转自：http://blog.csdn.net/caoshangpa/article/details/53008018
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PT  | Encoding Name | Audio/Video (A/V) | Clock Rate (Hz) | Channels | Reference |
|---|---|---|---|---|---|
| 0 | PCMU | A | 8000 | 1 | [RFC3551] |
| 1 | Reserved | ||||
| 2 | Reserved | ||||
| 3 | GSM | A | 8000 | 1 | [RFC3551] |
| 4 | G723 | A | 8000 | 1 | [Vineet_Kumar][RFC3551] |
| 5 | DVI4 | A | 8000 | 1 | [RFC3551] |
| 6 | DVI4 | A | 16000 | 1 | [RFC3551] |
| 7 | LPC | A | 8000 | 1 | [RFC3551] |
| 8 | PCMA | A | 8000 | 1 | [RFC3551] |
| 9 | G722 | A | 8000 | 1 | [RFC3551] |
| 10 | L16 | A | 44100 | 2 | [RFC3551] |
| 11 | L16 | A | 44100 | 1 | [RFC3551] |
| 12 | QCELP | A | 8000 | 1 | [RFC3551] |
| 13 | CN | A | 8000 | 1 | [RFC3389] |
| 14 | MPA | A | 90000 | [RFC3551][RFC2250] | |
| 15 | G728 | A | 8000 | 1 | [RFC3551] |
| 16 | DVI4 | A | 11025 | 1 | [Joseph_Di_Pol] |
| 17 | DVI4 | A | 22050 | 1 | [Joseph_Di_Pol] |
| 18 | G729 | A | 8000 | 1 | [RFC3551] |
| 19 | Reserved | A | |||
| 20 | Unassigned | A | |||
| 21 | Unassigned | A | |||
| 22 | Unassigned | A | |||
| 23 | Unassigned | A | |||
| 24 | Unassigned | V | |||
| 25 | CelB | V | 90000 | [RFC2029] | |
| 26 | JPEG | V | 90000 | [RFC2435] | |
| 27 | Unassigned | V | |||
| 28 | nv | V | 90000 | [RFC3551] | |
| 29 | Unassigned | V | |||
| 30 | Unassigned | V | |||
| 31 | H261 | V | 90000 | [RFC4587] | |
| 32 | MPV | V | 90000 | [RFC2250] | |
| 33 | MP2T | AV | 90000 | [RFC2250] | |
| 34 | H263 | V | 90000 | [Chunrong_Zhu] | |
| 35-71 | Unassigned | ? | |||
| 72-76 | Reserved for RTCP conflict avoidance | [RFC3551] | |||
| 77-95 | Unassigned | ? | |||
| 96-127 | dynamic | ? | [RFC3551] |
除了上表中明确指定PT值的负载类型，还有些负载类型由于诞生的较晚，没有具体的PT值，只能使用动态（dynamic）PT值，即96到127，这就是为什么大家普遍指定H264的PT值为96。下表中列出了没有具体PT值的负载类型。
| Media Type | Subtype | Clock Rate (Hz) | Channels (audio) | Reference |
|---|---|---|---|---|
| application | 1d-interleaved-parityfec | [RFC6015] | ||
| application | h224 | 4800 | [RFC4573] | |
| application | parityfec | [RFC3009] | ||
| application | raptorfec | [RFC6682] | ||
| application | rtx | [RFC4588] | ||
| application | smpte336m | [RFC6597] | ||
| application | ulpfec | [RFC5109] | ||
| audio | 1d-interleaved-parityfec | [RFC6015] | ||
| audio | 32kadpcm | 8000 | [RFC3802][RFC2421] | |
| audio | ac3 | [RFC4184] | ||
| audio | AMR | 8000 | [RFC4867][RFC3267] | |
| audio | AMR-WB | 16000 | [RFC4867][RFC3267] | |
| audio | amr-wb+ | 72000 | [RFC4352] | |
| audio | atrac3 | 44100 | [RFC5584] | |
| audio | ATRAC-ADVANCED-LOSSLESS | [RFC5584] | ||
| audio | atrac-x | [RFC5584] | ||
| audio | BV16 | 8000 | [RFC4298] | |
| audio | BV32 | 16000 | [RFC4298] | |
| audio | clearmode | 8000 | 1 | [RFC4040] |
| audio | CN | [RFC3389] | ||
| audio | DAT12 | [RFC3190] | ||
| audio | dsr-es201108 | [RFC3557] | ||
| audio | dsr-es202050 | 8000 | [RFC4060] | |
| audio | dsr-es202211 | 8000 | [RFC4060] | |
| audio | dsr-es202212 | 8000 | [RFC4060] | |
| audio | DV | [RFC6469] | ||
| audio | eac3 | [RFC4598] | ||
| audio | EVRC | 8000 | 1 | [RFC4788] |
| audio | EVRC0 | 8000 | 1 | [RFC4788] |
| audio | EVRC1 | 8000 | 1 | [RFC4788] |
| audio | EVRCB | 8000 | 1 | [RFC4788] |
| audio | EVRCB0 | 8000 | 1 | [RFC4788] |
| audio | EVRCB1 | 8000 | 1 | [RFC4788] |
| audio | EVRCWB | [RFC5188] | ||
| audio | EVRCWB0 | [RFC5188] | ||
| audio | EVRCWB1 | [RFC5188] | ||
| audio | fwdred | [RFC6354] | ||
| audio | g719 | 48000 | [RFC5404] | |
| audio | G7221 | 16000 | 1 | [RFC5577] |
| audio | G726-16 | 8000 | 1 | [RFC3551][RFC4856] |
| audio | G726-24 | 8000 | 1 | [RFC3551][RFC4856] |
| audio | G726-32 | 8000 | 1 | [RFC3551][RFC4856] |
| audio | G726-40 | 8000 | 1 | [RFC3551][RFC4856] |
| audio | G729D | 8000 | 1 | [RFC3551][RFC4856] |
| audio | G729E | 8000 | 1 | [RFC3551][RFC4856] |
| audio | GSM-EFR | 8000 | 1 | [RFC3551][RFC4856] |
| audio | L8 | [RFC3551][RFC4856] | ||
| audio | raptorfec | [RFC6682] | ||
| audio | RED | [RFC2198][RFC3555] | ||
| audio | rtx | [RFC4588] | ||
| audio | VDVI | 1 | [RFC3551][RFC4856] | |
| audio | L20 | [RFC3190] | ||
| audio | L24 | [RFC3190] | ||
| audio | MP4A-LATM | [RFC3016] | ||
| audio | mpa-robust | 90000 | [RFC5219] | |
| audio | parityfec | [RFC5109] | ||
| audio | SMV | 8000 | 1 | [RFC3558] |
| audio | SMV0 | 8000 | 1 | [RFC3558] |
| audio | t140c | [RFC4351] | ||
| audio | t38 | [RFC4612] | ||
| audio | telephone-event | [RFC4733] | ||
| audio | tone | [RFC4733] | ||
| audio | DVI4 | [RFC4856] | ||
| audio | G722 | [RFC4856] | ||
| audio | G723 | [RFC4856] | ||
| audio | G728 | [RFC4856] | ||
| audio | G729 | [RFC4856] | ||
| audio | GSM | [RFC4856] | ||
| audio | L16 | [RFC4856] | ||
| audio | LPC | [RFC4856] | ||
| audio | PCMA | [RFC4856] | ||
| audio | PCMU | [RFC4856] | ||
| audio | G7291 | 16000 | [RFC4749][RFC5459] | |
| audio | GSM-HR-08 | 8000 | [RFC5993] | |
| audio | iLBC | 8000 | [RFC3952] | |
| audio | ip-mr_v2.5 | 16000 | [RFC6262] | |
| audio | MPA | 90000 | [RFC3555] | |
| audio | mpeg4-generic | [RFC3640][RFC5691][RFC6295] | ||
| audio | PCMA-WB | 16000 | [RFC5391] | |
| audio | PCMU-WB | 16000 | [RFC5391] | |
| audio | QCELP | [RFC3555] | ||
| audio | rtp-midi | [RFC6295] | ||
| audio | speex | [RFC5574] | ||
| audio | uemclip | [RFC5686] | ||
| audio | ulpfec | [RFC5109] | ||
| audio | VMR-WB | 16000 | [RFC4348][RFC4424] | |
| audio | vorbis | [RFC5215] | ||
| audio | vorbis-config | [RFC5215] | ||
| text | 1d-interleaved-parityfec | [RFC6015] | ||
| text | fwdred | [RFC6354] | ||
| text | parityfec | [RFC3009] | ||
| text | raptorfec | [RFC6682] | ||
| text | red | 1000 | [RFC4102] | |
| text | rtx | [RFC4588] | ||
| text | t140 | 1000 | [RFC4103] | |
| text | ulpfec | [RFC5109] | ||
| video | BMPEG | 90000 | [RFC2343][RFC3555] | |
| video | 1d-interleaved-parityfec | [RFC6015] | ||
| video | 3gpp-tt | [RFC4396] | ||
| video | BT656 | 90000 | [RFC2431][RFC3555] | |
| video | celB | [RFC3555] | ||
| video | DV | 90000 | [RFC6469] | |
| video | H261 | [RFC4587] | ||
| video | H263 | 90000 | [RFC4628] | |
| video | H263-1998 | 90000 | [RFC4629] | |
| video | H263-2000 | 90000 | [RFC4629] | |
| video | H264 | [RFC6184] | ||
| video | H264-RCDO | 90000 | [RFC6185] | |
| video | H264-SVC | [RFC6190] | ||
| video | JPEG | [RFC3555] | ||
| video | JPEG2000 | [RFC5371] | ||
| video | MP1S | 90000 | [RFC2250][RFC3555] | |
| video | MP2P | 90000 | [RFC2250][RFC3555] | |
| video | MP2T | [RFC3555] | ||
| video | MP4V-ES | 90000 | [RFC3016] | |
| video | mpeg4-generic | [RFC3640] | ||
| video | MPV | [RFC3555] | ||
| video | nv | [RFC4856] | ||
| video | parityfec | [RFC5109] | ||
| video | pointer | 90000 | [RFC2862] | |
| video | raptorfec | [RFC6682] | ||
| video | raw | 90000 | [RFC4175] | |
| video | rtx | [RFC4588] | ||
| video | SMPTE292M | [RFC3497] | ||
| video | ulpfec | [RFC5109] | ||
| video | vc1 | 90000 | [RFC4425] |
