draft-ietf-avt-profile-new-08.txt   draft-ietf-avt-profile-new-09.txt 
Internet Engineering Task Force AVT WG Internet Engineering Task Force AVT WG
Internet Draft Schulzrinne/Casner Internet Draft Schulzrinne/Casner
draft-ietf-avt-profile-new-08.txt Columbia U./Cisco Systems draft-ietf-avt-profile-new-09.txt Columbia U./Packet Design
January 14, 2000 July 14, 2000
Expires: July 14, 2000 Expires: January 14, 2001
RTP Profile for Audio and Video Conferences with Minimal Control RTP Profile for Audio and Video Conferences with Minimal Control
STATUS OF THIS MEMO STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress". material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This memorandum is a revision of RFC 1890 in preparation for This memorandum is a revision of RFC 1890 in preparation for
advancement from Proposed Standard to Draft Standard status. Readers advancement from Proposed Standard to Draft Standard status. Readers
are encouraged to use the PostScript form of this draft to see where are encouraged to use the PostScript form of this draft to see where
changes from RFC 1890 are marked by change bars. changes from RFC 1890 are marked by change bars.
This document describes a profile called "RTP/AVP" for the use of the This document describes a profile called "RTP/AVP" for the use of the
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bandwidth and separately for active senders and passive bandwidth and separately for active senders and passive
receivers. receivers.
o No specific action is taken in this document to address o No specific action is taken in this document to address
generic payload formats; it is assumed that if any generic generic payload formats; it is assumed that if any generic
payload formats are developed, they can be specified in payload formats are developed, they can be specified in
separate RFCs and that the session parameters they require for separate RFCs and that the session parameters they require for
operation can be specified in the MIME registration of those operation can be specified in the MIME registration of those
formats. formats.
o The specification of the CN (comfort noise) payload format o The specification of the CN (comfort noise) payload format has
has been removed to a separate draft so that it may be been removed to a separate draft so that it may be enhanced as
enhanced as a result of additional work in ITU-T. That draft a result of additional work in ITU-T. That draft is intended
is intended for publication at Proposed Standard status. for publication at Proposed Standard status. Static payload
Static payload type 13 is marked reserved here for the use of type 13 is marked reserved here for the use of that payload
that payload format (since CN has already been implemented format (since CN has already been implemented from earlier
from earlier drafts of this profile). Static payload type 19 drafts of this profile). Static payload type 19 is also
is also reserved because some revisions of the draft assigned reserved because some revisions of the draft assigned that
that number to CN to avoid an historic use of 13. number to CN to avoid an historic use of 13.
o The requirement for congestion control in RTP is addressed in
the RTP spec with an explanation that the behavior is context
specific and should be defined in RTP profiles. Text has been
added to this profile in Section 2 to describe the
requirements only in general terms because specific algorithms
have not been devised yet for multicast congestion control.
1 Introduction 1 Introduction
This profile defines aspects of RTP left unspecified in the RTP This profile defines aspects of RTP left unspecified in the RTP
Version 2 protocol definition (RFC XXXX) [1]. This profile is Version 2 protocol definition (RFC XXXX) [1]. This profile is
intended for the use within audio and video conferences with minimal intended for the use within audio and video conferences with minimal
session control. In particular, no support for the negotiation of session control. In particular, no support for the negotiation of
parameters or membership control is provided. The profile is expected parameters or membership control is provided. The profile is expected
to be useful in sessions where no negotiation or membership control to be useful in sessions where no negotiation or membership control
are used (e.g., using the static payload types and the membership are used (e.g., using the static payload types and the membership
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remove leading and trailing white space characters; (3) remove leading and trailing white space characters; (3)
replace one or more contiguous white space characters by a replace one or more contiguous white space characters by a
single space (ASCII or UTF-8 0x20); (4) convert all letters single space (ASCII or UTF-8 0x20); (4) convert all letters
to lower case and replace sequences of characters and non- to lower case and replace sequences of characters and non-
spacing accents with a single character, where possible. A spacing accents with a single character, where possible. A
minimum length of 16 key characters (after applying the minimum length of 16 key characters (after applying the
transformation) SHOULD be enforced by the application, transformation) SHOULD be enforced by the application,
while applications MUST allow up to 256 characters of while applications MUST allow up to 256 characters of
input. input.
Congestion: RTP and this profile may be used in the context of
enhanced network service, for example, through Integrated
Services (RFC 1633) [3] or Differentiated Services (RFC
2475) [4], or they may be used with best effort service.
If enhanced service is being used, RTP receivers SHOULD
monitor packet loss to ensure that the service that was
requested is actually being delivered. If it is not, then
they SHOULD assume that they are receiving best-effort
service and behave accordingly.
If best-effort service is being used, RTP receivers SHOULD
monitor packet loss to ensure that the packet loss rate is
within acceptable parameters. Packet loss is considered
acceptable if a TCP flow across the same network path and
experiencing the same network conditions would achieve an
average throughput that is not less the RTP flow is
achieving. This condition can be satisfied by implementing
congestion control mechanisms to adapt the transmission
rate (or the number of layers subscribed for a layered
multicast session), or by arranging for a receiver to leave
the session if the loss rate is unacceptably high.
Underlying protocol: The profile specifies the use of RTP over Underlying protocol: The profile specifies the use of RTP over
unicast and multicast UDP as well as TCP. (This does not unicast and multicast UDP as well as TCP. (This does not
preclude the use of these definitions when RTP is carried preclude the use of these definitions when RTP is carried
by other lower-layer protocols.) by other lower-layer protocols.)
Transport mapping: The standard mapping of RTP and RTCP to Transport mapping: The standard mapping of RTP and RTCP to
transport-level addresses is used. transport-level addresses is used.
Encapsulation: A minimal TCP encapsulation is defined. Encapsulation: A minimal TCP encapsulation is defined.
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is expected that additional encodings beyond the set listed here will is expected that additional encodings beyond the set listed here will
be created in the future and specified in additional payload format be created in the future and specified in additional payload format
RFCs. RFCs.
This profile also assigns to each encoding a short name which MAY be This profile also assigns to each encoding a short name which MAY be
used by higher-level control protocols, such as the Session used by higher-level control protocols, such as the Session
Description Protocol (SDP), RFC 2327 [5], to identify encodings Description Protocol (SDP), RFC 2327 [5], to identify encodings
selected for a particular RTP session. selected for a particular RTP session.
In some contexts it may be useful to refer to these encodings in the In some contexts it may be useful to refer to these encodings in the
form of a MIME content-type. To facilitate this, RFC YYYY [3] form of a MIME content-type. To facilitate this, RFC YYYY [6]
provides registrations for all of the encodings names listed here as provides registrations for all of the encodings names listed here as
MIME subtype names under the "audio" and "video" MIME types through MIME subtype names under the "audio" and "video" MIME types through
the MIME registration procedure as specified in RFC 2048 [4]. the MIME registration procedure as specified in RFC 2048 [7].
Any additional encodings specified for use under this profile (or Any additional encodings specified for use under this profile (or
others) may also be assigned names registered as MIME subtypes with others) may also be assigned names registered as MIME subtypes with
the Internet Assigned Numbers Authority (IANA). This registry the Internet Assigned Numbers Authority (IANA). This registry
provides a means to insure that the names assigned to the additional provides a means to insure that the names assigned to the additional
encodings are kept unique. RFC YYYY specifies the information that is encodings are kept unique. RFC YYYY specifies the information that is
required for the registration of RTP encodings. required for the registration of RTP encodings.
In addition to assigning names to encodings, this profile also also In addition to assigning names to encodings, this profile also also
assigns static RTP payload type numbers to some of them. However, the assigns static RTP payload type numbers to some of them. However, the
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number of sampling periods per second. For N-channel encodings, each number of sampling periods per second. For N-channel encodings, each
sampling period (say, 1/8000 of a second) generates N samples. (This sampling period (say, 1/8000 of a second) generates N samples. (This
terminology is standard, but somewhat confusing, as the total number terminology is standard, but somewhat confusing, as the total number
of samples generated per second is then the sampling rate times the of samples generated per second is then the sampling rate times the
channel count.) channel count.)
If multiple audio channels are used, channels are numbered left-to- If multiple audio channels are used, channels are numbered left-to-
right, starting at one. In RTP audio packets, information from right, starting at one. In RTP audio packets, information from
lower-numbered channels precedes that from higher-numbered channels. lower-numbered channels precedes that from higher-numbered channels.
For more than two channels, the convention followed by the AIFF-C For more than two channels, the convention followed by the AIFF-C
audio interchange format SHOULD be followed [6], using the following audio interchange format SHOULD be followed [8], using the following
notation, unless some other convention is specified for a particular notation, unless some other convention is specified for a particular
encoding or payload format: encoding or payload format:
l left l left
r right r right
c center c center
S surround S surround
F front F front
R rear R rear
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RTP packets SHALL contain a whole number of frames, with frames RTP packets SHALL contain a whole number of frames, with frames
inserted according to age within a packet, so that the oldest frame inserted according to age within a packet, so that the oldest frame
(to be played first) occurs immediately after the RTP packet header. (to be played first) occurs immediately after the RTP packet header.
The RTP timestamp reflects the instant at which the first sample in The RTP timestamp reflects the instant at which the first sample in
the first frame was sampled, that is, the oldest information in the the first frame was sampled, that is, the oldest information in the
packet. packet.
4.5 Audio Encodings 4.5 Audio Encodings
The characteristics of the audio encodings described in this document
are shown in Table 1; they are listed in order of their payload type
in Table 4. While most audio codecs are only specified for a fixed
sampling rate, some sample-based algorithms (indicated by an entry of
"var." in the sampling rate column of Table 1) may be used with
name of sampling default name of sampling default
encoding sample/frame bits/sample rate ms/frame ms/packet encoding sample/frame bits/sample rate ms/frame ms/packet
__________________________________________________________________ __________________________________________________________________
1016 frame N/A 8,000 30 30 1016 frame N/A 8,000 30 30
DVI4 sample 4 var. 20 DVI4 sample 4 var. 20
G722 sample 8 16,000 20 G722 sample 8 16,000 20
G723 frame N/A 8,000 30 30 G723 frame N/A 8,000 30 30
G726-32 sample 4 8,000 20 G726-32 sample 4 8,000 20
G728 frame N/A 8,000 2.5 20 G728 frame N/A 8,000 2.5 20
G729 frame N/A 8,000 10 20 G729 frame N/A 8,000 10 20
G729D frame N/A 8,000 10 20
G729E frame N/A 8,000 10 20
GSM frame N/A 8,000 20 20 GSM frame N/A 8,000 20 20
GSM-HR frame N/A 8,000 20 20 GSM-HR frame N/A 8,000 20 20
GSM-EFR frame N/A 8,000 20 20 GSM-EFR frame N/A 8,000 20 20
L8 sample 8 var. 20 L8 sample 8 var. 20
L16 sample 16 var. 20 L16 sample 16 var. 20
LPC frame N/A 8,000 20 20 LPC frame N/A 8,000 20 20
MPA frame N/A var. var. MPA frame N/A var. var.
PCMA sample 8 var. 20 PCMA sample 8 var. 20
PCMU sample 8 var. 20 PCMU sample 8 var. 20
QCELP frame N/A 8,000 20 20 QCELP frame N/A 8,000 20 20
VDVI sample var. var. 20 VDVI sample var. var. 20
Table 1: Properties of Audio Encodings (N/A: not applicable; var.: Table 1: Properties of Audio Encodings (N/A: not applicable; var.:
variable) variable)
The characteristics of the audio encodings described in this document
are shown in Table 1; they are listed in order of their payload type
in Table 4. While most audio codecs are only specified for a fixed
sampling rate, some sample-based algorithms (indicated by an entry of
"var." in the sampling rate column of Table 1) may be used with
different sampling rates, resulting in different coded bit rates. different sampling rates, resulting in different coded bit rates.
When used with a sampling rate other than that for which a static When used with a sampling rate other than that for which a static
payload type is defined, non-RTP means beyond the scope of this memo payload type is defined, non-RTP means beyond the scope of this memo
MUST be used to define a dynamic payload type and MUST indicate the MUST be used to define a dynamic payload type and MUST indicate the
selected RTP timestamp clock rate, which is usually the same as the selected RTP timestamp clock rate, which is usually the same as the
sampling rate for audio. sampling rate for audio.
4.5.1 1016 4.5.1 1016
Encoding 1016 is a frame based encoding using code-excited linear Encoding 1016 is a frame based encoding using code-excited linear
prediction (CELP) and is specified in Federal Standard FED-STD 1016 prediction (CELP) and is specified in Federal Standard FED-STD 1016
[7,8,9,10]. [9,10,11,12].
4.5.2 DVI4 4.5.2 DVI4
DVI4 is specified, with pseudo-code, in [11] as the IMA ADPCM wave DVI4 is specified, with pseudo-code, in [13] as the IMA ADPCM wave
type. type.
However, the encoding defined here as DVI4 differs in three respects However, the encoding defined here as DVI4 differs in three respects
from this recommendation: from this recommendation:
o The RTP DVI4 header contains the predicted value rather than o The RTP DVI4 header contains the predicted value rather than
the first sample value contained the IMA ADPCM block header. the first sample value contained the IMA ADPCM block header.
o IMA ADPCM blocks contain an odd number of samples, since the o IMA ADPCM blocks contain an odd number of samples, since the
first sample of a block is contained just in the header first sample of a block is contained just in the header
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10 SID frame 4 10 SID frame 4
11 reserved 11 reserved
It is possible to switch between the two rates at any 30 ms frame It is possible to switch between the two rates at any 30 ms frame
boundary. Both (5.3 kb/s and 6.3 kb/s) rates are a mandatory part of boundary. Both (5.3 kb/s and 6.3 kb/s) rates are a mandatory part of
the encoder and decoder. This coder was optimized to represent speech the encoder and decoder. This coder was optimized to represent speech
with near-toll quality at the above rates using a limited amount of with near-toll quality at the above rates using a limited amount of
complexity. complexity.
The packing of the encoded bit stream into octets and the The packing of the encoded bit stream into octets and the
transmission order of the octets is specified in G.723.1. transmission order of the octets is specified in Rec. G.723.1 and is
the same as that produced by the G.723 C code reference
implementation. For the 6.3 kb/s data rate, this packing is
illustrated as follows, where the header (HDR) bits are always "0 0"
as shown in Fig. 1 to indicate operation at 6.3 kb/s, and the Z bit
is always set to zero. The diagrams show the bit packing in "network
byte order," also known as big-endian order. The bits of each 32-bit
word are numbered 0 to 31, with the most significant bit on the left
and numbered 0. The octets (bytes) of each word are transmitted most
significant octet first. The bits of each data field are numbered in
the order of the bit stream representation of the encoding (least
significant bit first). The vertical bars indicate the boundaries
between field fragments.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LPC |HDR| LPC | LPC | ACL0 |LPC|
| | | | | | |
|0 0 0 0 0 0|0 0|1 1 1 1 0 0 0 0|2 2 1 1 1 1 1 1|0 0 0 0 0 0|2 2|
|5 4 3 2 1 0| |3 2 1 0 9 8 7 6|1 0 9 8 7 6 5 4|5 4 3 2 1 0|3 2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACL2 |ACL|A| GAIN0 |ACL|ACL| GAIN0 | GAIN1 |
| | 1 |C| | 3 | 2 | | |
|0 0 0 0 0|0 0|0|0 0 0 0|0 0|0 0|1 1 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
|4 3 2 1 0|1 0|6|3 2 1 0|1 0|6 5|1 0 9 8 7 6 5 4|7 6 5 4 3 2 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAIN2 | GAIN1 | GAIN2 | GAIN3 | GRID | GAIN3 |
| | | | | | |
|0 0 0 0|1 1 0 0|1 1 0 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0|1 1 0 0|
|3 2 1 0|1 0 9 8|1 0 9 8 7 6 5 4|7 6 5 4 3 2 1 0|3 2 1 0|1 0 9 8|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSBPOS |Z|POS| MSBPOS | POS0 |POS| POS0 |
| | | 0 | | | 1 | |
|0 0 0 0 0 0 0|0|0 0|1 1 1 0 0 0|0 0 0 0 0 0 0 0|0 0|1 1 1 1 1 1|
|6 5 4 3 2 1 0| |1 0|2 1 0 9 8 7|9 8 7 6 5 4 3 2|1 0|5 4 3 2 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| POS1 | POS2 | POS1 | POS2 | POS3 | POS2 |
| | | | | | |
|0 0 0 0 0 0 0 0|0 0 0 0|1 1 1 1|1 1 0 0 0 0 0 0|0 0 0 0|1 1 1 1|
|9 8 7 6 5 4 3 2|3 2 1 0|3 2 1 0|1 0 9 8 7 6 5 4|3 2 1 0|5 4 3 2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| POS3 | PSIG0 |POS|PSIG2| PSIG1 | PSIG3 |PSIG2|
| | | 3 | | | | |
|1 1 0 0 0 0 0 0|0 0 0 0 0 0|1 1|0 0 0|0 0 0 0 0|0 0 0 0 0|0 0 0|
|1 0 9 8 7 6 5 4|5 4 3 2 1 0|3 2|2 1 0|4 3 2 1 0|4 3 2 1 0|5 4 3|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: G.723 (6.3 kb/s) bit packing
For the 5.3 kb/s data rate, the header (HDR) bits are always "0 1",
as shown in Fig. 2, to indicate operation at 5.3 kb/s.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LPC |HDR| LPC | LPC | ACL0 |LPC|
| | | | | | |
|0 0 0 0 0 0|0 1|1 1 1 1 0 0 0 0|2 2 1 1 1 1 1 1|0 0 0 0 0 0|2 2|
|5 4 3 2 1 0| |3 2 1 0 9 8 7 6|1 0 9 8 7 6 5 4|5 4 3 2 1 0|3 2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACL2 |ACL|A| GAIN0 |ACL|ACL| GAIN0 | GAIN1 |
| | 1 |C| | 3 | 2 | | |
|0 0 0 0 0|0 0|0|0 0 0 0|0 0|0 0|1 1 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
|4 3 2 1 0|1 0|6|3 2 1 0|1 0|6 5|1 0 9 8 7 6 5 4|7 6 5 4 3 2 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAIN2 | GAIN1 | GAIN2 | GAIN3 | GRID | GAIN3 |
| | | | | | |
|0 0 0 0|1 1 0 0|1 1 0 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0|1 1 0 0|
|3 2 1 0|1 0 9 8|1 0 9 8 7 6 5 4|7 6 5 4 3 2 1 0|4 3 2 1|1 0 9 8|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| POS0 | POS1 | POS0 | POS1 | POS2 |
| | | | | |
|0 0 0 0 0 0 0 0|0 0 0 0|1 1 0 0|1 1 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
|7 6 5 4 3 2 1 0|3 2 1 0|1 0 9 8|1 0 9 8 7 6 5 4|7 6 5 4 3 2 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| POS3 | POS2 | POS3 | PSIG1 | PSIG0 | PSIG3 | PSIG2 |
| | | | | | | |
|0 0 0 0|1 1 0 0|1 1 0 0 0 0 0 0|0 0 0 0|0 0 0 0|0 0 0 0|0 0 0 0|
|3 2 1 0|1 0 9 8|1 0 9 8 7 6 5 4|3 2 1 0|3 2 1 0|3 2 1 0|3 2 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: G.723 (5.3 kb/s) bit packing
The packing of G.723.1 SID (silence) frames, which are indicated by
the header (HDR) bits having the pattern "1 0", is depicted in Fig.
3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LPC |HDR| LPC | LPC | GAIN |LPC|
| | | | | | |
|0 0 0 0 0 0|1 0|1 1 1 1 0 0 0 0|2 2 1 1 1 1 1 1|0 0 0 0 0 0|2 2|
|5 4 3 2 1 0| |3 2 1 0 9 8 7 6|1 0 9 8 7 6 5 4|5 4 3 2 1 0|3 2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: G.723 SID mode bit packing
4.5.5 G726-32 4.5.5 G726-32
ITU-T Recommendation G.726 describes, among others, the algorithm ITU-T Recommendation G.726 describes, among others, the algorithm
recommended for conversion of a single 64 kbit/s A-law or mu-law PCM recommended for conversion of a single 64 kbit/s A-law or mu-law PCM
channel encoded at 8000 samples/sec to and from a 32 kbit/s channel. channel encoded at 8000 samples/sec to and from a 32 kbit/s channel.
The conversion is applied to the PCM stream using an Adaptive The conversion is applied to the PCM stream using an Adaptive
Differential Pulse Code Modulation (ADPCM) transcoding technique. Differential Pulse Code Modulation (ADPCM) transcoding technique.
G.726 describes codecs operating at 16 kb/s (2 bits/sample), 24 kb/s G.726 describes codecs operating at 16 kb/s (2 bits/sample), 24 kb/s
(3 bits/sample), 32 kb/s (4 bits/sample), 40 kb/s (5 bits/sample). (3 bits/sample), 32 kb/s (4 bits/sample), 40 kb/s (5 bits/sample).
skipping to change at page 15, line 44 skipping to change at page 19, line 42
G729 is specified in ITU-T Recommendation G.729, "Coding of speech at G729 is specified in ITU-T Recommendation G.729, "Coding of speech at
8 kbit/s using conjugate structure-algebraic code excited linear 8 kbit/s using conjugate structure-algebraic code excited linear
prediction (CS-ACELP)". A reduced-complexity version of the G.729 prediction (CS-ACELP)". A reduced-complexity version of the G.729
algorithm is specified in Annex A to Rec. G.729. The speech coding algorithm is specified in Annex A to Rec. G.729. The speech coding
algorithms in the main body of G.729 and in G.729 Annex A are fully algorithms in the main body of G.729 and in G.729 Annex A are fully
interoperable with each other, so there is no need to further interoperable with each other, so there is no need to further
distinguish between them. The G.729 and G.729 Annex A codecs were distinguish between them. The G.729 and G.729 Annex A codecs were
optimized to represent speech with high quality, where G.729 Annex A optimized to represent speech with high quality, where G.729 Annex A
trades some speech quality for an approximate 50% complexity trades some speech quality for an approximate 50% complexity
reduction [12]. reduction [14]. See the next Section (4.5.8) for other data rates
added in later G.729 Annexes. For all data rates, the sampling
frequency (and RTP timestamp clock rate) is 8000 Hz.
A voice activity detector (VAD) and comfort noise generator (CNG) A voice activity detector (VAD) and comfort noise generator (CNG)
algorithm in Annex B of G.729 is RECOMMENDED for digital simultaneous algorithm in Annex B of G.729 is RECOMMENDED for digital simultaneous
voice and data applications and can be used in conjunction with G.729 voice and data applications and can be used in conjunction with G.729
or G.729 Annex A. A G.729 or G.729 Annex A frame contains 10 octets, or G.729 Annex A. A G.729 or G.729 Annex A frame contains 10 octets,
while the G.729 Annex B comfort noise frame occupies 2 octets: while the G.729 Annex B comfort noise frame occupies 2 octets.
A G729 RTP packet may consist of zero or more G.729 or G.729 Annex A
frames, followed by zero or one G.729 Annex B frames. The presence of
a comfort noise frame can be deduced from the length of the RTP
payload. The default packetization interval is 20 ms (two frames),
but in some situations it may be desireable to send 10 ms packets. An
example would be a transition from speech to comfort noise in the
first 10 ms of the packet. For some applications, a longer
packetization interval may be required to reduce the packet rate.
The transmitted parameters of a G.729/G.729A 10-ms frame, consisting
of 80 bits, are defined in Recommendation G.729, Table 8/G.729. The
mapping of the these parameters is given below in Fig. 4. The
diagrams show the bit packing in "network byte order," also known as
big-endian order. The bits of each 32-bit word are numbered 0 to 31,
with the most significant bit on the left and numbered 0. The octets
(bytes) of each word are transmitted most significant octet first.
The bits of each data field are numbered in the order as produced by
the G.729 C code reference implementation.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| L1 | L2 | L3 | P1 |P| C1 |
|0| | | | |0| |
| |0 1 2 3 4 5 6|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4 5 6 7| |0 1 2 3 4|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C1 | S1 | GA1 | GB1 | P2 | C2 |
| 1 1 1| | | | | |
|5 6 7 8 9 0 1 2|0 1 2 3|0 1 2|0 1 2 3|0 1 2 3 4|0 1 2 3 4 5 6 7|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C2 | S2 | GA2 | GB2 |
| 1 1 1| | | |
|8 9 0 1 2|0 1 2 3|0 1 2|0 1 2 3|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: G.729 and G.729A bit packing
The packing of the G.729 Annex B comfort noise frame is shown in Fig.
5.
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| LSF1 | LSF2 | GAIN |R| |L| LSF1 | LSF2 | GAIN |R|
|S| | | |E| |S| | | |E|
|F|0 1 2 3 4|0 1 2 3|0 1 2 3 4|S| |F| | | |S|
|0| | | |V| RESV = Reserved (zero) |0|0 1 2 3 4|0 1 2 3|0 1 2 3 4|V| RESV = Reserved (zero)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An RTP packet may consist of zero or more G.729 or G.729 Annex A Figure 5: G.729 Annex B bit packing
frames, followed by zero or one G.729 Annex B payloads. The presence
of a comfort noise frame can be deduced from the length of the RTP 4.5.8 G729D and G729E
Annexes D and E to ITU-T Recommendation G.729 provide additional data
rates. Because the data rate is not signaled in the bitstream, the
different data rates are given distinct RTP encoding names which are
mapped to distinct payload type numbers. G729D indicates a 6.4 kbit/s
coding mode (G.729 Annex D, for momentary reduction in channel
capacity), while G729E indicates an 11.8 kbit/s mode (G.729 Annex E,
for improved performance with a wide range of narrow-band input
signals, e.g. music and background noise). Annex E has two operating
modes, backward adaptive and forward adaptive, which are signaled by
the first two bits in each frame (the most significant two bits of
the first octet).
The voice activity detector (VAD) and comfort noise generator (CNG)
algorithm specified in Annex B of G.729 may be used with Annex D and
Annex E frames in addition to G.729 and G.729 Annex A frames. The
algorithm details for the operation of Annexes D and E with the Annex
B CNG are specified in G.729 Annexes F and G. Note that Annexes F and
G do not introduce any new encodings.
For G729D, an RTP packet may consist of zero or more G.729 Annex D
frames, followed by zero or one G.729 Annex B frame. Similarly, for
G729E, an RTP packet may consist of zero or more G.729 Annex E
frames, followed by zero or one G.729 Annex B frame. The presence of
a comfort noise frame can be deduced from the length of the RTP
payload. payload.
The transmitted parameters of a G.729/G.729A 10-ms frame, consisting A single RTP packet must contain frames of only one data rate,
of 80 bits, are defined in Recommendation G.729, Table 8/G.729. optionally followed by one comfort noise frame. The data rate may be
changed from packet to packet by changing the payload type number.
G.729 Annexes D, E and H describe what the encoding and decoding
algorithms must do to accommodate a change in data rate.
The mapping of the these parameters is given below. Bits are numbered For G729D, the bits of a G.729 Annex D frame are formatted as shown
as Internet order, that is, the most significant bit is bit 0. below in Fig. 6 (cf. Table D.1/G.729). The frame length is 64 bits.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| L1 | L2 | L3 | P1 |P| C1 | |L| L1 | L2 | L3 | P1 | C1 |
|0| | | | |0| | |0| | | | | |
| |0 1 2 3 4 5 6|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4 5 6 7| |0 1 2 3 4| | |0 1 2 3 4 5 6|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4 5 6 7|0 1 2 3 4 5|
| | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C1 |S1 | GA1 | GB1 | P2 | C2 |S2 | GA2 | GB2 |
| | | | | | | | | |
|6 7 8|0 1|0 1 2|0 1 2|0 1 2 3|0 1 2 3 4 5 6 7 8|0 1|0 1 2|0 1 2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 5 6 Figure 6: G.729 Annex D bit packing
2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
The net bit rate for the G.729 Annex E algorithm is 11.8 kbit/s and a
total of 118 bits are used. Two bits are appended as "don't care"
bits to complete an integer number of octets for the frame. For
G729E, the bits of a data frame are formatted as shown in the next
two diagrams (cf. Table E.1/G.729). The fields for the G729E forward
adaptive mode are packed as shown in Fig. 7.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C1 | S1 | GA1 | GB1 | P2 | C2 | |0 0|L| L1 | L2 | L3 | P1 |P| C0_1|
| |0| | | | |0| |
| | |0 1 2 3 4 5 6|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4 5 6 7| |0 1 2|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C1_1 | C2_1 | C3_1 | C4_1 |
| | | | | |
|3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GA1 | GB1 | P2 | C0_2 | C1_2 | C2_2 |
| | | | | | | | | | | | | |
|5 6 7 8 9 1 1 1|0 1 2 3|0 1 2|0 1 2 3|0 1 2 3 4|0 1 2 3 4 5 6 7| |0 1 2|0 1 2 3|0 1 2 3 4|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4 5|
| 0 1 2| | | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C3_2 | C4_2 | GA2 | GB2 |DC |
| | | | | | |
|6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2|0 1 2 3|0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7 Figure 7: G.729 Annex E (forward adaptive mode) bit packing
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C2 | S2 | GA2 | GB2 |
| | | | |
|8 9 1 1 1|0 1 2 3|0 1 2|0 1 2 3|
| 0 1 2| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.5.8 GSM The fields for the G729E backward adaptive mode are packed as shown
in Fig. 8.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1| P1 |P| C0_1 | C1_1 |
| | |0| 1 1 1| |
| |0 1 2 3 4 5 6 7|0|0 1 2 3 4 5 6 7 8 9 0 1 2|0 1 2 3 4 5 6 7|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C2_1 | C3_1 | C4_1 |GA1 | GB1 |P2 |
| | | | | | | |
|8 9|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2|0 1 2 3|0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C0_2 | C1_2 | C2_2 |
| | 1 1 1| | |
|2 3 4|0 1 2 3 4 5 6 7 8 9 0 1 2|0 1 2 3 4 5 6 7 8 9|0 1 2 3 4 5|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C3_2 | C4_2 | GA2 | GB2 |DC |
| | | | | | |
|6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2|0 1 2 3|0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: G.729 Annex E (backward adaptive mode) bit packing
4.5.9 GSM
GSM (group speciale mobile) denotes the European GSM 06.10 standard GSM (group speciale mobile) denotes the European GSM 06.10 standard
for full-rate speech transcoding, ETS 300 961, which is based on for full-rate speech transcoding, ETS 300 961, which is based on
RPE/LTP (residual pulse excitation/long term prediction) coding at a RPE/LTP (residual pulse excitation/long term prediction) coding at a
rate of 13 kb/s [13,14,15]. The text of the standard can be obtained rate of 13 kb/s [15,16,17]. The text of the standard can be obtained
from from
ETSI (European Telecommunications Standards Institute) ETSI (European Telecommunications Standards Institute)
ETSI Secretariat: B.P.152 ETSI Secretariat: B.P.152
F-06561 Valbonne Cedex F-06561 Valbonne Cedex
France France
Phone: +33 92 94 42 00 Phone: +33 92 94 42 00
Fax: +33 93 65 47 16 Fax: +33 93 65 47 16
Blocks of 160 audio samples are compressed into 33 octets, for an Blocks of 160 audio samples are compressed into 33 octets, for an
effective data rate of 13,200 b/s. effective data rate of 13,200 b/s.
4.5.8.1 General Packaging Issues 4.5.9.1 General Packaging Issues
The GSM standard (ETS 300 961) specifies the bit stream produced by The GSM standard (ETS 300 961) specifies the bit stream produced by
the codec, but does not specify how these bits should be packed for the codec, but does not specify how these bits should be packed for
transmission. The packetization specified here has subsequently been transmission. The packetization specified here has subsequently been
adopted in ETSI Technical Specification TS 101 318. Some software adopted in ETSI Technical Specification TS 101 318. Some software
implementations of the GSM codec use a different packing than that implementations of the GSM codec use a different packing than that
specified here. specified here.
In the GSM packing used by RTP, the bits SHALL be packed beginning In the GSM packing used by RTP, the bits SHALL be packed beginning
from the most significant bit. Every 160 sample GSM frame is coded from the most significant bit. Every 160 sample GSM frame is coded
into one 33 octet (264 bit) buffer. Every such buffer begins with a 4 into one 33 octet (264 bit) buffer. Every such buffer begins with a 4
bit signature (0xD), followed by the MSB encoding of the fields of bit signature (0xD), followed by the MSB encoding of the fields of
the frame. The first octet thus contains 1101 in the 4 most the frame. The first octet thus contains 1101 in the 4 most
significant bits (0-3) and the 4 most significant bits of F1 (0-3) in significant bits (0-3) and the 4 most significant bits of F1 (0-3) in
the 4 least significant bits (4-7). The second octet contains the 2 the 4 least significant bits (4-7). The second octet contains the 2
least significant bits of F1 in bits 0-1, and F2 in bits 2-7, and so least significant bits of F1 in bits 0-1, and F2 in bits 2-7, and so
on. The order of the fields in the frame is described in Table 2. on. The order of the fields in the frame is described in Table 2.
4.5.8.2 GSM variable names and numbers 4.5.9.2 GSM variable names and numbers
In the RTP encoding we have the bit pattern described in Table 3,
where F.i signifies the ith bit of the field F, bit 0 is the most
significant bit, and the bits of every octet are numbered from 0 to 7
from most to least significant.
4.5.10 GSM-HR
GSM-HR denotes GSM 06.20 half rate speech transcoding, specified in
ETS 300 969 which is available from ETSI at the address given in
Section 4.5.9. This codec has a frame length of 112 bits (14 octets).
Packing of the fields in the codec bit stream into octets for
transmission in RTP is done in a manner similar to that specified
here for the original GSM 06.10 codec and is specified in ETSI
Technical Specification TS 101 318.
4.5.11 GSM-EFR
GSM-EFR denotes GSM 06.60 enhanced full rate speech transcoding,
specified in ETS 300 969 which is available from ETSI at the address
given in Section 4.5.9. This codec has a frame length of 244 bits.
For transmission in RTP, each codec frame is packed into a 31 octet
(248 bit) buffer beginning with a 4-bit signature 0xC in a manner
similar to that specified here for the original GSM 06.10 codec. The
packing is specified in ETSI Technical Specification TS 101 318.
4.5.12 L8
L8 denotes linear audio data samples, using 8-bits of precision with
an offset of 128, that is, the most negative signal is encoded as
zero.
field field name bits field field name bits field field name bits field field name bits
________________________________________________ ________________________________________________
1 LARc[0] 6 39 xmc[22] 3 1 LARc[0] 6 39 xmc[22] 3
2 LARc[1] 6 40 xmc[23] 3 2 LARc[1] 6 40 xmc[23] 3
3 LARc[2] 5 41 xmc[24] 3 3 LARc[2] 5 41 xmc[24] 3
4 LARc[3] 5 42 xmc[25] 3 4 LARc[3] 5 42 xmc[25] 3
5 LARc[4] 4 43 Nc[2] 7 5 LARc[4] 4 43 Nc[2] 7
6 LARc[5] 4 44 bc[2] 2 6 LARc[5] 4 44 bc[2] 2
7 LARc[6] 3 45 Mc[2] 2 7 LARc[6] 3 45 Mc[2] 2
8 LARc[7] 3 46 xmaxc[2] 6 8 LARc[7] 3 46 xmaxc[2] 6
skipping to change at page 18, line 47 skipping to change at page 26, line 48
32 xmc[15] 3 70 xmc[45] 3 32 xmc[15] 3 70 xmc[45] 3
33 xmc[16] 3 71 xmc[46] 3 33 xmc[16] 3 71 xmc[46] 3
34 xmc[17] 3 72 xmc[47] 3 34 xmc[17] 3 72 xmc[47] 3
35 xmc[18] 3 73 xmc[48] 3 35 xmc[18] 3 73 xmc[48] 3
36 xmc[19] 3 74 xmc[49] 3 36 xmc[19] 3 74 xmc[49] 3
37 xmc[20] 3 75 xmc[50] 3 37 xmc[20] 3 75 xmc[50] 3
38 xmc[21] 3 76 xmc[51] 3 38 xmc[21] 3 76 xmc[51] 3
Table 2: Ordering of GSM variables Table 2: Ordering of GSM variables
In the RTP encoding we have the bit pattern described in Table 3, 4.5.13 L16
where F.i signifies the ith bit of the field F, bit 0 is the most
significant bit, and the bits of every octet are numbered from 0 to 7
from most to least significant.
L16 denotes uncompressed audio data samples, using 16-bit signed
representation with 65535 equally divided steps between minimum and
Octet Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7 Octet Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
_____________________________________________________________________________ _____________________________________________________________________________
0 1 1 0 1 LARc0.0 LARc0.1 LARc0.2 LARc0.3 0 1 1 0 1 LARc0.0 LARc0.1 LARc0.2 LARc0.3
1 LARc0.4 LARc0.5 LARc1.0 LARc1.1 LARc1.2 LARc1.3 LARc1.4 LARc1.5 1 LARc0.4 LARc0.5 LARc1.0 LARc1.1 LARc1.2 LARc1.3 LARc1.4 LARc1.5
2 LARc2.0 LARc2.1 LARc2.2 LARc2.3 LARc2.4 LARc3.0 LARc3.1 LARc3.2 2 LARc2.0 LARc2.1 LARc2.2 LARc2.3 LARc2.4 LARc3.0 LARc3.1 LARc3.2
3 LARc3.3 LARc3.4 LARc4.0 LARc4.1 LARc4.2 LARc4.3 LARc5.0 LARc5.1 3 LARc3.3 LARc3.4 LARc4.0 LARc4.1 LARc4.2 LARc4.3 LARc5.0 LARc5.1
4 LARc5.2 LARc5.3 LARc6.0 LARc6.1 LARc6.2 LARc7.0 LARc7.1 LARc7.2 4 LARc5.2 LARc5.3 LARc6.0 LARc6.1 LARc6.2 LARc7.0 LARc7.1 LARc7.2
5 Nc0.0 Nc0.1 Nc0.2 Nc0.3 Nc0.4 Nc0.5 Nc0.6 bc0.0 5 Nc0.0 Nc0.1 Nc0.2 Nc0.3 Nc0.4 Nc0.5 Nc0.6 bc0.0
6 bc0.1 Mc0.0 Mc0.1 xmaxc00 xmaxc01 xmaxc02 xmaxc03 xmaxc04 6 bc0.1 Mc0.0 Mc0.1 xmaxc00 xmaxc01 xmaxc02 xmaxc03 xmaxc04
7 xmaxc05 xmc0.0 xmc0.1 xmc0.2 xmc1.0 xmc1.1 xmc1.2 xmc2.0 7 xmaxc05 xmc0.0 xmc0.1 xmc0.2 xmc1.0 xmc1.1 xmc1.2 xmc2.0
skipping to change at page 19, line 44 skipping to change at page 27, line 42
26 Nc3.0 Nc3.1 Nc3.2 Nc3.3 Nc3.4 Nc3.5 Nc3.6 bc3.0 26 Nc3.0 Nc3.1 Nc3.2 Nc3.3 Nc3.4 Nc3.5 Nc3.6 bc3.0
27 bc3.1 Mc3.0 Mc3.1 xmaxc30 xmaxc31 xmaxc32 xmaxc33 xmaxc34 27 bc3.1 Mc3.0 Mc3.1 xmaxc30 xmaxc31 xmaxc32 xmaxc33 xmaxc34
28 xmaxc35 xmc39.0 xmc39.1 xmc39.2 xmc40.0 xmc40.1 xmc40.2 xmc41.0 28 xmaxc35 xmc39.0 xmc39.1 xmc39.2 xmc40.0 xmc40.1 xmc40.2 xmc41.0
29 xmc41.1 xmc41.2 xmc42.0 xmc42.1 xmc42.2 xmc43.0 xmc43.1 xmc43.2 29 xmc41.1 xmc41.2 xmc42.0 xmc42.1 xmc42.2 xmc43.0 xmc43.1 xmc43.2
30 xmc44.0 xmc44.1 xmc44.2 xmc45.0 xmc45.1 xmc45.2 xmc46.0 xmc46.1 30 xmc44.0 xmc44.1 xmc44.2 xmc45.0 xmc45.1 xmc45.2 xmc46.0 xmc46.1
31 xmc46.2 xmc47.0 xmc47.1 xmc47.2 xmc48.0 xmc48.1 xmc48.2 xmc49.0 31 xmc46.2 xmc47.0 xmc47.1 xmc47.2 xmc48.0 xmc48.1 xmc48.2 xmc49.0
32 xmc49.1 xmc49.2 xmc50.0 xmc50.1 xmc50.2 xmc51.0 xmc51.1 xmc51.2 32 xmc49.1 xmc49.2 xmc50.0 xmc50.1 xmc50.2 xmc51.0 xmc51.1 xmc51.2
Table 3: GSM payload format Table 3: GSM payload format
4.5.9 GSM-HR
GSM-HR denotes GSM 06.20 half rate speech transcoding, specified in
ETS 300 969 which is available from ETSI at the address given in
Section 4.5.8. This codec has a frame length of 112 bits (14 octets).
Packing of the fields in the codec bit stream into octets for
transmission in RTP is done in a manner similar to that specified
here for the original GSM 06.10 codec and is specified in ETSI
Technical Specification TS 101 318.
4.5.10 GSM-EFR
GSM-EFR denotes GSM 06.60 enhanced full rate speech transcoding,
specified in ETS 300 969 which is available from ETSI at the address
given in Section 4.5.8. This codec has a frame length of 244 bits.
For transmission in RTP, each codec frame is packed into a 31 octet
(248 bit) buffer beginning with a 4-bit signature 0xC in a manner
similar to that specified here for the original GSM 06.10 codec. The
packing is specified in ETSI Technical Specification TS 101 318.
4.5.11 L8
L8 denotes linear audio data samples, using 8-bits of precision with
an offset of 128, that is, the most negative signal is encoded as
zero.
4.5.12 L16
L16 denotes uncompressed audio data samples, using 16-bit signed
representation with 65535 equally divided steps between minimum and
maximum signal level, ranging from -32768 to 32767. The value is maximum signal level, ranging from -32768 to 32767. The value is
represented in two's complement notation and transmitted in network represented in two's complement notation and transmitted in network
byte order (most significant byte first). byte order (most significant byte first).
4.5.13 LPC 4.5.14 LPC
LPC designates an experimental linear predictive encoding contributed LPC designates an experimental linear predictive encoding contributed
by Ron Frederick, Xerox PARC, which is based on an implementation by Ron Frederick, which is based on an implementation written by Ron
written by Ron Zuckerman, Motorola, posted to the Usenet group Zuckerman posted to the Usenet group comp.dsp on June 26, 1992. The
comp.dsp on June 26, 1992. The codec generates 14 octets for every codec generates 14 octets for every frame. The framesize is set to 20
frame. The framesize is set to 20 ms, resulting in a bit rate of ms, resulting in a bit rate of 5,600 b/s.
5,600 b/s.
4.5.14 MPA 4.5.15 MPA
MPA denotes MPEG-1 or MPEG-2 audio encapsulated as elementary MPA denotes MPEG-1 or MPEG-2 audio encapsulated as elementary
streams. The encoding is defined in ISO standards ISO/IEC 11172-3 streams. The encoding is defined in ISO standards ISO/IEC 11172-3
and 13818-3. The encapsulation is specified in RFC 2250 [16]. and 13818-3. The encapsulation is specified in RFC 2250 [18].
The encoding may be at any of three levels of complexity, called The encoding may be at any of three levels of complexity, called
Layer I, II and III. The selected layer as well as the sampling rate Layer I, II and III. The selected layer as well as the sampling rate
and channel count are indicated in the payload. The RTP timestamp and channel count are indicated in the payload. The RTP timestamp
clock rate is always 90000, independent of the sampling rate. MPEG-1 clock rate is always 90000, independent of the sampling rate. MPEG-1
audio supports sampling rates of 32, 44.1, and 48 kHz (ISO/IEC audio supports sampling rates of 32, 44.1, and 48 kHz (ISO/IEC
11172-3, section 1.1; "Scope"). MPEG-2 supports sampling rates of 16, 11172-3, section 1.1; "Scope"). MPEG-2 supports sampling rates of 16,
22.05 and 24 kHz. The number of samples per frame is fixed, but the 22.05 and 24 kHz. The number of samples per frame is fixed, but the
frame size will vary with the sampling rate and bit rate. frame size will vary with the sampling rate and bit rate.
4.5.15 PCMA and PCMU 4.5.16 PCMA and PCMU
PCMA and PCMU are specified in ITU-T Recommendation G.711. Audio data PCMA and PCMU are specified in ITU-T Recommendation G.711. Audio data
is encoded as eight bits per sample, after logarithmic scaling. PCMU is encoded as eight bits per sample, after logarithmic scaling. PCMU
denotes mu-law scaling, PCMA A-law scaling. A detailed description is denotes mu-law scaling, PCMA A-law scaling. A detailed description is
given by Jayant and Noll [17]. Each G.711 octet SHALL be octet- given by Jayant and Noll [19]. Each G.711 octet SHALL be octet-
aligned in an RTP packet. The sign bit of each G.711 octet SHALL aligned in an RTP packet. The sign bit of each G.711 octet SHALL
correspond to the most significant bit of the octet in the RTP packet correspond to the most significant bit of the octet in the RTP packet
(i.e., assuming the G.711 samples are handled as octets on the host (i.e., assuming the G.711 samples are handled as octets on the host
machine, the sign bit SHALL be the most signficant bit of the octet machine, the sign bit SHALL be the most signficant bit of the octet
as defined by the host machine format). The 56 kb/s and 48 kb/s modes as defined by the host machine format). The 56 kb/s and 48 kb/s modes
of G.711 are not applicable to RTP, since PCMA and PCMU MUST always of G.711 are not applicable to RTP, since PCMA and PCMU MUST always
be transmitted as 8-bit samples. be transmitted as 8-bit samples.
4.5.16 QCELP 4.5.17 QCELP
The Electronic Industries Association (EIA) & Telecommunications The Electronic Industries Association (EIA) & Telecommunications
Industry Association (TIA) standard IS-733, "TR45: High Rate Speech Industry Association (TIA) standard IS-733, "TR45: High Rate Speech
Service Option for Wideband Spread Spectrum Communications Systems," Service Option for Wideband Spread Spectrum Communications Systems,"
defines the QCELP audio compression algorithm for use in wireless defines the QCELP audio compression algorithm for use in wireless
CDMA applications. The QCELP CODEC compresses each 20 milliseconds of CDMA applications. The QCELP CODEC compresses each 20 milliseconds of
8000 Hz, 16- bit sampled input speech into one of four different size 8000 Hz, 16- bit sampled input speech into one of four different size
output frames: Rate 1 (266 bits), Rate 1/2 (124 bits), Rate 1/4 (54 output frames: Rate 1 (266 bits), Rate 1/2 (124 bits), Rate 1/4 (54
bits) or Rate 1/8 (20 bits). For typical speech patterns, this bits) or Rate 1/8 (20 bits). For typical speech patterns, this
results in an average output of 6.8 k bits/sec for normal mode and results in an average output of 6.8 k bits/sec for normal mode and
4.7 k bits/sec for reduced rate mode. The packetization of the QCELP 4.7 k bits/sec for reduced rate mode. The packetization of the QCELP
audio codec is described in [18]. audio codec is described in [20].
4.5.17 RED
4.5.18 RED
The redundant audio payload format "RED" is specified by RFC 2198 The redundant audio payload format "RED" is specified by RFC 2198
[19]. It defines a means by which multiple redundant copies of an [21]. It defines a means by which multiple redundant copies of an
audio packet may be transmitted in a single RTP stream. Each packet audio packet may be transmitted in a single RTP stream. Each packet
in such a stream contains, in addition to the audio data for that in such a stream contains, in addition to the audio data for that
packetization interval, a (more heavily compressed) copy of the data packetization interval, a (more heavily compressed) copy of the data
from a previous packetization interval. This allows an approximation from a previous packetization interval. This allows an approximation
of the data from lost packets to be recovered upon decoding of a of the data from lost packets to be recovered upon decoding of a
subsequent packet, giving much improved sound quality when compared subsequent packet, giving much improved sound quality when compared
with silence substitution for lost packets. with silence substitution for lost packets.
4.5.18 VDVI 4.5.19 VDVI
VDVI is a variable-rate version of DVI4, yielding speech bit rates of VDVI is a variable-rate version of DVI4, yielding speech bit rates of
between 10 and 25 kb/s. It is specified for single-channel operation between 10 and 25 kb/s. It is specified for single-channel operation
only. Samples are packed into octets starting at the most- only. Samples are packed into octets starting at the most-
significant bit. The last octet is padded with 1 bits if the last significant bit. The last octet is padded with 1 bits if the last
sample does not fill the last octet. This padding is distinct from sample does not fill the last octet. This padding is distinct from
the valid codewords. The receiver needs to detect the padding the valid codewords. The receiver needs to detect the padding
because there is no explicit count of samples in the packet. because there is no explicit count of samples in the packet.
It uses the following encoding: It uses the following encoding:
skipping to change at page 23, line 24 skipping to change at page 30, line 36
and otherwise set to zero. Thus, it is not necessary to wait for a and otherwise set to zero. Thus, it is not necessary to wait for a
following packet with a different timestamp to detect that a new following packet with a different timestamp to detect that a new
frame should be displayed. frame should be displayed.
5.1 BT656 5.1 BT656
The encoding is specified in ITU-R Recommendation BT.656-3, The encoding is specified in ITU-R Recommendation BT.656-3,
"Interfaces for Digital Component Video Signals in 525-Line and 625- "Interfaces for Digital Component Video Signals in 525-Line and 625-
Line Television Systems operating at the 4:2:2 Level of Line Television Systems operating at the 4:2:2 Level of
Recommendation ITU-R BT.601 (Part A)". The packetization and RTP- Recommendation ITU-R BT.601 (Part A)". The packetization and RTP-
specific properties are described in RFC 2431 [20]. specific properties are described in RFC 2431 [22].
5.2 CelB 5.2 CelB
The CELL-B encoding is a proprietary encoding proposed by Sun The CELL-B encoding is a proprietary encoding proposed by Sun
Microsystems. The byte stream format is described in RFC 2029 [21]. Microsystems. The byte stream format is described in RFC 2029 [23].
5.3 JPEG 5.3 JPEG
The encoding is specified in ISO Standards 10918-1 and 10918-2. The The encoding is specified in ISO Standards 10918-1 and 10918-2. The
RTP payload format is as specified in RFC 2435 [22]. RTP payload format is as specified in RFC 2435 [24].
5.4 H261 5.4 H261
The encoding is specified in ITU-T Recommendation H.261, "Video codec The encoding is specified in ITU-T Recommendation H.261, "Video codec
for audiovisual services at p x 64 kbit/s". The packetization and for audiovisual services at p x 64 kbit/s". The packetization and
RTP-specific properties are described in RFC 2032 [23]. RTP-specific properties are described in RFC 2032 [25].
5.5 H263 5.5 H263
The encoding is specified in the 1996 version of ITU-T Recommendation The encoding is specified in the 1996 version of ITU-T Recommendation
H.263, "Video coding for low bit rate communication". The H.263, "Video coding for low bit rate communication". The
packetization and RTP-specific properties are described in RFC 2190 packetization and RTP-specific properties are described in RFC 2190
[24]. The H263-1998 payload format is RECOMMENDED over this one for [26]. The H263-1998 payload format is RECOMMENDED over this one for
use by new implementations. use by new implementations.
5.6 H263-1998 5.6 H263-1998
The encoding is specified in the 1998 version of ITU-T Recommendation The encoding is specified in the 1998 version of ITU-T Recommendation
H.263, "Video coding for low bit rate communication". The H.263, "Video coding for low bit rate communication". The
packetization and RTP-specific properties are described in RFC 2429 packetization and RTP-specific properties are described in RFC 2429
[25]. Because the 1998 version of H.263 is a superset of the 1996 [27]. Because the 1998 version of H.263 is a superset of the 1996
syntax, this payload format can also be used with the 1996 version of syntax, this payload format can also be used with the 1996 version of
H.263, and is RECOMMENDED for this use by new implementations. This H.263, and is RECOMMENDED for this use by new implementations. This
payload format does not replace RFC 2190, which continues to be used payload format does not replace RFC 2190, which continues to be used
by existing implementations, and may be required for backward by existing implementations, and may be required for backward
compatibility in new implementations. Implementations using the new compatibility in new implementations. Implementations using the new
features of the 1998 version of H.263 MUST use the payload format features of the 1998 version of H.263 MUST use the payload format
described in RFC 2429. described in RFC 2429.
5.7 MPV 5.7 MPV
MPV designates the use of MPEG-1 and MPEG-2 video encoding elementary MPV designates the use of MPEG-1 and MPEG-2 video encoding elementary
streams as specified in ISO Standards ISO/IEC 11172 and 13818-2, streams as specified in ISO Standards ISO/IEC 11172 and 13818-2,
respectively. The RTP payload format is as specified in RFC 2250 respectively. The RTP payload format is as specified in RFC 2250
[16], Section 3. [18], Section 3.
5.8 MP2T 5.8 MP2T
MP2T designates the use of MPEG-2 transport streams, for either audio MP2T designates the use of MPEG-2 transport streams, for either audio
or video. The RTP payoad format is described in RFC 2250 [16], or video. The RTP payoad format is described in RFC 2250 [18],
Section 2. Section 2.
5.9 MP1S 5.9 MP1S
MP1S designates an MPEG-1 systems stream, encapsulated according to MP1S designates an MPEG-1 systems stream, encapsulated according to
RFC 2250 [16]. RFC 2250 [18].
5.10 MP2P 5.10 MP2P
MP2P designates an MPEG-2 program stream, encapsulated according to MP2P designates an MPEG-2 program stream, encapsulated according to
RFC 2250 [16]. RFC 2250 [18].
5.11 BMPEG 5.11 BMPEG
BMPEG designates an experimental payload format for MPEG-1 and MPEG-2 BMPEG designates an experimental payload format for MPEG-1 and MPEG-2
which specifies bundled (multiplexed) transport of audio and video which specifies bundled (multiplexed) transport of audio and video
elementary streams in one RTP stream as an alternative to the MP1S elementary streams in one RTP stream as an alternative to the MP1S
and MP2P formats. The packetization is described in RFC 2343 [26]. and MP2P formats. The packetization is described in RFC 2343 [28].
5.12 nv 5.12 nv
The encoding is implemented in the program `nv', version 4, developed The encoding is implemented in the program `nv', version 4, developed
at Xerox PARC by Ron Frederick. Further information is available from at Xerox PARC by Ron Frederick. Further information is available from
the author: the author:
Ron Frederick Ron Frederick
Xerox Palo Alto Research Center Entera, Inc.
3333 Coyote Hill Road 40971 Encyclopedia Circle
Palo Alto, CA 94304 Fremont, CA 94538
United States United States
electronic mail: frederic@parc.xerox.com electronic mail: ronf@entera.com
6 Payload Type Definitions 6 Payload Type Definitions
Tables 4 and 5 define this profile's static payload type values for Tables 4 and 5 define this profile's static payload type values for
the PT field of the RTP data header. In addition, payload type the PT field of the RTP data header. In addition, payload type
values in the range 96-127 MAY be defined dynamically through a values in the range 96-127 MAY be defined dynamically through a
conference control protocol, which is beyond the scope of this conference control protocol, which is beyond the scope of this
document. For example, a session directory could specify that for a document. For example, a session directory could specify that for a
given session, payload type 96 indicates PCMU encoding, 8,000 Hz given session, payload type 96 indicates PCMU encoding, 8,000 Hz
sampling rate, 2 channels. Entries in Tables 4 and 5 with payload sampling rate, 2 channels. Entries in Tables 4 and 5 with payload
skipping to change at page 26, line 32 skipping to change at page 33, line 40
14 MPA A 90000 (see text) 14 MPA A 90000 (see text)
15 G728 A 8000 1 15 G728 A 8000 1
16 DVI4 A 11025 1 16 DVI4 A 11025 1
17 DVI4 A 22050 1 17 DVI4 A 22050 1
18 G729 A 8000 1 18 G729 A 8000 1
19 reserved A 19 reserved A
20 unassigned A 20 unassigned A
21 unassigned A 21 unassigned A
22 unassigned A 22 unassigned A
23 unassigned A 23 unassigned A
dyn G729D A 8000 1
dyn G729E A 8000 1
dyn GSM-HR A 8000 1 dyn GSM-HR A 8000 1
dyn GSM-EFR A 8000 1 dyn GSM-EFR A 8000 1
dyn L8 A var. var. dyn L8 A var. var.
dyn RED A (see text) dyn RED A (see text)
dyn VDVI A var. 1 dyn VDVI A var. 1
Table 4: Payload types (PT) for audio encodings Table 4: Payload types (PT) for audio encodings
7 RTP over TCP and Similar Byte Stream Protocols
Under special circumstances, it may be necessary to carry RTP in
protocols offering a byte stream abstraction, such as TCP, possibly
multiplexed with other data. If the application does not define its
own method of delineating RTP and RTCP packets, it SHOULD prefix each
packet with a two-octet length field in network order (most
significant octet first).
(Note: RTSP [27] provides its own encapsulation and does not need an
PT encoding media type clock rate PT encoding media type clock rate
name (Hz) name (Hz)
____________________________________________ ____________________________________________
24 unassigned V 24 unassigned V
25 CelB V 90000 25 CelB V 90000
26 JPEG V 90000 26 JPEG V 90000
27 unassigned V 27 unassigned V
28 nv V 90000 28 nv V 90000
29 unassigned V 29 unassigned V
30 unassigned V 30 unassigned V
skipping to change at page 27, line 30 skipping to change at page 34, line 30
77-95 unassigned ? 77-95 unassigned ?
96-127 dynamic ? 96-127 dynamic ?
dyn BT656 V 90000 dyn BT656 V 90000
dyn H263-1998 V 90000 dyn H263-1998 V 90000
dyn MP1S V 90000 dyn MP1S V 90000
dyn MP2P V 90000 dyn MP2P V 90000
dyn BMPEG V 90000 dyn BMPEG V 90000
Table 5: Payload types (PT) for video and combined encodings Table 5: Payload types (PT) for video and combined encodings
7 RTP over TCP and Similar Byte Stream Protocols
Under special circumstances, it may be necessary to carry RTP in
protocols offering a byte stream abstraction, such as TCP, possibly
multiplexed with other data. If the application does not define its
own method of delineating RTP and RTCP packets, it SHOULD prefix each
packet with a two-octet length field in network order (most
significant octet first).
(Note: RTSP [29] provides its own encapsulation and does not need an
extra length indication.) extra length indication.)
8 Port Assignment 8 Port Assignment
As specified in the RTP protocol definition, RTP data SHOULD be As specified in the RTP protocol definition, RTP data SHOULD be
carried on an even UDP or TCP port number and the corresponding RTCP carried on an even UDP or TCP port number and the corresponding RTCP
packets SHOULD be carried on the next higher (odd) port number. packets SHOULD be carried on the next higher (odd) port number.
Applications operating under this profile MAY use any such UDP or TCP Applications operating under this profile MAY use any such UDP or TCP
port pair. For example, the port pair MAY be allocated randomly by a port pair. For example, the port pair MAY be allocated randomly by a
skipping to change at page 28, line 26 skipping to change at page 35, line 36
1890 and codifies existing practice. The changes are listed below. 1890 and codifies existing practice. The changes are listed below.
o Additional payload formats and/or expanded descriptions were o Additional payload formats and/or expanded descriptions were
included for G722, G723, G726, G728, G729, GSM, GSM-HR, GSM- included for G722, G723, G726, G728, G729, GSM, GSM-HR, GSM-
EFR, QCELP, RED, VDVI, BT656, H263, H263-1998, MP1S, MP2P and EFR, QCELP, RED, VDVI, BT656, H263, H263-1998, MP1S, MP2P and
BMPEG. BMPEG.
o Static payload types 4, 12, 16, 17, 18 and 34 were added, and o Static payload types 4, 12, 16, 17, 18 and 34 were added, and
13 and 19 were reserved. 13 and 19 were reserved.
o Requirements for congestion control were added in Section 2.
o A new Section "IANA Considerations" was added to specify the o A new Section "IANA Considerations" was added to specify the
regstration of the name for this profile and to establish a regstration of the name for this profile and to establish a
new policy that no additional registration of static payload new policy that no additional registration of static payload
types for this profile will be made beyond those included in types for this profile will be made beyond those included in
Tables 4 and 5, but that additional encoding names may be Tables 4 and 5, but that additional encoding names may be
registered as MIME subtypes for binding to dynamic payload registered as MIME subtypes for binding to dynamic payload
types. types.
o In Section 4.1, the requirement level for setting of the o In Section 4.1, the requirement level for setting of the
marker bit on the first packet after silence for audio was marker bit on the first packet after silence for audio was
skipping to change at page 29, line 13 skipping to change at page 36, line 24
o A minimal TCP encapsulation is defined. o A minimal TCP encapsulation is defined.
o The security considerations and full copyright sections were o The security considerations and full copyright sections were
added. added.
o According to Peter Hoddie of Apple, only pre-1994 Macintosh o According to Peter Hoddie of Apple, only pre-1994 Macintosh
used the 22254.54 rate and none the 11127.27 rate, so the used the 22254.54 rate and none the 11127.27 rate, so the
latter was dropped from the discussion of suggested sampling latter was dropped from the discussion of suggested sampling
frequencies. frequencies.
o Table 1 was corrected to move some values from the o Table 1 was corrected to move some values from the "ms/packet"
"ms/packet" column to the "default ms/packet" column where column to the "default ms/packet" column where they belonged.
they belonged.
o A note has been added for G722 to clarify a discrepancy o A note has been added for G722 to clarify a discrepancy
between the actual sampling rate and the RTP timestamp clock between the actual sampling rate and the RTP timestamp clock
rate. rate.
o Small clarifications of the text have been made in several o Small clarifications of the text have been made in several
places, some in response to questions from readers. In places, some in response to questions from readers. In
particular: particular:
- A definition for "media type" is given in Section 1.1 to - A definition for "media type" is given in Section 1.1 to
skipping to change at page 30, line 24 skipping to change at page 37, line 35
into the stream which are complex to decode and cause the receiver to into the stream which are complex to decode and cause the receiver to
be overloaded. However, the encodings described in this profile do be overloaded. However, the encodings described in this profile do
not exhibit any significant non-uniformity. not exhibit any significant non-uniformity.
As with any IP-based protocol, in some circumstances a receiver may As with any IP-based protocol, in some circumstances a receiver may
be overloaded simply by the receipt of too many packets, either be overloaded simply by the receipt of too many packets, either
desired or undesired. Network-layer authentication MAY be used to desired or undesired. Network-layer authentication MAY be used to
discard packets from undesired sources, but the processing cost of discard packets from undesired sources, but the processing cost of
the authentication itself may be too high. In a multicast the authentication itself may be too high. In a multicast
environment, pruning of specific sources may be implemented in future environment, pruning of specific sources may be implemented in future
versions of IGMP [28] and in multicast routing protocols to allow a versions of IGMP [30] and in multicast routing protocols to allow a
receiver to select which sources are allowed to reach it. receiver to select which sources are allowed to reach it.
11 Full Copyright Statement 11 Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published and or assist in its implmentation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind, distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
skipping to change at page 31, line 26 skipping to change at page 38, line 36
Henning Schulzrinne Henning Schulzrinne
Dept. of Computer Science Dept. of Computer Science
Columbia University Columbia University
1214 Amsterdam Avenue 1214 Amsterdam Avenue
New York, NY 10027 New York, NY 10027
USA USA
electronic mail: schulzrinne@cs.columbia.edu electronic mail: schulzrinne@cs.columbia.edu
Stephen L. Casner Stephen L. Casner
Cisco Systems, Inc. Packet Design, Inc.
170 West Tasman Drive 66 Willow Place
San Jose, CA 95134 Menlo Park, CA 94025
United States United States
electronic mail: casner@cisco.com electronic mail: casner@acm.org
A Bibliography A Bibliography
[1] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, "RTP: A [1] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, "RTP: A
transport protocol for real-time applications," Internet Draft, transport protocol for real-time applications," Internet Draft,
Internet Engineering Task Force, Feb. 1999 Work in progress, revision Internet Engineering Task Force, Feb. 1999 Work in progress, revision
to RFC 1889. to RFC 1889.
[2] S. Bradner, "Key words for use in RFCs to Indicate Requirement [2] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels," RFC 2119, Internet Engineering Task Force, Mar. 1997. Levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.
[3] P. Hoschka, "MIME Type Registration of RTP Payload Types," [3] R. Braden, D. Clark, S. Shenker, "Integrated Services in the
Internet Draft, Internet Engineering Task Force, Feb. 1999 Work in Internet Architecture: an Overview," Request for Comments
progress. (Informational) RFC 1633, Internet Engineering Task Force, June 1994.
[4] N. Freed, J. Klensin, and J. Postel, "Multipurpose Internet Mail [4] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, "An
Extensions (MIME) Part Four: Registration Procedures," RFC 2048, Architecture for Differentiated Service," Request for Comments
Internet Engineering Task Force, Nov. 1996. (Proposed Standard) RFC 2475, Internet Engineering Task Force, Dec.
1998.
[5] M. Handley and V. Jacobson, "SDP: Session Description Protocol," [5] M. Handley and V. Jacobson, "SDP: Session Description Protocol,"
Request for Comments (Proposed Standard) RFC 2327, Internet Request for Comments (Proposed Standard) RFC 2327, Internet
Engineering Task Force, Apr. 1998. Engineering Task Force, Apr. 1998.
[6] Apple Computer, "Audio interchange file format AIFF-C," Aug. [6] P. Hoschka, "MIME Type Registration of RTP Payload Types,"
Internet Draft, Internet Engineering Task Force, Feb. 1999 Work in
progress.
[7] N. Freed, J. Klensin, and J. Postel, "Multipurpose Internet Mail
Extensions (MIME) Part Four: Registration Procedures," RFC 2048,
Internet Engineering Task Force, Nov. 1996.
[8] Apple Computer, "Audio interchange file format AIFF-C," Aug.
1991. (also ftp://ftp.sgi.com/sgi/aiff-c.9.26.91.ps.Z). 1991. (also ftp://ftp.sgi.com/sgi/aiff-c.9.26.91.ps.Z).
[7] Office of Technology and Standards, "Telecommunications: Analog [9] Office of Technology and Standards, "Telecommunications: Analog
to digital conversion of radio voice by 4,800 bit/second code excited to digital conversion of radio voice by 4,800 bit/second code excited
linear prediction (celp)," Federal Standard FS-1016, GSA, Room 6654; linear prediction (celp)," Federal Standard FS-1016, GSA, Room 6654;
7th & D Street SW; Washington, DC 20407 (+1-202-708-9205), 1990. 7th & D Street SW; Washington, DC 20407 (+1-202-708-9205), 1990.
[8] J. P. Campbell, Jr., T. E. Tremain, and V. C. Welch, "The [10] J. P. Campbell, Jr., T. E. Tremain, and V. C. Welch, "The
proposed Federal Standard 1016 4800 bps voice coder: CELP," Speech proposed Federal Standard 1016 4800 bps voice coder: CELP," Speech
Technology , vol. 5, pp. 58--64, April/May 1990. Technology , vol. 5, pp. 58--64, April/May 1990.
[9] J. P. Campbell, Jr., T. E. Tremain, and V. C. Welch, "The federal [11] J. P. Campbell, Jr., T. E. Tremain, and V. C. Welch, "The
standard 1016 4800 bps CELP voice coder," Digital Signal Processing , federal standard 1016 4800 bps CELP voice coder," Digital Signal
vol. 1, no. 3, pp. 145--155, 1991. Processing , vol. 1, no. 3, pp. 145--155, 1991.
[10] J. P. Campbell, Jr., T. E. Tremain, and V. C. Welch, "The DoD [12] J. P. Campbell, Jr., T. E. Tremain, and V. C. Welch, "The DoD
4.8 kbps standard (proposed federal standard 1016)," in Advances in 4.8 kbps standard (proposed federal standard 1016)," in Advances in
Speech Coding (B. Atal, V. Cuperman, and A. Gersho, eds.), ch. 12, Speech Coding (B. Atal, V. Cuperman, and A. Gersho, eds.), ch. 12,
pp. 121--133, Kluwer Academic Publishers, 1991. pp. 121--133, Kluwer Academic Publishers, 1991.
[11] IMA Digital Audio Focus and Technical Working Groups, [13] IMA Digital Audio Focus and Technical Working Groups,
"Recommended practices for enhancing digital audio compatibility in "Recommended practices for enhancing digital audio compatibility in
multimedia systems (version 3.00)," tech. rep., Interactive multimedia systems (version 3.00)," tech. rep., Interactive
Multimedia Association, Annapolis, Maryland, Oct. 1992. Multimedia Association, Annapolis, Maryland, Oct. 1992.
[12] D. Deleam and J.-P. Petit, "Real-time implementations of the [14] D. Deleam and J.-P. Petit, "Real-time implementations of the
recent ITU-T low bit rate speech coders on the TI TMS320C54X DSP: recent ITU-T low bit rate speech coders on the TI TMS320C54X DSP:
results, methodology, and applications," in Proc. of International results, methodology, and applications," in Proc. of International
Conference on Signal Processing, Technology, and Applications Conference on Signal Processing, Technology, and Applications
(ICSPAT) , (Boston, Massachusetts), pp. 1656--1660, Oct. 1996. (ICSPAT) , (Boston, Massachusetts), pp. 1656--1660, Oct. 1996.
[13] M. Mouly and M.-B. Pautet, The GSM system for mobile [15] M. Mouly and M.-B. Pautet, The GSM system for mobile
communications Lassay-les-Chateaux, France: Europe Media Duplication, communications Lassay-les-Chateaux, France: Europe Media Duplication,
1993. 1993.
[14] J. Degener, "Digital speech compression," Dr. Dobb's Journal , [16] J. Degener, "Digital speech compression," Dr. Dobb's Journal ,
Dec. 1994. Dec. 1994.
[15] S. M. Redl, M. K. Weber, and M. W. Oliphant, An Introduction to [17] S. M. Redl, M. K. Weber, and M. W. Oliphant, An Introduction to
GSM Boston: Artech House, 1995. GSM Boston: Artech House, 1995.
[16] D. Hoffman, G. Fernando, V. Goyal, and M. Civanlar, "RTP payload [18] D. Hoffman, G. Fernando, V. Goyal, and M. Civanlar, "RTP payload
format for MPEG1/MPEG2 video," Request for Comments (Proposed format for MPEG1/MPEG2 video," Request for Comments (Proposed
Standard) RFC 2250, Internet Engineering Task Force, Jan. 1998. Standard) RFC 2250, Internet Engineering Task Force, Jan. 1998.
[17] N. S. Jayant and P. Noll, Digital Coding of Waveforms-- [19] N. S. Jayant and P. Noll, Digital Coding of Waveforms--
Principles and Applications to Speech and Video Englewood Cliffs, New Principles and Applications to Speech and Video Englewood Cliffs, New
Jersey: Prentice-Hall, 1984. Jersey: Prentice-Hall, 1984.
[18] K. McKay, "RTP Payload Format for PureVoice(tm) Audio", Request [20] K. McKay, "RTP Payload Format for PureVoice(tm) Audio", Request
for Comments (Proposed Standard) RFC 2658, Internet Engineering Task for Comments (Proposed Standard) RFC 2658, Internet Engineering Task
Force, Aug. 1999. Force, Aug. 1999.
[19] C. Perkins, I. Kouvelas, O. Hodson, V. Hardman, M. Handley, J.C. [21] C. Perkins, I. Kouvelas, O. Hodson, V. Hardman, M. Handley, J.C.
Bolot, A. Vega-Garcia, and S. Fosse-Parisis, "RTP Payload for Bolot, A. Vega-Garcia, and S. Fosse-Parisis, "RTP Payload for
Redundant Audio Data," Request for Comments (Proposed Standard) RFC Redundant Audio Data," Request for Comments (Proposed Standard) RFC
2198, Internet Engineering Task Force, Sep. 1997. 2198, Internet Engineering Task Force, Sep. 1997.
[20] D. Tynan, "RTP payload format for BT.656 Video Encoding," [22] D. Tynan, "RTP payload format for BT.656 Video Encoding,"
Request for Comments (Proposed Standard) RFC 2431, Internet Request for Comments (Proposed Standard) RFC 2431, Internet
Engineering Task Force, Oct. 1998. Engineering Task Force, Oct. 1998.
[21] M. Speer and D. Hoffman, "RTP payload format of sun's CellB [23] M. Speer and D. Hoffman, "RTP payload format of sun's CellB
video encoding," Request for Comments (Proposed Standard) RFC 2029, video encoding," Request for Comments (Proposed Standard) RFC 2029,
Internet Engineering Task Force, Oct. 1996. Internet Engineering Task Force, Oct. 1996.
[22] L. Berc, W. Fenner, R. Frederick, and S. McCanne, "RTP payload [24] L. Berc, W. Fenner, R. Frederick, and S. McCanne, "RTP payload
format for JPEG-compressed video," Request for Comments (Proposed format for JPEG-compressed video," Request for Comments (Proposed
Standard) RFC 2435, Internet Engineering Task Force, Oct. 1996. Standard) RFC 2435, Internet Engineering Task Force, Oct. 1996.
[23] T. Turletti and C. Huitema, "RTP payload format for H.261 video [25] T. Turletti and C. Huitema, "RTP payload format for H.261 video
streams," Request for Comments (Proposed Standard) RFC 2032, Internet streams," Request for Comments (Proposed Standard) RFC 2032, Internet
Engineering Task Force, Oct. 1996. Engineering Task Force, Oct. 1996.
[24] C. Zhu, "RTP payload format for H.263 video streams," Request [26] C. Zhu, "RTP payload format for H.263 video streams," Request
for Comments (Proposed Standard) RFC 2190, Internet Engineering Task for Comments (Proposed Standard) RFC 2190, Internet Engineering Task
Force, Sep. 1997. Force, Sep. 1997.
[25] C. Bormann, L. Cline, G. Deisher, T. Gardos, C. Maciocco, D. [27] C. Bormann, L. Cline, G. Deisher, T. Gardos, C. Maciocco, D.
Newell, J. Ott, G. Sullivan, S. Wenger, C. Zhu, "RTP Payload Format Newell, J. Ott, G. Sullivan, S. Wenger, C. Zhu, "RTP Payload Format
for the 1998 Version of ITU-T Rec. H.263 Video (H.263+)," Request for for the 1998 Version of ITU-T Rec. H.263 Video (H.263+)," Request for
Comments (Proposed Standard) RFC 2429, Internet Engineering Task Comments (Proposed Standard) RFC 2429, Internet Engineering Task
Force, Oct. 1998. Force, Oct. 1998.
[26] M. Civanlar, G. Cash, B. Haskell, "RTP Payload Format for [28] M. Civanlar, G. Cash, B. Haskell, "RTP Payload Format for
Bundled MPEG," Request for Comments (Experimental) RFC 2343, Internet Bundled MPEG," Request for Comments (Experimental) RFC 2343, Internet
Engineering Task Force, May 1998. Engineering Task Force, May 1998.
[27] H. Schulzrinne, A. Rao, and R. Lanphier, "Real time streaming [29] H. Schulzrinne, A. Rao, and R. Lanphier, "Real time streaming
protocol (RTSP)," Request for Comments (Proposed Standard) RFC 2326, protocol (RTSP)," Request for Comments (Proposed Standard) RFC 2326,
Internet Engineering Task Force, Apr. 1998. Internet Engineering Task Force, Apr. 1998.
[28] S. Deering, "Host Extensions for IP Multicasting," Request for [30] S. Deering, "Host Extensions for IP Multicasting," Request for
Comments RFC 1112, STD 5, Internet Engineering Task Force, Aug. 1989. Comments RFC 1112, STD 5, Internet Engineering Task Force, Aug. 1989.
Current Locations of Related Resources Current Locations of Related Resources
Note: Several sections below refer to the ITU-T Software Tool Library Note: Several sections below refer to the ITU-T Software Tool Library
(STL). It is available from the ITU Sales Service, Place des Nations, (STL). It is available from the ITU Sales Service, Place des Nations,
CH-1211 Geneve 20, Switzerland (also check http://www.itu.int. The CH-1211 Geneve 20, Switzerland (also check http://www.itu.int. The
ITU-T STL is covered by a license defined in ITU-T Recommendation ITU-T STL is covered by a license defined in ITU-T Recommendation
G.191, "Software tools for speech and audio coding standardization". G.191, "Software tools for speech and audio coding standardization".
skipping to change at page 35, line 24 skipping to change at page 42, line 39
G726-32 G726-32
G726-32 is specified in the ITU-T Recommendation G.726, "40, 32, 24, G726-32 is specified in the ITU-T Recommendation G.726, "40, 32, 24,
and 16 kb/s Adaptive Differential Pulse Code Modulation (ADPCM)". An and 16 kb/s Adaptive Differential Pulse Code Modulation (ADPCM)". An
implementation of the G.726 algorithm is available as part of the implementation of the G.726 algorithm is available as part of the
ITU-T STL, described above. ITU-T STL, described above.
G729 G729
The reference C code implementation defining the G.729 algorithm and The reference C code implementation defining the G.729 algorithm and
its Annexes A and B are available as an integral part of its Annexes A through I are available as an integral part of
Recommendation G.729 from the ITU Sales Service, listed above. Both Recommendation G.729 from the ITU Sales Service, listed above. Annex
the algorithm and the C code are covered by a specific license. The I contains the integrated C source code for all G.729 operating
contact information for obtaining the license is listed in the C modes. The G.729 algorithm and associated C code are covered by a
code. specific license. The contact information for obtaining the license
is available from the ITU-T Secretariat.
GSM GSM
A reference implementation was written by Carsten Borman and Jutta A reference implementation was written by Carsten Borman and Jutta
Degener (TU Berlin, Germany). It is available at Degener (TU Berlin, Germany). It is available at
ftp://ftp.cs.tu-berlin.de/pub/local/kbs/tubmik/gsm/ ftp://ftp.cs.tu-berlin.de/pub/local/kbs/tubmik/gsm/
Although the RPE-LTP algorithm is not an ITU-T standard, there is a C Although the RPE-LTP algorithm is not an ITU-T standard, there is a C
code implementation of the RPE-LTP algorithm available as part of the code implementation of the RPE-LTP algorithm available as part of the
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Although the RPE-LTP algorithm is not an ITU-T standard, there is a C Although the RPE-LTP algorithm is not an ITU-T standard, there is a C
code implementation of the RPE-LTP algorithm available as part of the code implementation of the RPE-LTP algorithm available as part of the
ITU-T STL. The STL implementation is an adaptation of the TU Berlin ITU-T STL. The STL implementation is an adaptation of the TU Berlin
version. version.
LPC LPC
An implementation is available at An implementation is available at
ftp://parcftp.xerox.com/pub/net-research/lpc.tar.Z ftp://parcftp.xerox.com/pub/net-research/lpc.tar.Z
PCMU, PCMA PCMU, PCMA
An implementation of these algorithm is available as part of the An implementation of these algorithm is available as part of the
ITU-T STL, described above. Code to convert between linear and mu-law ITU-T STL, described above. Code to convert between linear and mu-law
companded data is also available in [11]. companded data is also available in [13].
Table of Contents Table of Contents
1 Introduction ........................................ 3 1 Introduction ........................................ 3
1.1 Terminology ......................................... 3 1.1 Terminology ......................................... 3
2 RTP and RTCP Packet Forms and Protocol Behavior ..... 3 2 RTP and RTCP Packet Forms and Protocol Behavior ..... 4
3 IANA Considerations ................................. 6 3 IANA Considerations ................................. 7
3.1 Registering Additional Encodings .................... 6 3.1 Registering Additional Encodings .................... 7
4 Audio ............................................... 8 4 Audio ............................................... 8
4.1 Encoding-Independent Rules .......................... 8 4.1 Encoding-Independent Rules .......................... 8
4.2 Operating Recommendations ........................... 9 4.2 Operating Recommendations ........................... 10
4.3 Guidelines for Sample-Based Audio Encodings ......... 9 4.3 Guidelines for Sample-Based Audio Encodings ......... 10
4.4 Guidelines for Frame-Based Audio Encodings .......... 10 4.4 Guidelines for Frame-Based Audio Encodings .......... 11
4.5 Audio Encodings ..................................... 11 4.5 Audio Encodings ..................................... 11
4.5.1 1016 ................................................ 12 4.5.1 1016 ................................................ 12
4.5.2 DVI4 ................................................ 12 4.5.2 DVI4 ................................................ 12
4.5.3 G722 ................................................ 13 4.5.3 G722 ................................................ 14
4.5.4 G723 ................................................ 13 4.5.4 G723 ................................................ 14
4.5.5 G726-32 ............................................. 14 4.5.5 G726-32 ............................................. 18
4.5.6 G728 ................................................ 14 4.5.6 G728 ................................................ 18
4.5.7 G729 ................................................ 15 4.5.7 G729 ................................................ 19
4.5.8 GSM ................................................. 17 4.5.8 G729D and G729E ..................................... 21
4.5.8.1 General Packaging Issues ............................ 17 4.5.9 GSM ................................................. 24
4.5.8.2 GSM variable names and numbers ...................... 17 4.5.9.1 General Packaging Issues ............................ 24
4.5.9 GSM-HR .............................................. 19 4.5.9.2 GSM variable names and numbers ...................... 25
4.5.10 GSM-EFR ............................................. 20 4.5.10 GSM-HR .............................................. 25
4.5.11 L8 .................................................. 20 4.5.11 GSM-EFR ............................................. 25
4.5.12 L16 ................................................. 20 4.5.12 L8 .................................................. 25
4.5.13 LPC ................................................. 20 4.5.13 L16 ................................................. 26
4.5.14 MPA ................................................. 20 4.5.14 LPC ................................................. 27
4.5.15 PCMA and PCMU ....................................... 21 4.5.15 MPA ................................................. 28
4.5.16 QCELP ............................................... 21 4.5.16 PCMA and PCMU ....................................... 28
4.5.17 RED ................................................. 21 4.5.17 QCELP ............................................... 28
4.5.18 VDVI ................................................ 21 4.5.18 RED ................................................. 28
5 Video ............................................... 22 4.5.19 VDVI ................................................ 29
5.1 BT656 ............................................... 23 5 Video ............................................... 29
5.2 CelB ................................................ 23 5.1 BT656 ............................................... 30
5.3 JPEG ................................................ 23 5.2 CelB ................................................ 30
5.4 H261 ................................................ 23 5.3 JPEG ................................................ 30
5.5 H263 ................................................ 23 5.4 H261 ................................................ 30
5.6 H263-1998 ........................................... 23 5.5 H263 ................................................ 31
5.7 MPV ................................................. 24 5.6 H263-1998 ........................................... 31
5.8 MP2T ................................................ 24 5.7 MPV ................................................. 31
5.9 MP1S ................................................ 24 5.8 MP2T ................................................ 31
5.10 MP2P ................................................ 24 5.9 MP1S ................................................ 31
5.11 BMPEG ............................................... 24 5.10 MP2P ................................................ 31
5.12 nv .................................................. 24 5.11 BMPEG ............................................... 31
6 Payload Type Definitions ............................ 25 5.12 nv .................................................. 32
7 RTP over TCP and Similar Byte Stream Protocols ...... 26 6 Payload Type Definitions ............................ 32
8 Port Assignment ..................................... 27 7 RTP over TCP and Similar Byte Stream Protocols ...... 34
9 Changes from RFC 1890 ............................... 28 8 Port Assignment ..................................... 34
10 Security Considerations ............................. 29 9 Changes from RFC 1890 ............................... 35
11 Full Copyright Statement ............................ 30 10 Security Considerations ............................. 37
12 Acknowledgements .................................... 31 11 Full Copyright Statement ............................ 37
13 Addresses of Authors ................................ 31 12 Acknowledgements .................................... 38
A Bibliography ........................................ 31 13 Addresses of Authors ................................ 38
A Bibliography ........................................ 38
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