[Ffmpeg-devel] Bug in snow revision 1.50 - broken lossless mode

[Michael Niedermayer]

Hi

On Wednesday 13 April 2005 14:53, Yartrebo wrote:
> On Wed, 2005-04-13 at 12:13 +0200, Michael Niedermayer wrote:
> > Hi
> >
> > On Wednesday 13 April 2005 06:03, Yartrebo wrote:
> > > Michael, those rescaled IDWT coefficients (revision 1.50) appear to
> > > have broken lossless mode quite bad. It's all fuzzy now and is similar
> > > in quality to quant=10 or 20. It happens for all inputs I've tried.
> >
> > the regression tests worked yesterday and they do test lossless with the
> > 5/3 wavelet
> > the 9/7 wavelet is with the scaling merged not bijective with fixed point
> > numbers, its bijective if rational or real numbers are used, but as the
> > 5/3 wavelet is superior for lossless (at least it was in my tests) thats
> > really irrelevant
> > but then again, dont hesitate to look at the lifting steps for the 9/7
> > wavelet, maybe you can come up with a better solution so that this
> > dissadvantage can be avoided
> >
> > [...]
>
> In that case, it would be nice to make 5/3 the default for lossless. It
> really doesn't make snow look good to have the default mode (9/7,
> lossless) look so ugly.

the default of option A should not depend on option B, its confusing and 
problematic, there should be a check for this and the encoder should die with 
an error if 9/7 is used in lossless mode (patch welcome)

[...]
-- 
Michael

"nothing is evil in the beginning. Even Sauron was not so." -- Elrond