[Libav-user] Repeating frames
T.Glover at nottingham.ac.uk
Thu Oct 25 11:50:56 CEST 2012
I'm using avcodec_decode_video2() to decode h264 frames encoded by
x264 one frame at a time. The stream is being transmitted over a lossy physical layer wireless channel prior to decoding. I'm trying to implement logic to re-display the last good picture if the current picture fails to decode for whatever reason. The logic I tried was to simply memcpy(lastGoodFrame, currFrame, sizeof(AVFrame)) each time got_picture_ptr is true and if got_picture_ptr is false then I display lastGoodFrame instead of currFrame. However, I'm getting unexpected behavior and blocking patterns. I suspect that this is due to libav doing interframe prediction decoding. Is this the case? Is there a way to do what I'm trying to accomplish?
Re-displaying the last picture is probably not what you want to do - at best your stream will appear frozen with the last good image while the successive ones are not displayed, and then jump about when correctly decoded images arrive. I would ascertain just how much data is being lost and where it happens, if you can, and potentially follow some of the options I previously posted.
Try your software over your own internal network, i.e. plug all the computers into their own switch/router. This will then give you an idea if there are inherent issues with your software, or the network really is a factor, or your software is not coping too well with a lossy network, or indeed something else.
Good luck with it!
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