rate is within acceptable parameters. Packet loss is that the packet loss rate is within acceptable parameters. Packet
considered acceptable if a TCP flow across the same network path, and loss is considered acceptable if a TCP flow across the same network
experiencing the same network conditions, would achieve an average path, and experiencing the same network conditions, would achieve
throughput, measured on a reasonable timescale, that is not less than an average throughput, measured on a reasonable timescale, that is
the RTP flow is achieving. This condition can be satisfied by not less than the RTP flow is achieving. This condition can be
implementing congestion control mechanisms to adapt the transmission satisfied by implementing congestion control mechanisms to adapt
rate (or the number of layers subscribed for a layered multicast the transmission rate (or the number of layers subscribed for a
session), or by arranging for a receiver to leave the session if the layered multicast session), or by arranging for a receiver to leave
loss rate is unacceptably high. the session if the loss rate is unacceptably high.
The bit rate adaptation necessary for obeying the congestion control The bit rate adaptation necessary for obeying the congestion
principle is easily achievable when real-time encoding is used. control principle is easily achievable when real-time encoding is
However, when pre-encoded content is being transmitted, bandwidth used. However, when pre-encoded content is being transmitted,
adaptation requires the availability of more than one coded bandwidth adaptation requires the availability of more than one
representation of the same content, at different bit rates, or the coded representation of the same content, at different bit rates,
existence of non-reference pictures or sub-sequences [22] in the or the existence of non-reference pictures or sub-sequences [22] in
bitstream. The switching between the different representations can the bitstream. The switching between the different representations
normally be performed in the same RTP session; e.g., by employing a can normally be performed in the same RTP session; e.g., by
concept known as SI/SP slices of the Extended Profile, or by employing a concept known as SI/SP slices of the Extended Profile,
switching streams at IDR picture boundaries. Only when non- or by switching streams at IDR picture boundaries. Only when non-
downgradable parameters (such as the profile part of the downgradable parameters (such as the profile part of the
profile/level ID) are required to be changed does it become necessary profile/level ID) are required to be changed does it become
to terminate and re-start the media stream. This may be accomplished necessary to terminate and re-start the media stream. This may be
by using a different RTP payload type. accomplished by using a different RTP payload type.
MANEs MAY follow the suggestions outlined in section 7.3 and remove MANEs MAY follow the suggestions outlined in section 7.3 and remove
certain unusable packets from the packet stream when that stream was certain unusable packets from the packet stream when that stream
damaged due to previous packet losses. This can help reduce the was damaged due to previous packet losses. This can help reduce
network load in certain special cases. the network load in certain special cases.
11. IANA Consideration 11. IANA Consideration
The H264 media subtype name specified by RFC 3984 should be updated The H264 media subtype name specified by RFC 3984 should be updated
as defined in section 8.1 of this memo. as defined in section 8.1 of this memo.
12. Informative Appendix: Application Examples 12. Informative Appendix: Application Examples
This payload specification is very flexible in its use, in order to This payload specification is very flexible in its use, in order to
cover the extremely wide application space anticipated for H.264. cover the extremely wide application space anticipated for H.264.
However, this great flexibility also makes it difficult for an However, this great flexibility also makes it difficult for an
implementer to decide on a reasonable packetization scheme. Some implementer to decide on a reasonable packetization scheme. Some
information on how to apply this specification to real-world information on how to apply this specification to real-world
scenarios is likely to appear in the form of academic publications scenarios is likely to appear in the form of academic publications
and a test model software and description in the near future. and a test model software and description in the near future.
However, some preliminary usage scenarios are described here as well. However, some preliminary usage scenarios are described here as
well.
12.1. Video Telephony according to ITU-T Recommendation H.241 Annex A 12.1. Video Telephony according to ITU-T Recommendation H.241 Annex A
H.323-based video telephony systems that use H.264 as an optional H.323-based video telephony systems that use H.264 as an optional
video compression scheme are required to support H.241 Annex A [3] as video compression scheme are required to support H.241 Annex A [3]
a packetization scheme. The packetization mechanism defined in this as a packetization scheme. The packetization mechanism defined in
Annex is technically identical with a small subset of this this Annex is technically identical with a small subset of this
specification. specification.
When a system operates according to H.241 Annex A, parameter set NAL When a system operates according to H.241 Annex A, parameter set
units are sent in-band. Only Single NAL unit packets are used. Many NAL units are sent in-band. Only Single NAL unit packets are used.
such systems are not sending IDR pictures regularly, but only when Many such systems are not sending IDR pictures regularly, but only
required by user interaction or by control protocol means; e.g., when when required by user interaction or by control protocol means;
switching between video channels in a Multipoint Control Unit or for e.g., when switching between video channels in a Multipoint Control
error recovery requested by feedback. Unit or for error recovery requested by feedback.
12.2. Video Telephony, No Slice Data Partitioning, No NAL Unit 12.2. Video Telephony, No Slice Data Partitioning, No NAL Unit
Aggregation Aggregation
The RTP part of this scheme is implemented and tested (though not the The RTP part of this scheme is implemented and tested (though not
control-protocol part; see below). the control-protocol part; see below).
In most real-world video telephony applications, picture parameters In most real-world video telephony applications, picture parameters
such as picture size or optional modes never change during the such as picture size or optional modes never change during the
lifetime of a connection. Therefore, all necessary parameter sets lifetime of a connection. Therefore, all necessary parameter sets
(usually only one) are sent as a side effect of the capability (usually only one) are sent as a side effect of the capability
exchange/announcement process, e.g., according to the SDP syntax exchange/announcement process, e.g., according to the SDP syntax
specified in section 8.2 of this document. As all necessary specified in section 8.2 of this document. As all necessary
parameter set information is established before the RTP session parameter set information is established before the RTP session
starts, there is no need for sending any parameter set NAL units. starts, there is no need for sending any parameter set NAL units.
Slice data partitioning is not used, either. Thus, the RTP packet Slice data partitioning is not used, either. Thus, the RTP packet
stream basically consists of NAL units that carry single coded slices. stream basically consists of NAL units that carry single coded
slices.
The encoder chooses the size of coded slice NAL units so that they The encoder chooses the size of coded slice NAL units so that they
offer the best performance. Often, this is done by adapting the offer the best performance. Often, this is done by adapting the
coded slice size to the MTU size of the IP network. For small coded slice size to the MTU size of the IP network. For small
picture sizes, this may result in a one-picture-per-one-packet picture sizes, this may result in a one-picture-per-one-packet
strategy. Intra refresh algorithms clean up the loss of packets and strategy. Intra refresh algorithms clean up the loss of packets
the resulting drift-related artifacts. and the resulting drift-related artifacts.
12.3. Video Telephony, Interleaved Packetization Using NAL Unit 12.3. Video Telephony, Interleaved Packetization Using NAL Unit
Aggregation Aggregation
This scheme allows better error concealment and is used in H.263 This scheme allows better error concealment and is used in H.263
based designs using RFC 2429 packetization [11]. It has been based designs using RFC 4629 packetization [11]. It has been
implemented, and good results were reported [13]. implemented, and good results were reported [13].
The VCL encoder codes the source picture so that all macroblocks (MBs) The VCL encoder codes the source picture so that all macroblocks
of one MB line are assigned to one slice. All slices with even MB (MBs) of one MB line are assigned to one slice. All slices with
row addresses are combined into one STAP, and all slices with odd MB even MB row addresses are combined into one STAP, and all slices
row addresses into another. Those STAPs are transmitted as RTP with odd MB row addresses into another. Those STAPs are
packets. The establishment of the parameter sets is performed as transmitted as RTP packets. The establishment of the parameter
discussed above. sets is performed as discussed above.
Note that the use of STAPs is essential here, as the high number of Note that the use of STAPs is essential here, as the high number of
individual slices (18 for a CIF picture) would lead to unacceptably individual slices (18 for a CIF picture) would lead to unacceptably
high IP/UDP/RTP header overhead (unless the source coding tool FMO is high IP/UDP/RTP header overhead (unless the source coding tool FMO
used, which is not assumed in this scenario). Furthermore, some is used, which is not assumed in this scenario). Furthermore, some
wireless video transmission systems, such as H.324M and the IP-based wireless video transmission systems, such as H.324M and the IP-
video telephony specified in 3GPP, are likely to use relatively small based video telephony specified in 3GPP, are likely to use
transport packet size. For example, a typical MTU size of H.223 AL3 relatively small transport packet size. For example, a typical MTU
SDU is around 100 bytes [17]. Coding individual slices according to size of H.223 AL3 SDU is around 100 bytes [17]. Coding individual
this packetization scheme provides further advantage in communication slices according to this packetization scheme provides further
between wired and wireless networks, as individual slices are likely advantage in communication between wired and wireless networks, as
to be smaller than the preferred maximum packet size of wireless individual slices are likely to be smaller than the preferred
systems. Consequently, a gateway can convert the STAPs used in a maximum packet size of wireless systems. Consequently, a gateway
wired network into several RTP packets with only one NAL unit, which can convert the STAPs used in a wired network into several RTP
are preferred in a wireless network, and vice versa. packets with only one NAL unit, which are preferred in a wireless
network, and vice versa.
12.4. Video Telephony with Data Partitioning 12.4. Video Telephony with Data Partitioning
This scheme has been implemented and has been shown to offer good This scheme has been implemented and has been shown to offer good
performance, especially at higher packet loss rates [13]. performance, especially at higher packet loss rates [13].
Data Partitioning is known to be useful only when some form of Data Partitioning is known to be useful only when some form of
unequal error protection is available. Normally, in single-session unequal error protection is available. Normally, in single-session
RTP environments, even error characteristics are assumed; i.e., the RTP environments, even error characteristics are assumed; i.e., the
packet loss probability of all packets of the session is the same packet loss probability of all packets of the session is the same
statistically. However, there are means to reduce the packet loss statistically. However, there are means to reduce the packet loss
probability of individual packets in an RTP session. A FEC packet probability of individual packets in an RTP session. A FEC packet
according to RFC 2733 [18], for example, specifies which media according to RFC 2733 [18], for example, specifies which media
packets are associated with the FEC packet. packets are associated with the FEC packet.
In all cases, the incurred overhead is substantial but is in the same In all cases, the incurred overhead is substantial but is in the
order of magnitude as the number of bits that have otherwise been same order of magnitude as the number of bits that have otherwise
spent for intra information. However, this mechanism does not add been spent for intra information. However, this mechanism does not
any delay to the system. add any delay to the system.
Again, the complete parameter set establishment is performed through Again, the complete parameter set establishment is performed
control protocol means. through control protocol means.
12.5. Video Telephony or Streaming with FUs and Forward Error Correction 12.5. Video Telephony or Streaming with FUs and Forward Error
Correction
This scheme has been implemented and has been shown to provide good This scheme has been implemented and has been shown to provide good
performance, especially at higher packet loss rates [19]. performance, especially at higher packet loss rates [19].
The most efficient means to combat packet losses for scenarios where The most efficient means to combat packet losses for scenarios
retransmissions are not applicable is forward error correction (FEC). where retransmissions are not applicable is forward error
Although application layer, end-to-end use of FEC is often less correction (FEC). Although application layer, end-to-end use of
efficient than an FEC-based protection of individual links FEC is often less efficient than an FEC-based protection of
(especially when links of different characteristics are in the individual links (especially when links of different
transmission path), application layer, end-to-end FEC is unavoidable characteristics are in the transmission path), application layer,
in some scenarios. RFC 5109 [18] provides means to use generic, end-to-end FEC is unavoidable in some scenarios. RFC 5109 [18]
application layer, end-to-end FEC in packet-loss environments. A provides means to use generic, application layer, end-to-end FEC in
binary forward error correcting code is generated by applying the XOR packet-loss environments. A binary forward error correcting code
operation to the bits at the same bit position in different packets. is generated by applying the XOR operation to the bits at the same
The binary code can be specified by the parameters (n,k) in which k bit position in different packets. The binary code can be
is the number of information packets used in the connection and n is specified by the parameters (n,k) in which k is the number of
the total number of packets generated for k information packets; i.e., information packets used in the connection and n is the total
n-k parity packets are generated for k information packets. number of packets generated for k information packets; i.e., n-k
parity packets are generated for k information packets.
When a code is used with parameters (n,k) within the RFC 5109 When a code is used with parameters (n,k) within the RFC 5109
framework, the following properties are well known: framework, the following properties are well known:
a) If applied over one RTP packet, RFC 5109 provides only packet a) If applied over one RTP packet, RFC 5109 provides only packet
repetition. repetition.
b) RFC 5109 is most bit rate efficient if XOR-connected packets have b) RFC 5109 is most bit rate efficient if XOR-connected packets
equal length. have equal length.
c) At the same packet loss probability p and for a fixed k, the c) At the same packet loss probability p and for a fixed k, the
greater the value of n is, the smaller the residual error greater the value of n is, the smaller the residual error
probability becomes. For example, for a packet loss probability probability becomes. For example, for a packet loss probability
of 10%, k=1, and n=2, the residual error probability is about 1%, of 10%, k=1, and n=2, the residual error probability is about 1%,
whereas for n=3, the residual error probability is about 0.1%. whereas for n=3, the residual error probability is about 0.1%.
d) At the same packet loss probability p and for a fixed code rate d) At the same packet loss probability p and for a fixed code rate
k/n, the greater the value of n is, the smaller the residual error k/n, the greater the value of n is, the smaller the residual
probability becomes. For example, at a packet loss probability of error probability becomes. For example, at a packet loss
p=10%, k=1 and n=2, the residual error rate is about 1%, whereas probability of p=10%, k=1 and n=2, the residual error rate is
for an extended Golay code with k=12 and n=24, the residual error about 1%, whereas for an extended Golay code with k=12 and n=24,
rate is about 0.01%. the residual error rate is about 0.01%.
For applying RFC 5109 in combination with H.264 baseline coded video For applying RFC 5109 in combination with H.264 baseline coded
without using FUs, several options might be considered: video without using FUs, several options might be considered:
1) The video encoder produces NAL units for which each video frame is 1) The video encoder produces NAL units for which each video frame
coded in a single slice. Applying FEC, one could use a simple is coded in a single slice. Applying FEC, one could use a
code; e.g., (n=2, k=1). That is, each NAL unit would basically simple code; e.g., (n=2, k=1). That is, each NAL unit would
just be repeated. The disadvantage is obviously the bad code basically just be repeated. The disadvantage is obviously the
performance according to d), above, and the low flexibility, as bad code performance according to d), above, and the low
only (n, k=1) codes can be used. flexibility, as only (n, k=1) codes can be used.
2) The video encoder produces NAL units for which each video frame is 2) The video encoder produces NAL units for which each video frame
encoded in one or more consecutive slices. Applying FEC, one is encoded in one or more consecutive slices. Applying FEC, one
could use a better code, e.g., (n=24, k=12), over a sequence of could use a better code, e.g., (n=24, k=12), over a sequence of
NAL units. Depending on the number of RTP packets per frame, a NAL units. Depending on the number of RTP packets per frame, a
loss may introduce a significant delay, which is reduced when more loss may introduce a significant delay, which is reduced when
RTP packets are used per frame. Packets of completely different more RTP packets are used per frame. Packets of completely
length might also be connected, which decreases bit rate different length might also be connected, which decreases bit
efficiency according to b), above. However, with some care and rate efficiency according to b), above. However, with some care
for slices of 1kb or larger, similar length (100-200 bytes and for slices of 1kb or larger, similar length (100-200 bytes
difference) may be produced, which will not lower the bit difference) may be produced, which will not lower the bit
efficiency catastrophically. efficiency catastrophically.
3) The video encoder produces NAL units, for which a certain frame 3) The video encoder produces NAL units, for which a certain frame
contains k slices of possibly almost equal length. Then, applying contains k slices of possibly almost equal length. Then,
FEC, a better code, e.g., (n=24, k=12), can be used over the applying FEC, a better code, e.g., (n=24, k=12), can be used
sequence of NAL units for each frame. The delay compared to that over the sequence of NAL units for each frame. The delay
of 2), above, may be reduced, but several disadvantages are compared to that of 2), above, may be reduced, but several
obvious. First, the coding efficiency of the encoded video is disadvantages are obvious. First, the coding efficiency of the
lowered significantly, as slice-structured coding reduces intra- encoded video is lowered significantly, as slice-structured
frame prediction and additional slice overhead is necessary. coding reduces intra-frame prediction and additional slice
Second, pre-encoded content or, when operating over a gateway, the overhead is necessary. Second, pre-encoded content or, when
video is usually not appropriately coded with k slices such that operating over a gateway, the video is usually not appropriately
FEC can be applied. Finally, the encoding of video producing k coded with k slices such that FEC can be applied. Finally, the
slices of equal length is not straightforward and might require encoding of video producing k slices of equal length is not
more than one encoding pass. straightforward and might require more than one encoding pass.
Many of the mentioned disadvantages can be avoided by applying FUs in Many of the mentioned disadvantages can be avoided by applying FUs
combination with FEC. Each NAL unit can be split into any number of in combination with FEC. Each NAL unit can be split into any
FUs of basically equal length; therefore, FEC with a reasonable k and number of FUs of basically equal length; therefore, FEC with a
n can be applied, even if the encoder made no effort to produce reasonable k and n can be applied, even if the encoder made no
slices of equal length. For example, a coded slice NAL unit effort to produce slices of equal length. For example, a coded
containing an entire frame can be split to k FUs, and a parity check slice NAL unit containing an entire frame can be split to k FUs,
code (n=k+1, k) can be applied. However, this has the disadvantage and a parity check code (n=k+1, k) can be applied. However, this
that unless all created fragments can be recovered, the whole slice has the disadvantage that unless all created fragments can be
will be lost. Thus a larger section is lost than would be if the recovered, the whole slice will be lost. Thus a larger section is
frame had been split into several slices. lost than would be if the frame had been split into several slices.
The presented technique makes it possible to achieve good The presented technique makes it possible to achieve good
transmission error tolerance, even if no additional source coding transmission error tolerance, even if no additional source coding
layer redundancy (such as periodic intra frames) is present. layer redundancy (such as periodic intra frames) is present.
Consequently, the same coded video sequence can be used to achieve Consequently, the same coded video sequence can be used to achieve
the maximum compression efficiency and quality over error-free the maximum compression efficiency and quality over error-free
transmission and for transmission over error-prone networks. transmission and for transmission over error-prone networks.
Furthermore, the technique allows the application of FEC to pre- Furthermore, the technique allows the application of FEC to pre-
encoded sequences without adding delay. In this case, pre-encoded encoded sequences without adding delay. In this case, pre-encoded
sequences that are not encoded for error-prone networks can still be sequences that are not encoded for error-prone networks can still
transmitted almost reliably without adding extensive delays. In be transmitted almost reliably without adding extensive delays. In
addition, FUs of equal length result in a bit rate efficient use of addition, FUs of equal length result in a bit rate efficient use of
RFC 5109. RFC 5109.
If the error probability depends on the length of the transmitted If the error probability depends on the length of the transmitted
packet (e.g., in case of mobile transmission [15]), the benefits of packet (e.g., in case of mobile transmission [15]), the benefits of
applying FUs with FEC are even more obvious. Basically, the applying FUs with FEC are even more obvious. Basically, the
flexibility of the size of FUs allows appropriate FEC to be applied flexibility of the size of FUs allows appropriate FEC to be applied
for each NAL unit and unequal error protection of NAL units. for each NAL unit and unequal error protection of NAL units.
When FUs and FEC are used, the incurred overhead is substantial but When FUs and FEC are used, the incurred overhead is substantial but
is in the same order of magnitude as the number of bits that have to is in the same order of magnitude as the number of bits that have
be spent for intra-coded macroblocks if no FEC is applied. In [19], to be spent for intra-coded macroblocks if no FEC is applied. In
it was shown that the overall performance of the FEC-based approach [19], it was shown that the overall performance of the FEC-based
enhanced quality when using the same error rate and same overall bit approach enhanced quality when using the same error rate and same
rate, including the overhead. overall bit rate, including the overhead.
12.6. Low Bit-Rate Streaming 12.6. Low Bit-Rate Streaming
This scheme has been implemented with H.263 and non-standard RTP This scheme has been implemented with H.263 and non-standard RTP
packetization and has given good results [20]. There is no technical packetization and has given good results [20]. There is no
reason why similarly good results could not be achievable with H.264. technical reason why similarly good results could not be achievable
with H.264.
In today's Internet streaming, some of the offered bit rates are In today's Internet streaming, some of the offered bit rates are
relatively low in order to allow terminals with dial-up modems to relatively low in order to allow terminals with dial-up modems to
access the content. In wired IP networks, relatively large packets, access the content. In wired IP networks, relatively large packets,
say 500 - 1500 bytes, are preferred to smaller and more frequently say 500 - 1500 bytes, are preferred to smaller and more frequently
occurring packets in order to reduce network congestion. Moreover, occurring packets in order to reduce network congestion. Moreover,
use of large packets decreases the amount of RTP/UDP/IP header use of large packets decreases the amount of RTP/UDP/IP header
overhead. For low bit-rate video, the use of large packets means overhead. For low bit-rate video, the use of large packets means
that sometimes up to few pictures should be encapsulated in one that sometimes up to few pictures should be encapsulated in one
packet. packet.
However, loss of a packet including many coded pictures would have However, loss of a packet including many coded pictures would have
drastic consequences for visual quality, as there is practically no drastic consequences for visual quality, as there is practically no
other way to conceal a loss of an entire picture than to repeat the other way to conceal a loss of an entire picture than to repeat the
previous one. One way to construct relatively large packets and previous one. One way to construct relatively large packets and
maintain possibilities for successful loss concealment is to maintain possibilities for successful loss concealment is to
construct MTAPs that contain interleaved slices from several pictures. construct MTAPs that contain interleaved slices from several
An MTAP should not contain spatially adjacent slices from the same pictures. An MTAP should not contain spatially adjacent slices
picture or spatially overlapping slices from any picture. If a from the same picture or spatially overlapping slices from any
packet is lost, it is likely that a lost slice is surrounded by picture. If a packet is lost, it is likely that a lost slice is
spatially adjacent slices of the same picture and spatially surrounded by spatially adjacent slices of the same picture and
corresponding slices of the temporally previous and succeeding spatially corresponding slices of the temporally previous and
pictures. Consequently, concealment of the lost slice is likely to succeeding pictures. Consequently, concealment of the lost slice
be relatively successful. is likely to be relatively successful.
12.7. Robust Packet Scheduling in Video Streaming 12.7. Robust Packet Scheduling in Video Streaming
Robust packet scheduling has been implemented with MPEG-4 Part 2 and Robust packet scheduling has been implemented with MPEG-4 Part 2
simulated in a wireless streaming environment [21]. There is no and simulated in a wireless streaming environment [21]. There is
technical reason why similar or better results could not be no technical reason why similar or better results could not be
achievable with H.264. achievable with H.264.
Streaming clients typically have a receiver buffer that is capable of Streaming clients typically have a receiver buffer that is capable
storing a relatively large amount of data. Initially, when a of storing a relatively large amount of data. Initially, when a
streaming session is established, a client does not start playing the streaming session is established, a client does not start playing
stream back immediately. Rather, it typically buffers the incoming the stream back immediately. Rather, it typically buffers the
data for a few seconds. This buffering helps maintain continuous incoming data for a few seconds. This buffering helps maintain
playback, as, in case of occasional increased transmission delays or continuous playback, as, in case of occasional increased
network throughput drops, the client can decode and play buffered transmission delays or network throughput drops, the client can
data. Otherwise, without initial buffering, the client has to freeze decode and play buffered data. Otherwise, without initial
the display, stop decoding, and wait for incoming data. The buffering, the client has to freeze the display, stop decoding, and
buffering is also necessary for either automatic or selective wait for incoming data. The buffering is also necessary for either
retransmission in any protocol level. If any part of a picture is automatic or selective retransmission in any protocol level. If
lost, a retransmission mechanism may be used to resend the lost data. any part of a picture is lost, a retransmission mechanism may be
If the retransmitted data is received before its scheduled decoding used to resend the lost data. If the retransmitted data is
or playback time, the loss is recovered perfectly. Coded pictures received before its scheduled decoding or playback time, the loss
can be ranked according to their importance in the subjective quality is recovered perfectly. Coded pictures can be ranked according to
of the decoded sequence. For example, non-reference pictures, such their importance in the subjective quality of the decoded sequence.
as conventional B pictures, are subjectively least important, as For example, non-reference pictures, such as conventional B
their absence does not affect decoding of any other pictures. In pictures, are subjectively least important, as their absence does
addition to non-reference pictures, the ITU-T H.264 | ISO/IEC 14496- not affect decoding of any other pictures. In addition to non-
10 standard includes a temporal scalability method called sub- reference pictures, the ITU-T H.264 | ISO/IEC 14496-10 standard
sequences [22]. Subjective ranking can also be made on coded slice includes a temporal scalability method called sub-sequences [22].
data partition or slice group basis. Coded slices and coded slice Subjective ranking can also be made on coded slice data partition
data partitions that are subjectively the most important can be sent or slice group basis. Coded slices and coded slice data partitions
earlier than their decoding order indicates, whereas coded slices and that are subjectively the most important can be sent earlier than
coded slice data partitions that are subjectively the least important their decoding order indicates, whereas coded slices and coded
can be sent later than their natural coding order indicates. slice data partitions that are subjectively the least important can
be sent later than their natural coding order indicates.
Consequently, any retransmitted parts of the most important slices Consequently, any retransmitted parts of the most important slices
and coded slice data partitions are more likely to be received before and coded slice data partitions are more likely to be received
their scheduled decoding or playback time compared to the least before their scheduled decoding or playback time compared to the
important slices and slice data partitions. least important slices and slice data partitions.
13. Informative Appendix: Rationale for Decoding Order Number 13. Informative Appendix: Rationale for Decoding Order Number
13.1. Introduction 13.1. Introduction
The Decoding Order Number (DON) concept was introduced mainly to The Decoding Order Number (DON) concept was introduced mainly to
enable efficient multi-picture slice interleaving (see section 12.6) enable efficient multi-picture slice interleaving (see section 12.6)
and robust packet scheduling (see section 12.7). In both of these and robust packet scheduling (see section 12.7). In both of these
applications, NAL units are transmitted out of decoding order. DON applications, NAL units are transmitted out of decoding order. DON
indicates the decoding order of NAL units and should be used in the indicates the decoding order of NAL units and should be used in the
receiver to recover the decoding order. Example use cases for receiver to recover the decoding order. Example use cases for
efficient multi-picture slice interleaving and for robust packet efficient multi-picture slice interleaving and for robust packet
scheduling are given in sections 13.2 and 13.3, respectively. scheduling are given in sections 13.2 and 13.3, respectively.
Section 13.4 describes the benefits of the DON concept in error Section 13.4 describes the benefits of the DON concept in error
resiliency achieved by redundant coded pictures. Section 13.5 resiliency achieved by redundant coded pictures. Section 13.5
summarizes considered alternatives to DON and justifies why DON was summarizes considered alternatives to DON and justifies why DON was
chosen to this RTP payload specification. chosen to this RTP payload specification.
13.2. Example of Multi-Picture Slice Interleaving 13.2. Example of Multi-Picture Slice Interleaving
An example of multi-picture slice interleaving follows. A subset of An example of multi-picture slice interleaving follows. A subset
a coded video sequence is depicted below in output order. R denotes of a coded video sequence is depicted below in output order. R
a reference picture, N denotes a non-reference picture, and the denotes a reference picture, N denotes a non-reference picture, and
number indicates a relative output time. the number indicates a relative output time.
... R1 N2 R3 N4 R5 ... ... R1 N2 R3 N4 R5 ...
The decoding order of these pictures from left to right is as follows: The decoding order of these pictures from left to right is as
follows:
... R1 R3 N2 R5 N4 ... ... R1 R3 N2 R5 N4 ...
The NAL units of pictures R1, R3, N2, R5, and N4 are marked with a The NAL units of pictures R1, R3, N2, R5, and N4 are marked with a
DON equal to 1, 2, 3, 4, and 5, respectively. DON equal to 1, 2, 3, 4, and 5, respectively.
Each reference picture consists of three slice groups that are Each reference picture consists of three slice groups that are
scattered as follows (a number denotes the slice group number for scattered as follows (a number denotes the slice group number for
each macroblock in a QCIF frame): each macroblock in a QCIF frame):
skipping to change at page 85, line 17 skipping to change at page 87, line 33
1 2 0 1 2 0 1 2 0 1 2 1 2 0 1 2 0 1 2 0 1 2
0 1 2 0 1 2 0 1 2 0 1 0 1 2 0 1 2 0 1 2 0 1
2 0 1 2 0 1 2 0 1 2 0 2 0 1 2 0 1 2 0 1 2 0
1 2 0 1 2 0 1 2 0 1 2 1 2 0 1 2 0 1 2 0 1 2
0 1 2 0 1 2 0 1 2 0 1 0 1 2 0 1 2 0 1 2 0 1
2 0 1 2 0 1 2 0 1 2 0 2 0 1 2 0 1 2 0 1 2 0
1 2 0 1 2 0 1 2 0 1 2 1 2 0 1 2 0 1 2 0 1 2
For the sake of simplicity, we assume that all the macroblocks of a For the sake of simplicity, we assume that all the macroblocks of a
slice group are included in one slice. Three MTAPs are constructed slice group are included in one slice. Three MTAPs are constructed
from three consecutive reference pictures so that each MTAP contains from three consecutive reference pictures so that each MTAP
three aggregation units, each of which contains all the macroblocks contains three aggregation units, each of which contains all the
from one slice group. The first MTAP contains slice group 0 of macroblocks from one slice group. The first MTAP contains slice
picture R1, slice group 1 of picture R3, and slice group 2 of picture group 0 of picture R1, slice group 1 of picture R3, and slice group
R5. The second MTAP contains slice group 1 of picture R1, slice 2 of picture R5. The second MTAP contains slice group 1 of picture
group 2 of picture R3, and slice group 0 of picture R5. The third R1, slice group 2 of picture R3, and slice group 0 of picture R5.
MTAP contains slice group 2 of picture R1, slice group 0 of picture The third MTAP contains slice group 2 of picture R1, slice group 0
R3, and slice group 1 of picture R5. Each non-reference picture is of picture R3, and slice group 1 of picture R5. Each non-reference
encapsulated into an STAP-B. picture is encapsulated into an STAP-B.
Consequently, the transmission order of NAL units is the following: Consequently, the transmission order of NAL units is the following:
R1, slice group 0, DON 1, carried in MTAP,RTP SN: N R1, slice group 0, DON 1, carried in MTAP,RTP SN: N
R3, slice group 1, DON 2, carried in MTAP,RTP SN: N R3, slice group 1, DON 2, carried in MTAP,RTP SN: N
R5, slice group 2, DON 4, carried in MTAP,RTP SN: N R5, slice group 2, DON 4, carried in MTAP,RTP SN: N
R1, slice group 1, DON 1, carried in MTAP,RTP SN: N+1 R1, slice group 1, DON 1, carried in MTAP,RTP SN: N+1
R3, slice group 2, DON 2, carried in MTAP,RTP SN: N+1 R3, slice group 2, DON 2, carried in MTAP,RTP SN: N+1
R5, slice group 0, DON 4, carried in MTAP,RTP SN: N+1 R5, slice group 0, DON 4, carried in MTAP,RTP SN: N+1
R1, slice group 2, DON 1, carried in MTAP,RTP SN: N+2 R1, slice group 2, DON 1, carried in MTAP,RTP SN: N+2
R3, slice group 1, DON 2, carried in MTAP,RTP SN: N+2 R3, slice group 1, DON 2, carried in MTAP,RTP SN: N+2
R5, slice group 0, DON 4, carried in MTAP,RTP SN: N+2 R5, slice group 0, DON 4, carried in MTAP,RTP SN: N+2
N2, DON 3, carried in STAP-B, RTP SN: N+3 N2, DON 3, carried in STAP-B, RTP SN: N+3
N4, DON 5, carried in STAP-B, RTP SN: N+4 N4, DON 5, carried in STAP-B, RTP SN: N+4
The receiver is able to organize the NAL units back in decoding order The receiver is able to organize the NAL units back in decoding
based on the value of DON associated with each NAL unit. order based on the value of DON associated with each NAL unit.
If one of the MTAPs is lost, the spatially adjacent and temporally If one of the MTAPs is lost, the spatially adjacent and temporally
co-located macroblocks are received and can be used to conceal the co-located macroblocks are received and can be used to conceal the
loss efficiently. If one of the STAPs is lost, the effect of the loss efficiently. If one of the STAPs is lost, the effect of the
loss does not propagate temporally. loss does not propagate temporally.
13.3. Example of Robust Packet Scheduling 13.3. Example of Robust Packet Scheduling
An example of robust packet scheduling follows. The communication An example of robust packet scheduling follows. The communication
system used in the example consists of the following components in system used in the example consists of the following components in
skipping to change at page 86, line 24 skipping to change at page 88, line 40
o encoded picture buffer o encoded picture buffer
o transmitter o transmitter
o transmission channel o transmission channel
o receiver o receiver
o receiver buffer o receiver buffer
o decoder o decoder
o decoded picture buffer o decoded picture buffer
o display o display
The video communication system used in the example operates as The video communication system used in the example operates as
follows. Note that processing of the video stream happens gradually follows. Note that processing of the video stream happens
and at the same time in all components of the system. The source gradually and at the same time in all components of the system.
video sequence is shot and captured to a pre-encoding buffer. The The source video sequence is shot and captured to a pre-encoding
pre-encoding buffer can be used to order pictures from sampling order buffer. The pre-encoding buffer can be used to order pictures from
to encoding order or to analyze multiple uncompressed frames for bit sampling order to encoding order or to analyze multiple
rate control purposes, for example. In some cases, the pre-encoding uncompressed frames for bit rate control purposes, for example. In
buffer may not exist; instead, the sampled pictures are encoded right some cases, the pre-encoding buffer may not exist; instead, the
away. The encoder encodes pictures from the pre-encoding buffer and sampled pictures are encoded right away. The encoder encodes
stores the output; i.e., coded pictures, to the encoded picture pictures from the pre-encoding buffer and stores the output; i.e.,
buffer. The transmitter encapsulates the coded pictures from the coded pictures, to the encoded picture buffer. The transmitter
encoded picture buffer to transmission packets and sends them to a encapsulates the coded pictures from the encoded picture buffer to
receiver through a transmission channel. The receiver stores the transmission packets and sends them to a receiver through a
received packets to the receiver buffer. The receiver buffering transmission channel. The receiver stores the received packets to
process typically includes buffering for transmission delay jitter. the receiver buffer. The receiver buffering process typically
The receiver buffer can also be used to recover correct decoding includes buffering for transmission delay jitter. The receiver
order of coded data. The decoder reads coded data from the receiver buffer can also be used to recover correct decoding order of coded
buffer and produces decoded pictures as output into the decoded data. The decoder reads coded data from the receiver buffer and
picture buffer. The decoded picture buffer is used to recover the produces decoded pictures as output into the decoded picture buffer.
output (or display) order of pictures. Finally, pictures are The decoded picture buffer is used to recover the output (or
displayed. display) order of pictures. Finally, pictures are displayed.
In the following example figures, I denotes an IDR picture, R denotes In the following example figures, I denotes an IDR picture, R
a reference picture, N denotes a non-reference picture, and the denotes a reference picture, N denotes a non-reference picture, and
number after I, R, or N indicates the sampling time relative to the the number after I, R, or N indicates the sampling time relative to
previous IDR picture in decoding order. Values below the sequence of the previous IDR picture in decoding order. Values below the
pictures indicate scaled system clock timestamps. The system clock sequence of pictures indicate scaled system clock timestamps. The
is initialized arbitrarily in this example, and time runs from left system clock is initialized arbitrarily in this example, and time
to right. Each I, R, and N picture is mapped into the same timeline runs from left to right. Each I, R, and N picture is mapped into
compared to the previous processing step, if any, assuming that the same timeline compared to the previous processing step, if any,
encoding, transmission, and decoding take no time. Thus, events assuming that encoding, transmission, and decoding take no time.
happening at the same time are located in the same column throughout Thus, events happening at the same time are located in the same
all example figures. column throughout all example figures.
A subset of a sequence of coded pictures is depicted below in A subset of a sequence of coded pictures is depicted below in
sampling order. sampling order.
... N58 N59 I00 N01 N02 R03 N04 N05 R06 ... N58 N59 I00 N01 ... ... N58 N59 I00 N01 N02 R03 N04 N05 R06 ... N58 N59 I00 N01 ...
... --|---|---|---|---|---|---|---|---|- ... -|---|---|---|- ... ... --|---|---|---|---|---|---|---|---|- ... -|---|---|---|- ...
... 58 59 60 61 62 63 64 65 66 ... 128 129 130 131 ... ... 58 59 60 61 62 63 64 65 66 ... 128 129 130 131 ...
Figure 16 Sequence of pictures in sampling order Figure 16 Sequence of pictures in sampling order
The sampled pictures are buffered in the pre-encoding buffer to The sampled pictures are buffered in the pre-encoding buffer to
arrange them in encoding order. In this example, we assume that the arrange them in encoding order. In this example, we assume that
non-reference pictures are predicted from both the previous and the the non-reference pictures are predicted from both the previous and
next reference picture in output order, except for the non-reference the next reference picture in output order, except for the non-
pictures immediately preceding an IDR picture, which are predicted reference pictures immediately preceding an IDR picture, which are
only from the previous reference picture in output order. Thus, the predicted only from the previous reference picture in output order.
pre-encoding buffer has to contain at least two pictures, and the Thus, the pre-encoding buffer has to contain at least two pictures,
buffering causes a delay of two picture intervals. The output of the and the buffering causes a delay of two picture intervals. The
pre-encoding buffering process and the encoding (and decoding) order output of the pre-encoding buffering process and the encoding (and
of the pictures are as follows: decoding) order of the pictures are as follows:
... N58 N59 I00 R03 N01 N02 R06 N04 N05 ... ... N58 N59 I00 R03 N01 N02 R06 N04 N05 ...
... -|---|---|---|---|---|---|---|---|- ... ... -|---|---|---|---|---|---|---|---|- ...
... 60 61 62 63 64 65 66 67 68 ... ... 60 61 62 63 64 65 66 67 68 ...
Figure 17 Re-ordered pictures in the pre-encoding buffer Figure 17 Re-ordered pictures in the pre-encoding buffer
The encoder or the transmitter can set the value of DON for each The encoder or the transmitter can set the value of DON for each
picture to a value of DON for the previous picture in decoding order picture to a value of DON for the previous picture in decoding
plus one. order plus one.
For the sake of simplicity, let us assume that: For the sake of simplicity, let us assume that:
o the frame rate of the sequence is constant, o the frame rate of the sequence is constant,
o each picture consists of only one slice, o each picture consists of only one slice,
o each slice is encapsulated in a single NAL unit packet, o each slice is encapsulated in a single NAL unit packet,
o there is no transmission delay, and o there is no transmission delay, and
o pictures are transmitted at constant intervals (that is, 1 / o pictures are transmitted at constant intervals (that is, 1 /
(frame rate)). (frame rate)).
When pictures are transmitted in decoding order, they are received as When pictures are transmitted in decoding order, they are received
follows: as follows:
... N58 N59 I00 R03 N01 N02 R06 N04 N05 ... ... N58 N59 I00 R03 N01 N02 R06 N04 N05 ...
... -|---|---|---|---|---|---|---|---|- ... ... -|---|---|---|---|---|---|---|---|- ...
... 60 61 62 63 64 65 66 67 68 ... ... 60 61 62 63 64 65 66 67 68 ...
Figure 18 Received pictures in decoding order Figure 18 Received pictures in decoding order
The OPTIONAL sprop-interleaving-depth media type parameter is set to The OPTIONAL sprop-interleaving-depth media type parameter is set
0, as the transmission (or reception) order is identical to the to 0, as the transmission (or reception) order is identical to the
decoding order. decoding order.
The decoder has to buffer for one picture interval initially in its The decoder has to buffer for one picture interval initially in its
decoded picture buffer to organize pictures from decoding order to decoded picture buffer to organize pictures from decoding order to
output order as depicted below: output order as depicted below:
... N58 N59 I00 N01 N02 R03 N04 N05 R06 ... ... N58 N59 I00 N01 N02 R03 N04 N05 R06 ...
... -|---|---|---|---|---|---|---|---|- ... ... -|---|---|---|---|---|---|---|---|- ...
... 61 62 63 64 65 66 67 68 69 ... ... 61 62 63 64 65 66 67 68 69 ...
Figure 19 Output order Figure 19 Output order
The amount of required initial buffering in the decoded picture The amount of required initial buffering in the decoded picture
buffer can be signaled in the buffering period SEI message or with buffer can be signaled in the buffering period SEI message or with
the num_reorder_frames syntax element of H.264 video usability the num_reorder_frames syntax element of H.264 video usability
information. num_reorder_frames indicates the maximum number of information. num_reorder_frames indicates the maximum number of
frames, complementary field pairs, or non-paired fields that precede frames, complementary field pairs, or non-paired fields that
any frame, complementary field pair, or non-paired field in the precede any frame, complementary field pair, or non-paired field in
sequence in decoding order and that follow it in output order. For the sequence in decoding order and that follow it in output order.
the sake of simplicity, we assume that num_reorder_frames is used to For the sake of simplicity, we assume that num_reorder_frames is
indicate the initial buffer in the decoded picture buffer. In this used to indicate the initial buffer in the decoded picture buffer.
example, num_reorder_frames is equal to 1. In this example, num_reorder_frames is equal to 1.
It can be observed that if the IDR picture I00 is lost during It can be observed that if the IDR picture I00 is lost during
transmission and a retransmission request is issued when the value of transmission and a retransmission request is issued when the value
the system clock is 62, there is one picture interval of time (until of the system clock is 62, there is one picture interval of time
the system clock reaches timestamp 63) to receive the retransmitted (until the system clock reaches timestamp 63) to receive the
IDR picture I00. retransmitted IDR picture I00.
Let us then assume that IDR pictures are transmitted two frame Let us then assume that IDR pictures are transmitted two frame
intervals earlier than their decoding position; i.e., the pictures intervals earlier than their decoding position; i.e., the pictures
are transmitted as follows: are transmitted as follows:
... I00 N58 N59 R03 N01 N02 R06 N04 N05 ... ... I00 N58 N59 R03 N01 N02 R06 N04 N05 ...
... --|---|---|---|---|---|---|---|---|- ... ... --|---|---|---|---|---|---|---|---|- ...
... 62 63 64 65 66 67 68 69 70 ... ... 62 63 64 65 66 67 68 69 70 ...
Figure 20 Interleaving: Early IDR pictures in sending order Figure 20 Interleaving: Early IDR pictures in sending order
skipping to change at page 89, line 4 skipping to change at page 91, line 22
Let us then assume that IDR pictures are transmitted two frame Let us then assume that IDR pictures are transmitted two frame
intervals earlier than their decoding position; i.e., the pictures intervals earlier than their decoding position; i.e., the pictures
are transmitted as follows: are transmitted as follows:
... I00 N58 N59 R03 N01 N02 R06 N04 N05 ... ... I00 N58 N59 R03 N01 N02 R06 N04 N05 ...
... --|---|---|---|---|---|---|---|---|- ... ... --|---|---|---|---|---|---|---|---|- ...
... 62 63 64 65 66 67 68 69 70 ... ... 62 63 64 65 66 67 68 69 70 ...
Figure 20 Interleaving: Early IDR pictures in sending order Figure 20 Interleaving: Early IDR pictures in sending order
The OPTIONAL sprop-interleaving-depth media type parameter is set The OPTIONAL sprop-interleaving-depth media type parameter is set
equal to 1 according to its definition. (The value of sprop- equal to 1 according to its definition. (The value of sprop-
interleaving-depth in this example can be derived as follows: Picture interleaving-depth in this example can be derived as follows:
I00 is the only picture preceding picture N58 or N59 in transmission Picture I00 is the only picture preceding picture N58 or N59 in
order and following it in decoding order. Except for pictures I00, transmission order and following it in decoding order. Except for
N58, and N59, the transmission order is the same as the decoding pictures I00, N58, and N59, the transmission order is the same as
order of pictures. As a coded picture is encapsulated into exactly the decoding order of pictures. As a coded picture is encapsulated
one NAL unit, the value of sprop-interleaving-depth is equal to the into exactly one NAL unit, the value of sprop-interleaving-depth is
maximum number of pictures preceding any picture in transmission equal to the maximum number of pictures preceding any picture in
order and following the picture in decoding order.) transmission order and following the picture in decoding order.)
The receiver buffering process contains two pictures at a time The receiver buffering process contains two pictures at a time
according to the value of the sprop-interleaving-depth parameter and according to the value of the sprop-interleaving-depth parameter
orders pictures from the reception order to the correct decoding and orders pictures from the reception order to the correct
order based on the value of DON associated with each picture. The decoding order based on the value of DON associated with each
output of the receiver buffering process is as follows: picture. The output of the receiver buffering process is as
follows:
... N58 N59 I00 R03 N01 N02 R06 N04 N05 ... ... N58 N59 I00 R03 N01 N02 R06 N04 N05 ...
... -|---|---|---|---|---|---|---|---|- ... ... -|---|---|---|---|---|---|---|---|- ...
... 63 64 65 66 67 68 69 70 71 ... ... 63 64 65 66 67 68 69 70 71 ...
Figure 21 Interleaving: Receiver buffer Figure 21 Interleaving: Receiver buffer
Again, an initial buffering delay of one picture interval is needed Again, an initial buffering delay of one picture interval is needed
to organize pictures from decoding order to output order, as depicted to organize pictures from decoding order to output order, as
below: depicted below:
... N58 N59 I00 N01 N02 R03 N04 N05 ... ... N58 N59 I00 N01 N02 R03 N04 N05 ...
... -|---|---|---|---|---|---|---|- ... ... -|---|---|---|---|---|---|---|- ...
... 64 65 66 67 68 69 70 71 ... ... 64 65 66 67 68 69 70 71 ...
Figure 22 Interleaving: Receiver buffer after reordering Figure 22 Interleaving: Receiver buffer after reordering
Note that the maximum delay that IDR pictures can undergo during Note that the maximum delay that IDR pictures can undergo during
transmission, including possible application, transport, or link transmission, including possible application, transport, or link
layer retransmission, is equal to three picture intervals. Thus, the layer retransmission, is equal to three picture intervals. Thus,
loss resiliency of IDR pictures is improved in systems supporting the loss resiliency of IDR pictures is improved in systems
retransmission compared to the case in which pictures were supporting retransmission compared to the case in which pictures
transmitted in their decoding order. were transmitted in their decoding order.
13.4. Robust Transmission Scheduling of Redundant Coded Slices 13.4. Robust Transmission Scheduling of Redundant Coded Slices
A redundant coded picture is a coded representation of a picture or a A redundant coded picture is a coded representation of a picture or
part of a picture that is not used in the decoding process if the a part of a picture that is not used in the decoding process if the
corresponding primary coded picture is correctly decoded. There corresponding primary coded picture is correctly decoded. There
should be no noticeable difference between any area of the decoded should be no noticeable difference between any area of the decoded
primary picture and a corresponding area that would result from primary picture and a corresponding area that would result from
application of the H.264 decoding process for any redundant picture application of the H.264 decoding process for any redundant picture
in the same access unit. A redundant coded slice is a coded slice in the same access unit. A redundant coded slice is a coded slice
that is a part of a redundant coded picture. that is a part of a redundant coded picture.
Redundant coded pictures can be used to provide unequal error Redundant coded pictures can be used to provide unequal error
protection in error-prone video transmission. If a primary coded protection in error-prone video transmission. If a primary coded
representation of a picture is decoded incorrectly, a corresponding representation of a picture is decoded incorrectly, a corresponding
redundant coded picture can be decoded. Examples of applications and redundant coded picture can be decoded. Examples of applications
coding techniques using the redundant codec picture feature include and coding techniques using the redundant codec picture feature
the video redundancy coding [23] and the protection of "key pictures" include the video redundancy coding [23] and the protection of "key
in multicast streaming [24]. pictures" in multicast streaming [24].
One property of many error-prone video communications systems is that One property of many error-prone video communications systems is
transmission errors are often bursty. Therefore, they may affect that transmission errors are often bursty. Therefore, they may
more than one consecutive transmission packets in transmission order. affect more than one consecutive transmission packets in
In low bit-rate video communication, it is relatively common that an transmission order. In low bit-rate video communication, it is
entire coded picture can be encapsulated into one transmission packet. relatively common that an entire coded picture can be encapsulated
Consequently, a primary coded picture and the corresponding redundant into one transmission packet. Consequently, a primary coded
coded pictures may be transmitted in consecutive packets in picture and the corresponding redundant coded pictures may be
transmission order. To make the transmission scheme more tolerant of transmitted in consecutive packets in transmission order. To make
bursty transmission errors, it is beneficial to transmit the primary the transmission scheme more tolerant of bursty transmission errors,
coded picture and redundant coded picture separated by more than a it is beneficial to transmit the primary coded picture and
single packet. The DON concept enables this. redundant coded picture separated by more than a single packet.
The DON concept enables this.
13.5. Remarks on Other Design Possibilities 13.5. Remarks on Other Design Possibilities
The slice header syntax structure of the H.264 coding standard The slice header syntax structure of the H.264 coding standard
contains the frame_num syntax element that can indicate the decoding contains the frame_num syntax element that can indicate the
order of coded frames. However, the usage of the frame_num syntax decoding order of coded frames. However, the usage of the
element is not feasible or desirable to recover the decoding order, frame_num syntax element is not feasible or desirable to recover
due to the following reasons: the decoding order, due to the following reasons:
o The receiver is required to parse at least one slice header per o The receiver is required to parse at least one slice header per
coded picture (before passing the coded data to the decoder). coded picture (before passing the coded data to the decoder).
o Coded slices from multiple coded video sequences cannot be o Coded slices from multiple coded video sequences cannot be
interleaved, as the frame number syntax element is reset to 0 in interleaved, as the frame number syntax element is reset to 0 in
each IDR picture. each IDR picture.
o The coded fields of a complementary field pair share the same o The coded fields of a complementary field pair share the same
value of the frame_num syntax element. Thus, the decoding order value of the frame_num syntax element. Thus, the decoding order
of the coded fields of a complementary field pair cannot be of the coded fields of a complementary field pair cannot be
recovered based on the frame_num syntax element or any other recovered based on the frame_num syntax element or any other
syntax element of the H.264 coding syntax. syntax element of the H.264 coding syntax.
The RTP payload format for transport of MPEG-4 elementary streams [25] The RTP payload format for transport of MPEG-4 elementary streams
enables interleaving of access units and transmission of multiple [25] enables interleaving of access units and transmission of
access units in the same RTP packet. An access unit is specified in multiple access units in the same RTP packet. An access unit is
the H.264 coding standard to comprise all NAL units associated with a specified in the H.264 coding standard to comprise all NAL units
primary coded picture according to subclause 7.4.1.2 of [1]. associated with a primary coded picture according to subclause
Consequently, slices of different pictures cannot be interleaved, and 7.4.1.2 of [1]. Consequently, slices of different pictures cannot
the multi-picture slice interleaving technique (see section 12.6) for be interleaved, and the multi-picture slice interleaving technique
improved error resilience cannot be used. (see section 12.6) for improved error resilience cannot be used.
14. Acknowledgements 14. Acknowledgements
Stephan Wenger, Miska Hannuksela, Thomas Stockhammer, Magnus Stephan Wenger, Miska Hannuksela, Thomas Stockhammer, Magnus
Westerlund, and David Singer are thanked as the authors of RFC 3984. Westerlund, and David Singer are thanked as the authors of RFC 3984.
Dave Lindbergh, Philippe Gentric, Gonzalo Camarillo, Gary Sullivan, Dave Lindbergh, Philippe Gentric, Gonzalo Camarillo, Gary Sullivan,
Joerg Ott, and Colin Perkins are thanked for careful review during Joerg Ott, and Colin Perkins are thanked for careful review during
the development of RFC 3984. Randell Jesup, Stephen Botzko, Magnus the development of RFC 3984. Randell Jesup, Stephen Botzko, Magnus
Westerlund, Alex Eleftheriadis, Thomas Schierl, and Tom Taylor are Westerlund, Alex Eleftheriadis, Thomas Schierl, and Tom Taylor are
thanked for their valuable comments and inputs during the development thanked for their valuable comments and inputs during the
of this memo. development of this memo.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
15. References 15. References
15.1. Normative References 15.1. Normative References
[1] ITU-T Recommendation H.264, "Advanced video coding for generic [1] ITU-T Recommendation H.264, "Advanced video coding for
audiovisual services", November 2007. generic audiovisual services", November 2007.
[2] ISO/IEC International Standard 14496-10:2008. [2] ISO/IEC International Standard 14496-10:2008.
[3] ITU-T Recommendation H.241, "Extended video procedures and [3] ITU-T Recommendation H.241, "Extended video procedures and
control signals for H.300 series terminals", May 2006. control signals for H.300 series terminals", May 2006.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement [4] Bradner, S., "Key words for use in RFCs to Indicate
Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[5] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, [5] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64, "RTP: A Transport Protocol for Real-Time Applications", STD
RFC 3550, July 2003. 64, RFC 3550, July 2003.
[6] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [6] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[7] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", [7] Josefsson, S., "The Base16, Base32, and Base64 Data
RFC 3548, July 2003. Encodings", RFC 3548, July 2003.
[8] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with [8] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002. Session Description Protocol (SDP)", RFC 3264, June 2002.
[9] Lennox, J., Ott, J., and Schierl, T., "Source-Specific Media [9] Lennox, J., Ott, J., and Schierl, T., "Source-Specific Media
Attributes in the Session Description Protocol", draft-ietf- Attributes in the Session Description Protocol", draft-ietf-
mmusic-sdp-source-attributes-02 (work in progress), October mmusic-sdp-source-attributes-02 (work in progress), October
2008. 2008.
15.2. Informative References 15.2. Informative References
[10] Luthra, A., Sullivan, G.J., and T. Wiegand (eds.), Special [10] Luthra, A., Sullivan, G.J., and T. Wiegand (eds.), Special
Issue on H.264/AVC. IEEE Transactions on Circuits and Systems Issue on H.264/AVC. IEEE Transactions on Circuits and Systems
on Video Technology, July 2003. on Video Technology, July 2003.
[11] Bormann, C., Cline, L., Deisher, G., Gardos, T., Maciocco, C., [11] Ott, J., Bormann, C., Sullivan, G., Wenger, S., and R. Even
Newell, D., Ott, J., Sullivan, G., Wenger, S., and C. Zhu, "RTP (Ed.), "RTP Payload Format for ITU-T Rec. H.263 Video", RFC
Payload Format for the 1998 Version of ITU-T Rec. H.263 Video 4629, January 2007.
(H.263+)", RFC 2429, October 1998.
[12] ISO/IEC IS 14496-2. [12] ISO/IEC IS 14496-2.
[13] Wenger, S., "H.26L over IP", IEEE Transaction on Circuits and [13] Wenger, S., "H.26L over IP", IEEE Transaction on Circuits and
Systems for Video technology, Vol. 13, No. 7, July 2003. Systems for Video technology, Vol. 13, No. 7, July 2003.
[14] Wenger, S., "H.26L over IP: The IP Network Adaptation Layer", [14] Wenger, S., "H.26L over IP: The IP Network Adaptation Layer",
Proceedings Packet Video Workshop 02, April 2002. Proceedings Packet Video Workshop 02, April 2002.
[15] Stockhammer, T., Hannuksela, M.M., and S. Wenger, "H.26L/JVT [15] Stockhammer, T., Hannuksela, M.M., and S. Wenger, "H.26L/JVT
Coding Network Abstraction Layer and IP-based Transport" in Coding Network Abstraction Layer and IP-based Transport" in
Proc. ICIP 2002, Rochester, NY, September 2002. Proc. ICIP 2002, Rochester, NY, September 2002.
[16] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video [16] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
Conferences with Minimal Control", STD 65, RFC 3551, July 2003. Video Conferences with Minimal Control", STD 65, RFC 3551,
July 2003.
[17] ITU-T Recommendation H.223, "Multiplexing protocol for low bit [17] ITU-T Recommendation H.223, "Multiplexing protocol for low
rate multimedia communication", July 2001. bit rate multimedia communication", July 2001.
[18] Li, A., "RTP Payload Format for Generic Forward Error [18] Li, A., "RTP Payload Format for Generic Forward Error
Correction", RFC 5109, December 2007. Correction", RFC 5109, December 2007.
[19] Stockhammer, T., Wiegand, T., Oelbaum, T., and F. Obermeier, [19] Stockhammer, T., Wiegand, T., Oelbaum, T., and F. Obermeier,
"Video Coding and Transport Layer Techniques for H.264/AVC- "Video Coding and Transport Layer Techniques for H.264/AVC-
Based Transmission over Packet-Lossy Networks", IEEE Based Transmission over Packet-Lossy Networks", IEEE
International Conference on Image Processing (ICIP 2003), International Conference on Image Processing (ICIP 2003),
Barcelona, Spain, September 2003. Barcelona, Spain, September 2003.
[20] Varsa, V. and M. Karczewicz, "Slice interleaving in compressed [20] Varsa, V. and M. Karczewicz, "Slice interleaving in
video packetization", Packet Video Workshop 2000. compressed video packetization", Packet Video Workshop 2000.
[21] Kang, S.H. and A. Zakhor, "Packet scheduling algorithm for [21] Kang, S.H. and A. Zakhor, "Packet scheduling algorithm for
wireless video streaming," International Packet Video Workshop wireless video streaming," International Packet Video
2002. Workshop 2002.
[22] Hannuksela, M.M., "Enhanced concept of GOP", JVT-B042, [22] Hannuksela, M.M., "Enhanced concept of GOP", JVT-B042,
available http://ftp3.itu.int/av-arch/video-site/0201_Gen/JVT- available http://ftp3.itu.int/av-arch/video-
B042.doc, anuary 2002. site/0201_Gen/JVT-B042.doc, anuary 2002.
[23] Wenger, S., "Video Redundancy Coding in H.263+", 1997 [23] Wenger, S., "Video Redundancy Coding in H.263+", 1997
International Workshop on Audio-Visual Services over Packet International Workshop on Audio-Visual Services over Packet
Networks, September 1997. Networks, September 1997.
[24] Wang, Y.-K., Hannuksela, M.M., and M. Gabbouj, "Error Resilient [24] Wang, Y.-K., Hannuksela, M.M., and M. Gabbouj, "Error
Video Coding Using Unequally Protected Key Pictures", in Proc. Resilient Video Coding Using Unequally Protected Key
International Workshop VLBV03, September 2003. Pictures", in Proc. International Workshop VLBV03, September
2003.
[25] van der Meer, J., Mackie, D., Swaminathan, V., Singer, D., and [25] van der Meer, J., Mackie, D., Swaminathan, V., Singer, D.,
P. Gentric, "RTP Payload Format for Transport of MPEG-4 and P. Gentric, "RTP Payload Format for Transport of MPEG-4
Elementary Streams", RFC 3640, November 2003. Elementary Streams", RFC 3640, November 2003.
[26] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [26] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC Norrman, "The Secure Real-time Transport Protocol (SRTP)",
3711, March 2004. RFC 3711, March 2004.
[27] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming [27] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
Protocol (RTSP)", RFC 2326, April 1998. Streaming Protocol (RTSP)", RFC 2326, April 1998.
[28] Handley, M., Perkins, C., and E. Whelan, "Session Announcement [28] Handley, M., Perkins, C., and E. Whelan, "Session
Protocol", RFC 2974, October 2000. Announcement Protocol", RFC 2974, October 2000.
[29] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117, [29] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117,
January 2008. January 2008.
[30] Wenger, S., Chandra, U., and M. Westerlund, "Codec Control [30] Wenger, S., Chandra, U., and M. Westerlund, "Codec Control
Messages in the RTP Audio-Visual Profile with Feedback (AVPF)", Messages in the RTP Audio-Visual Profile with Feedback
RFC 5104, February 2008. (AVPF)", RFC 5104, February 2008.
16. Authors' Addresses 16. Authors' Addresses
Ye-Kui Wang Ye-Kui Wang
Huawei Technologies Huawei Technologies
400 Somerset Corporate Blvd 400 Somerset Corp Blvd, Suite 602
Bridgewater, NJ 08807 Bridgewater, NJ 08807
USA USA
Phone: +1-908-393-4758 Phone: +1-908-541-3518
EMail: yekuiwang@huawei.com EMail: yekuiwang@huawei.com
Roni Even Roni Even
14 David Hamelech 14 David Hamelech
Tel Aviv 64953 Tel Aviv 64953
Israel Israel
Phone: +972-545481099 Phone: +972-545481099
Email: ron.even.tlv@gmail.com Email: ron.even.tlv@gmail.com
Tom Kristensen Tom Kristensen
TANDBERG TANDBERG
Philip Pedersens vei 22 Philip Pedersens vei 22
N-1366 Lysaker N-1366 Lysaker
Norway Norway
Phone: +47 67125125 Phone: +47 67125125
Email: tom.kristensen@tandberg.com, tomkri@ifi.uio.no Email: tom.kristensen@tandberg.com, tomkri@ifi.uio.no
17. Backward Compatibility to RFC 3984 17. Backward Compatibility to RFC 3984
skipping to change at page 95, line 4 skipping to change at page 97, line 29
The technical changes are listed in section 18. The technical changes are listed in section 18.
Items 1), 2), 3), 7), 9), 10), 12), 13) are bug-fix type of changes, Items 1), 2), 3), 7), 9), 10), 12), 13) are bug-fix type of changes,
and do not incur any backward compatibility issues. and do not incur any backward compatibility issues.
Item 4), addition of six new media type parameters, does not incur Item 4), addition of six new media type parameters, does not incur
any backward compatibility issues for SDP Offer/Answer based any backward compatibility issues for SDP Offer/Answer based
applications, as legacy RFC 3984 receivers ignore these parameters, applications, as legacy RFC 3984 receivers ignore these parameters,
and it is fine for legacy RFC 3984 senders not to use these and it is fine for legacy RFC 3984 senders not to use these
parameters as they are optional. However, there is a backward parameters as they are optional. However, there is a backward
compatibility issue for SDP declarative usage based applications, e.g. compatibility issue for SDP declarative usage based applications,
those using RTSP and SAP, because the SDP receiver per RFC 3984 e.g. those using RTSP and SAP, because the SDP receiver per RFC
cannot accept a session for which the SDP includes an unrecognized 3984 cannot accept a session for which the SDP includes an
parameter. Therefore, the RTSP or SAP server may have to prepare two unrecognized parameter. Therefore, the RTSP or SAP server may have
sets of streams, one for legacy RFC 3984 receivers and one for to prepare two sets of streams, one for legacy RFC 3984 receivers
receivers according to this memo. and one for receivers according to this memo.
Items 5), 6) and 11) are related to out-of-band transport of Items 5), 6) and 11) are related to out-of-band transport of
parameter sets. There are following backward compatibility issues. parameter sets. There are following backward compatibility issues.
1) When a legacy sender per RFC 3984 includes parameter sets for a 1) When a legacy sender per RFC 3984 includes parameter sets for a
level different than the default level indicated by profile-level- level different than the default level indicated by profile-
id to sprop-parameter-sets, the parameter value of sprop- level-id to sprop-parameter-sets, the parameter value of sprop-
parameter-sets is invalid to the receiver per this memo and parameter-sets is invalid to the receiver per this memo and
therefore the session may be rejected. therefore the session may be rejected.
2) In SDP Offer/Answer between a legacy offerer per RFC 3984 and an 2) In SDP Offer/Answer between a legacy offerer per RFC 3984 and an
answerer per this memo, when the answerer includes in the answer answerer per this memo, when the answerer includes in the answer
parameter sets that are not a superset of the parameter sets parameter sets that are not a superset of the parameter sets
included in the offer, the parameter value of sprop-parameter-sets included in the offer, the parameter value of sprop-parameter-
is invalid to offerer and the session may not be initiated sets is invalid to offerer and the session may not be initiated
properly (related to change item 11)). properly (related to change item 11)).
3) When one endpoint A per this memo includes in-band-parameter-sets 3) When one endpoint A per this memo includes in-band-parameter-
equal to 1, the other side B per RFC 3984 does not understand that sets equal to 1, the other side B per RFC 3984 does not
it must transmit parameter sets in-band and B may still exclude understand that it must transmit parameter sets in-band and B
parameter sets in the in-band stream it is sending. Consequently may still exclude parameter sets in the in-band stream it is
endpoint A cannot decode the stream it receives. sending. Consequently endpoint A cannot decode the stream it
receives.
Item 7), allowance of conveying sprop-parameter-sets and sprop-level- Item 7), allowance of conveying sprop-parameter-sets and sprop-
parameter-sets using the "fmtp" source attribute as specified in level-parameter-sets using the "fmtp" source attribute as specified
section 6.3 of [9], is similar as item 4). It does not incur any in section 6.3 of [9], is similar as item 4). It does not incur
backward compatibility issues for SDP Offer/Answer based applications, any backward compatibility issues for SDP Offer/Answer based
as legacy RFC 3984 receivers ignore the "fmtp" source attribute, and applications, as legacy RFC 3984 receivers ignore the "fmtp" source
it is fine for legacy RFC 3984 senders not to use the "fmtp" source attribute, and it is fine for legacy RFC 3984 senders not to use
attribute as it is optional. However, there is a backward the "fmtp" source attribute as it is optional. However, there is a
compatibility issue for SDP declarative usage based applications, e.g. backward compatibility issue for SDP declarative usage based
those using RTSP and SAP, because the SDP receiver per RFC 3984 applications, e.g. those using RTSP and SAP, because the SDP
cannot accept a session for which the SDP includes an unrecognized receiver per RFC 3984 cannot accept a session for which the SDP
parameter (i.e., the "fmtp" source attribute). Therefore, the RTSP includes an unrecognized parameter (i.e., the "fmtp" source
or SAP server may have to prepare two sets of streams, one for legacy attribute). Therefore, the RTSP or SAP server may have to prepare
RFC 3984 receivers and one for receivers according to this memo. two sets of streams, one for legacy RFC 3984 receivers and one for
receivers according to this memo.
Item 14) removed that use of out-of-band transport of parameter sets Item 14) removed that use of out-of-band transport of parameter
is recommended. As out-of-band transport of parameter sets is still sets is recommended. As out-of-band transport of parameter sets is
allowed, this change does not incur any backward compatibility issues. still allowed, this change does not incur any backward
compatibility issues.
Item 15) does not incur any backward compatibility issues as the Item 15) does not incur any backward compatibility issues as the
added subsection 8.5 is informative.