[Ffmpeg-devel] Corrupted image data H.263

Martyn mcantale
Thu Jan 5 19:10:19 CET 2006

Hi all,

I'm using a combination of eXosip and jrtplib together with libavcodec to
implement a SIP client which can stream audio and video. So far so good except
that the output from libavcodec appears to be corrupted in that the bottom third
of the image is perfect with the top two thirds of the image being blurry and
'smeared' (for want of a better word!).

Has anyone come across something like this before? I am having to concatenate
the payload from several consecutive RTP packets before passing this resulting
frame to the H.263 decoder although from the sequence numbers of the packets it
doesn't appear that any are being lost. The H.263 decoding and subsequent
conversion to RGB from YUV420P appears to work just fine (in that there are no
errors!) - I'm at a loss to explain what's going on, especially since a
softphone (Kapanga) connecting to the same video source seems to render the
video stream correctly.

Secondly, I'm assuming that when a frame is segmented across several RTP packets
I will just be able to concatenate the payloads of consecutive RTP packets until
I get one that has the marker bit set (i.e. end of frame). Is this correct?

Any help anyone could give here would be much appreciated. I'm using the CVS
version of ffmpeg from last night.


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