draft-ietf-avt-rtp-rfc3984bis-01.txt   draft-ietf-avt-rtp-rfc3984bis-02.txt 
Audio/Video Transport WG Y.-K. Wang Audio/Video Transport WG Y.-K. Wang
Internet Draft Nokia Internet Draft Nokia
Intended status: Standards track R. Even Intended status: Standards track R. Even
Expires: May 2009 Self-employed Expires: June 2009 Self-employed
T. Kristensen T. Kristensen
Tandberg Tandberg
November 3, 2008 December 16, 2008
RTP Payload Format for H.264 Video RTP Payload Format for H.264 Video
draft-ietf-avt-rtp-rfc3984bis-01.txt draft-ietf-avt-rtp-rfc3984bis-02.txt
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Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
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
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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 intends to obsolete RFC 3984. Changes from RFC 3984 are This memo intends to obsolete RFC 3984. Changes from RFC 3984 are
summarized in section 17. Issues on backward compatibility to RFC summarized in section 17. Issues on backward compatibility to RFC
3984 are discussed in section 16. 3984 are discussed in section 16.
Table of Contents Table of Contents
1. Introduction...................................................4 1. Introduction...................................................3
1.1. The H.264 Codec...........................................4 1.1. The H.264 Codec...........................................3
1.2. Parameter Set Concept.....................................5 1.2. Parameter Set Concept.....................................3
1.3. Network Abstraction Layer Unit Types......................6 1.3. Network Abstraction Layer Unit Types......................3
2. Conventions....................................................7 2. Conventions....................................................3
3. Scope..........................................................7 3. Scope..........................................................3
4. Definitions and Abbreviations..................................7 4. Definitions and Abbreviations..................................3
4.1. Definitions...............................................7 4.1. Definitions...............................................3
4.2. Abbreviations.............................................9 4.2. Abbreviations.............................................3
5. RTP Payload Format............................................10 5. RTP Payload Format.............................................3
5.1. RTP Header Usage.........................................10 5.1. RTP Header Usage..........................................3
5.2. Payload Structures.......................................13 5.2. Payload Structures........................................3
5.3. NAL Unit Header Usage....................................14 5.3. NAL Unit Header Usage.....................................3
5.4. Packetization Modes......................................16 5.4. Packetization Modes.......................................3
5.5. Decoding Order Number (DON)..............................17 5.5. Decoding Order Number (DON)...............................3
5.6. Single NAL Unit Packet...................................20 5.6. Single NAL Unit Packet....................................3
5.7. Aggregation Packets......................................21 5.7. Aggregation Packets.......................................3
5.7.1. Single-Time Aggregation Packet......................23 5.7.1. Single-Time Aggregation Packet.......................3
5.7.2. Multi-Time Aggregation Packets (MTAPs)..............25 5.7.2. Multi-Time Aggregation Packets (MTAPs)...............3
5.7.3. Fragmentation Units (FUs)...........................29 5.7.3. Fragmentation Units (FUs)............................3
6. Packetization Rules...........................................33 6. Packetization Rules............................................3
6.1. Common Packetization Rules...............................33 6.1. Common Packetization Rules................................3
6.2. Single NAL Unit Mode.....................................34 6.2. Single NAL Unit Mode......................................3
6.3. Non-Interleaved Mode.....................................34 6.3. Non-Interleaved Mode......................................3
6.4. Interleaved Mode.........................................34 6.4. Interleaved Mode..........................................3
7. De-Packetization Process......................................35 7. De-Packetization Process.......................................3
7.1. Single NAL Unit and Non-Interleaved Mode.................35 7.1. Single NAL Unit and Non-Interleaved Mode..................3
7.2. Interleaved Mode.........................................35 7.2. Interleaved Mode..........................................3
7.2.1. Size of the De-interleaving Buffer..................36 7.2.1. Size of the De-interleaving Buffer...................3
7.2.2. De-interleaving Process.............................36 7.2.2. De-interleaving Process..............................3
7.3. Additional De-Packetization Guidelines...................38 7.3. Additional De-Packetization Guidelines....................3
8. Payload Format Parameters.....................................39 8. Payload Format Parameters......................................3
8.1. Media Type Registration..................................39 8.1. Media Type Registration...................................3
8.2. SDP Parameters...........................................55 8.2. SDP Parameters............................................3
8.2.1. Mapping of Payload Type Parameters to SDP...........55 8.2.1. Mapping of Payload Type Parameters to SDP............3
8.2.2. Usage with the SDP Offer/Answer Model...............56 8.2.2. Usage with the SDP Offer/Answer Model................3
8.2.3. Usage in Declarative Session Descriptions...........64 8.2.3. Usage in Declarative Session Descriptions............3
8.3. Examples.................................................65 8.3. Examples..................................................3
8.4. Parameter Set Considerations.............................70 8.4. Parameter Set Considerations..............................3
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)..................................73 Parameter Sets (Informative)...................................3
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..............................................73 Refresh Point...............................................3
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 a
Decoder Refresh Point......................................74 Decoder Refresh Point.......................................3
9. Security Considerations.......................................74 9. Security Considerations........................................3
10. Congestion Control...........................................75 10. Congestion Control............................................3
11. IANA Consideration...........................................76 11. IANA Consideration............................................3
12. Informative Appendix: Application Examples...................76 12. Informative Appendix: Application Examples....................3
12.1. Video Telephony according to ITU-T Recommendation H.241 12.1. Video Telephony according to ITU-T Recommendation H.241
Annex A.......................................................76 Annex A........................................................3
12.2. Video Telephony, No Slice Data Partitioning, No NAL Unit 12.2. Video Telephony, No Slice Data Partitioning, No NAL Unit
Aggregation...................................................77 Aggregation....................................................3
12.3. Video Telephony, Interleaved Packetization Using NAL Unit 12.3. Video Telephony, Interleaved Packetization Using NAL Unit
Aggregation...................................................77 Aggregation....................................................3
12.4. Video Telephony with Data Partitioning..................78 12.4. Video Telephony with Data Partitioning...................3
12.5. Video Telephony or Streaming with FUs and Forward Error 12.5. Video Telephony or Streaming with FUs and Forward Error
Correction....................................................78 Correction.....................................................3
12.6. Low Bit-Rate Streaming..................................81 12.6. Low Bit-Rate Streaming...................................3
12.7. Robust Packet Scheduling in Video Streaming.............81 12.7. Robust Packet Scheduling in Video Streaming..............3
13. Informative Appendix: Rationale for Decoding Order Number....82 13. Informative Appendix: Rationale for Decoding Order Number.....3
13.1. Introduction............................................82 13.1. Introduction.............................................3
13.2. Example of Multi-Picture Slice Interleaving.............83 13.2. Example of Multi-Picture Slice Interleaving..............3
13.3. Example of Robust Packet Scheduling.....................84 13.3. Example of Robust Packet Scheduling......................3
13.4. Robust Transmission Scheduling of Redundant Coded Slices88 13.4. Robust Transmission Scheduling of Redundant Coded Slices.3
13.5. Remarks on Other Design Possibilities...................89 13.5. Remarks on Other Design Possibilities....................3
14. Acknowledgements.............................................89 14. Acknowledgements..............................................3
15. References...................................................90 15. References....................................................3
15.1. Normative References....................................90 15.1. Normative References.....................................3
15.2. Informative References..................................90 15.2. Informative References...................................3
Authors' Addresses...............................................92 Authors' Addresses................................................3
Intellectual Property Statement..................................93 Intellectual Property Statement...................................3
Disclaimer of Validity...........................................93 Disclaimer of Validity............................................3
Acknowledgement..................................................93 Acknowledgement...................................................3
16. Backward Compatibility to RFC 3984...........................94 16. Backward Compatibility to RFC 3984............................3
17. Changes from RFC 3984........................................95 17. Changes from RFC 3984.........................................3
18. Open issues..................................................96
1. Introduction 1. Introduction
This memo intends to obsolete RFC 3984. Changes from RFC 3984 are This memo intends to obsolete RFC 3984. Changes from RFC 3984 are
summarized in section 17. Issues on backward compatibility to RFC summarized in section 17. Issues on backward compatibility to RFC
3984 are discussed in section 16. 3984 are discussed in section 16.
1.1. The H.264 Codec 1.1. The H.264 Codec
This memo specifies an RTP payload specification for the video coding This memo specifies an RTP payload specification for the video coding
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ISO/IEC counterpart of the coding standard. ISO/IEC counterpart of the coding standard.
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 covers
all forms of digital compressed video from, low bit-rate Internet all forms of digital compressed video from, low bit-rate Internet
streaming applications to HDTV broadcast and Digital Cinema streaming applications to HDTV broadcast and Digital Cinema
applications with nearly lossless coding. Compared to the current applications with nearly lossless coding. Compared to the current
state of technology, the overall performance of H.264 is such that state of technology, the overall performance of H.264 is such that
bit rate savings of 50% or more are reported. Digital Satellite TV bit rate savings of 50% or more are reported. Digital Satellite TV
quality, for example, was reported to be achievable at 1.5 Mbit/s, quality, for example, was reported to be achievable at 1.5 Mbit/s,
compared to the current operation point of MPEG 2 video at around 3.5 compared to the current operation point of MPEG 2 video at around 3.5
Mbit/s [9]. Mbit/s [10].
The codec specification [1] itself distinguishes conceptually between The codec specification [1] itself distinguishes conceptually between
a video coding layer (VCL) and a network abstraction layer (NAL). a video coding layer (VCL) and a network abstraction layer (NAL).
The VCL contains the signal processing functionality of the codec; The VCL contains the signal processing functionality of the codec;
mechanisms such as transform, quantization, and motion compensated mechanisms such as transform, quantization, and motion compensated
prediction; and a loop filter. It follows the general concept of prediction; and a loop filter. It follows the general concept of
most of today's video codecs, a macroblock-based coder that uses most of today's video codecs, a macroblock-based coder that uses
inter picture prediction with motion compensation and transform inter picture prediction with motion compensation and transform
coding of the residual signal. The VCL encoder outputs slices: a bit coding of the residual signal. The VCL encoder outputs slices: a bit
string that contains the macroblock data of an integer number of string that contains the macroblock data of an integer number of
macroblocks, and the information of the slice header (containing the macroblocks, and the information of the slice header (containing the
spatial address of the first macroblock in the slice, the initial spatial address of the first macroblock in the slice, the initial
quantization parameter, and similar information). Macroblocks in quantization parameter, and similar information). Macroblocks in
slices are arranged in scan order unless a different macroblock slices are arranged in scan order unless a different macroblock
allocation is specified, by using the so-called Flexible Macroblock allocation is specified, by using the so-called Flexible Macroblock
Ordering syntax. In-picture prediction is used only within a slice. Ordering syntax. In-picture prediction is used only within a slice.
More information is provided in [9]. 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 is
not relevant. 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-
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standards). Also, there are NAL units that affect many pictures and standards). Also, there are NAL units that affect many pictures and
that are, therefore, inherently timeless. For this reason, the that are, therefore, inherently timeless. For this reason, the
handling of the RTP timestamp requires some special considerations handling of the RTP timestamp requires some special considerations
for NAL units for which the sampling or presentation time is not for NAL units for which the sampling or presentation time is not
defined or, at transmission time, unknown. 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 duplication
of RFC 2429 [10] or MPEG-4's Header Extension Code (HEC) [11] of RFC 2429 [11] or MPEG-4's Header Extension Code (HEC) [12]
unnecessary. This was achieved by decoupling information relevant to unnecessary. This was achieved by decoupling information relevant to
more than one slice from the media stream. This higher layer meta more than one slice from the media stream. This higher layer meta
information should be sent reliably, asynchronously, and in advance information should be sent reliably, asynchronously, and in advance
from the RTP packet stream that contains the slice packets. from the RTP packet stream that contains the slice packets.
(Provisions for sending this information in-band are also available (Provisions for sending this information in-band are also available
for applications that do not have an out-of-band transport channel for applications that do not have an out-of-band transport channel
appropriate for the purpose.) The combination of the higher-level appropriate for the purpose.) The combination of the higher-level
parameters is called a parameter set. The H.264 specification parameters is called a parameter set. The H.264 specification
includes two types of parameter sets: sequence parameter set and includes two types of parameter sets: sequence parameter set and
picture parameter set. An active sequence parameter set remains picture parameter set. An active sequence parameter set remains
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This mechanism allows the decoupling of the transmission of parameter This mechanism allows the decoupling of the transmission of parameter
sets from the packet stream, and the transmission of them by external sets from the packet stream, and the transmission of them by external
means (e.g., as a side effect of the capability exchange), or through means (e.g., as a side effect of the capability exchange), or through
a (reliable or unreliable) control protocol. It may even be possible a (reliable or unreliable) control protocol. It may even be possible
that they are never transmitted but are fixed by an application that they are never transmitted but are fixed by an application
design specification. 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 [12], [13], Tutorial information on the NAL design can be found in [13], [14],
and [14]. 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 co-
serves as the payload header of this RTP payload format. The payload serves as the payload header of this RTP payload format. The payload
of a NAL unit follows immediately. 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 in
[1], but the essential properties of the NAL unit type octet are [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:
+---------------+ +---------------+
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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 contains
errors or losses. 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 of
DON are in the range of 0 to 65535, inclusive. After reaching DON are in the range of 0 to 65535, inclusive. After reaching
the maximum value, the value of DON wraps around to 0. 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 NAL
unit would be transported in its own RTP packet. unit would be transported in its own RTP packet.
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certain aspects of the RTP payload headers or the RTP payload and certain aspects of the RTP payload headers or the RTP payload and
reacting to the contents. 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 those packets to congestion on a certain link, it can identify and remove
whose dropping has the smallest negative impact on the user those packets whose elimination produces the least adverse
experience and remove them in order to remove the congestion effect on the user experience.
and/or keep the delay low.
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 in
[3]. Static macroblocks free up additional processing cycles for [3]. Static macroblocks free up additional processing cycles for
the handling of non-static macroblocks. Based on a given amount the handling of non-static macroblocks. Based on a given amount
of video processing resources and a given resolution, a higher of video processing resources and a given resolution, a higher
number of static macroblocks enables a correspondingly higher number of static macroblocks enables a correspondingly higher
frame rate. 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 all
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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 [13]. 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 A
profile in use. 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 if
the video bitstream conforms to a profile in which data 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 the
Main or Baseline profiles. Main or Baseline profiles.
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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 MUST
enforce the following packetization rule: 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 unit
packets, or mix both concepts, in an RTP translator. The RTP packets, or mix both concepts, in an RTP translator. The RTP
translator SHOULD take into account at least the following 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 [17], 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 RTCP
as per RFC 3550. 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-mode
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11, and bit 4 (constraint_set3_flag) of the profile-iop byte 11, and bit 4 (constraint_set3_flag) of the profile-iop byte
is equal to 1, the default level is level 1b. 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 profile_idc
and profile-iop that represent the same sub-profile. 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 full
set of coding tools supported by one profile. In the set of coding tools supported by one profile. In the
following, x may be either 0 or 1, and other notions as following, x may be either 0 or 1, while the profile names
follows. CB: Constrained Baseline profile, B: Baseline are indicated as follows. CB: Constrained Baseline profile,
profile, M: Main profile, E: Extended profile, H: High B: Baseline profile, M: Main profile, E: Extended profile,
profile, H10: High 10 profile, H42: High 4:2:2 profile, H: High profile, H10: High 10 profile, H42: High 4:2:2
H44: High 4:4:4 Predictive profile, H10I: High 10 Intra profile, H44: High 4:4:4 Predictive profile, H10I: High 10
profile, H42I: High 4:2:2 Intra profile, H44I: High 4:4:4 Intra profile, H42I: High 4:2:2 Intra profile, H44I: High
Intra profile, and C44I: CAVLC 4:4:4 Intra profile. 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 x1xx0000 CB 42 (B) x1xx0000
4D 1xxx0000 same as: 4D (M) 1xxx0000
58 11xx0000 same as: 58 (E) 11xx0000
64, 6E, 7A or F4 1xx00000 same as: 64 (H), 6E (H10), 1xx00000
B 42 x0xx0000 7A (H42), or F4 (H44)
58 10xx0000 B 42 (B) x0xx0000
M 4D 0x0x0000 same as: 58 (E) 10xx0000
64,6E,7A or F4 01000000 M 4D (M) 0x0x0000
same as: 64 (H), 6E (H10), 01000000
7A (H42), or F4 (H44)
E 58 00xx0000 E 58 00xx0000
H 64 00000000 H 64 00000000
H10 6E 00000000 H10 6E 00000000
H42 7A 00000000 H42 7A 00000000
H44 F4 00000000 H44 F4 00000000
H10I 64 00010000 H10I 64 00010000
H42I 7A 00010000 H42I 7A 00010000
H44I F4 00010000 H44I F4 00010000
C44I 2C 00010000 C44I 2C 00010000
Note that other combinations of profile_idc and profile-iop For example, in the table above, profile_idc equal to 58
(note listed in Table 13) may represent a sub-profile (Extended) with profile-iop equal to 11xx0000 indicates the
equivalent to the common subset of coding tools for more than same sub-profile corresponding to profile_idc equal to 42
one profile. Note also that a decoder conforming to a certain (Baseline) with profile-iop equal to x1xx0000. Note that
profile may be able to decode bitstreams conforming to other other combinations of profile_idc and profile-iop (note listed
profiles. For example, a decoder conforming to the High 4:4:4 in Table 5) may represent a sub-profile equivalent to the
profile at certain level must be able to decode bitstreams common subset of coding tools for more than one profile. Note
confirming to the Constrained Baseline, Main, High, High 10 or also that a decoder conforming to a certain profile may be
High 4:2:2 profile at the same or a lower level. able to decode bitstreams conforming to other profiles. For
example, a decoder conforming to the High 4:4:4 profile at
certain level must be able to decode bitstreams confirming to
the Constrained Baseline, Main, High, High 10 or High 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,
skipping to change at page 42, line 19 skipping to change at page 42, line 25
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]). The
one-of-N codec selection procedure may also be used to one-of-N codec selection procedure may also be used to
provide different combinations of profile_idc and profile- provide different combinations of profile_idc and profile-
iop that represent the same sub-profile. When there are a iop that represent the same sub-profile. When there are
lot of different combinations of profile_idc and profile- many different combinations of profile_idc and profile-iop
iop that represent the same sub-profile, using the one-of-N that represent the same sub-profile, using the one-of-N
codec selection procedure may result into large-sized SDP codec selection procedure may result into a fairly large
message. Therefore, a receiver should understand the SDP message. Therefore, a receiver should understand the
different equivalent combinations of profile_idc and different equivalent combinations of profile_idc and
profile-iop that represent the same sub-profile, and be profile-iop that represent the same sub-profile, and be
ready to accept an offer using any of the equivalent ready to accept an offer using any of the equivalent
combinations. 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 implied. without additional constraints at Level 1 MUST be implied.
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
skipping to change at page 47, line 49 skipping to change at page 48, line 7
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 any
capability exchange procedure. The value of the parameter is capability exchange procedure. The value of the parameter is
the base64 [7] representation of the initial parameter set NAL a comma (',') separated list of base64 [7] representations of
units as specified in sections 7.3.2.1 and 7.3.2.2 of [1]. parameter set NAL units as specified in sections 7.3.2.1 and
7.3.2.2 of [1]. Note that the number of bytes in a parameter
The parameter sets are conveyed in decoding order, and no set NAL unit is typically less than 10, but a picture
framing of the parameter set NAL units takes place. A comma parameter set NAL unit can contain several hundreds of bytes.
(',') is used to separate any pair of parameter sets in the
list. Note that the number of bytes in a parameter set NAL
unit is typically less than 10, 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 in
the SDP Offer/Answer model, each with its own sprop- 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 double-buffer identifiers). Therefore, a receiver should buffer all
all sprop-parameter-sets and make them available to the sprop-parameter-sets and make them available to the decoder
decoder instance that decodes a certain payload type. 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 equal
to the default level. 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
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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 to
the preceding PLId. the preceding PLId.
Informative note: This parameter allows for efficient level Informative note: This parameter allows for efficient level
downgrade in SDP Offer/Answer and out-of-band transport of downgrade in SDP Offer/Answer and out-of-band transport of
parameter sets, simultaneously. parameter sets, simultaneously.
use-level-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 will ignore the sprop-level-parameter-sets parameter, and does not
sprop-level-parameter-sets when present. The value 1 understand the "fmtp" source attribute as specified in section
indicates that the receiver understands the sprop-level- 6.3 of [9], and will ignore sprop-level-parameter-sets when
parameter-sets parameter and is capable of using parameter present, and will ignore sprop-parameter-sets when conveyed
sets contained therein. using the "fmtp" source attribute. The value 1 indicates that
the receiver understands the sprop-level-parameter-sets
parameter, and understands the "fmtp" source attribute as
specified in section 6.3 of [9], and is capable of using
parameter sets contained in the sprop-level-parameter-sets or
contained in the sprop-parameter-sets that is conveyed using
the "fmtp" source attribute.
Informative note: An RFC 3984 receiver does not understand Informative note: An RFC 3984 receiver does not understand
both sprop-level-parameter-sets and use-level-parameter- sprop-level-parameter-sets, use-level-src-parameter-sets,
sets. Therefore, during SDP Offer/Answer, an RFC 3984 or the "fmtp" source attribute as specified in section 6.3
of [9]. Therefore, during SDP Offer/Answer, an RFC 3984
receiver as the answerer will simply ignore sprop-level- receiver as the answerer will simply ignore sprop-level-
parameter-sets, when present in an offer. Assume that the parameter-sets, when present in an offer, and sprop-
offered payload type was accepted at a level lower than the parameter-sets, when conveyed using the "fmtp" source
default level. If the offered payload type included sprop- attribute as specified in section 6.3 of [9]. Assume that
level-parameter-sets, and the offerer sees that the the offered payload type was accepted at a level lower than
answerer has not included use-level-parameter-sets equal to the default level. If the offered payload type included
1 in the answer, the offerer gets to know that in-band sprop-level-parameter-sets or included sprop-parameter-sets
transport of parameter sets is needed. conveyed using the "fmtp" source attribute, and the offerer
sees that the answerer has not included use-level-src-
sprop-ssrc: parameter-sets equal to 1 in the answer, the offerer gets
This parameter MAY be used to signal the properties of an RTP to know that in-band transport of parameter sets is needed.
packet stream. It specifies the SSRC values in the RTP header
of all RTP packets in the RTP packet stream. The syntax of
this parameter is the same as the syntax of the SSRC field in
the RTP header.
Informative note: This parameter allows for out-of-band
transport of parameter sets in topologies like Topo-Video-
switch-MCU [28].
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
skipping to change at page 56, line 14 skipping to change at page 56, line 21
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 (the
media subtype). 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-pic-
cap", "sprop-parameter-sets", "sprop-level-parameter-sets", "use- cap", "use-level-src-parameter-sets", "packetization-mode",
level-parameter-sets", "sprop-ssrc", "packetization-mode", "sprop- "sprop-interleaving-depth", "sprop-deint-buf-req", "deint-buf-
interleaving-depth", "sprop-deint-buf-req", "deint-buf-cap", cap", "sprop-init-buf-time", "sprop-max-don-diff", "max-rcmd-nalu-
"sprop-init-buf-time", "sprop-max-don-diff", "max-rcmd-nalu-size", size", "sar-understood", and "sar-supported", when present, MUST
"sar-understood", and "sar-supported", when present, MUST be be included in the "a=fmtp" line of SDP. These parameters are
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. separated list of parameter=value pairs.
o The OPTIONAL parameters "sprop-parameter-sets" and "sprop-level-
parameter-sets", when present, MUST be included in the "a=fmtp"
line of SDP or conveyed using the "fmtp" source attribute as
specified in section 6.3 of [9]. For a particular media format
(i.e., RTP payload type), a "sprop-parameter-sets" or "sprop-
level-parameter-sets" MUST NOT be both included in the "a=fmtp"
line of SDP and conveyed using the "fmtp" source attribute. When
included in the "a=fmtp" line of SDP, these parameters are
expressed as a media type string, in the form of a semicolon
separated list of parameter=value pairs. When conveyed using the
"fmtp" source attribute, these parameters are only associated with
the given source and payload type as parts of the "fmtp" source
attribute.
Informative note: Conveyance of "sprop-parameter-sets" and
"sprop-level-parameter-sets" using the "fmtp" source attribute
allows for out-of-band transport of parameter sets 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=<base64 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 [8]
for negotiation for unicast usage, the following limitations and for negotiation for unicast usage, the following limitations and
rules apply: rules apply:
o The parameters identifying a media format configuration for H.264 o The parameters identifying a media format configuration for H.264
are "profile-level-id" and "packetization-mode", when present. are "profile-level-id" and "packetization-mode", when present.
These media format configuration parameters (except for the level These media format configuration parameters (except for the level
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equal to 66, 77 or 88 and level_idc is equal to 11. 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: An offerer, when receiving the answer, 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
media type (i.e., video/H264) and the above media format 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 already
declared, in order to determine whether the configuration in declared. This will enable it to determine whether the
question is new or equivalent to a configuration already configuration in question is new or if it is equivalent to
offered. configuration already offered, since a different payload 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", "sprop-init-buf-time", and "sprop-ssrc" "sprop-max-don-diff", and "sprop-init-buf-time" describe the
describe the properties of the RTP packet stream that the offerer properties of the RTP packet stream that the offerer or answerer
or answerer is sending for the media format configuration. This is sending for the media format configuration. This differs from
differs from the normal usage of the Offer/Answer parameters: the normal usage of the Offer/Answer parameters: normally such
normally such parameters declare the properties of the stream that parameters declare the properties of the stream that the offerer
the offerer or the answerer is able to receive. When dealing with or the answerer is able to receive. When dealing with H.264, the
H.264, the offerer assumes that the answerer will be able to offerer assumes that the answerer will be able to receive media
receive media encoded using the configuration being offered. 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; sent by the declaring entity with the same configuration;
i.e., they are dependent on their source. Rather than being i.e., they are dependent on their source. Rather than being
bound to the payload type, the values may have to be applied bound to the payload type, the values may have to be applied
to another payload type when being sent, as they apply for the to another payload type when being sent, as they apply for the
configuration. 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-
skipping to change at page 58, line 41 skipping to change at page 59, line 15
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 "deint-
buf-cap". For interleaved streams, it is also RECOMMENDED to buf-cap". For interleaved streams, it is also RECOMMENDED to
consider offering multiple payload types with different buffering consider offering multiple payload types with different buffering
requirements when the capabilities of the receiver are unknown. 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, is used for out-of-band transport of parameter, when present (included in the "a=fmtp" line of SDP or
parameter sets. However, when out-of-band transport of parameter conveyed using the "fmtp" source attribute as specified in section
sets is used, parameter sets MAY still be additionally transported 6.3 of [9]), is used for out-of-band transport of parameter sets.
in-band. If neither "sprop-parameter-sets" nor "sprop-level- However, when out-of-band transport of parameter sets is used,
parameter-sets" is present, then only in-band transport of parameter sets MAY still be additionally transported in-band. If
parameter sets is used. neither "sprop-parameter-sets" nor "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" and
"sprop-level-parameter-sets". An answer MAY include "sprop- "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".
When an offered payload type is accepted without level downgrade, When an offered payload type is accepted without level downgrade,
i.e. the default level is accepted, the following applies. i.e. the default level is accepted, the following applies.
o The answerer MUST be prepared to use the parameter sets o When there is a "sprop-parameter-sets" included in the
included in "sprop-parameter-sets", when present, for "a=fmtp" line of SDP, the answerer MUST be prepared to use
decoding the incoming NAL unit stream, and ignore "sprop- the parameter sets included in "sprop-parameter-sets" for
level-parameter-sets", when present. decoding the incoming NAL unit stream.
o When there is a "sprop-parameter-sets" conveyed using the
"fmtp" source attribute as specified in section 6.3 of [9],
and the answerer understands the "fmtp" source attribute, it
MUST be prepared to use the parameter sets included in
"sprop-parameter-sets" for decoding the incoming NAL unit
stream, and it MUST include either "use-level-src-parameter-
sets" equal to 1 or the "fmtp" source attribute in the
answer.
o When there is a "sprop-parameter-sets" conveyed using the
"fmtp" source attribute as specified in section 6.3 of [9],
and the answerer does not understand the "fmtp" source
attribute, in-band transport of parameter sets MUST be used,
and the answerer MUST NOT include "use-level-src-parameter-
sets" equal to 1 or the "fmtp" source attribute in the
answer.
o When "sprop-parameter-sets" is not present, in-band o When "sprop-parameter-sets" is not present, in-band
transport of parameter sets MUST be used. transport of parameter sets MUST be used, and the answer
MUST NOT include "use-level-src-parameter-sets" equal to 1.
o The answerer MUST ignore "sprop-level-parameter-sets", when
present (either included in the "a=fmtp" line of SDP or
conveyed using the "fmtp" source attribute).
When level downgrade is in use, i.e., a level lower than the When level downgrade is in use, i.e., a level lower than the
default level offered is accepted, the following applies. default level offered is accepted, the following applies.
o If "use-level-parameter-sets" is not present in the answer o The answerer MUST ignore "sprop-parameter-sets", when
for the accepted payload type or the value is equal to 0 in present (either included in the "a=fmtp" line of SDP or
the answer for the accepted payload type, the answerer MUST conveyed using the "fmtp" source attribute).
ignore "sprop-parameter-sets" and "sprop-level-parameter-
sets", when present in the offer for the accepted payload
type.
o Otherwise (the "use-level-parameter-sets" is present in the o If "use-level-src-parameter-sets" equal to 1 the "fmtp"
answer for the accepted payload type and the value is equal source attribute are not present in the answer for the
to 1), the answerer MUST be prepared to use the parameter accepted payload type, the answerer MUST ignore "sprop-
sets that are included in "sprop-level-parameter-sets" for level-parameter-sets", when present.
the accepted level, when present, for decoding the incoming
NAL unit stream, and ignore all other parameter sets o Otherwise ("use-level-src-parameter-sets" equal to 1 or the
included in "sprop-level-parameter-sets" and "sprop- "fmtp" source attribute is present in the answer for the
parameter-sets", when present. accepted payload type), the answerer MUST be prepared to use
the parameter sets that are included in "sprop-level-
parameter-sets" for the accepted level, when present, for
decoding the incoming NAL unit stream, and ignore all other
parameter sets included in "sprop-level-parameter-sets".
o When no parameter sets for the accepted level are present in o When no parameter sets for the accepted level are present in
the "sprop-level-parameter-sets", in-band transport of the "sprop-level-parameter-sets", in-band transport of
parameter sets MUST be used. parameter sets MUST be used.
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 the
offerer-to-answerer direction. All parameter sets included in offerer-to-answerer direction. All parameter sets included in
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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, as
they are used for decoding two different video streams, one from they are used for decoding two different video streams, one from
the answerer to the offerer, and the other in the opposite 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
present and "sprop-ssrc" is present, the receiver of the conveyed using the "fmtp" source attribute in as specified in
parameters MUST store the parameter sets included in the "sprop- section 6.3 of [9], the receiver of the parameters MUST store the
parameter-sets" or "sprop-level-parameter-sets" for the accepted parameter sets included in the "sprop-parameter-sets" or "sprop-
level and associate them to "sprop-ssrc". Parameter sets level-parameter-sets" for the accepted level and associate them
associated with one "sprop-ssrc" MUST only be used to decode NAL to the source given as a part of the "fmtp" source attribute.
units conveyed in packets with SSRC equal to the associated Parameter sets associated with one source MUST only be used to
"sprop-ssrc". The "sprop-ssrc" MAY be used in topologies like decode NAL units conveyed in RTP packets from the same source.
Topo-Video-switch-MCU [28] to enable out-of-band transport of When this mechanism is in use, SSRC collision detection and
parameter sets. When "sprop-ssrc" is used, and SSRC collision is resolution MUST be performed as specified in [9].
detected, the connection needs to be renegotiated using a new
random SSRC. Informative note: Conveyance of "sprop-parameter-sets" and
"sprop-level-parameter-sets" using the "fmtp" source attribute
may be used in topologies like Topo-Video-switch-MCU [29] to
enable out-of-band transport of parameter sets.
For streams being delivered over multicast, the following rules For streams being delivered over multicast, the following rules
apply: 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", i.e. the level part of "profile-level-id" is not level-id") MUST be used symmetrically; i.e., the answerer MUST
downgradable for Offer/Answer in multicast) MUST be used either maintain all configuration parameters or remove the media
symmetrically; i.e., the answerer MUST either maintain all format (payload type) completely. Note that this implies that the
configuration parameters or remove the media format (payload type) level part of "profile-level-id" for Offer/Answer in multicast is
completely. 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.
Below are the complete lists of how the different parameters shall be Table 6 lists the interpretation of all the 20 media type parameters
interpreted in the different combinations of offer or answer and that MUST be used for the different direction attributes.
direction attribute.
o In offers and answers for which "a=sendrecv" or no direction
attribute is used, the following interpretation of the parameters
MUST be used.
Declaring actual configuration for sending and receiving streams:
- profile-level-id
- packetization-mode
Declaring actual properties of the stream to be sent:
- sprop-deint-buf-req
- sprop-interleaving-depth
- sprop-max-don-diff
- sprop-init-buf-time
- sprop-ssrc
Declaring receiver capabilities:
- max-mbps
- max-smbps
- max-fs
- max-cpb
- max-dpb
- max-br
- redundant-pic-cap
- deint-buf-cap
- max-rcmd-nalu-size
- sar-understood
- sar-supported
- use-level-parameter-sets
Out-of-band transporting of parameter sets:
- sprop-parameter-sets
- sprop-level-parameter-sets
o In offers and answers for which "a=recvonly" is used, the
following interpretation of the parameters MUST be used.
Declaring actual configuration for receiving streams:
- profile-level-id
- packetization-mode
Declaring receiver capabilities:
- max-mbps
- max-smbps
- max-fs
- max-cpb
- max-dpb
- max-br
- redundant-pic-cap
- deint-buf-cap
- max-rcmd-nalu-size
- sar-understood
- sar-supported
- use-level-parameter-sets
Not usable (when present, they SHOULD be ignored):
- sprop-deint-buf-req
- sprop-interleaving-depth
- sprop-parameter-sets
- sprop-level-parameter-sets
- sprop-max-don-diff
- sprop-init-buf-time
- sprop-ssrc
o In offers or answers for which "a=sendonly" is used, the following
interpretation of the parameters MUST be used.
Declaring actual configuration or properties for sending streams:
- profile-level-id
- packetization-mode
- sprop-deint-buf-req
- sprop-max-don-diff
- sprop-init-buf-time
- sprop-interleaving-depth
- sprop-ssrc
Out-of-band transporting of parameter sets:
- sprop-parameter-sets Table 6. Interpretation of parameters for different direction
- sprop-level-parameter-sets attributes.
Not usable(when present, they SHOULD be ignored): sendonly --+
recvonly --+ |
sendrecv --+ | |
| | |
profile-level-id C C P
packetization-mode C C P
sprop-deint-buf-req P - P
sprop-interleaving-depth P - P
sprop-max-don-diff P - P
sprop-init-buf-time P - P
max-mbps R R -
max-smbps R R -
max-fs R R -
max-cpb R R -
max-dpb R R -
max-br R R -
redundant-pic-cap R R -
deint-buf-cap R R -
max-rcmd-nalu-size R R -
sar-understood R R -
sar-supported R R -
use-level-src-parameter-sets R R -
sprop-parameter-sets S - S
sprop-level-parameter-sets S - S
- max-mbps Legend:
- max-smbps
- max-fs
- max-cpb
- max-dpb
- max-br
- redundant-pic-cap
- deint-buf-cap
- max-rcmd-nalu-size
- sar-understood
- sar-supported
- use-level-parameter-sets
Furthermore, the following considerations are necessary: C: configuration for sending and receiving streams
P: properties of the stream to be sent
R: receiver capabilities
S: out-of-band parameter sets
-: not usable, when present SHOULD be ignored
o 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 possible behavior. Thus a sender MAY select to set its encoder using
using only lower/less or equal values of these parameters. only lower/less or equal values of these parameters.
o Parameters declaring a configuration point are not downgradable, Parameters declaring a configuration point are not downgradable, with
with the exception of the level part of the "profile-level-id" the exception of the level part of the "profile-level-id" parameter
parameter for unicast usage. This expresses values a receiver for unicast usage. This expresses values a receiver expects to be
expects to be used and must be used verbatim on the sender side. used and must be used verbatim on the sender side.
o 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 express a configuration that is acceptable for the sender to receive
receive streams. In order to achieve high interoperability streams. In order to achieve high interoperability levels, it is
levels, it is often advisable to offer multiple alternative often advisable to offer multiple alternative configurations; e.g.,
configurations; e.g., for the packetization mode. It is for the packetization mode. It is impossible to offer multiple
impossible to offer multiple configurations in a single payload configurations in a single payload type. Thus, when multiple
type. Thus, when multiple configuration offers are made, each configuration offers are made, each offer requires its own RTP
offer requires its own RTP payload type associated with the offer. payload type associated with the offer.
o 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. only supports a subset of the payload format's functionality. This
This ensures that a receiver is capable of understanding when an ensures that a receiver is capable of understanding when an offer to
offer to receive media can be downgraded to what is supported by receive media can be downgraded to what is supported by the receiver
the receiver of the offer. of the offer.
o 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
properties parameters that the media sender will use. This also property parameters that the media sender will use. This also has
has the effect that the offerer has to be able to receive this the effect that the offerer has to be able to receive this media
media format configuration, not only to send it. format configuration, not only to send it.
o 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 "sendonly", respectively. This may have further implications on the
the system. 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 in
RTSP [26] or SAP [27], the following considerations are necessary. 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 properties.
For example, in this case, the parameter "profile-level-id" For example, in this case, the parameter "profile-level-id"
declares only the values used by the stream, not the capabilities declares only the values used by the stream, not the capabilities
for receiving streams. This results in that the following for receiving streams. This results in that the following
interpretation of the parameters MUST be used: 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
- sprop-ssrc
Out-of-band transporting of parameter sets: Out-of-band transporting of parameter sets:
- sprop-parameter-sets - sprop-parameter-sets
- sprop-level-parameter-sets - sprop-level-parameter-sets
Not usable(when present, they SHOULD be ignored): Not usable(when present, they SHOULD be ignored):
- max-mbps - max-mbps
- max-smbps - max-smbps
- max-fs - max-fs
- max-cpb - max-cpb
- max-dpb - max-dpb
- max-br - max-br
- redundant-pic-cap - redundant-pic-cap
- max-rcmd-nalu-size - max-rcmd-nalu-size
- deint-buf-cap - deint-buf-cap
- sar-understood - sar-understood
- sar-supported - sar-supported
- use-level-parameter-sets - use-level-src-parameter-sets
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 media
codec specific parts of the SDP are shown. Some lines are wrapped codec specific parts of the SDP are shown. Some lines are wrapped
due to text constraints. 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=<base64 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=<base64 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=<base64 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 support
for PT 100 are also included. In all three cases the parameter for PT 100 are also included. In all three cases the parameter
"sprop-parameter-sets" conveys the initial parameter sets that are "sprop-parameter-sets" conveys the initial parameter sets that are
required by the answerer when receiving a stream from the offerer required by the answerer when receiving a stream from the offerer
when this configuration is accepted. Note that the value for "sprop- when this configuration is accepted. Note that the value for "sprop-
parameter-sets" could be different for each payload type. 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=<base64 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=<base64 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=<base64 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 offerer
is willing to receive, whereas the answer indicates the same for what is willing to receive, whereas the answer indicates the same for what
the answerer accepts to receive. In this case the offerer declared the answerer accepts to receive. In this case the offerer declared
that it is willing to receive payload type 98. The answerer accepts that it is willing to receive payload type 98. The answerer accepts
this by declaring an equivalent payload type 97; i.e., it has this by declaring an equivalent payload type 97; i.e., it has
identical values for the two parameters "profile-level-id" and identical values for the two parameters "profile-level-id" and
"packetization-mode" (since "packetization-mode" is equal to 0, "packetization-mode" (since "packetization-mode" is equal to 0,
"sprop-deint-buf-req" is not present). As the offered payload type "sprop-deint-buf-req" is not present). As the offered payload type
98 is accepted, the answerer needs to store parameter sets included 98 is accepted, the answerer needs to store parameter sets included
in sprop-parameter-sets=<base64 data#0> in case the offer finally in sprop-parameter-sets=<parameter sets data#0> in case the offer
decides to use this configuration. In the answer, the answerer finally decides to use this configuration. In the answer, the
includes the parameter sets in sprop-parameter-sets=<base64 data#3> answerer includes the parameter sets in sprop-parameter-
that the answerer would use in the stream sent from the answerer if sets=<parameter sets data#3> that the answerer would use in the
this configuration is finally used. 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=<base64 to store parameter sets included in sprop-parameter-sets=<parameter
data#1> and sprop-parameter-sets=<base64 data#2> in case the offer sets data#1> and sprop-parameter-sets=<parameter sets data#2> in case
finally decides to use either of these two configurations. The the offer finally decides to use either of these two configurations.
answerer provides the initial parameter sets for the answerer-to- The answerer provides the initial parameter sets for the answerer-to-
offerer direction, i.e. the parameter sets in sprop-parameter- offerer direction, i.e. the parameter sets in sprop-parameter-
sets=<base64 data#4> and sprop-parameter-sets=<base64 data#5>, for sets=<parameter sets data#4> and sprop-parameter-sets=<parameter sets
payload types 99 and 100, respectively, that it will use to send the data#5>, for payload types 99 and 100, respectively, that it will use
payload types. The answerer also provides the offerer with its to send the payload types. The answerer also provides the offerer
memory limit for de-interleaving operations by providing a "deint- with its memory limit for de-interleaving operations by providing a
buf-cap" parameter. This is only useful if the offerer decides on "deint-buf-cap" parameter. This is only useful if the offerer
making a second offer, where it can take the new value into account. decides on making a second offer, where it can take the new value
The "max-rcmd-nalu-size" indicates that the answerer can efficiently into account. The "max-rcmd-nalu-size" indicates that the answerer
process NALUs up to the size of 3980 bytes. However, there is no can efficiently process NALUs up to the size of 3980 bytes. However,
guarantee that the network supports this size. 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=<base-64 data#1> and store parameter sets in sprop-parameter- sets=<parameter sets data#1> and store parameter sets in sprop-
sets=<base-64 data#0> for decoding the incoming NAL unit stream. The parameter-sets=<parameter sets data#0> for decoding the incoming NAL
offerer must store the parameter sets in sprop-parameter-sets=<base- unit stream. The offerer must store the parameter sets in sprop-
64 data#2> in the answer for decoding the incoming NAL unit stream. parameter-sets=<parameter sets data#2> in the answer for decoding the
Note that in this example, parameter sets in sprop-parameter- incoming NAL unit stream. Note that in this example, parameter sets
sets=<base-64 data#2> must be associated with level 3.0. in sprop-parameter-sets=<parameter sets data#2> must 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=<base-64 data#0>; sprop-parameter-sets=<parameter sets data#0>;
sprop-level-parameter-sets=<base-64 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=<base-64 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) is
accepted with level downgrading (the accepted level is 1b), and both accepted with level downgrading (the accepted level is 1b), 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-parameter-sets=<base-64 in the offer. The answerer must ignore sprop-parameter-
data#0> and all parameter sets not for the accepted level (level 1b) sets=<parameter sets data#0> and all parameter sets not for the
in sprop-level-parameter-sets=<base-64 data#1>, and must store accepted level (level 1b) in sprop-level-parameter-sets=<parameter
parameter sets for the accepted level (level 1b) in sprop-level- sets data#1>, and must store parameter sets for the accepted level
parameter-sets=<base-64 data#1> for decoding the incoming NAL unit (level 1b) in sprop-level-parameter-sets=<parameter sets data#1> for
stream. The offerer must store the parameter sets in sprop- decoding the incoming NAL unit stream. The offerer must store the
parameter-sets=<base-64 data#2> in the answer for decoding the parameter sets in sprop-parameter-sets=<parameter sets data#2> in the
incoming NAL unit stream. Note that in this example, parameter sets answer for decoding the incoming NAL unit stream. Note that in this
in sprop-parameter-sets=<base-64 data#2> must be associated with example, parameter sets in sprop-parameter-sets=<parameter sets
level 1b. 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=<base-64 data#0>; sprop-parameter-sets=<parameter sets data#0>;
sprop-level-parameter-sets=<base-64 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=<base-64 data#2>; sprop-parameter-sets=<parameter sets data#2>;
use-level-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) is
accepted with level downgrading (the accepted level is 1b), and both accepted with level downgrading (the accepted level is 1b), 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. However, the answerer is a legacy RFC 3984 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-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, the
answerer must ignore both sprop-parameter-sets=<base-64 data#0> and answerer must ignore both sprop-parameter-sets=<parameter sets
sprop-level-parameter-sets=<base-64 data#1>, and the offerer must data#0> and sprop-level-parameter-sets=<parameter sets data#1>, and
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=<base-64 data#0>; sprop-parameter-sets=<parameter sets data#0>;
sprop-level-parameter-sets=<base-64 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
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=<base-64 data#0> must be Parameter sets in sprop-parameter-sets=<parameter sets data#0> must
stored and used used by the encoder of the offerer and the decoder of be stored and used used by the encoder of the offerer and the decoder
the answerer, and parameter sets in sprop-parameter-sets=<base-64 of the answerer, and parameter sets in sprop-parameter-
data#1>must be used by the encoder of the answerer and the decoder of sets=<parameter sets data#1>must be used by the encoder of the
the offerer. Note that sprop-parameter-sets=<base-64 data#0> is answerer and the decoder of the offerer. Note that sprop-parameter-
basically independent of sprop-parameter-sets=<base-64 data#1>. sets=<parameter sets data#0> is basically independent of 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=<base-64 data#0> sprop-parameter-sets=<parameter sets data#0>
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=<base-64 data#1> sprop-parameter-sets=<parameter sets data#1>
In the following example, the offer is accepted without level In the following example, the offer is accepted without level
downgrading, and neither "sprop-parameter-sets" nor "sprop-level- downgrading, and neither "sprop-parameter-sets" nor "sprop-level-
parameter-sets" is present in the offer, meaning that there is no parameter-sets" is present in the offer, meaning that there is no
out-of-band transmission of parameter sets, which then have to be out-of-band transmission of parameter sets, which then have to be
transported in-band. transported in-band.
Offer SDP: Offer SDP:
m=video 49170 RTP/AVP 98 m=video 49170 RTP/AVP 98
skipping to change at page 69, line 41 skipping to change at page 69, line 19
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=<base-64 data#0> contains level_idc indicating sprop-parameter-sets=<parameter sets data#0> contains level_idc
Level 3.0, therefore cannot be used as the answerer wants Level 2.0 indicating Level 3.0, therefore cannot be used as the answerer wants
and must be ignored by the answerer, and in-band parameter sets must Level 2.0 and must be ignored by the answerer, and in-band parameter
be used. 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=<base-64 data#0> sprop-parameter-sets=<parameter sets data#0>
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 offer is also accepted with level In the following example, the offer is also accepted with level
downgrading, and neither "sprop-parameter-sets" nor "sprop-level- downgrading, and neither "sprop-parameter-sets" nor "sprop-level-
skipping to change at page 70, line 26 skipping to change at page 70, line 4
parameter-sets" is present in the offer, meaning that there is no parameter-sets" is present in the offer, meaning that there is no
out-of-band transmission of parameter sets, which then have to be out-of-band transmission of parameter sets, which then have to be
transported in-band. transported 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=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
(MCU) in a Topo-Video-switch-MCU like topology [29], offering
parameter sets received (using out-of-band transport) from three
other participants B, C, and D, and receiving parameter sets from the
participant A, which is the answerer. The participants are
identified by their values of CNAME, which are mapped to different
SSRC values. The same codec configuration is used by all the four
participants. The participant A stores and associates the parameter
sets included in <parameter sets data#B>, <parameter sets data#C>,
and <parameter sets data#D> to participants B, C, and D,
respectively, and uses <parameter sets data#B> for decoding NAL units
carried in RTP packets originated from participant B only, uses
<parameter sets data#C> for decoding NAL units carried in RTP packets
originated from participant C only, and uses <parameter sets data#D>
for decoding NAL units carried in RTP packets originated from
participant D only.
Offer SDP:
m=video 49170 RTP/AVP 98
a=ssrc:SSRC-B cname:CNAME-B
a=ssrc:SSRC-C cname:CNAME-C
a=ssrc:SSRC-D cname:CNAME-D
a=ssrc:SSRC-B fmtp:98
sprop-parameter-sets=<parameter sets data#B>
a=ssrc:SSRC-C fmtp:98
sprop-parameter-sets=<parameter sets data#C>
a=ssrc:SSRC-D fmtp:98
sprop-parameter-sets=<parameter sets data#D>
a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
packetization-mode=1
Answer SDP:
m=video 49170 RTP/AVP 98
a=ssrc:SSRC-A cname:CNAME-A
a=ssrc:SSRC-A fmtp:98
sprop-parameter-sets=<parameter sets data#A>
a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=42A01E; //Baseline profile, Level 3.0
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 has
normally fatal results to the decoding process. Corruption could normally fatal results to the decoding process. Corruption could
occur, for example, due to the erroneous transmission or loss of a occur, for example, due to the erroneous transmission or loss of a
parameter set NAL unit, but also due to the untimely transmission of parameter set NAL unit, but also due to the untimely transmission of
skipping to change at page 71, line 24 skipping to change at page 71, line 43
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. This Offer/Answer model and in the previous sections of this memo. This
section contains guidelines on how principles A and B should be section contains guidelines on how principles A and B should be
implemented within session control protocols. It is independent of implemented within session control protocols. It is independent of
the particular protocol used. Principle C is supported by the RTP the particular protocol used. Principle C is supported by the RTP
payload format defined in this specification. There are topologies payload format defined in this specification. There are topologies
like Topo-Video-switch-MCU [28] for which the use of principle C may like Topo-Video-switch-MCU [29] for which the use of principle C may
be desirable. 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 payload
using a reliable method of delivering of RTP (see below), as a loss using a reliable method of delivering of RTP (see below), as a loss
of a parameter set of either type will likely prevent decoding of a of a parameter set of either type will likely prevent decoding of a
considerable portion of the corresponding RTP packet stream. 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
skipping to change at page 72, line 28 skipping to change at page 72, line 44
set in question is not needed by any NALU present in the network set in question is not needed by any NALU present in the network
or receiver buffers. Otherwise, decoding with a wrong parameter or receiver buffers. Otherwise, decoding with a wrong parameter
set may occur. To lessen this problem, it is RECOMMENDED either set may occur. To lessen this problem, it is RECOMMENDED either
to overwrite only those parameter sets that have not been used for to overwrite only those parameter sets that have not been used for
a sufficiently long time (to ensure that all related NALUs have a sufficiently long time (to ensure that all related NALUs have
been consumed), or to add a new parameter set instead (which may been consumed), or to add a new parameter set instead (which may
have negative consequences for the efficiency of the video have negative consequences for the efficiency of the video
coding). coding).
Informative note: In some topologies like Topo-Video-switch- Informative note: In some topologies like Topo-Video-switch-
MCU [28] 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 parameter
sets coming from different sources with the source identification sets coming from different sources with the source identification
whenever possible, e.g. by using sprop-ssrc for out-of-band whenever possible, e.g. by conveying out-of-band transported
transported parameter sets, as different sources typically use parameter sets, as different sources typically use independent
independent parameter set identifier value spaces. 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 and
C in the same RTP session may lead to inconsistencies of the 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 the
control and the RTP channel. Therefore, principles B and C MUST control and the RTP channel. Therefore, principles B and C MUST
NOT both be used in the same session unless sufficient 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 format
specification corresponding to H.241 is used) or topologies, it is specification corresponding to H.241 is used) or topologies, it is
not possible to employ out-of-band parameter set transmission. In not possible to employ out-of-band parameter set transmission. In
this case, parameter sets have to be transmitted in-band. Here, the this case, parameter sets have to be transmitted in-band. Here, the
synchronization with the non-parameter-set-data in the bitstream is synchronization with the non-parameter-set-data in the bitstream is
implicit, but the possibility of a loss has to be taken into account. implicit, but the possibility of a loss has to be taken into account.
The loss probability should be reduced using the mechanisms discussed The loss probability should be reduced using the mechanisms discussed
above. In case a loss of a parameter set is detected, recovery may above. In case a loss of a parameter set is detected, recovery may
be achieved by using a Decoder Refresh Point procedure, for example, be achieved by using a Decoder Refresh Point procedure, for example,
using RTCP feedback Full Intra Request (FIR) [29]. Two example using RTCP feedback Full Intra Request (FIR) [30]. Two example
Decoder Refresh Point procedures are provided in the informative Decoder Refresh Point procedures are provided in the informative
Section 8.5. 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 risk
associated with updating the parameter sets delivered out-of-band. associated with updating the parameter sets delivered out-of-band.
If receivers miss some in-band updates (for example, because of a If receivers miss some in-band updates (for example, because of a
loss or a late tune-in), those receivers attempt to decode the loss or a late tune-in), those receivers attempt to decode the
bitstream using out-dated parameters. It is therefore RECOMMENDED bitstream using out-dated parameters. It is therefore RECOMMENDED
that parameter set IDs be partitioned between the out-of-band and that parameter set IDs be partitioned between the out-of-band and
skipping to change at page 74, line 50 skipping to change at page 75, line 21
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 may
be re-sent at any time for redundancy. Caution should be taken when be re-sent at any time for redundancy. Caution should be taken when
parameter set updates are present, as described above in Section 8.4. 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,
[15]). 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 SRTP
[25]. Because the data compression used with this payload format is [26]. Because the data compression used with this payload format is
applied end-to-end, any encryption needs to be performed after applied end-to-end, any encryption needs to be performed after
compression. A potential denial-of-service threat exists for data compression. A potential denial-of-service threat exists for data
encodings using compression techniques that have non-uniform 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 and
that cause the receiver to be overloaded. H.264 is particularly that cause the receiver to be overloaded. H.264 is particularly
vulnerable to such attacks, as it is extremely simple to generate vulnerable to such attacks, as it is extremely simple to generate
datagrams containing NAL units that affect the decoding process of datagrams containing NAL units that affect the decoding process of
many future NAL units. Therefore, the usage of data origin many future NAL units. Therefore, the usage of data origin
authentication and data integrity protection of at least the RTP authentication and data integrity protection of at least the RTP
packet is RECOMMENDED; for example, with SRTP [25]. 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 the
application and on the transport and signaling protocols employed. application and on the transport and signaling protocols employed.
Thus, although SRTP is given as an example above, other possible Thus, although SRTP is given as an example above, other possible
choices exist. 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, and
MUST restrict their domain of applicability to the presentation MUST restrict their domain of applicability to the presentation
skipping to change at page 75, line 39 skipping to change at page 76, line 11
confidentiality protection will prevent a MANE from performing media- confidentiality protection will prevent a MANE from performing media-
aware operations other than discarding complete packets. And in the aware operations other than discarding complete packets. And in the
case of confidentiality protection it will even be prevented from case of confidentiality protection it will even be prevented from
performing discarding of packets in a media aware way. To allow any performing discarding of packets in a media aware way. To allow any
MANE to perform its operations, it will be required to be a trusted MANE to perform its operations, it will be required to be a trusted
entity which is included in the security context establishment. 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 3550
[5], and with any applicable RTP profile; e.g., RFC 3551 [15]. An [5], and with any applicable RTP profile; e.g., RFC 3551 [16]. An
additional requirement if best-effort service is being used is: users additional requirement if best-effort service is being used is: users
of this payload format MUST monitor packet loss to ensure that the of this payload format MUST monitor packet loss to ensure that the
packet loss rate is within acceptable parameters. Packet loss is packet loss rate is within acceptable parameters. Packet loss is
considered acceptable if a TCP flow across the same network path, and considered acceptable if a TCP flow across the same network path, and
experiencing the same network conditions, would achieve an average experiencing the same network conditions, would achieve an average
throughput, measured on a reasonable timescale that is not less than throughput, measured on a reasonable timescale that is not less than
the RTP flow is achieving. This condition can be satisfied by the RTP flow is achieving. This condition can be satisfied by
implementing congestion control mechanisms to adapt the transmission implementing congestion control mechanisms to adapt the transmission
rate (or the number of layers subscribed for a layered multicast rate (or the number of layers subscribed for a layered multicast
session), or by arranging for a receiver to leave the session if the session), or by arranging for a receiver to leave the session if the
loss rate is unacceptably high. loss rate is unacceptably high.
The bit rate adaptation necessary for obeying the congestion control The bit rate adaptation necessary for obeying the congestion control
principle is easily achievable when real-time encoding is used. principle is easily achievable when real-time encoding is used.
However, when pre-encoded content is being transmitted, bandwidth However, when pre-encoded content is being transmitted, bandwidth
adaptation requires the availability of more than one coded adaptation requires the availability of more than one coded
representation of the same content, at different bit rates, or the representation of the same content, at different bit rates, or the
existence of non-reference pictures or sub-sequences [21] in the existence of non-reference pictures or sub-sequences [22] in the
bitstream. The switching between the different representations can bitstream. The switching between the different representations can
normally be performed in the same RTP session; e.g., by employing a normally be performed in the same RTP session; e.g., by employing a
concept known as SI/SP slices of the Extended Profile, or by concept known as SI/SP slices of the Extended Profile, or by
switching streams at IDR picture boundaries. Only when non- 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 necessary
to terminate and re-start the media stream. This may be accomplished to terminate and re-start the media stream. This may be accomplished
by using a different RTP payload type. 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
skipping to change at page 77, line 36 skipping to change at page 78, line 12
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 and
the resulting drift-related artifacts. 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 [10]. It has been based designs using RFC 2429 packetization [11]. It has been
implemented, and good results were reported [12]. implemented, and good results were reported [13].
The VCL encoder codes the source picture so that all macroblocks The VCL encoder codes the source picture so that all macroblocks
(MBs) of one MB line are assigned to one slice. All slices with even (MBs) of one MB line are assigned to one slice. All slices with even
MB row addresses are combined into one STAP, and all slices with odd MB row addresses are combined into one STAP, and all slices with odd
MB row addresses into another. Those STAPs are transmitted as RTP MB row addresses into another. Those STAPs are transmitted as RTP
packets. The establishment of the parameter sets is performed as packets. The establishment of the parameter sets is performed as
discussed above. 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 is
used, which is not assumed in this scenario). Furthermore, some 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-based
video telephony specified in 3GPP, are likely to use relatively small video telephony specified in 3GPP, are likely to use relatively small
transport packet size. For example, a typical MTU size of H.223 AL3 transport packet size. For example, a typical MTU size of H.223 AL3
SDU is around 100 bytes [16]. Coding individual slices according to SDU is around 100 bytes [17]. Coding individual slices according to
this packetization scheme provides further advantage in communication this packetization scheme provides further advantage in communication
between wired and wireless networks, as individual slices are likely between wired and wireless networks, as individual slices are likely
to be smaller than the preferred maximum packet size of wireless to be smaller than the preferred maximum packet size of wireless
systems. Consequently, a gateway can convert the STAPs used in a systems. Consequently, a gateway can convert the STAPs used in a
wired network into several RTP packets with only one NAL unit, which wired network into several RTP packets with only one NAL unit, which
are preferred in a wireless network, and vice versa. 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 [12]. 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 [17], 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 same
order of magnitude as the number of bits that have otherwise been order of magnitude as the number of bits that have otherwise been
spent for intra information. However, this mechanism does not add spent for intra information. However, this mechanism does not add
any delay to the system. any delay to the system.
Again, the complete parameter set establishment is performed through Again, the complete parameter set establishment is performed through
control protocol means. 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 [18]. 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 where
retransmissions are not applicable is forward error correction (FEC). retransmissions are not applicable is forward error correction (FEC).
Although application layer, end-to-end use of FEC is often less Although application layer, end-to-end use of FEC is often less
efficient than an FEC-based protection of individual links efficient than an FEC-based protection of individual links
(especially when links of different characteristics are in the (especially when links of different characteristics are in the
transmission path), application layer, end-to-end FEC is unavoidable transmission path), application layer, end-to-end FEC is unavoidable
in some scenarios. RFC 2733 [17] provides means to use generic, in some scenarios. RFC 5109 [18] provides means to use generic,
application layer, end-to-end FEC in packet-loss environments. A application layer, end-to-end FEC in packet-loss environments. A
binary forward error correcting code is generated by applying the XOR binary forward error correcting code is generated by applying the XOR
operation to the bits at the same bit position in different packets. operation to the bits at the same bit position in different packets.
The binary code can be specified by the parameters (n,k) in which k The binary code can be specified by the parameters (n,k) in which k
is the number of information packets used in the connection and n is is the number of information packets used in the connection and n is
the total number of packets generated for k information packets; the total number of packets generated for k information packets;
i.e., n-k parity packets are generated for k information packets. i.e., n-k parity packets are generated for k information packets.
[Ed. (YkW): from Randell: References to RFC 2733 should be updated to
(and checked against) RFC 5109. There are a lot of calculations and
the like that should be checked. Also update [17] to RFC 5109. ]
When a code is used with parameters (n,k) within the RFC 2733 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 2733 provides only packet a) If applied over one RTP packet, RFC 5109 provides only packet
repetition. repetition.
b) RFC 2733 is most bit rate efficient if XOR-connected packets have b) RFC 5109 is most bit rate efficient if XOR-connected packets have
equal length. 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 error
probability becomes. For example, at a packet loss probability of probability becomes. For example, at a packet loss probability of
p=10%, k=1 and n=2, the residual error rate is about 1%, whereas p=10%, k=1 and n=2, the residual error rate is about 1%, whereas
for an extended Golay code with k=12 and n=24, the residual error for an extended Golay code with k=12 and n=24, the residual error
rate is about 0.01%. rate is about 0.01%.
For applying RFC 2733 in combination with H.264 baseline coded video For applying RFC 5109 in combination with H.264 baseline coded video
without using FUs, several options might be considered: 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 is
coded in a single slice. Applying FEC, one could use a simple coded in a single slice. Applying FEC, one could use a simple
code; e.g., (n=2, k=1). That is, each NAL unit would basically code; e.g., (n=2, k=1). That is, each NAL unit would basically
just be repeated. The disadvantage is obviously the bad code just be repeated. The disadvantage is obviously the bad code
performance according to d), above, and the low flexibility, as performance according to d), above, and the low flexibility, as
only (n, k=1) codes can be used. 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 is
skipping to change at page 80, line 45 skipping to change at page 81, line 22
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 be
transmitted almost reliably without adding extensive delays. In 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 2733. 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 [14]), 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 to
be spent for intra-coded macroblocks if no FEC is applied. In [18], be spent for intra-coded macroblocks if no FEC is applied. In [19],
it was shown that the overall performance of the FEC-based approach it was shown that the overall performance of the FEC-based approach
enhanced quality when using the same error rate and same overall bit enhanced quality when using the same error rate and same overall bit
rate, including the overhead. 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 [19]. There is no technical packetization and has given good results [20]. There is no technical
reason why similarly good results could not be achievable with H.264. 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
skipping to change at page 81, line 47 skipping to change at page 82, line 24
the same picture or spatially overlapping slices from any picture. the same picture or spatially overlapping slices from any picture.
If a packet is lost, it is likely that a lost slice is surrounded by If a packet is lost, it is likely that a lost slice is surrounded by
spatially adjacent slices of the same picture and spatially spatially adjacent slices of the same picture and spatially
corresponding slices of the temporally previous and succeeding corresponding slices of the temporally previous and succeeding
pictures. Consequently, concealment of the lost slice is likely to pictures. Consequently, concealment of the lost slice is likely to
be relatively successful. 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 and
simulated in a wireless streaming environment [20]. There is no simulated in a wireless streaming environment [21]. There is no
technical reason why similar or better results could not be 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 of
storing a relatively large amount of data. Initially, when a 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 the
stream back immediately. Rather, it typically buffers the incoming stream back immediately. Rather, it typically buffers the incoming
data for a few seconds. This buffering helps maintain continuous data for a few seconds. This buffering helps maintain continuous
playback, as, in case of occasional increased transmission delays or playback, as, in case of occasional increased transmission delays or
network throughput drops, the client can decode and play buffered network throughput drops, the client can decode and play buffered
skipping to change at page 82, line 25 skipping to change at page 82, line 48
retransmission in any protocol level. If any part of a picture is retransmission in any protocol level. If any part of a picture is
lost, a retransmission mechanism may be used to resend the lost data. lost, a retransmission mechanism may be used to resend the lost data.
If the retransmitted data is received before its scheduled decoding If the retransmitted data is received before its scheduled decoding
or playback time, the loss is recovered perfectly. Coded pictures or playback time, the loss is recovered perfectly. Coded pictures
can be ranked according to their importance in the subjective quality can be ranked according to their importance in the subjective quality
of the decoded sequence. For example, non-reference pictures, such of the decoded sequence. For example, non-reference pictures, such
as conventional B pictures, are subjectively least important, as as conventional B pictures, are subjectively least important, as
their absence does not affect decoding of any other pictures. In their absence does not affect decoding of any other pictures. In
addition to non-reference pictures, the ITU-T H.264 | ISO/IEC 14496- addition to non-reference pictures, the ITU-T H.264 | ISO/IEC 14496-
10 standard includes a temporal scalability method called sub- 10 standard includes a temporal scalability method called sub-
sequences [21]. Subjective ranking can also be made on coded slice sequences [22]. Subjective ranking can also be made on coded slice
data partition or slice group basis. Coded slices and coded slice data partition or slice group basis. Coded slices and coded slice
data partitions that are subjectively the most important can be sent data partitions that are subjectively the most important can be sent
earlier than their decoding order indicates, whereas coded slices and earlier than their decoding order indicates, whereas coded slices and
coded slice data partitions that are subjectively the least important coded slice data partitions that are subjectively the least important
can be sent later than their natural coding order indicates. 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 before
their scheduled decoding or playback time compared to the least their scheduled decoding or playback time compared to the least
important slices and slice data partitions. important slices and slice data partitions.
skipping to change at page 88, line 34 skipping to change at page 89, line 13
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 and
coding techniques using the redundant codec picture feature include coding techniques using the redundant codec picture feature include
the video redundancy coding [22] and the protection of "key pictures" the video redundancy coding [23] and the protection of "key pictures"
in multicast streaming [23]. 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 that
transmission errors are often bursty. Therefore, they may affect transmission errors are often bursty. Therefore, they may affect
more than one consecutive transmission packets in transmission order. more than one consecutive transmission packets in transmission order.
In low bit-rate video communication, it is relatively common that an In low bit-rate video communication, it is relatively common that an
entire coded picture can be encapsulated into one transmission entire coded picture can be encapsulated into one transmission
packet. Consequently, a primary coded picture and the corresponding packet. Consequently, a primary coded picture and the corresponding
redundant coded pictures may be transmitted in consecutive packets in redundant coded pictures may be transmitted in consecutive packets in
transmission order. To make the transmission scheme more tolerant of transmission order. To make the transmission scheme more tolerant of
bursty transmission errors, it is beneficial to transmit the primary bursty transmission errors, it is beneficial to transmit the primary
skipping to change at page 89, line 27 skipping to change at page 89, line 50
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 The RTP payload format for transport of MPEG-4 elementary streams
[24] enables interleaving of access units and transmission of [25] enables interleaving of access units and transmission of
multiple access units in the same RTP packet. An access unit is multiple access units in the same RTP packet. An access unit is
specified in the H.264 coding standard to comprise all NAL units specified in the H.264 coding standard to comprise all NAL units
associated with a primary coded picture according to subclause associated with a primary coded picture according to subclause
7.4.1.2 of [1]. Consequently, slices of different pictures cannot be 7.4.1.2 of [1]. Consequently, slices of different pictures cannot be
interleaved, and the multi-picture slice interleaving technique (see interleaved, and the multi-picture slice interleaving technique (see
section 12.6) for improved error resilience cannot be used. 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, and the development of RFC 3984. Randell Jesup, Stephen Botzko, Magnus
Magnus Westerlund are thanked for their valuable comments during the Westerlund, Alex Eleftheriadis, and Thomas Schierl are thanked for
development of this RFC. their valuable comments and inputs during the 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 generic
audiovisual services", November 2007. [Ed. (YkW): This should audiovisual services", November 2007.
be updated after a later version is approved.]
[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 Requirement
Levels", BCP 14, RFC 2119, March 1997. 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,
skipping to change at page 90, line 34 skipping to change at page 91, line 5
[6] Handley, M. and V. Jacobson, "SDP: Session Description [6] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998. Protocol", RFC 2327, April 1998.
[7] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", [7] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
RFC 3548, July 2003. 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
Attributes in the Session Description Protocol", draft-ietf-
mmusic-sdp-source-attributes-02 (work in progress), October
2008.
15.2. Informative References 15.2. Informative References
[9] 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.
[10] Bormann, C., Cline, L., Deisher, G., Gardos, T., Maciocco, C., [11] Bormann, C., Cline, L., Deisher, G., Gardos, T., Maciocco, C.,
Newell, D., Ott, J., Sullivan, G., Wenger, S., and C. Zhu, "RTP Newell, D., Ott, J., Sullivan, G., Wenger, S., and C. Zhu, "RTP
Payload Format for the 1998 Version of ITU-T Rec. H.263 Video Payload Format for the 1998 Version of ITU-T Rec. H.263 Video
(H.263+)", RFC 2429, October 1998. (H.263+)", RFC 2429, October 1998.
[11] ISO/IEC IS 14496-2. [12] ISO/IEC IS 14496-2.
[12] 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.
[13] 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.
[14] 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.
[15] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video [16] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
Conferences with Minimal Control", STD 65, RFC 3551, July 2003. Conferences with Minimal Control", STD 65, RFC 3551, July 2003.
[16] ITU-T Recommendation H.223, "Multiplexing protocol for low bit [17] ITU-T Recommendation H.223, "Multiplexing protocol for low bit
rate multimedia communication", July 2001. rate multimedia communication", July 2001.
[17] Rosenberg, J. and H. Schulzrinne, "An RTP Payload Format for [18] Li, A., "RTP Payload Format for Generic Forward Error
Generic Forward Error Correction", RFC 2733, December 1999. Correction", RFC 5109, December 2007.
[18] 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.
[19] Varsa, V. and M. Karczewicz, "Slice interleaving in compressed [20] Varsa, V. and M. Karczewicz, "Slice interleaving in compressed
video packetization", Packet Video Workshop 2000. video packetization", Packet Video Workshop 2000.
[20] 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 Workshop
2002. 2002.
[21] 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-site/0201_Gen/JVT-
B042.doc, anuary 2002. B042.doc, anuary 2002.
[22] 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.
[23] Wang, Y.-K., Hannuksela, M.M., and M. Gabbouj, "Error Resilient [24] Wang, Y.-K., Hannuksela, M.M., and M. Gabbouj, "Error Resilient
Video Coding Using Unequally Protected Key Pictures", in Proc. Video Coding Using Unequally Protected Key Pictures", in Proc.
International Workshop VLBV03, September 2003. International Workshop VLBV03, September 2003.
[24] van der Meer, J., Mackie, D., Swaminathan, V., Singer, D., and [25] van der Meer, J., Mackie, D., Swaminathan, V., Singer, D., and
P. Gentric, "RTP Payload Format for Transport of MPEG-4 P. Gentric, "RTP Payload Format for Transport of MPEG-4
Elementary Streams", RFC 3640, November 2003. Elementary Streams", RFC 3640, November 2003.
[25] 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)", RFC
3711, March 2004. 3711, March 2004.
[26] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming [27] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming
Protocol (RTSP)", RFC 2326, April 1998. Protocol (RTSP)", RFC 2326, April 1998.
[27] Handley, M., Perkins, C., and E. Whelan, "Session Announcement [28] Handley, M., Perkins, C., and E. Whelan, "Session Announcement
Protocol", RFC 2974, October 2000. Protocol", RFC 2974, October 2000.
[28] Westerlund, M. and Wenger, S., "RTP Topologies", RFC 5117, [29] Westerlund, M. and Wenger, S., "RTP Topologies", RFC 5117,
January 2008. January 2008.
[29] Wenger, S., Chandra, U., and Westerlund, M., "Codec Control [30] Wenger, S., Chandra, U., and Westerlund, M., "Codec Control
Messages in the RTP Audio-Visual Profile with Feedback (AVPF)", Messages in the RTP Audio-Visual Profile with Feedback (AVPF)",
RFC 5104, February 2008. RFC 5104, February 2008.
Authors' Addresses Authors' Addresses
Ye-Kui Wang Ye-Kui Wang
Nokia Research Center Nokia Research Center
P.O. Box 1000 P.O. Box 1000
33721 Tampere 33721 Tampere
Finland Finland
skipping to change at page 94, line 13 skipping to change at page 94, line 44
Internet Society. Internet Society.
16. Backward Compatibility to RFC 3984 16. Backward Compatibility to RFC 3984
The current document is a revision of RFC 3984 and intends to The current document is a revision of RFC 3984 and intends to
obsolete it. This section addresses the backward compatibility obsolete it. This section addresses the backward compatibility
issues. issues.
The technical changes are listed in section 17. The technical changes are listed in section 17.
Items 1), 2), 3), 7), 8), 9), 11), 12) 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 five 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, compatibility issue for SDP declarative usage based applications,
e.g. 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 3984
cannot accept a session for which the SDP includes an unrecognized cannot accept a session for which the SDP includes an unrecognized
parameter. Therefore, the RTSP or SAP server may have to prepare two parameter. Therefore, the RTSP or SAP server may have to prepare two
sets of streams, one for legacy RFC 3984 receivers and one for sets of streams, one for legacy RFC 3984 receivers and one for
receivers according to this memo. receivers according to this memo.
Items 5), 6) and 10) are related to out-of-band transport of Items 5), 6) and 11) are related to out-of-band transport of
parameter sets. When a sender according to this memo is parameter sets. When a sender according to this memo is
communicating with a legacy receiver according to RFC 3984, there is communicating with a legacy receiver according to RFC 3984, there is
no backward compatibility issue. When the legacy receiver sees an SDP no backward compatibility issue. When the legacy receiver sees an SDP
message with no parameter-add the value of parameter-add is inferred message with no parameter-add the value of parameter-add is inferred
to be equal to 1 by the legacy receiver (related to change item 5)). to be equal to 1 by the legacy receiver (related to change item 5)).
As RFC 3984 allows inclusion of any parameter sets in sprop- As RFC 3984 allows inclusion of any parameter sets in sprop-
parameter-sets, it is fine to the legacy receiver to include parameter-sets, it is fine to the legacy receiver to include
parameter sets only for the default level in sprop-parameter-sets parameter sets only for the default level in sprop-parameter-sets
(related to change item 6)). When there are new parameters e.g. (related to change item 6)). When there are new parameters e.g.
sprop-level-parameter-sets present, the legacy receiver simply sprop-level-parameter-sets present, the legacy receiver simply
ignores them (related to change item 10)). When a legacy sender ignores them (related to change item 11)). When a legacy sender
according to RFC 3984 is communicating with a receiver according to according to RFC 3984 is communicating with a receiver according to
this memo, there is one backward compatibility issue. When the this memo, there is one backward compatibility issue. When the
legacy sender includes parameter sets for a level different than the legacy sender includes parameter sets for a level different than the
default level indicated by profile-level-id to sprop-parameter-sets, default level indicated by profile-level-id to sprop-parameter-sets,
the parameter value of sprop-parameter-sets is invalid to the the parameter value of sprop-parameter-sets is invalid to the
receiver and therefore the session may be rejected. In SDP receiver and therefore the session may be rejected. In SDP
Offer/Answer between a legacy offerer according to RFC 3984 and an Offer/Answer between a legacy offerer according to RFC 3984 and an
answerer according to this memo, when the answerer includes in the answerer according to this memo, when the answerer includes in the
answer parameter sets that are not a superset of the parameter sets answer parameter sets that are not a superset of the parameter sets
included in the offer, the parameter value of sprop-parameter-sets is included in the offer, the parameter value of sprop-parameter-sets is
invalid to offerer and the session may not be initiated properly invalid to offerer and the session may not be initiated properly
(related to change item 10)). (related to change item 11)).
Item 13) removed that use of out-of-band transport of parameter sets Item 7), allowance of conveying sprop-parameter-sets and sprop-level-
parameter-sets using the "fmtp" source attribute as specified in
section 6.3 of [9], is similar as item 4). It does not incur any
backward compatibility issues for SDP Offer/Answer based
applications, as legacy RFC 3984 receivers ignore the "fmtp" source
attribute, and it is fine for legacy RFC 3984 senders not to use the
"fmtp" source attribute as it is optional. However, there is a
backward compatibility issue for SDP declarative usage based
applications, e.g. those using RTSP and SAP, because the SDP receiver
per RFC 3984 cannot accept a session for which the SDP includes an
unrecognized parameter (i.e., the "fmtp" source attribute).
Therefore, the RTSP or SAP server may have to prepare 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
is recommended. As out-of-band transport of parameter sets is still is recommended. As out-of-band transport of parameter sets is still
allowed, this change does not incur any backward compatibility allowed, this change does not incur any backward compatibility
issues. issues.
Item 14) 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. added subsection 8.5 is informative.
17. Changes from RFC 3984 17. Changes from RFC 3984
Following is the list of technical changes (including bug fixes) from Following is the list of technical changes (including bug fixes) from
RFC 3984. Besides this list of technical changes, numerous editorial RFC 3984. Besides this list of technical changes, numerous editorial
changes have been made, but not documented in this memo. changes have been made, but not documented in this memo.
1) In subsections 5.4, 5.5, 6.2, 6,3 and 6.4, removed that the 1) In subsections 5.4, 5.5, 6.2, 6,3 and 6.4, removed that the
packetization mode in use may be signaled by external means. packetization mode in use may be signaled by external means.
skipping to change at page 95, line 47 skipping to change at page 96, line 47
arrives. arrives.
to to
The parameter is the maximum value of (decoding time of the NAL The 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 and
instantaneous transmission, the same timeline for transmission instantaneous transmission, the same timeline for transmission
and decoding, and that decoding starts when the first packet and decoding, and that decoding starts when the first packet
arrives. arrives.
4) Added six new media type parameters, namely max-smbps, sprop- 4) Added five new media type parameters, namely max-smbps, sprop-
level-parameter-sets, use-level-parameter-sets, sprop-ssrc, sar- level-parameter-sets, use-level-src-parameter-sets, sar-understood
understood and sar-supported. and sar-supported.
5) In subsection 8.1, removed the specification of parameter-add. 5) In subsection 8.1, removed the specification of parameter-add.
Other descriptions of parameter-add (in subsections 8.2 and 8.4) Other descriptions of parameter-add (in subsections 8.2 and 8.4)
are also removed. are also removed.
6) In subsection 8.1, added a constraint to sprop-parameter-sets such 6) In subsection 8.1, added a constraint to sprop-parameter-sets such
that it can only contain parameter sets for the same profile and that it can only contain parameter sets for the same profile and
level as indicated by profile-level-id. level as indicated by profile-level-id.
7) In subsection 8.2.2, removed sprop-deint-buf-req from being part 7) In subsection 8.2.1, added that sprop-parameter-sets and sprop-
level-parameter-sets may be either included in the "a=fmtp" line
of SDP or conveyed using the "fmtp" source attribute as specified
in section 6.3 of [9].
8) In subsection 8.2.2, removed sprop-deint-buf-req from being part
of the media format configuration in usage with the SDP of the media format configuration in usage with the SDP
Offer/Answer model. Offer/Answer model.
8) In subsection 8.2.2, made it clear that level is downgradable in 9) In subsection 8.2.2, made it clear that level is downgradable in
the SDP Offer/Answer model, i.e. the use of the level part of the SDP Offer/Answer model, i.e. the use of the level part of
"profile-level-id" does not need to be symmetric (the level "profile-level-id" does not need to be symmetric (the level
included in the answer can be lower than or equal to the level included in the answer can be lower than or equal to the level
included in the offer). included in the offer).
9) In subsection 8.2.2, removed that the capability parameters may be 10)In subsection 8.2.2, removed that the capability parameters may be
used to declare encoding capabilities. used to declare encoding capabilities.
10)In subsection 8.2.2, added rules on how to use sprop-parameter- 11)In subsection 8.2.2, added rules on how to use sprop-parameter-
sets and sprop-level-parameter-sets for out-of-band transport of sets and sprop-level-parameter-sets for out-of-band transport of
parameter sets, with or without level downgrading. parameter sets, with or without level downgrading.
11)In subsection 8.2.2, clarified the rules of using the media type 12)In subsection 8.2.2, clarified the rules of using the media type
parameters with SDP Offer/Answer for multicast. parameters with SDP Offer/Answer for multicast.
12)In subsection 8.2.2, completed and corrected the list of how 13)In subsection 8.2.2, completed and corrected the list of how
different media type parameters shall be interpreted in the different media type parameters shall be interpreted in the
different combinations of offer or answer and direction attribute. different combinations of offer or answer and direction attribute.
13)In subsection 8.4, changed the text such that both out-of-band and 14)In subsection 8.4, changed the text such that both out-of-band and
in-band transport of parameter sets are allowed and neither is in-band transport of parameter sets are allowed and neither is
recommended or required. recommended or required.
14)Added subsection 8.5 (informative) providing example methods for 15)Added subsection 8.5 (informative) providing example methods for
decoder refresh to handle parameter set losses. decoder refresh to handle parameter set losses.
18. Open issues
The issues remaining open are:
1) (From Randell) References to RFC 2733 should be updated to (and
checked against) RFC 5109. There are a lot of calculations and
the like that should be checked. Also update [17] to RFC 5109.
 End of changes. 157 change blocks. 
496 lines changed or deleted 535 lines changed or added

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