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

The technical parameters of payload formats for audio and video streams are standardised. [1] 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. [2]

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/sRFC 3551
1reserved (previously FS-1016 CELP)audio18000reserved, previously FS-1016 CELP audio 4.8 kbit/sRFC 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/sRFC 3551, previously RFC 1890
3GSMaudio180002020European GSM Full Rate audio 13 kbit/s (GSM 06.10)RFC 3551
4G723audio180003030ITU-T G.723.1 audioRFC 3551
5DVI4audio18000any20 IMA ADPCM audio 32 kbit/sRFC 3551
6DVI4audio116000any20 IMA ADPCM audio 64 kbit/sRFC 3551
7LPCaudio18000any20Experimental Linear Predictive Coding audio 5.6 kbit/sRFC 3551
8PCMAaudio18000any20ITU-T G.711 PCM A-Law audio 64 kbit/sRFC 3551
9G722audio18000 [note 2] any20ITU-T G.722 audio 64 kbit/sRFC 3551
10L16audio244100any20 Linear PCM 16-bit Stereo audio 1411.2 kbit/s, [3] [4] : 62  [5] : 18  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 onlyRFC 3551, RFC 2250
15G728audio180002.520ITU-T G.728 audio 16 kbit/sRFC 3551
16DVI4audio111025any20 IMA ADPCM audio 44.1 kbit/sRFC 3551
17DVI4audio122050any20IMA ADPCM audio 88.2 kbit/sRFC 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 [6] RFC 2029
26JPEGvideo90000 JPEG videoRFC 2435
28nvvideo90000 Xerox PARC's Network Video (nv) [7] [8] RFC 3551, Page 32
31H261video90000ITU-T H.261 videoRFC 4587
32MPVvideo90000MPEG-1 and MPEG-2 videoRFC 2250
33MP2Taudio/video90000MPEG-2 transport stream RFC 2250
34H263video90000 H.263 video, first version (1996)RFC 3551, RFC 2190
72–76reservedreserved because RTCP packet types 200–204 would otherwise be indistinguishable from RTP payload types 72–76 with the marker bit setRFC 3550, RFC 3551
77–95unassignednote that RTCP packet type 207 (XR, Extended Reports) would be indistinguishable from RTP payload types 79 with the marker bit setRFC 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 videoRFC 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/sRFC 3952
dynamicPCMA-WBaudio1160005ITU-T G.711.1 A-lawRFC 5391
dynamicPCMU-WBaudio1160005ITU-T G.711.1 μ-lawRFC 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 CRFC 5577
dynamicG726-16audio18000any20ITU-T G.726 audio 16 kbit/sRFC 3551
dynamicG726-24audio18000any20ITU-T G.726 audio 24 kbit/sRFC 3551
dynamicG726-32audio18000any20ITU-T G.726 audio 32 kbit/sRFC 3551
dynamicG726-40audio18000any20ITU-T G.726 audio 40 kbit/sRFC 3551
dynamicG729Daudio180001020ITU-T G.729 Annex DRFC 3551
dynamicG729Eaudio180001020ITU-T G.729 Annex ERFC 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 audioRFC 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 audioRFC 4352
dynamic (or profile)vorbisaudio(various)(various) Vorbis audioRFC 5215
dynamic (or profile)opusaudio1, 248000 [note 3] 2.5–6020 Opus audioRFC 7587
dynamic (or profile)speexaudio18000, 16000, 3200020 Speex audioRFC 5574
dynamicmpa-robustaudio1, 29000024–72Loss-Tolerant MP3 audioRFC 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 StreamsRFC 3640
dynamicVP8video90000 VP8 videoRFC 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 offsetRFC 3551 Section 4.5.10 and Table 5
dynamicDAT12audio(various)(various)any20 (by analogy with L16)IEC 61119 12-bit nonlinear audioRFC 3190 Section 3
dynamicL16audio(various)(various)any20 Linear PCM 16-bit audioRFC 3551 Section 4.5.11, RFC 2586
dynamicL20audio(various)(various)any20 (by analogy with L16) Linear PCM 20-bit audioRFC 3190 Section 4
dynamicL24audio(various)(various)any20 (by analogy with L16) Linear PCM 24-bit audioRFC 3190 Section 4
dynamicrawvideo90000Uncompressed VideoRFC 4175
dynamicac3audio(various)32000, 44100, 48000 Dolby AC-3 audioRFC 4184
dynamiceac3audio(various)32000, 44100, 48000 Enhanced AC-3 audioRFC 4598
dynamict140text1000 Text over IP RFC 4103
dynamicEVRC
EVRC0
EVRC1		audio8000 EVRC audioRFC 4788
dynamicEVRCB
EVRCB0
EVRCB1		audio8000 EVRC-B audioRFC 4788
dynamicEVRCWB
EVRCWB0
EVRCWB1		audio16000 EVRC-WB audioRFC 5188
dynamicjpeg2000video90000 JPEG 2000 videoRFC 5371
dynamicUEMCLIPaudio8000, 16000 UEMCLIP audioRFC 5686
dynamicATRAC3audio44100 ATRAC3 audioRFC 5584
dynamicATRAC-Xaudio44100, 48000 ATRAC3+ audioRFC 5584
dynamicATRAC-ADVANCED-LOSSLESSaudio(various) ATRAC Advanced Lossless audioRFC 5584
dynamicDVvideo90000 DV videoRFC 6469 (previously RFC 3189)
dynamicBT656video ITU-R BT.656 videoRFC 3555
dynamicBMPEGvideoBundled MPEG-2 videoRFC 2343
dynamicSMPTE292Mvideo SMPTE 292M videoRFC 3497
dynamicREDaudioRedundant Audio DataRFC 2198
dynamicVDVIaudioVariable-rate DVI4 audioRFC 3551
dynamicMP1SvideoMPEG-1 Systems Streams videoRFC 2250
dynamicMP2PvideoMPEG-2 Program Streams videoRFC 2250
dynamictoneaudio8000 (default)toneRFC 4733
dynamictelephone-eventaudio8000 (default) DTMF toneRFC 4733
dynamicaptxaudio2 – 6(equal to sampling rate)4000 ÷ sample rate4 [note 4] aptX audioRFC 7310
dynamicjxsvvideo90000 JPEG XS videoRFC 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 1–60 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] : 14 
  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

References

  1. 1 2 H. Schulzrinne; S. Casner (July 2003). RTP Profile for Audio and Video Conferences with Minimal Control. Network Working Group. doi: 10.17487/RFC3551 . STD 65. RFC 3551.Internet Standard 65. Updated by RFC  8860, 5761 and 7007. Obsoletes RFC  1890.
  2. ↑ T. Terriberry (August 2013). Update to Remove DVI4 from the Recommended Codecs for the RTP Profile for Audio and Video Conferences with Minimal Control (RTP/AVP). Internet Engineering Task Force. doi: 10.17487/RFC7007 . ISSN   2070-1721. RFC 7007.Proposed Standard. Updates RFC  3551.
  3. ↑ J. Salsman; H. Alvestrand (May 1999). The Audio/L16 MIME content type. Network Working Group. doi: 10.17487/RFC2586 . RFC 2586.Informational.
  4. ↑ R. Kumar; M. Mostafa (May 2001). Conventions for the use of the Session Description Protocol (SDP) for ATM Bearer Connections. Network Working Group. doi: 10.17487/RFC3108 . RFC 3108.Proposed Standard.
  5. ↑ S. Casner (March 2007). Media Type Registration of Payload Formats in the RTP Profile for Audio and Video Conferences. Network Working Group. doi: 10.17487/RFC4856 . RFC 4856.Proposed Standard. Obsoletes RFC  3555.
  6. ↑ XIL Programmer's Guide, Chapter 22 "CellB Codec". August 1997. Retrieved on 2014-07-19.
  7. ↑ nv - network video on Henning Schulzrinne's website, Network Video on The University of Toronto's website, Retrieved on 2009-07-09.
  8. ↑ Ron Frederick Github with source code
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