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.

Audio and video payload types[edit]

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:

  • RFC 3551, Standard 65, RTP Profile for Audio and Video Conferences with Minimal Control
  • RFC 4856, Media Type Registration of Payload Formats in the RTP Profile for Audio and Video Conferences
  • RFC 3190, RTP Payload Format for 12-bit DAT Audio and 20- and 24-bit Linear Sampled Audio
  • RFC 6184, RTP Payload Format for H.264 Video
  • RFC 3640, RTP Payload Format for Transport of MPEG-4 Elementary Streams
  • RFC 6416, RTP Payload Format for MPEG-4 Audio/Visual Streams
  • RFC 2250, RTP Payload Format for MPEG1/MPEG2 Video
  • RFC 7798, RTP Payload Format for High Efficiency Video Coding (HEVC)
  • RFC 2435, RTP Payload Format for JPEG-compressed Video
  • RFC 4587, RTP Payload Format for H.261 Video Streams
  • RFC 2658, RTP Payload Format for PureVoice Audio Video
  • RFC 4175, RTP Payload Format for Uncompressed Video
  • RFC 7587, RTP Payload Format for the Opus Speech and Audio Codec

Payload identifiers 96–127 are used for payloads defined dynamically during a session. It is recommended to dynamically assigned 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) Name Type No. of channels Clock rate (Hz)[note 1] 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 FS-1016 CELP) audio 1 8000 reserved, previously FS-1016 CELP audio 4.8 kbit/s RFC 3551, previously RFC 1890
2 reserved (previously G721 or G726-32) audio 1 8000 reserved, previously ITU-T G.721 ADPCM audio 32 kbit/s or ITU-T G.726 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 audio 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 audio 64 kbit/s RFC 3551
7 LPC audio 1 8000 any 20 Experimental Linear Predictive Coding audio 5.6 kbit/s 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[note 2] any 20 ITU-T G.722 audio 64 kbit/s 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, 2 90000 8–72 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 audio 44.1 kbit/s RFC 3551
17 DVI4 audio 1 22050 any 20 IMA ADPCM audio 88.2 kbit/s RFC 3551
18 G729 audio 1 8000 10 20 ITU-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
19 reserved (previously CN) audio reserved, previously comfort noise RFC 3551
25 CELB video 90000 Sun CellB video[5] RFC 2029
26 JPEG video 90000 JPEG video RFC 2435
28 nv video 90000 Xerox PARC's Network Video (nv)[6] RFC 3551, Page 32
31 H261 video 90000 ITU-T H.261 video RFC 4587
32 MPV video 90000 MPEG-1 and MPEG-2 video RFC 2250
33 MP2T audio/video 90000 MPEG-2 transport stream RFC 2250
34 H263 video 90000 H.263 video, first version (1996) RFC 3551, RFC 2190
72–76 reserved reserved because RTCP packet types 200–204 would otherwise be indistinguishable from RTP payload types 72–76 with the marker bit set RFC 3550, RFC 3551
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 AVC video 90000 H.264 video (MPEG-4 Part 10) RFC 6184, previously RFC 3984
dynamic (or profile) H264 SVC video 90000 H.264 video RFC 6190
dynamic (or profile) H265 video 90000 H.265 video (HEVC) RFC 7798
dynamic (or profile) theora video 90000 Theora video draft-barbato-avt-rtp-theora
dynamic iLBC audio 1 8000 20, 30 20, 30 Internet low Bitrate Codec 13.33 or 15.2 kbit/s RFC 3952
dynamic PCMA-WB audio 1 16000 5 ITU-T G.711.1 A-law RFC 5391
dynamic PCMU-WB audio 1 16000 5 ITU-T G.711.1 μ-law RFC 5391
dynamic G718 audio 32000 (placeholder) 20 ITU-T G.718 draft-ietf-payload-rtp-g718
dynamic G719 audio (various) 48000 20 ITU-T G.719 RFC 5404
dynamic G7221 audio 16000, 32000 20 ITU-T G.722.1 and G.722.1 Annex C RFC 5577
dynamic G726-16 audio 1 8000 any 20 ITU-T G.726 audio 16 kbit/s RFC 3551
dynamic G726-24 audio 1 8000 any 20 ITU-T G.726 audio 24 kbit/s RFC 3551
dynamic G726-32 audio 1 8000 any 20 ITU-T G.726 audio 32 kbit/s RFC 3551
dynamic G726-40 audio 1 8000 any 20 ITU-T G.726 audio 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 13.3–40 Extended Adaptive Multi Rate – WideBand audio RFC 4352
dynamic (or profile) vorbis audio (various) (various) Vorbis audio RFC 5215
dynamic (or profile) opus audio 1, 2 48000[note 3] 2.5–60 20 Opus audio RFC 7587
dynamic (or profile) speex audio 1 8000, 16000, 32000 20 Speex audio RFC 5574
dynamic mpa-robust audio 1, 2 90000 24–72 Loss-Tolerant MP3 audio RFC 5219 (previously RFC 3119)
dynamic (or profile) MP4A-LATM audio 90000 or others MPEG-4 Audio RFC 6416 (previously RFC 3016)
dynamic (or profile) MP4V-ES video 90000 or others MPEG-4 Visual RFC 6416 (previously RFC 3016)
dynamic (or profile) mpeg4-generic audio/video 90000 or other MPEG-4 Elementary Streams RFC 3640
dynamic VP8 video 90000 VP8 video RFC 7741
dynamic VP9 video 90000 VP9 video draft-ietf-payload-vp9
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) (various) any 20 (by analogy with L16) IEC 61119 12-bit nonlinear audio RFC 3190 Section 3
dynamic L16 audio (various) (various) any 20 Linear PCM 16-bit audio RFC 3551 Section 4.5.11, RFC 2586
dynamic L20 audio (various) (various) any 20 (by analogy with L16) Linear PCM 20-bit audio RFC 3190 Section 4
dynamic L24 audio (various) (various) any 20 (by analogy with L16) Linear PCM 24-bit audio RFC 3190 Section 4
dynamic raw video 90000 Uncompressed Video RFC 4175
dynamic ac3 audio (various) 32000, 44100, 48000 Dolby AC-3 audio RFC 4184
dynamic eac3 audio (various) 32000, 44100, 48000 Enhanced AC-3 audio RFC 4598
dynamic t140 text 1000 Text over IP RFC 4103
dynamic EVRC
EVRC0
EVRC1
audio 8000 EVRC audio RFC 4788
dynamic EVRCB
EVRCB0
EVRCB1
audio 8000 EVRC-B audio RFC 4788
dynamic EVRCWB
EVRCWB0
EVRCWB1
audio 16000 EVRC-WB audio RFC 5188
dynamic jpeg2000 video 90000 JPEG 2000 video RFC 5371
dynamic UEMCLIP audio 8000, 16000 UEMCLIP audio RFC 5686
dynamic ATRAC3 audio 44100 ATRAC3 audio RFC 5584
dynamic ATRAC-X audio 44100, 48000 ATRAC3+ audio RFC 5584
dynamic ATRAC-ADVANCED-LOSSLESS audio (various) ATRAC Advanced Lossless audio RFC 5584
dynamic DV video 90000 DV video RFC 3189
dynamic BT656 video ITU-R BT.656 video RFC 3555
dynamic BMPEG video Bundled MPEG-2 video RFC 2343
dynamic SMPTE292M video SMPTE 292M video RFC 3497
dynamic RED audio Redundant Audio Data RFC 2198
dynamic VDVI audio Variable-rate DVI4 audio RFC 3551
dynamic MP1S video MPEG-1 Systems Streams video RFC 2250
dynamic MP2P video MPEG-2 Program Streams video RFC 2250
dynamic tone audio 8000 (default) tone RFC 4733
dynamic telephone-event audio 8000 (default) DTMF tone RFC 4733
dynamic aptx audio 2 – 6 (equal to sampling rate) 4000 ÷ sample rate 4[note 4] aptX audio RFC 7310
  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]
  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[edit]

  • RFC 4103, RTP Payload Format for Text Conversation

MIDI payload[edit]

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. ^ 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.

External links[edit]