[FFmpeg-devel] MJPG decoder picture quality

[Michael Niedermayer]

On Tue, Jun 08, 2010 at 08:04:19PM -0400, Pavel Pavlov wrote:
> > -----Original Message-----
> > bounces at mplayerhq.hu] On Behalf Of Michael Niedermayer
> > > I use libavcodec's jpeg decoder and I noticed that some pictures weren't
> > looking good. Knowing that these pictures were meant to be very high quality, I
> > decided to check out what was wrong.
> > > I couldn't find anything wrong, other that the fact that pictures that come out
> > of libavcodec's MJPG decoder don't looks as good as they are supposed to.
> > > As a simple test I took a picture that comes from win7 install :
> > > http://dev5.summit-tech.ca/pps/ffmpeg/Tulips.jpg
> > > Here's how this picture gets decoded by ffmpeg:
> > > http://dev5.summit-tech.ca/pps/ffmpeg/Tulips_yuv444.png
> > 
> > you need -sws_flags +accurate_rnd+full_chroma_int the scalers defaults are
> > tuned a bit toward realtime speed for video decoding.
> > This may arguably be something we should change for ffmpeg, iam not sure ...
> > 
> 
>  [Pavel Pavlov] 
> I use libavcodec, not the ffmpeg cmd line app.

you post on a development list, we assume you know how to convert that ;)


> 
> 
> > 
> > > Here's doubled pixel compare image:
> > > http://dev5.summit-tech.ca/pps/ffmpeg/Tulips_compare_200.png (On the
> > > left, regular windows image viewer, on the right is MJPG from
> > > libavcodec)
> > >
> > > I also saved raw yuv444:
> > > http://dev5.summit-tech.ca/pps/ffmpeg/Tulips_1024x768.yuv.bin
> > > Seems that ffplay can't open raw images (would be useful for
> > > development purposes), so I use yay.exe that can view raw yuv images:
> > > http://dev5.summit-tech.ca/pps/ffmpeg/yay.exe
> > 
> > -f rawvideo -pix_fmt yuv444p -s 1024x768 or something like that
> > 
> 
> [Pavel Pavlov] 
> I tried: ffplay -f rawvideo Tulips_1024x768.yuv.bin -pix_fmt yuv444p -s 1024x768
> It didn't work (window is just a black square).

could be your hw not supporting such large overlays and SDL
send us a patch that finally frees ffplay from SDL

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is not what we do, but why we do it that matters.
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