[MPlayer-dev-eng] Problem decoding a H.263+ stream

[Ross Finlayson]

[This is really a question for the developer(s) of the "ffmpeg" codec 
library, but Fabrice Bellard has not yet responded to my email to him.  So, 
I wonder if anyone on this mailing list is familiar with the "ffmpeg" 
H.263(+) decoding software, and can help me out here.]

As you know, I have recently modified the "mplayer" media player to play 
RTP streams: <http://www.live.com/mplayer/>.  However, I find that when I 
try playing a H.263+ video stream, mplayer is crashing in the "ffmpeg" 
codec.  The problem is occurring halfway through the first video 
frame.  The codec successfully decodes about half of the macroblocks in the 
first frame (this first frame is an "I" frame, of course), but then 
encounters an error.

The error is occuring in the call to get_vlc2() at line 2696 of 
"h263.c".  This call is returning -1, which causes the macroblock decode to 
fail, which subsequently triggers the error concealment code (which then 
causes a crash, because this is the first frame, and there's no 'previous' 
frame at this point).

Unfortunately, I don't yet know enough about the H.263+ codec to know for 
sure why macroblock decoding is failing halfway through the first 
frame.  So, I wonder if anyone who's familiar with this code could find the 
time to build the new "mplayer" (with RTP streaming support), and 
demonstrate this error for themselves.

If you build the LIVE.COM libraries and "mplayer" (following the 
instructions at <http://www.live.com/mplayer/>), and run
     mplayer -fps 15 
rtsp://darwin.horizonlive.com:554/finlayson/sample-h263-ulaw-8000.mov
you should see the error occur.

	Ross.