draft-ietf-avt-profile-new-10.txt   draft-ietf-avt-profile-new-11.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-10.txt Columbia U./Packet Design draft-ietf-avt-profile-new-11.txt Columbia U./Packet Design
March 2, 2001 July 20, 2001
Expires: August 2, 2001 Expires: January 2002
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
skipping to change at page 2, line 31 skipping to change at page 2, line 31
Standard status. These latter references are intended to be non- Standard status. These latter references are intended to be non-
normative.] normative.]
Readers are directed to Appendix 9, Changes from RFC 1890, for a Readers are directed to Appendix 9, Changes from RFC 1890, for a
listing of the changes that have been made in this draft. The listing of the changes that have been made in this draft. The
changes from RFC 1890 are marked with change bars in the PostScript changes from RFC 1890 are marked with change bars in the PostScript
form of this draft. form of this draft.
The changes in this revision of the draft from the previous one are: The changes in this revision of the draft from the previous one are:
o An paragraph further explaining the requirements for congestion o Added back G723, GSM-EFR, H263 (1996), MP2T payload formats
control was added to Section 2 based on the discussion at IETF since reports of interoperable implementations of these were
49. received.
o Packetization of G.726 audio at rates 40, 24 and 16 kb/s is
specified in addition to 32 kb/s.
o The mapping of a user pass-phrase string into an encryption key
was deleted from Section 2 because two interoperable
implementations were not found.
o The specification of a two-byte encapsulation for RTP over TCP o Added references to optional parameters in the payload format
was deleted because two interoperable implementations were not MIME registrations [6] for G723, G729, L16, MPA and MPV.
found.
o The audio payload formats 1016, G723, GSM-HR and GSM-EFR were o Clarified that the marker bit for audio is set only when
removed because two interoperable implementations were not packets are intentionally not sent during silence.
found.
o The video payload formats H263, BT656, MP2T, MP1S, MP2P and o Removed a reference in the Security Considerations section to
BMPEG were removed because two interoperable implementations the previously removed mapping of a user pass-phrase into an
were not found. encryption key.
This version of the draft is intended to be complete for Last Call. This version of the draft is intended to be complete for Last Call.
The following open issues from previous drafts have been addressed: The following open issues from previous drafts have been addressed:
o The procedure for registering RTP encoding names as MIME o The procedure for registering RTP encoding names as MIME
subtypes was moved to a separate RFC-to-be that may also serve subtypes was moved to a separate RFC-to-be that may also serve
to specify how (some of) the encodings here may be used with to specify how (some of) the encodings here may be used with
mail and other not-RTP transports. That procedure is not mail and other not-RTP transports. That procedure is not
required to implement this profile, but may be used in those required to implement this profile, but may be used in those
contexts where it is needed. contexts where it is needed.
skipping to change at page 6, line 22 skipping to change at page 6, line 12
requested is actually being delivered. If it is not, then requested is actually being delivered. If it is not, then
they SHOULD assume that they are receiving best-effort they SHOULD assume that they are receiving best-effort
service and behave accordingly. service and behave accordingly.
If best-effort service is being used, RTP receivers SHOULD If best-effort service is being used, RTP receivers SHOULD
monitor packet loss to ensure that the packet loss rate is monitor packet loss to ensure that the packet loss rate is
within acceptable parameters. Packet loss is considered within acceptable parameters. Packet loss is considered
acceptable if a TCP flow across the same network path and acceptable if a TCP flow across the same network path and
experiencing the same network conditions would achieve an experiencing the same network conditions would achieve an
average throughput, measured on a reasonable timescale, average throughput, measured on a reasonable timescale,
that is not less the RTP flow is achieving. This condition that is not less than the RTP flow is achieving. This
can be satisfied by implementing congestion control condition can be satisfied by implementing congestion
mechanisms to adapt the transmission rate (or the number of control mechanisms to adapt the transmission rate (or the
layers subscribed for a layered multicast session), or by number of layers subscribed for a layered multicast
arranging for a receiver to leave the session if the loss session), or by arranging for a receiver to leave the
rate is unacceptably high. session if the loss rate is unacceptably high.
The comparison to TCP cannot be specified exactly, but is The comparison to TCP cannot be specified exactly, but is
intended as an "order-of-magnitude" comparison in timescale intended as an "order-of-magnitude" comparison in timescale
and throughput. The timescale on which TCP throughput is and throughput. The timescale on which TCP throughput is
measured is the round-trip time of the connection. In measured is the round-trip time of the connection. In
essence, this requirement states that it is not acceptable essence, this requirement states that it is not acceptable
to deploy an application (using RTP or any other transport to deploy an application (using RTP or any other transport
protocol) on the best-effort Internet which consumes protocol) on the best-effort Internet which consumes
bandwidth arbitrarily and does not compete fairly with TCP bandwidth arbitrarily and does not compete fairly with TCP
within an order of magnitude. within an order of magnitude.
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: This profile leaves to applications the Encapsulation: This profile leaves to applications the
specification of RTP encapsulation in protocols other specification of RTP encapsulation in protocols other than
than UDP. UDP.
3 IANA Considerations 3 IANA Considerations
The RTP specification establishes a registry of profile names for use The RTP specification establishes a registry of profile names for use
by higher-level control protocols, such as the Session Description by higher-level control protocols, such as the Session Description
Protocol (SDP), RFC 2327 [5], to refer to transport methods. This Protocol (SDP), RFC 2327 [5], to refer to transport methods. This
profile registers the name "RTP/AVP". profile registers the name "RTP/AVP".
3.1 Registering Additional Encodings 3.1 Registering Additional Encodings
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payload types will be assigned beyond the ones defined in this payload types will be assigned beyond the ones defined in this
document. Establishing this policy avoids the problem of trying to document. Establishing this policy avoids the problem of trying to
create a set of criteria for accepting static assignments and create a set of criteria for accepting static assignments and
encourages the implementation and deployment of the dynamic payload encourages the implementation and deployment of the dynamic payload
type mechanisms. type mechanisms.
4 Audio 4 Audio
4.1 Encoding-Independent Rules 4.1 Encoding-Independent Rules
For applications which send either no packets or comfort-noise For applications which send either no packets or occasional comfort-
packets during silence, the first packet of a talkspurt, that is, the noise packets during silence, the first packet of a talkspurt, that
first packet after a silence period, SHOULD be distinguished by is, the first packet after a silence period during which packets have
setting the marker bit in the RTP data header to one. The marker bits not been transmitted contiguously, SHOULD be distinguished by setting
in all other packets is zero. The beginning of a talkspurt MAY be the marker bit in the RTP data header to one. The marker bits in all
used to adjust the playout delay to reflect changing network delays. other packets is zero. The beginning of a talkspurt MAY be used to
adjust the playout delay to reflect changing network delays.
Applications without silence suppression MUST set the marker bit to Applications without silence suppression MUST set the marker bit to
zero. zero.
The RTP clock rate used for generating the RTP timestamp is The RTP clock rate used for generating the RTP timestamp is
independent of the number of channels and the encoding; it equals the independent of the number of channels and the encoding; it equals the
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.)
skipping to change at page 12, line 4 skipping to change at page 11, line 37
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 The characteristics of the audio encodings described in this document
are shown in Table 1; they are listed in order of their payload type 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 in Table 4. While most audio codecs are only specified for a fixed
sampling rate, some sample-based algorithms (indicated by an entry of sampling rate, some sample-based algorithms (indicated by an entry of
"var." in the sampling rate column of Table 1) may be used with "var." in the sampling rate column of Table 1) may be used with
different sampling rates, resulting in different coded bit rates.
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
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
sampling rate for audio.
4.5.1 DVI4
DVI4 is specified, with pseudo-code, in [9] as the IMA ADPCM wave
type.
However, the encoding defined here as DVI4 differs in three respects
from this recommendation:
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
__________________________________________________________________ __________________________________________________________________
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
G726-40 sample 5 8,000 20 G726-40 sample 5 8,000 20
G726-32 sample 4 8,000 20 G726-32 sample 4 8,000 20
G726-24 sample 3 8,000 20 G726-24 sample 3 8,000 20
G726-16 sample 2 8,000 20 G726-16 sample 2 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 G729D frame N/A 8,000 10 20
G729E 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-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)
different sampling rates, resulting in different coded bit rates.
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
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
sampling rate for audio.
4.5.1 DVI4
DVI4 is specified, with pseudo-code, in [9] as the IMA ADPCM wave
type.
However, the encoding defined here as DVI4 differs in three respects
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
(uncompressed), followed by an even number of compressed (uncompressed), followed by an even number of compressed
samples. DVI4 has an even number of compressed samples only, samples. DVI4 has an even number of compressed samples only,
using the `predict' word from the header to decode the first using the `predict' word from the header to decode the first
sample. sample.
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transmitted in the G.722 octet, which is the most significant bit of transmitted in the G.722 octet, which is the most significant bit of
the higher sub-band sample, SHALL correspond to the most significant the higher sub-band sample, SHALL correspond to the most significant
bit of the octet in the RTP packet. bit of the octet in the RTP packet.
Even though the actual sampling rate for G.722 audio is 16000 Hz, the Even though the actual sampling rate for G.722 audio is 16000 Hz, the
RTP clock rate for the G722 payload format is 8000 Hz because that RTP clock rate for the G722 payload format is 8000 Hz because that
value was erroneously assigned in RFC 1890 and must remain unchanged value was erroneously assigned in RFC 1890 and must remain unchanged
for backward compatibility. The octet rate or sample-pair rate is for backward compatibility. The octet rate or sample-pair rate is
8000 Hz. 8000 Hz.
4.5.3 G726-40, G726-32, G726-24, and G726-16 4.5.3 G723
G723 is specified in ITU Recommendation G.723.1, "Dual-rate speech
coder for multimedia communications transmitting at 5.3 and 6.3
kbit/s". The G.723.1 5.3/6.3 kbit/s codec was defined by the ITU-T as
a mandatory codec for ITU-T H.324 GSTN videophone terminal
applications. The algorithm has a floating point specification in
Annex B to G.723.1, a silence compression algorithm in Annex A to
G.723.1 and an encoded signal bit-error sensitivity specification in
G.723.1 Annex C.
This Recommendation specifies a coded representation that can be used
for compressing the speech signal component of multi-media services
at a very low bit rate. Audio is encoded in 30 ms frames, with an
additional delay of 7.5 ms due to look-ahead. A G.723.1 frame can be
one of three sizes: 24 octets (6.3 kb/s frame), 20 octets (5.3 kb/s
frame), or 4 octets. These 4-octet frames are called SID frames
(Silence Insertion Descriptor) and are used to specify comfort noise
parameters. There is no restriction on how 4, 20, and 24 octet frames
are intermixed. The least significant two bits of the first octet in
the frame determine the frame size and codec type:
bits content octets/frame
00 high-rate speech (6.3 kb/s) 24
01 low-rate speech (5.3 kb/s) 20
10 SID frame 4
11 reserved
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
the encoder and decoder. The MIME registration for G723 in RFC YYYY
[6] specifies parameters that MAY be used with MIME or SDP to
restrict to a single data rate or to restrict the use of SID frames.
This coder was optimized to represent speech with near-toll quality
at the above rates using a limited amount of complexity.
The packing of the encoded bit stream into octets and the
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
4.5.4 G726-40, G726-32, G726-24, and G726-16
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 recommended for conversion of a single 64 kbit/s A-law or mu-law PCM
PCM channel encoded at 8000 samples/sec to and from a 40, 32, 24, channel encoded at 8000 samples/sec to and from a 40, 32, 24, or 16
or 16 kbit/s channel. The conversion is applied to the PCM stream kbit/s channel. The conversion is applied to the PCM stream using an
using an Adaptive Differential Pulse Code Modulation (ADPCM) Adaptive Differential Pulse Code Modulation (ADPCM) transcoding
transcoding technique. The ADPCM representation consists of a technique. The ADPCM representation consists of a series of codewords
series of codewords with a one-to-one correspondance to the samples with a one-to-one correspondance to the samples in the PCM stream.
in the PCM stream. The G726 data rates of 40, 32, 24, and 16 The G726 data rates of 40, 32, 24, and 16 kbit/s have codewords of 5,
kbit/s have codewords of 5, 4, 3, and 2 bits respectively. 4, 3, and 2 bits respectively.
The 16 and 24 kbit/s encodings do not provide toll quality speech. The 16 and 24 kbit/s encodings do not provide toll quality speech.
They are designed for used in overloaded Digital Circuit They are designed for used in overloaded Digital Circuit
Multiplication Equipment (DCME). ITU-T G.726 recommends that the Multiplication Equipment (DCME). ITU-T G.726 recommends that the 16
16 and 24 kbit/s encodings should be alternated with higher data and 24 kbit/s encodings should be alternated with higher data rate
rate encodings to provide an average sample size of between 3.5 and encodings to provide an average sample size of between 3.5 and 3.7
3.7 bits per sample. bits per sample.
The encodings of G.726 are here denoted as G726-40, G726-32, The encodings of G.726 are here denoted as G726-40, G726-32, G726-24,
G726-24, and G726-16. Prior to 1990, G721 described the 32 kbit/s and G726-16. Prior to 1990, G721 described the 32 kbit/s ADPCM
ADPCM encoding, and G723 described the 40, 32, and 16 kbit/s encoding, and G723 described the 40, 32, and 16 kbit/s encodings.
encodings. Thus, G726-32 designates the same algorithm as G721 in Thus, G726-32 designates the same algorithm as G721 in RFC 1890.
RFC 1890.
A stream of G726 codewords contains no information on the encoding A stream of G726 codewords contains no information on the encoding
being used, therefore transitions between G726 encoding types is being used, therefore transitions between G726 encoding types is not
not permitted within a sequence of packed codewords. Applications permitted within a sequence of packed codewords. Applications MUST
MUST determine the encoding type of packed codewords from the RTP determine the encoding type of packed codewords from the RTP payload
payload identifier. identifier.
No payload-specific header information SHALL be included as part No payload-specific header information SHALL be included as part of
of the audio data. A stream of G726 codewords MUST be packed into the audio data. A stream of G726 codewords MUST be packed into octets
octets as follows: the first codeword is placed into the first as follows: the first codeword is placed into the first octet such
octet such that the least significant bit of the codeword aligns that the least significant bit of the codeword aligns with the least
with the least significant bit in the octet, the second codeword significant bit in the octet, the second codeword is then packed so
is then packed so that its least significant bit coincides with that its least significant bit coincides with the least significant
the least significant unoccupied bit in the octet. When a unoccupied bit in the octet. When a complete codeword cannot be
complete codeword cannot be placed into an octet, the bits placed into an octet, the bits overlapping the octet boundary are
overlapping the octet boundary are placed into the least placed into the least significant bits of the next octet. Packing
significant bits of the next octet. Packing MUST end with a MUST end with a completely packed final octet. The number of
completely packed final octet. The number of codewords packed codewords packed will therefore be a multiple of 8, 2, 8, and 4 for
will therefore be a multiple of 8, 2, 8, and 4 for G726-40, G726-40, G726-32, G726-24, and G726-16 respectively. An example of
G726-32, G726-24, and G726-16 respectively. An examples of the the packing scheme for G726-32 codewords is as shown:
packing scheme for G726-32 codewords is as shown:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|B B B B|A A A A|D D D D|C C C C| ... |B B B B|A A A A|D D D D|C C C C| ...
|0 1 2 3|0 1 2 3|0 1 2 3|0 1 2 3| |0 1 2 3|0 1 2 3|0 1 2 3|0 1 2 3|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
An example of the packing scheme for G726-24 codewords is: An example of the packing scheme for G726-24 codewords is:
0 1 2 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|C C|B B B|A A A|F|E E E|D D D|C|H H H|G G G|F F| ... |C C|B B B|A A A|F|E E E|D D D|C|H H H|G G G|F F| ...
|1 2|0 1 2|0 1 2|2|0 1 2|0 1 2|0|0 1 2|0 1 2|0 1| |1 2|0 1 2|0 1 2|2|0 1 2|0 1 2|0|0 1 2|0 1 2|0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
4.5.4 G728 4.5.5 G728
G728 is specified in ITU-T Recommendation G.728, "Coding of speech at G728 is specified in ITU-T Recommendation G.728, "Coding of speech at
16 kbit/s using low-delay code excited linear prediction". 16 kbit/s using low-delay code excited linear prediction".
A G.278 encoder translates 5 consecutive audio samples into a 10-bit A G.278 encoder translates 5 consecutive audio samples into a 10-bit
codebook index, resulting in a bit rate of 16 kb/s for audio sampled codebook index, resulting in a bit rate of 16 kb/s for audio sampled
at 8,000 samples per second. The group of five consecutive samples is at 8,000 samples per second. The group of five consecutive samples is
called a vector. Four consecutive vectors, labeled V1 to V4 (where V1 called a vector. Four consecutive vectors, labeled V1 to V4 (where V1
is to be played first by the receiver), build one G.728 frame. The is to be played first by the receiver), build one G.728 frame. The
four vectors of 40 bits are packed into 5 octets, labeled B1 through four vectors of 40 bits are packed into 5 octets, labeled B1 through
skipping to change at page 16, line 36 skipping to change at page 19, line 27
<---V1---><---V2---><---V3---><---V4---> vectors <---V1---><---V2---><---V3---><---V4---> vectors
<--B1--><--B2--><--B3--><--B4--><--B5--> octets <--B1--><--B2--><--B3--><--B4--><--B5--> octets
<------------- frame 1 ----------------> <------------- frame 1 ---------------->
In particular, B1 contains the eight most significant bits of V1, In particular, B1 contains the eight most significant bits of V1,
with the MSB of V1 being the MSB of B1. B2 contains the two least with the MSB of V1 being the MSB of B1. B2 contains the two least
significant bits of V1, the more significant of the two in its MSB, significant bits of V1, the more significant of the two in its MSB,
and the six most significant bits of V2. B1 SHALL be placed first in and the six most significant bits of V2. B1 SHALL be placed first in
the RTP packet and B5 last. the RTP packet and B5 last.
4.5.5 G729 4.5.6 G729
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 [10]. See the next Section (4.5.6) for other data rates reduction [10]. See the next Section (4.5.7) for other data rates
added in later G.729 Annexes. For all data rates, the sampling added in later G.729 Annexes. For all data rates, the sampling
frequency (and RTP timestamp clock rate) is 8000 Hz. 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. The
MIME registration for G729 in RFC YYYY [6] specifies a parameter that
MAY be used with MIME or SDP to restrict the use of comfort noise
frames.
A G729 RTP packet may consist of zero or more G.729 or G.729 Annex A 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 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 a comfort noise frame can be deduced from the length of the RTP
payload. The default packetization interval is 20 ms (two frames), payload. The default packetization interval is 20 ms (two frames),
but in some situations it may be desireable to send 10 ms packets. An 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 example would be a transition from speech to comfort noise in the
first 10 ms of the packet. For some applications, a longer first 10 ms of the packet. For some applications, a longer
packetization interval may be required to reduce the packet rate. packetization interval may be required to reduce the packet rate.
skipping to change at page 18, line 4 skipping to change at page 20, line 44
| |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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C1 | S1 | GA1 | GB1 | P2 | C2 | | C1 | S1 | GA1 | GB1 | P2 | C2 |
| 1 1 1| | | | | | | 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| |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 | | C2 | S2 | GA2 | GB2 |
| 1 1 1| | | | | 1 1 1| | | |
|8 9 0 1 2|0 1 2 3|0 1 2|0 1 2 3| |8 9 0 1 2|0 1 2 3|0 1 2|0 1 2 3|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The packing of the G.729 Annex B comfort noise frame is as follows:
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| | | |S| |F| | | |S|
|0|0 1 2 3 4|0 1 2 3|0 1 2 3 4|V| RESV = Reserved (zero) |0|0 1 2 3 4|0 1 2 3|0 1 2 3 4|V| RESV = Reserved (zero)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.5.6 G729D and G729E Figure 5: G.729 Annex B bit packing
4.5.7 G729D and G729E
Annexes D and E to ITU-T Recommendation G.729 provide additional data 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 rates. Because the data rate is not signaled in the bitstream, the
different data rates are given distinct RTP encoding names which are different data rates are given distinct RTP encoding names which are
mapped to distinct payload type numbers. G729D indicates a 6.4 kbit/s mapped to distinct payload type numbers. G729D indicates a 6.4 kbit/s
coding mode (G.729 Annex D, for momentary reduction in channel 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, 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 for improved performance with a wide range of narrow-band input
signals, e.g. music and background noise). Annex E has two operating signals, e.g. music and background noise). Annex E has two operating
modes, backward adaptive and forward adaptive, which are signaled by 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 two bits in each frame (the most significant two bits of
the first octet). the first octet).
The voice activity detector (VAD) and comfort noise generator (CNG) 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 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 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 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 B CNG are specified in G.729 Annexes F and G. Note that Annexes F and
G do not introduce any new encodings. G do not introduce any new encodings. The MIME registrations for
G729D and G729E in RFC YYYY [6] specify a parameter that MAY be used
with MIME or SDP to restrict the use of comfort noise frames.
For G729D, an RTP packet may consist of zero or more G.729 Annex D 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 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 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 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 a comfort noise frame can be deduced from the length of the RTP
payload. payload.
A single RTP packet must contain frames of only one data rate, A single RTP packet must contain frames of only one data rate,
optionally followed by one comfort noise frame. The data rate may be optionally followed by one comfort noise frame. The data rate may be
skipping to change at page 19, line 20 skipping to change at page 22, line 21
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| L1 | L2 | L3 | P1 | C1 | |L| L1 | L2 | L3 | P1 | 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 5| | |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 | | 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| |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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: G.729 Annex D bit packing
The net bit rate for the G.729 Annex E algorithm is 11.8 kbit/s and a 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" 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 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 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 two diagrams (cf. Table E.1/G.729). The fields for the G729E forward
adaptive mode are packed as follows: adaptive mode are packed as shown in Fig. 7.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0|L| L1 | L2 | L3 | P1 |P| C0_1| |0 0|L| L1 | L2 | L3 | P1 |P| C0_1|
| |0| | | | |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| | | |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 | | | 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| |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 | | GA1 | GB1 | P2 | C0_2 | C1_2 | C2_2 |
| | | | | | | | | | | | | |
|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|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C3_2 | C4_2 | GA2 | GB2 |DC | | | 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| |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 7: G.729 Annex E (forward adaptive mode) bit packing
The fields for the G729E backward adaptive mode are packed as shown The fields for the G729E backward adaptive mode are packed as shown
in Fig. 8. in Fig. 8.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1| P1 |P| C0_1 | C1_1 | |1 1| P1 |P| C0_1 | C1_1 |
| | |0| 1 1 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| | |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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 21, line 5 skipping to change at page 24, line 25
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C0_2 | C1_2 | C2_2 | | | C0_2 | C1_2 | C2_2 |
| | 1 1 1| | | | | 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| |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 | | | 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| |6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2|0 1 2 3|0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.5.7 GSM Figure 8: G.729 Annex E (backward adaptive mode) bit packing
4.5.8 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 [15,16,17]. The text of the standard can be obtained rate of 13 kb/s [11,12,13]. 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.
4.5.7.1 General Packaging Issues 4.5.8.1 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
skipping to change at page 21, line 43 skipping to change at page 25, line 18
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.
4.5.7.2 GSM variable names and numbers 4.5.8.2 GSM variable names and numbers
In the RTP encoding we have the bit pattern described in Table 3, 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 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 significant bit, and the bits of every octet are numbered from 0 to 7
from most to least significant. from most to least significant.
4.5.8 L8 4.5.9 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.
4.5.10 L8
L8 denotes linear audio data samples, using 8-bits of precision with 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 an offset of 128, that is, the most negative signal is encoded as
zero. zero.
4.5.11 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
represented in two's complement notation and transmitted in network
byte order (most significant byte first).
The MIME registration for L16 in RFC YYYY [6] specifies parameters
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 22, line 48 skipping to change at page 26, line 47
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
4.5.9 L16 that MAY be used with MIME or SDP to indicate that analog preemphasis
was applied to the signal before quantization or to indicate that a
multiple-channel audio stream follows a different channel ordering
convention than is specified in Section 4.1.
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 23, line 42 skipping to change at page 27, line 43
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
maximum signal level, ranging from -32768 to 32767. The value is 4.5.12 LPC
represented in two's complement notation and transmitted in network
byte order (most significant byte first).
4.5.10 LPC
LPC designates an experimental linear predictive encoding contributed LPC designates an experimental linear predictive encoding contributed
by Ron Frederick, which is based on an implementation written by Ron by Ron Frederick, which is based on an implementation written by Ron
Zuckerman posted to the Usenet group comp.dsp on June 26, 1992. The Zuckerman posted to the Usenet group comp.dsp on June 26, 1992. The
codec generates 14 octets for every frame. The framesize is set to 20 codec generates 14 octets for every frame. The framesize is set to 20
ms, resulting in a bit rate of 5,600 b/s. ms, resulting in a bit rate of 5,600 b/s.
4.5.11 MPA 4.5.13 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 [14]. and 13818-3. The encapsulation is specified in RFC 2250 [14].
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.
4.5.12 PCMA and PCMU The MIME registration for MPA in RFC YYYY [6] specifies parameters
that MAY be used with MIME or SDP to restrict the selection of layer,
channel count, sampling rate, and bit rate.
4.5.14 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 [15]. Each G.711 octet SHALL be octet- given by Jayant and Noll [15]. 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.
4.5.13 QCELP 4.5.15 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 [16]. audio codec is described in [16].
4.5.14 RED 4.5.16 RED
The redundant audio payload format "RED" is specified by RFC 2198 The redundant audio payload format "RED" is specified by RFC 2198
[17]. It defines a means by which multiple redundant copies of an [17]. 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.
4.5.15 VDVI 4.5.17 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 27, line 5 skipping to change at page 30, line 46
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 [19]. RTP payload format is as specified in RFC 2435 [19].
5.3 H261 5.3 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 [20]. RTP-specific properties are described in RFC 2032 [20].
5.4 H263-1998 5.4 H263
The encoding is specified in the 1996 version of ITU-T Recommendation
H.263, "Video coding for low bit rate communication". The
packetization and RTP-specific properties are described in RFC 2190
[21]. The H263-1998 payload format is RECOMMENDED over this one for
use by new implementations.
5.5 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
[21]. Because the 1998 version of H.263 is a superset of the 1996 [22]. 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.
5.5 MPV 5.6 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
[14], Section 3. [14], Section 3.
The MIME registration for MPV in RFC YYYY [6] specifies a parameter
that MAY be used with MIME or SDP to restrict the selection of the
type of MPEG video.
5.7 MP2T
MP2T designates the use of MPEG-2 transport streams, for either audio
or video. The RTP payoad format is described in RFC 2250 [14],
Section 2.
5.8 nv 5.8 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
Entera, Inc. Cacheflow Inc.
40971 Encyclopedia Circle 650 Almanor Avenue
Fremont, CA 94538 Sunnyvale, CA 94085
United States United States
electronic mail: ronf@entera.com electronic mail: ronf@cacheflow.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 29, line 5 skipping to change at page 32, line 40
this specification on the set of payload types allowed in a given this specification on the set of payload types allowed in a given
session. This set MAY, for example, be defined by the capabilities session. This set MAY, for example, be defined by the capabilities
of the applications used, negotiated by a conference control protocol of the applications used, negotiated by a conference control protocol
or established by agreement between the human participants. or established by agreement between the human participants.
Audio applications operating under this profile SHOULD, at a minimum, Audio applications operating under this profile SHOULD, at a minimum,
be able to send and/or receive payload types 0 (PCMU) and 5 (DVI4). be able to send and/or receive payload types 0 (PCMU) and 5 (DVI4).
This allows interoperability without format negotiation and ensures This allows interoperability without format negotiation and ensures
successful negotation with a conference control protocol. successful negotation with a conference control protocol.
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. The application MUST define its own
method of delineating RTP and RTCP packets (RTSP [23] provides an
example of such an encapsulation specification.)
8 Port Assignment
PT encoding media type clock rate channels PT encoding media type clock rate channels
name (Hz) name (Hz)
___________________________________________________ ___________________________________________________
0 PCMU A 8000 1 0 PCMU A 8000 1
1 reserved A 1 reserved A
2 G726-32 A 8000 1 2 G726-32 A 8000 1
3 GSM A 8000 1 3 GSM A 8000 1
4 reserved A 4 G723 A 8000 1
5 DVI4 A 8000 1 5 DVI4 A 8000 1
6 DVI4 A 16000 1 6 DVI4 A 16000 1
7 LPC A 8000 1 7 LPC A 8000 1
8 PCMA A 8000 1 8 PCMA A 8000 1
9 G722 A 8000 1 9 G722 A 8000 1
10 L16 A 44100 2 10 L16 A 44100 2
11 L16 A 44100 1 11 L16 A 44100 1
12 QCELP A 8000 1 12 QCELP A 8000 1
13 reserved A 13 reserved A
14 MPA A 90000 (see text) 14 MPA A 90000 (see text)
skipping to change at page 29, line 37 skipping to change at page 33, line 36
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 G726-40 A 8000 1 dyn G726-40 A 8000 1
dyn G726-24 A 8000 1 dyn G726-24 A 8000 1
dyn G726-16 A 8000 1 dyn G726-16 A 8000 1
dyn G729D A 8000 1 dyn G729D A 8000 1
dyn G729E A 8000 1 dyn G729E 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
As specified in the RTP protocol definition, RTP data SHOULD be
carried on an even UDP port number and the corresponding RTCP packets
SHOULD be carried on the next higher (odd) port number.
Applications operating under this profile MAY use any such UDP port
pair. For example, the port pair MAY be allocated randomly by a
session management program. A single fixed port number pair cannot be
required because multiple applications using this profile are likely
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
31 H261 V 90000 31 H261 V 90000
32 MPV V 90000 32 MPV V 90000
33 reserved V 33 MP2T AV 90000
34 reserved V 34 H263 V 90000
35-71 unassigned ? 35-71 unassigned ?
72-76 reserved N/A N/A 72-76 reserved N/A N/A
77-95 unassigned ? 77-95 unassigned ?
96-127 dynamic ? 96-127 dynamic ?
dyn BT656 V 90000
dyn H263-1998 V 90000 dyn H263-1998 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. The application MUST define its own
method of delineating RTP and RTCP packets (RTSP [22] provides an
example of such an encapsulation specification.)
8 Port Assignment
As specified in the RTP protocol definition, RTP data SHOULD be
carried on an even UDP port number and the corresponding RTCP
packets SHOULD be carried on the next higher (odd) port number.
Applications operating under this profile MAY use any such UDP port
pair. For example, the port pair MAY be allocated randomly by a
session management program. A single fixed port number pair cannot be
required because multiple applications using this profile are likely
to run on the same host, and there are some operating systems that do to run on the same host, and there are some operating systems that do
not allow multiple processes to use the same UDP port with different not allow multiple processes to use the same UDP port with different
multicast addresses. multicast addresses.
However, port numbers 5004 and 5005 have been registered for use with However, port numbers 5004 and 5005 have been registered for use with
this profile for those applications that choose to use them as the this profile for those applications that choose to use them as the
default pair. Applications that operate under multiple profiles MAY default pair. Applications that operate under multiple profiles MAY
use this port pair as an indication to select this profile if they use this port pair as an indication to select this profile if they
are not subject to the constraint of the previous paragraph. are not subject to the constraint of the previous paragraph.
Applications need not have a default and MAY require that the port Applications need not have a default and MAY require that the port
skipping to change at page 31, line 27 skipping to change at page 35, line 5
9 Changes from RFC 1890 9 Changes from RFC 1890
This RFC revises RFC 1890. It is mostly backwards-compatible with RFC This RFC revises RFC 1890. It is mostly backwards-compatible with RFC
1890 and codifies existing practice. The changes are listed below. 1890 and codifies existing practice. The changes are listed below.
o The mapping of a user pass-phrase string into an encryption o The mapping of a user pass-phrase string into an encryption
key was deleted from Section 2 because two interoperable key was deleted from Section 2 because two interoperable
implementations were not found. implementations were not found.
o The payload formats for 1016 audio and MP2T video were removed o The payload format for 1016 audio was removed and its static
and their static payload type assignments 1 and 33 were marked payload type assignment 1 was marked "reserved" because two
"reserved" because two interoperable implementations were not interoperable implementations were not found.
found.
o Additional payload formats and/or expanded descriptions were o Additional payload formats and/or expanded descriptions were
included for G722, G726, G728, G729, GSM, QCELP, RED, VDVI, included for G722, G723, G726, G728, G729, GSM, GSM-EFR,
and H263-1998. QCELP, RED, VDVI, H263 and H263-1998.
o Static payload types 12, 16, 17 and 18 were added, and 13 and o Static payload types 4, 12, 16, 17, 18 and 34 were added, and
19 were reserved. 13 and 19 were reserved.
o Requirements for congestion control were added in Section 2. 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. Non-normative references were added to RFC YYYY [6]
where MIME subtypes for all the listed payload formats are
registered, some with optional parameters for use of the
payload formats.
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
changed from "is" to "SHOULD be". changed from "is" to "SHOULD be", and clarified that the
marker bit is set only when packets are intentionally not
sent.
o Similarly, text was added to specify that the marker bit o Similarly, text was added to specify that the marker bit
SHOULD be set to one on the last packet of a video frame, and SHOULD be set to one on the last packet of a video frame, and
that video frames are distinguished by their timestamps. that video frames are distinguished by their timestamps.
o This profile follows the suggestion in the RTP spec that RTCP o This profile follows the suggestion in the RTP spec that RTCP
bandwidth may be specified separately from the session bandwidth may be specified separately from the session
bandwidth and separately for active senders and passive bandwidth and separately for active senders and passive
receivers. receivers.
skipping to change at page 33, line 12 skipping to change at page 36, line 42
- The terms MUST, SHOULD, MAY, etc. are used as defined in RFC - The terms MUST, SHOULD, MAY, etc. are used as defined in RFC
2119. 2119.
o A second author for this document was added. o A second author for this document was added.
10 Security Considerations 10 Security Considerations
Implementations using the profile defined in this specification are Implementations using the profile defined in this specification are
subject to the security considerations discussed in the RTP subject to the security considerations discussed in the RTP
specification [1]. This profile does not specify any different specification [1]. This profile does not specify any different
security services other than giving rules for mapping characters in a security services. The primary function of this profile is to list a
user-provided pass phrase to canonical form. The primary function of set of data compression encodings for audio and video media.
this profile is to list a set of data compression encodings for audio
and video media.
Confidentiality of the media streams is achieved by encryption. Confidentiality of the media streams is achieved by encryption.
Because the data compression used with the payload formats described Because the data compression used with the payload formats described
in this profile is applied end-to-end, encryption may be performed in this profile is applied end-to-end, encryption may be performed
after compression so there is no conflict between the two operations. after compression so there is no conflict between the two operations.
A potential denial-of-service threat exists for data encodings using A potential denial-of-service threat exists for data encodings using
compression techniques that have non-uniform receiver-end compression techniques that have non-uniform receiver-end
computational load. The attacker can inject pathological datagrams computational load. The attacker can inject pathological datagrams
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 [23] and in multicast routing protocols to allow a versions of IGMP [24] 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 (2000). All Rights Reserved. Copyright (C) The Internet Society (2001). 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 35, line 18 skipping to change at page 38, line 46
[4] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, "An [4] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, "An
Architecture for Differentiated Service," Request for Comments Architecture for Differentiated Service," Request for Comments
(Proposed Standard) RFC 2475, Internet Engineering Task Force, Dec. (Proposed Standard) RFC 2475, Internet Engineering Task Force, Dec.
1998. 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] P. Hoschka, "MIME Type Registration of RTP Payload Types," [6] S. Casner and P. Hoschka, "MIME Type Registration of RTP Payload
Internet Draft, Internet Engineering Task Force, Feb. 1999 Work in Types," Internet Draft, Internet Engineering Task Force, July 2001.
progress. Work in progress.
[7] N. Freed, J. Klensin, and J. Postel, "Multipurpose Internet Mail [7] N. Freed, J. Klensin, and J. Postel, "Multipurpose Internet Mail
Extensions (MIME) Part Four: Registration Procedures," RFC 2048, Extensions (MIME) Part Four: Registration Procedures," RFC 2048,
Internet Engineering Task Force, Nov. 1996. Internet Engineering Task Force, Nov. 1996.
[8] Apple Computer, "Audio interchange file format AIFF-C," Aug. [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).
[9] IMA Digital Audio Focus and Technical Working Groups, [9] IMA Digital Audio Focus and Technical Working Groups,
"Recommended practices for enhancing digital audio compatibility in "Recommended practices for enhancing digital audio compatibility in
skipping to change at page 36, line 30 skipping to change at page 40, line 11
Internet Engineering Task Force, Oct. 1996. Internet Engineering Task Force, Oct. 1996.
[19] L. Berc, W. Fenner, R. Frederick, and S. McCanne, "RTP payload [19] 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.
[20] T. Turletti and C. Huitema, "RTP payload format for H.261 video [20] 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.
[21] C. Bormann, L. Cline, G. Deisher, T. Gardos, C. Maciocco, D. [21] C. Zhu, "RTP payload format for H.263 video streams," Request
for Comments (Proposed Standard) RFC 2190, Internet Engineering Task
Force, Sep. 1997.
[22] 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.
[22] H. Schulzrinne, A. Rao, and R. Lanphier, "Real time streaming [23] 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.
[23] S. Deering, "Host Extensions for IP Multicasting," Request for [24] 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 37, line 25 skipping to change at page 41, line 4
Information on the UCS Transformation Format 8 (UTF-8) is available Information on the UCS Transformation Format 8 (UTF-8) is available
at at
http://www.stonehand.com/unicode/standard/utf8.html http://www.stonehand.com/unicode/standard/utf8.html
DVI4 DVI4
An implementation is available from Jack Jansen at An implementation is available from Jack Jansen at
ftp://ftp.cwi.nl/local/pub/audio/adpcm.shar ftp://ftp.cwi.nl/local/pub/audio/adpcm.shar
G722 G722
An implementation of the G.722 algorithm is available as part of the An implementation of the G.722 algorithm is available as part of the
ITU-T STL, described above. ITU-T STL, described above.
G723
The reference C code implementation defining the G.723.1 algorithm
and its Annexes A, B, and C are available as an integral part of
Recommendation G.723.1 from the ITU Sales Service, address listed
above. Both the algorithm and C code are covered by a specific
license. The ITU-T Secretariat should be contacted to obtain such
licensing information.
G726 G726
G726 is specified in the ITU-T Recommendation G.726, "40, 32, 24, G726 is specified in the ITU-T Recommendation G.726, "40, 32, 24, and
and 16 kb/s Adaptive Differential Pulse Code Modulation (ADPCM)". An 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 through I 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. Annex Recommendation G.729 from the ITU Sales Service, listed above. Annex
I contains the integrated C source code for all G.729 operating I contains the integrated C source code for all G.729 operating
modes. The G.729 algorithm and associated C code are covered by a modes. The G.729 algorithm and associated C code are covered by a
skipping to change at page 39, line 10 skipping to change at page 42, line 22
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 [9]. companded data is also available in [9].
Table of Contents Table of Contents
1 Introduction ........................................ 3 1 Introduction ........................................ 3
1.1 Terminology ......................................... 4 1.1 Terminology ......................................... 4
2 RTP and RTCP Packet Forms and Protocol Behavior ..... 4 2 RTP and RTCP Packet Forms and Protocol Behavior ..... 4
3 IANA Considerations ................................. 7 3 IANA Considerations ................................. 6
3.1 Registering Additional Encodings .................... 7 3.1 Registering Additional Encodings .................... 6
4 Audio ............................................... 8 4 Audio ............................................... 8
4.1 Encoding-Independent Rules .......................... 8 4.1 Encoding-Independent Rules .......................... 8
4.2 Operating Recommendations ........................... 10 4.2 Operating Recommendations ........................... 9
4.3 Guidelines for Sample-Based Audio Encodings ......... 10 4.3 Guidelines for Sample-Based Audio Encodings ......... 10
4.4 Guidelines for Frame-Based Audio Encodings .......... 11 4.4 Guidelines for Frame-Based Audio Encodings .......... 10
4.5 Audio Encodings ..................................... 11 4.5 Audio Encodings ..................................... 11
4.5.1 DVI4 ................................................ 12 4.5.1 DVI4 ................................................ 11
4.5.2 G722 ................................................ 14 4.5.2 G722 ................................................ 13
4.5.3 G726-40, G726-32, G726-24, and G726-16............... 14 4.5.3 G723 ................................................ 13
4.5.4 G728 ................................................ 16 4.5.4 G726-40, G726-32, G726-24, and G726-16 .............. 17
4.5.5 G729 ................................................ 16 4.5.5 G728 ................................................ 18
4.5.6 G729D and G729E ..................................... 18 4.5.6 G729 ................................................ 19
4.5.7 GSM ................................................. 21 4.5.7 G729D and G729E ..................................... 21
4.5.7.1 General Packaging Issues ............................ 21 4.5.8 GSM ................................................. 24
4.5.7.2 GSM variable names and numbers ...................... 21 4.5.8.1 General Packaging Issues ............................ 24
4.5.8 L8 .................................................. 21 4.5.8.2 GSM variable names and numbers ...................... 25
4.5.9 L16 ................................................. 22 4.5.9 GSM-EFR ............................................. 25
4.5.10 LPC ................................................. 23 4.5.10 L8 .................................................. 25
4.5.11 MPA ................................................. 24 4.5.11 L16 ................................................. 25
4.5.12 PCMA and PCMU ....................................... 24 4.5.12 LPC ................................................. 27
4.5.13 QCELP ............................................... 24 4.5.13 MPA ................................................. 28
4.5.14 RED ................................................. 24 4.5.14 PCMA and PCMU ....................................... 28
4.5.15 VDVI ................................................ 25 4.5.15 QCELP ............................................... 28
5 Video ............................................... 25 4.5.16 RED ................................................. 28
5.1 CelB ................................................ 26 4.5.17 VDVI ................................................ 29
5.2 JPEG ................................................ 26 5 Video ............................................... 29
5.3 H261 ................................................ 26 5.1 CelB ................................................ 30
5.4 H263-1998 ........................................... 27 5.2 JPEG ................................................ 30
5.5 MPV ................................................. 27 5.3 H261 ................................................ 30
5.8 nv .................................................. 27 5.4 H263 ................................................ 30
6 Payload Type Definitions ............................ 28 5.5 H263-1998 ........................................... 31
7 RTP over TCP and Similar Byte Stream Protocols ...... 30 5.6 MPV ................................................. 31
8 Port Assignment ..................................... 30 5.7 MP2T ................................................ 31
9 Changes from RFC 1890 ............................... 31 5.8 nv .................................................. 31
10 Security Considerations ............................. 33 6 Payload Type Definitions ............................ 31
11 Full Copyright Statement ............................ 33 7 RTP over TCP and Similar Byte Stream Protocols ...... 32
12 Acknowledgements .................................... 34 8 Port Assignment ..................................... 32
13 Addresses of Authors ................................ 34 9 Changes from RFC 1890 ............................... 34
A Bibliography ........................................ 34 10 Security Considerations ............................. 36
11 Full Copyright Statement ............................ 37
12 Acknowledgements .................................... 37
13 Addresses of Authors ................................ 38
A Bibliography ........................................ 38
 End of changes. 

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