RTP payload formats

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The Real-time Transport Protocol (RTP) specifies a general-purpose data format and network protocol for transmitting digital media streams on Internet Protocol (IP) networks. The details of media encoding, such as signal sampling rate, frame size and timing, are specified in an RTP payload format. The format parameters of the RTP payload are typically communicated between transmission endpoints with the Session Description Protocol (SDP), but other protocols, such as the Extensible Messaging and Presence Protocol (XMPP) may be used.

Contents

Audio and video payload types

RFC 3551, entitled RTP Profile for Audio and Video (RTP/AVP), specifies the technical parameters of payload formats for audio and video streams.

The standard also describes the process of registering new payload types with IANA; additional payload formats and payload types are defined in the following specifications:

Payload identifiers 96–127 are used for payloads defined dynamically during a session. It is recommended to dynamically assign port numbers, although port numbers 5004 and 5005 have been registered for use of the profile when a dynamically assigned port is not required.

Applications should always support PCMU (payload type 0); previously, DVI4 (payload type 5) was also recommended, but this was removed in 2013 by RFC 7007.

Payload type (PT)NameTypeNo. of channelsClock rate (Hz) [note 1] Frame size (byte)Default packet interval (ms)DescriptionReferences
0PCMUaudio18000any20ITU-T G.711 PCM μ-Law audio 64 kbit/s RFC 3551
1reserved (previously FS-1016 CELP)audio18000reserved, previously FS-1016 CELP audio 4.8 kbit/s RFC 3551, previously RFC 1890
2reserved (previously G721 or G726-32)audio18000reserved, previously ITU-T G.721 ADPCM audio 32 kbit/s or ITU-T G.726 audio 32 kbit/s RFC 3551, previously RFC 1890
3GSMaudio180002020European GSM Full Rate audio 13 kbit/s (GSM 06.10) RFC 3551
4G723audio180003030ITU-T G.723.1 audio RFC 3551
5DVI4audio18000any20 IMA ADPCM audio 32 kbit/s RFC 3551
6DVI4audio116000any20 IMA ADPCM audio 64 kbit/s RFC 3551
7LPCaudio18000any20Experimental Linear Predictive Coding audio 5.6 kbit/s RFC 3551
8PCMAaudio18000any20ITU-T G.711 PCM A-Law audio 64 kbit/s RFC 3551
9G722audio18000 [note 2] any20ITU-T G.722 audio 64 kbit/s RFC 3551 - Page 14
10L16audio244100any20 Linear PCM 16-bit Stereo audio 1411.2 kbit/s, [2] [3] [4] uncompressed RFC 3551, Page 27
11L16audio144100any20 Linear PCM 16-bit audio 705.6 kbit/s, uncompressed RFC 3551, Page 27
12QCELPaudio180002020 Qualcomm Code Excited Linear Prediction RFC 2658, RFC 3551
13CNaudio18000 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
14MPAaudio1, 2900008–72 MPEG-1 or MPEG-2 audio only RFC 3551, RFC 2250
15G728audio180002.520ITU-T G.728 audio 16 kbit/s RFC 3551
16DVI4audio111025any20 IMA ADPCM audio 44.1 kbit/s RFC 3551
17DVI4audio122050any20IMA ADPCM audio 88.2 kbit/s RFC 3551
18G729audio180001020ITU-T G.729 and G.729a audio 8 kbit/s; Annex B is implied unless the annexb=no parameter is used RFC 3551, Page 20, RFC 3555, Page 15
19reserved (previously CN)audioreserved, previously comfort noise RFC 3551
25CELLBvideo90000 Sun CellB video [5] RFC 2029
26JPEGvideo90000 JPEG video RFC 2435
28nvvideo90000 Xerox PARC's Network Video (nv) [6] [7] RFC 3551, Page 32
31H261video90000ITU-T H.261 video RFC 4587
32MPVvideo90000MPEG-1 and MPEG-2 video RFC 2250
33MP2Taudio/video90000MPEG-2 transport stream RFC 2250
34H263video90000 H.263 video, first version (1996) RFC 3551, RFC 2190
7276reservedreserved because RTCP packet types 200204 would otherwise be indistinguishable from RTP payload types 7276 with the marker bit set RFC 3550, RFC 3551
7795unassignednote that RTCP packet type 207 (XR, Extended Reports) would be indistinguishable from RTP payload types 79 with the marker bit set RFC 3551, RFC 3611
dynamicH263-1998video90000 H.263 video, second version (1998) RFC 3551, RFC 4629, RFC 2190
dynamicH263-2000video90000 H.263 video, third version (2000) RFC 4629
dynamic (or profile)H264 AVCvideo90000 H.264 video (MPEG-4 Part 10) RFC 6184, previously RFC 3984
dynamic (or profile)H264 SVCvideo90000 H.264 video RFC 6190
dynamic (or profile)H265video90000 H.265 video (HEVC) RFC 7798
dynamic (or profile)theoravideo90000 Theora video draft-barbato-avt-rtp-theora
dynamiciLBCaudio1800020, 3020, 30 Internet low Bitrate Codec 13.33 or 15.2 kbit/s RFC 3952
dynamicPCMA-WBaudio1160005ITU-T G.711.1 A-law RFC 5391
dynamicPCMU-WBaudio1160005ITU-T G.711.1 μ-law RFC 5391
dynamicG718audio32000 (placeholder)20ITU-T G.718 draft-ietf-payload-rtp-g718
dynamicG719audio(various)4800020ITU-T G.719 RFC 5404
dynamicG7221audio16000, 3200020ITU-T G.722.1 and G.722.1 Annex C RFC 5577
dynamicG726-16audio18000any20ITU-T G.726 audio 16 kbit/s RFC 3551
dynamicG726-24audio18000any20ITU-T G.726 audio 24 kbit/s RFC 3551
dynamicG726-32audio18000any20ITU-T G.726 audio 32 kbit/s RFC 3551
dynamicG726-40audio18000any20ITU-T G.726 audio 40 kbit/s RFC 3551
dynamicG729Daudio180001020ITU-T G.729 Annex D RFC 3551
dynamicG729Eaudio180001020ITU-T G.729 Annex E RFC 3551
dynamicG7291audio1600020ITU-T G.729.1 RFC 4749
dynamicGSM-EFRaudio180002020ITU-T GSM-EFR (GSM 06.60) RFC 3551
dynamicGSM-HR-08audio1800020ITU-T GSM-HR (GSM 06.20) RFC 5993
dynamic (or profile)AMRaudio(various)800020 Adaptive Multi-Rate audio RFC 4867
dynamic (or profile)AMR-WBaudio(various)1600020 Adaptive Multi-Rate Wideband audio (ITU-T G.722.2) RFC 4867
dynamic (or profile)AMR-WB+audio1, 2 or omit7200013.3–40 Extended Adaptive Multi Rate – WideBand audio RFC 4352
dynamic (or profile)vorbisaudio(various)(various) Vorbis audio RFC 5215
dynamic (or profile)opusaudio1, 248000 [note 3] 2.5–6020 Opus audio RFC 7587
dynamic (or profile)speexaudio18000, 16000, 3200020 Speex audio RFC 5574
dynamicmpa-robustaudio1, 29000024–72Loss-Tolerant MP3 audio RFC 5219 (previously RFC 3119)
dynamic (or profile)MP4A-LATMaudio90000 or others MPEG-4 Audio (includes AAC) RFC 6416 (previously RFC 3016)
dynamic (or profile)MP4V-ESvideo90000 or others MPEG-4 Visual RFC 6416 (previously RFC 3016)
dynamic (or profile)mpeg4-genericaudio/video90000 or other MPEG-4 Elementary Streams RFC 3640
dynamicVP8video90000 VP8 video RFC 7741
dynamicVP9video90000 VP9 video draft-ietf-payload-vp9
dynamicAV1video90000 AV1 video av1-rtp-spec
dynamicL8audio(various)(various)any20 Linear PCM 8-bit audio with 128 offset RFC 3551 Section 4.5.10 and Table 5
dynamicDAT12audio(various)(various)any20 (by analogy with L16)IEC 61119 12-bit nonlinear audio RFC 3190 Section 3
dynamicL16audio(various)(various)any20 Linear PCM 16-bit audio RFC 3551 Section 4.5.11, RFC 2586
dynamicL20audio(various)(various)any20 (by analogy with L16) Linear PCM 20-bit audio RFC 3190 Section 4
dynamicL24audio(various)(various)any20 (by analogy with L16) Linear PCM 24-bit audio RFC 3190 Section 4
dynamicrawvideo90000Uncompressed Video RFC 4175
dynamicac3audio(various)32000, 44100, 48000 Dolby AC-3 audio RFC 4184
dynamiceac3audio(various)32000, 44100, 48000 Enhanced AC-3 audio RFC 4598
dynamict140text1000 Text over IP RFC 4103
dynamicEVRC
EVRC0
EVRC1
audio8000 EVRC audio RFC 4788
dynamicEVRCB
EVRCB0
EVRCB1
audio8000 EVRC-B audio RFC 4788
dynamicEVRCWB
EVRCWB0
EVRCWB1
audio16000 EVRC-WB audio RFC 5188
dynamicjpeg2000video90000 JPEG 2000 video RFC 5371
dynamicUEMCLIPaudio8000, 16000 UEMCLIP audio RFC 5686
dynamicATRAC3audio44100 ATRAC3 audio RFC 5584
dynamicATRAC-Xaudio44100, 48000 ATRAC3+ audio RFC 5584
dynamicATRAC-ADVANCED-LOSSLESSaudio(various) ATRAC Advanced Lossless audio RFC 5584
dynamicDVvideo90000 DV video RFC 6469 (previously RFC 3189)
dynamicBT656video ITU-R BT.656 video RFC 3555
dynamicBMPEGvideoBundled MPEG-2 video RFC 2343
dynamicSMPTE292Mvideo SMPTE 292M video RFC 3497
dynamicREDaudioRedundant Audio Data RFC 2198
dynamicVDVIaudioVariable-rate DVI4 audio RFC 3551
dynamicMP1SvideoMPEG-1 Systems Streams video RFC 2250
dynamicMP2PvideoMPEG-2 Program Streams video RFC 2250
dynamictoneaudio8000 (default)tone RFC 4733
dynamictelephone-eventaudio8000 (default) DTMF tone RFC 4733
dynamicaptxaudio2 6(equal to sampling rate)4000 ÷ sample rate4 [note 4] aptX audio RFC 7310
dynamicjxsvvideo90000 JPEG XS video RFC 9134
dynamicscipaudio/video8000 or 90000 SCIP RFC 9607
  1. The "clock rate" is the rate at which the timestamp in the RTP header is incremented, which need not be the same as the codec's sampling rate. For instance, video codecs typically use a clock rate of 90000 so their frames can be more precisely aligned with the RTCP NTP timestamp, even though video sampling rates are typically in the range of 160 samples per second.
  2. Although the sampling rate for G.722 is 16000, its clock rate is 8000 to remain backwards compatible with RFC 1890, which incorrectly used this value. [1]
  3. Because Opus can change sampling rates dynamically, its clock rate is fixed at 48000, even when the codec will be operated at a lower sampling rate. The maxplaybackrate and sprop-maxcapturerate parameters in SDP can be used to indicate hints/preferences about the maximum sampling rate to encode/decode.
  4. For aptX, the packetization interval must be rounded down to the nearest packet interval that can contain an integer number of samples. So at sampling rates of 11025, 22050, or 44100, a packetization rate of "4" is rounded down to 3.99.

Text messaging payload

MIDI payload

See also

Related Research Articles

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References

  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. XIL Programmer's Guide, Chapter 22 "CellB Codec". August 1997. Retrieved on 2014-07-19.
  6. nv - network video on Henning Schulzrinne's website, Network Video on The University of Toronto's website, Retrieved on 2009-07-09.
  7. Ron Frederick Github with source code