[FFmpeg-devel] donation for snow

Kostya kostya.shishkov
Fri Nov 7 08:22:44 CET 2008

On Thu, Nov 06, 2008 at 08:53:58PM -0800, Jason Garrett-Glaser wrote:
> On Thu, Nov 6, 2008 at 8:45 PM, Stefan de Konink <stefan at konink.de> wrote:
> > On Thu, 6 Nov 2008, Jason Garrett-Glaser wrote:
> >
> >> That's odd.  My general experience with wavelets is that they give
> >> much worse "visual quality per PSNR" than DCT-based does.  That is,
> >> you can get many cases where a fully PSNR-optimal wavelet image is 3db
> >> PSNR better than a fully PSNR-optimal DCT image (e.g. JPEG2K vs JPEG)
> >> but the DCT-based one *still* looks better.
> >
> > the keywords are; psycho-visual model.
> Of course; you're preaching to the choir here ;)  I wrote x264's psy model.
> > But from the standpoint of Wavelets; would postprocessing with
> > psycho-visual aspects in mind not help to improve the actual
> > representation opposed to the optimal information carrier?
> The only kind of postprocessing that I've found universally helps is
> very slight fake grain and/or debanding, and only because it helps add
> dither to compensate for banding.
> The x264 psy model considerations all basically revolve around:
> 1.  Maximizing Preservation of detail.
> 2.  Places where detail preservation is not as important.
> Neither of these can contribute to a postprocessing model because
> postprocessing cannot really introduce new detail.

And I thought postprocessing is mostly for eliminating some stuff
from input.

>  IMO, in practice,
> most psy stuff has to be done encoder-side, or perhaps somehow in the
> spec itself.  That is one of the major problems of modern video
> encoding and formats; its still stuck in the stone age with regards to
> psy stuff, and most encoders have either no psy optimizations at all
> or extremely rudimentary ones that rely on random numbers pulled out
> of thin air.
> Interestingly enough, I've found most good video psy-opts have
> significant parallels in audio encoding.

Please be more specific, there are people here trying to write a decent
AAC encoder.
> Dark Shikari

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