[Ffmpeg-devel] libavcodec: possible QPEL decoding bug.

[Michael Niedermayer]

Hi

On Sat, Sep 10, 2005 at 12:44:17AM +0200, Marius the Mad wrote:
> 
> Hello.
> 
> My name is Mariusz Pociask. Milan Cutka, ffdshow developer, advised me
> to tell libavcodec developers about the problem I encountered. I hope
> I'm in the right place. :)
> 
> 
> The story so far:
> 
> I was playing with XviD and had severe problems with image quality.
> The picture was very noisy and muddy, similar to old MS MPEG4v2 encodes.
> One of the last things I tried was changing ffdshow's XviD decoder from
> libavcodec to XviD - and it improved things a lot.
> 
> 
> What it looks like:
> 
> frame 154 from my sample, decoded by:
> 
> XviD: http://img39.imageshack.us/img39/3341/154xvid6xt.png
> libavcodec: http://img39.imageshack.us/img39/4590/154avcodec2da.png
> 
> 
> Frame 283:
> 
> XviD: http://img39.imageshack.us/img39/6135/283xvid3tg.png
> libavcodec: http://img39.imageshack.us/img39/573/283avcodec5xl.png
> 
> 
> I didn't use any postprocessing here (apart from YV12->RGB32
> convertion during decoding).
> 
> 
> My clip triggering this behaviour is available here (below 10 MB):
> http://s1.putfile.com/videos/25007444149.avi
> 
> I know it was created using quite an old XviD build, but I used it after
> I tried the latest CVS compile - and they both worked the same way.
> 
> 
> Milan thinks it's a QPEL problem and I think he may be right - I tried
> some other samples I created without QPEL and everything was OK.

if you encoded this, could you provide a file with just qpel and no other
options turned on like gmc or mpeg quantizers?

[...]

-- 
Michael