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.
Payload types and formats The technical parameters of payload formats for audio and video streams are standardised. The standard also describes the process of registering new payload types with IANA.
Text messaging payload types Payload formats and types for text messaging are defined in the following specifications:
MIDI payload types Payload formats and types for MIDI are defined in the following specifications:
Audio and video payload types Payload formats and types for audio and video 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.
Payload type (PT)NameTypeNo. of channelsClock rate (Hz)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.Frame size (byte)Default packet interval (ms)DescriptionReferences0PCMUaudio18000any20ITU-T G.711 PCM μ-Law audio 64 kbit/s1reserved (previously FS-1016 CELP)audio18000reserved, previously FS-1016 CELP audio 4.8 kbit/s2reserved (previously G721 or G726-32)audio18000reserved, previously ITU-T G.721 ADPCM audio 32 kbit/s or ITU-T G.726 audio 32 kbit/s3GSMaudio180002020European GSM Full Rate audio 13 kbit/s (GSM 06.10)4G723audio180003030ITU-T G.723.1 audio5DVI4audio18000any20IMA ADPCM audio 32 kbit/s6DVI4audio116000any20IMA ADPCM audio 64 kbit/s7LPCaudio18000any20Experimental Linear Predictive Coding audio 5.6 kbit/s8PCMAaudio18000any20ITU-T G.711 PCM A-Law audio 64 kbit/s9G722audio18000any20ITU-T G.722 audio 64 kbit/s10L16audio244100any20Linear PCM 16-bit Stereo audio 1411.2 kbit/s, uncompressed 11L16audio144100any20Linear PCM 16-bit audio 705.6 kbit/s, uncompressed 12QCELPaudio180002020Qualcomm Code Excited Linear Prediction, 13CNaudio18000Comfort 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.14MPAaudio1, 2900008–72MPEG-1 or MPEG-2 audio only, 15G728audio180002.520ITU-T G.728 audio 16 kbit/s16DVI4audio111025any20IMA ADPCM audio 44.1 kbit/s17DVI4audio122050any20IMA ADPCM audio 88.2 kbit/s18G729audio180001020ITU-T G.729 and G.729a audio 8 kbit/s; Annex B is implied unless the annexb=no parameter is used, 19reserved (previously CN)audioreserved, previously comfort noise25CELLBvideo90000Sun CellB videoXIL Programmer's Guide, Chapter 22 "CellB Codec". August 1997. Retrieved on 2014-07-19.26JPEGvideo90000JPEG video28nvvideo90000Xerox PARC's Network Video (nv)nv - network video on Henning Schulzrinne's website, Network Video on The University of Toronto's website, Retrieved on 2009-07-09.Ron Frederick Github with source code31H261video90000ITU-T H.261 video32MPVvideo90000MPEG-1 and MPEG-2 video33MP2Taudio/video90000MPEG-2 transport stream34H263video90000H.263 video, first version (1996), 72–76reservedreserved because RTCP packet types 200–204 would otherwise be indistinguishable from RTP payload types 72–76 with the marker bit set, 77–95unassignednote that RTCP packet type 207 (XR, Extended Reports) would be indistinguishable from RTP payload types 79 with the marker bit set, dynamicH263-1998video90000H.263 video, second version (1998), , dynamicH263-2000video90000H.263 video, third version (2000)dynamic (or profile)H264 AVCvideo90000H.264 video (MPEG-4 Part 10)dynamic (or profile)H264 SVCvideo90000H.264 videodynamic (or profile)H265video90000H.265 video (HEVC)dynamic (or profile)theoravideo90000Theora videodraft-barbato-avt-rtp-theoradynamiciLBCaudio1800020, 3020, 30Internet low Bitrate Codec 13.33 or 15.2 kbit/sdynamicPCMA-WBaudio1160005ITU-T G.711.1 A-lawdynamicPCMU-WBaudio1160005ITU-T G.711.1 μ-lawdynamicG718audio32000 (placeholder)20ITU-T G.718draft-ietf-payload-rtp-g718dynamicG719audio(various)4800020ITU-T G.719dynamicG7221audio16000, 3200020ITU-T G.722.1 and G.722.1 Annex CdynamicG726-16audio18000any20ITU-T G.726 audio 16 kbit/sdynamicG726-24audio18000any20ITU-T G.726 audio 24 kbit/sdynamicG726-32audio18000any20ITU-T G.726 audio 32 kbit/sdynamicG726-40audio18000any20ITU-T G.726 audio 40 kbit/sdynamicG729Daudio180001020ITU-T G.729 Annex DdynamicG729Eaudio180001020ITU-T G.729 Annex EdynamicG7291audio1600020ITU-T G.729.1dynamicGSM-EFRaudio180002020ITU-T GSM-EFR (GSM 06.60)dynamicGSM-HR-08audio1800020ITU-T GSM-HR (GSM 06.20)dynamic (or profile)AMRaudio(various)800020Adaptive Multi-Rate audiodynamic (or profile)AMR-WBaudio(various)1600020Adaptive Multi-Rate Wideband audio (ITU-T G.722.2)dynamic (or profile)AMR-WB+audio1, 2 or omit7200013.3–40Extended Adaptive Multi Rate – WideBand audiodynamic (or profile)vorbisaudio(various)(various)Vorbis audiodynamic (or profile)opusaudio1, 2480002.5–6020Opus audiodynamic (or profile)speexaudio18000, 16000, 3200020Speex audiodynamicmpa-robustaudio1, 29000024–72Loss-Tolerant MP3 audiodynamic (or profile)MP4A-LATMaudio90000 or othersMPEG-4 Audio (includes AAC)dynamic (or profile)MP4V-ESvideo90000 or othersMPEG-4 Visualdynamic (or profile)mpeg4-genericaudio/video90000 or otherMPEG-4 Elementary StreamsdynamicVP8video90000VP8 videodynamicVP9video90000VP9 videodynamicAV1video90000AV1 videoav1-rtp-specdynamicL8audio(various)(various)any20Linear PCM 8-bit audio with 128 offsetdynamicDAT12audio(various)(various)any20 (by analogy with L16)IEC 61119 12-bit nonlinear audiodynamicL16audio(various)(various)any20Linear PCM 16-bit audio, dynamicL20audio(various)(various)any20 (by analogy with L16)Linear PCM 20-bit audiodynamicL24audio(various)(various)any20 (by analogy with L16)Linear PCM 24-bit audiodynamicrawvideo90000Uncompressed Videodynamicac3audio(various)32000, 44100, 48000Dolby AC-3 audiodynamiceac3audio(various)32000, 44100, 48000Enhanced AC-3 audiodynamict140text1000Text over IPdynamicEVRCEVRC0EVRC1audio8000EVRC audiodynamicEVRCBEVRCB0EVRCB1audio8000EVRC-B audiodynamicEVRCWBEVRCWB0EVRCWB1audio16000EVRC-WB audiodynamicjpeg2000video90000JPEG 2000 videodynamicUEMCLIPaudio8000, 16000UEMCLIP audiodynamicATRAC3audio44100ATRAC3 audiodynamicATRAC-Xaudio44100, 48000ATRAC3+ audiodynamicATRAC-ADVANCED-LOSSLESSaudio(various)ATRAC Advanced Lossless audiodynamicDVvideo90000DV videodynamicBT656videoITU-R BT.656 videodynamicBMPEGvideoBundled MPEG-2 videodynamicSMPTE292MvideoSMPTE 292M videodynamicREDaudioRedundant Audio DatadynamicVDVIaudioVariable-rate DVI4 audiodynamicMP1SvideoMPEG-1 Systems Streams videodynamicMP2PvideoMPEG-2 Program Streams videodynamictoneaudio8000 (default)tonedynamictelephone-eventaudio8000 (default)DTMF tonedynamicaptxaudio2 – 6(equal to sampling rate)4000 ÷ sample rate4For 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.aptX audiodynamicjxsvvideo90000JPEG XS videodynamicscipaudio/video8000 or 90000SCIP
See also Session Initiation Protocol H.323 Comparison of audio coding formats
References
External links IANA assignments of Real-Time Transport Protocol (RTP) Parameters