SDR Sessions - RTP

RTP Payload Types

The payload types are as follows (compare
RFC 1890, page 15, and (more up to date) IANA Assigned Numbers, for RTP, this is from where I borrowed the following list):
      PT         encoding      audio/video    clock rate    channels
                 name          (A/V)          (Hz)          (audio)
      _______________________________________________________________
      0          PCMU          A              8000          1     [RFC1890]
      1          1016          A              8000          1     [RFC1890]
      2          G721          A              8000          1     [RFC1890]
      3          GSM           A              8000          1     [RFC1890]
      4          G723          A              8000          1       [Kumar]
      5          DVI4          A              8000          1     [RFC1890]
      6          DVI4          A              16000         1     [RFC1890]
      7          LPC           A              8000          1     [RFC1890]
      8          PCMA          A              8000          1     [RFC1890]
      9          G722          A              8000          1     [RFC1890]
      10         L16           A              44100         2     [RFC1890]
      11         L16           A              44100         1     [RFC1890]
      12         reserved      A
      13         reserved      A
      14         MPA           A              90000         ?[RFC1890,2250]
      15         G728          A              8000          1     [RFC1890]
      16         DVI4          A             11025          1       [DiPol]
      17         DVI4          A             22050          1       [DiPol]
      18--22     unassigned    A
      23         reserved      A
      24         reserved      V
      25         CelB          V              90000               [RFC2029]
      26         JPEG          V              90000               [RFC2435]
      27         reserved      V
      28         nv            V              90000               [RFC1890]
      29         reserved      V
      30         reserved      V
      31         H261          V              90000               [RFC2032]
      32         MPV           V              90000               [RFC2250]
      33         MP2T          AV             90000               [RFC2250]
      34         H263          V              90000                   [Zhu]
      35--71     unassigned    ?
      72--76     reserved for RTCP conflict avoidance             [RFC1889]
      77--95     unassigned    ?
      96--127    dynamic       ?                                  [RFC1890]
The more common types are 0 (as generated by rat, e.g.) and 31; furthermore 3 (GSM), 14 (MPA = MPEG-I or -II audio encapsulated as elementary streams), 32 (MPV = MPEG-I or -II video encapsulated as elementary streams). The first two can be played with the Real player, as far as I know, don't know about the others. A short
grep AVP *.sdp | perl -pe 's/.* //' | sort -n | uniq -c
on 78 cache files gave once:
  29 0    (i.e., 29 times PT=0, etc.)
   3 3
   1 5
   7 14
  29 31
   7 32
   2 121

See also:

RTP        Transport Protocol for Real-Time Apps    Elective       1889
RTP-AV     RTP Audio/Video Profile                  Elective       1890
RTP-CELLB  RTP Payload Format of Sun's CellB        Elective       2029
RTP-H.261  RTP Payload Format for H.261             Elective       2032
RTP-JPEG   RTP Payload Format for JPEG-compressed   Elective       2035
---------  RTP Payload Format for H.263 Video ST    Elective       2190
RTP-RAD    RTP Payload for Redundant Audio Data     Elective       2198
RTP-MPEG   RTP Payload Format for MPEG1/MPEG2       Elective       2250
RTP-MPEG   RTP Payload Format for Bundled MPEG                     2343
--------   RTP Payload Format for H.263+                           2429
--------   RTP Payload Format for BT.656 Video Encoding            2431
--------   RTP Payload Format for JPEG-compressed Video            2435
--------   Compressing IP/UDP/RTP Headers                          2508
See also Henning Schulzrinne's very helpful RTP FAQ.
Written by Stefan, who should be doing something completely different.