RTP audio video profile

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Real-time audio and video conferencing and communication applications that use the Real-time Transport Protocol (RTP) employ Session Description Protocol (SDP) to describe the media streams carried in a multi-media session. This description format specifies the technical parameters of the media streams. Such a set of RTP parameters of the media stream and its compression or encoding methods is known as a media profile, or RTP audio video profile (RTP/AVP). Each profile is identified by a standardized payload type identifier.[1]

RTP/AVP audio and video payload types[edit]

Payload type (PT) Name Type No. of channels Clock rate (Hz) Frame size (ms) Default packet size (ms) Description References
0 PCMU audio 1 8000 any 20 ITU-T G.711 PCM µ-Law Audio 64 kbit/s RFC 3551
1 reserved (previously 1016) audio 1 8000 reserved, previously CELP Audio 4.8 kbit/s RFC 3551, previously RFC 1890
2 reserved (previously G721) audio 1 8000 reserved, previously ITU-T G.721 ADPCM Audio 32 kbit/s RFC 3551, previously RFC 1890
3 GSM audio 1 8000 20 20 European GSM Full Rate Audio 13 kbit/s (GSM 06.10) RFC 3551
4 G723 audio 1 8000 30 30 ITU-T G.723.1 RFC 3551
5 DVI4 audio 1 8000 any 20 IMA ADPCM Audio 32 kbit/s RFC 3551
6 DVI4 audio 1 16000 any 20 IMA ADPCM 64 kbit/s RFC 3551
7 LPC audio 1 8000 any 20 Experimental Linear Predictive Coding Audio RFC 3551
8 PCMA audio 1 8000 any 20 ITU-T G.711 PCM A-Law Audio 64 kbit/s RFC 3551
9 G722 audio 1 8000 any 20 ITU-T G.722 Audio RFC 3551 - Page 14
10 L16 audio 2 44100 any 20 Linear PCM 16-bit Stereo Audio 1411.2 kbit/s,[2][3][4] uncompressed RFC 3551, Page 27
11 L16 audio 1 44100 any 20 Linear PCM 16-bit Audio 705.6 kbit/s, uncompressed RFC 3551, Page 27
12 QCELP audio 1 8000 20 20 Qualcomm Code Excited Linear Prediction RFC 2658, RFC 3551
13 CN audio 1 8000 Comfort noise. Payload type used with audio codecs that do not support comfort noise as part of the codec itself such as G.711, G.722.1, G.722, G.726, G.727, G.728, GSM 06.10, Siren, and RTAudio. RFC 3389
14 MPA audio 1 90000 MPEG-1 or MPEG-2 Audio Only RFC 3551, RFC 2250
15 G728 audio 1 8000 2.5 20 ITU-T G.728 Audio 16 kbit/s RFC 3551
16 DVI4 audio 1 11025 any 20 IMA ADPCM RFC 3551
17 DVI4 audio 1 22050 any 20 IMA ADPCM RFC 3551
18 G729 audio 1 8000 10 20 ITU-T G.729 and G.729a RFC 3551, Page 20
25 CELB video 1 90000 Sun's CellB Video Encoding[5] RFC 2029
26 JPEG video 1 90000 JPEG Video RFC 2435
28 NV video 1 90000 Xerox PARC's Network Video (nv)[6] RFC 3551, Page 32
31 H261 video 1 90000 ITU-T H.261 Video RFC 4587
32 MPV video 1 90000 MPEG-1 and MPEG-2 Video RFC 2250
33 MP2T audio/video 1 90000 MPEG-2 transport stream Video RFC 2250
34 H263 video 90000 H.263 video, first version (1996) RFC 3551, RFC 2190
35 - 71 unassigned RFC 3551, Page 32
72 - 76 Reserved for RTCP conflict avoidance N/A N/A RFC 3551, Page 32
77 - 95 unassigned RFC 3551, Page 32
dynamic H263-1998 video 90000 H.263 video, second version (1998) RFC 3551, RFC 4629, RFC 2190
dynamic H263-2000 video 90000 H.263 video, third version (2000) RFC 4629
dynamic (or profile) H264 video 90000 H.264 video (MPEG-4 Part 10) RFC 6184, previously RFC 3984
dynamic (or profile) theora video 90000 Theora video draft-barbato-avt-rtp-theora-01
dynamic iLBC audio 1 8000 20 or 30 20 or 30, respectively Internet low Bitrate Codec 13.33 or 15.2 kbit/s RFC 3952
dynamic PCMA-WB audio 16000 5 ITU-T G.711.1, A-law RFC 5391
dynamic PCMU-WB audio 16000 5 ITU-T G.711.1, µ-law RFC 5391
dynamic G718 audio 32000 (placeholder) 20 ITU-T G.718 draft-ietf-avt-rtp-g718-03
dynamic G719 audio (various) 48000 20 ITU-T G.719 RFC 5404
dynamic G7221 audio 32000, 16000 20 ITU-T G.722.1 RFC 5577
dynamic G726-16 audio 1 8000 any 20 ITU-T G.726 audio with 16 kbit/s RFC 3551
dynamic G726-24 audio 1 8000 any 20 ITU-T G.726 audio with 24 kbit/s RFC 3551
dynamic G726-32 audio 1 8000 any 20 ITU-T G.726 audio with 32 kbit/s RFC 3551
dynamic G726-40 audio 1 8000 any 20 ITU-T G.726 audio with 40 kbit/s RFC 3551
dynamic G729D audio 1 8000 10 20 ITU-T G.729 Annex D RFC 3551
dynamic G729E audio 1 8000 10 20 ITU-T G.729 Annex E RFC 3551
dynamic G7291 audio 16000 20 ITU-T G.729.1 RFC 4749
dynamic GSM-EFR audio 1 8000 20 20 ITU-T GSM-EFR (GSM 06.60) RFC 3551
dynamic GSM-HR-08 audio 1 8000 20 ITU-T GSM-HR (GSM 06.20) RFC 5993
dynamic (or profile) AMR audio (various) 8000 20 Adaptive Multi-Rate audio RFC 4867
dynamic (or profile) AMR-WB audio (various) 16000 20 Adaptive Multi-Rate Wideband audio (ITU-T G.722.2) RFC 4867
dynamic (or profile) AMR-WB+ audio 1, 2 or omit 72000 80 (super-frame; internally divided in to transport frames of 13.33, 14.22, 15, 16, 17.78, 20, 21.33, 24, 26.67, 30, 35.55, or 40) Extended Adaptive Multi Rate – WideBand audio RFC 4352
dynamic (or profile) vorbis audio (various) any (must be a multiple of sample rate) as many Vorbis packets as fit within the path MTU, unless it exceeds an application's desired transmission latency RTP Payload Format for Vorbis Encoded Audio RFC 5215
dynamic (or profile) opus audio 1, 2 48000 2.5, 5, 10, 20, 40, or 60 20, minimum allowed value 3 (rounded from 2.5), maximum allowed value 120 (allowed values are 3, 5, 10, 20, 40, or 60 or an arbitrary multiple of Opus frame sizes rounded up to the next full integer value up to a maximum value of 120) RTP Payload Format for Opus Speech and Audio Codec draft
dynamic (or profile) speex audio 1 8000, 16000 or 32000 20 RTP Payload Format for the Speex Codec RFC 5574
dynamic (96-127) mpa-robust audio 90000 A More Loss-Tolerant RTP Payload Format for MP3 Audio RFC 5219
dynamic (or profile) MP4A-LATM audio 90000 or others recommended same as frame size RTP Payload Format for MPEG-4 Audio RFC 6416 (previously RFC 3016)
dynamic (or profile) MP4V-ES video 90000 or others recommended same as frame size RTP Payload Format for MPEG-4 Visual RFC 6416 (previously RFC 3016)
dynamic (or profile) mpeg4-generic audio/video 90000 or other RTP Payload Format for Transport of MPEG-4 Elementary Streams RFC 3640
dynamic VP8 video 90000 RTP Payload Format for Transport of VP8 Streams draft-ietf-payload-vp8-08
dynamic L8 audio (various) (various) any 20 Linear PCM 8-bit audio with 128 offset RFC 3551 Section 4.5.10 and Table 5
dynamic DAT12 audio (various) 8000, 11025, 16000, 22050, 24000, 32000, 44100, 48000 or others any 20 (by analogy with L16) IEC 61119 12-bit nonlinear audio RFC 3190 Section 3
dynamic L16 audio (various) 8000, 11025, 16000, 22050, 24000, 32000, 44100, 48000 or others any 20 Linear PCM 16-bit audio RFC 3551 Section 4.5.11, RFC 2586
dynamic L20 audio (various) 8000, 11025, 16000, 22050, 24000, 32000, 44100, 48000 or others any 20 (by analogy with L16) Linear PCM 20-bit audio RFC 3190 Section 4
dynamic L24 audio (various) 8000, 11025, 16000, 22050, 24000, 32000, 44100, 48000 or others any 20 (by analogy with L16) Linear PCM 24-bit audio RFC 3190 Section 4

RFC 3551 lists details of the codec, or a reference for the details is provided. Payload identifiers 96–127 are reserved for payloads defined dynamically during a session. The document recommends dynamically assigned port numbers, although 5004 and 5005 have been registered for use of the profile and can be used instead. The standard also describes the process of registering new payload types with IANA.

Applications operating under this profile should always support PCMU (payload type 0). Previously, DVI4 (payload type 5) was required, but this requirement was removed in August 2013 by RFC 7007 because "many RTP deployments do not support DVI4, and there is little reason to use it when much more modern codecs are available."

See also[edit]

References[edit]

  1. ^ RFC 3551, RTP Profile for Audio and Video Conferences with Minimal Control, H. Schulzrinne, S. Casner, The Internet Society (July 2003).
  2. ^ "RFC 2586 - The Audio/L16 MIME content type". May 1999. Retrieved 2010-03-16. 
  3. ^ "RFC 3108 - Conventions for the use of the Session Description Protocol (SDP) for ATM Bearer Connections". May 2001. Retrieved 2010-03-16. 
  4. ^ "RFC 4856 - Media Type Registration of Payload Formats in the RTP Profile for Audio and Video Conferences - Registration of Media Type audio/L16". March 2007. Retrieved 2010-03-16. 
  5. ^ SUN CellB Codec, Retrieved on 2009-07-09.
  6. ^ nv - network video on Henning Schulzrinne's website, Network Video on The University of Toronto's website, Retrieved on 2009-07-09.

External links[edit]