[MPlayer-dev-eng] key frame extractor / vo_jpeg use YV12 instead of RGB patch

[Michael Niedermayer]

Hi

On Fri, Mar 16, 2007 at 05:03:23PM -0700, Trent Piepho wrote:
> On Fri, 16 Mar 2007, Andreas Krebs wrote:
> > > You are not doing it quite right though.  The YUV data in video formats is
> > > almost never full range, but has something called ccir r.601 excursions.
> > > JFIF standard jpegs on the other had have full-range yuv data.  So, you
> > > must convert one to the other if you want to create standard jpeg files.
> >
> > I wasn't aware of this - thanks for letting me know. I guess this is the reason
> > why my images looked different than the images produced by the original vo_jpeg.
> >
> > this means I would have to scale each Y value to full range, is there
> > already an algorithm available for this? or better can I define a different YUV
> > format, so that the data passed to vo_jpeg already correctly scaled?
> > the Cb Cr values are not scaled - is this correct?
> 
> Chroma is scaled too.  swscaler has some support for JPEG range YUV data,
> if you look at the code you can see stubs for it.  I don't think it totally
> works.

swscaler itself supports it, mplayer and mencoder dont, problem is they
dont distinguish full range from non full range yuv
the easy way to correct this is to add few planar full range yuv formats
the hard way is to rewrite mplayer so it can use generic yuv descriptor
structure 

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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