[FFmpeg-user] Extracing H264 from RTP packets

[Joseph Rosensweig]

Hey all,

    Has anyone extracted h264 data from a wireshark RTP capture?
 Essentially what I have tried is to capture an h323 session and to extract
one of the H264 RTP streams using "Follow UDP Stream" and then saving the
sessions as a raw file.  Then I took the SDP for the session and attempted
to run it through ffmpeg:

$ cat polycom.sdp
v=0
o=- 1351021842 1 IN IP4 10.101.21.75
t=0 0
c=IN IP4 10.22.1.59
m=video 5002 RTP/AVP 109
a=rtpmap:109 H264/90000
a=fmtp:109
packetization-mode=1;max-fs=9216;max-mbps=276480;profile-level-id=42801e

$ ffmpeg -f rtp -i polycom.sdp -i polycom.rtp polycom_rtp.h264
FFmpeg version git-2d162e3, Copyright (c) 2000-2011 the FFmpeg developers
  built on Apr  4 2012 11:34:44 with gcc 4.4.3
  configuration: --enable-gpl --enable-libx264
/usr/include --enable-shared --enable-pic
  libavutil    50. 36. 0 / 50. 36. 0
  libavcore     0. 16. 1 /  0. 16. 1
  libavcodec   52.108. 0 / 52.108. 0
  libavformat  52. 94. 0 / 52. 94. 0
  libavdevice  52.  2. 3 / 52.  2. 3
  libavfilter   1. 74. 0 /  1. 74. 0
  libswscale    0. 12. 0 /  0. 12. 0
[rtp @ 0x174d510] Unsupported RTP version packet received
[rtp @ 0x174d510] Received too short packet
^C  Last message repeated 85803 times

   I get this unsupported message.  Is what I'm trying to do possible?

Thanks,

JD