Bug#688800: mplayer2: can not seek wvc1 videos

[Uoti Urpala]

On Wed, 2012-09-26 at 07:21 +0200, Reinhard Tartler wrote:
> > wvc1 videos are unseekable in mplayer2. For example if I try to seek 10 seconds
> > forward using right key, then the video freezes. A sample video is here:
> >
> > http://ftyps.com/unrelated/vc1_in_wmv.wmv
> 
> I can reproduce the problem with the default libavformat demuxer:
> 
> mplayer -demuxer lavfpref vc1_in_wmv.wmv
> 
> But not with the internal asf demuxer:
> 
> mplayer -demuxer asf vc1_in_wmv.wmv
> 
> Interestingly, avplay does not have any problems with seeking:
> 
> avplay vc1_in_wmv.wmv
> 
> This doesn't mean that libavformat was bugfree, this may as well
> indicate a problem in the way how mplayer2 drives libavformat.
> 
> Uoti, can you have a look at this? Thanks!

This is a bug in the libavcodec VC-1 decoder. It outputs a frame from
the old position after a seek flush. Actually, the codec object in
vc1dec.c seems to be completely missing the needed ".flush" field entry.

That it happens to work closer to normal with the internal demuxer is
just a side effect of a different timing mode used with the old demuxer;
the decoder misbehavior does not have the same effects in that case.