[Ffmpeg-devel] snow MC simplification

Michael Niedermayer michaelni
Tue Jan 17 12:16:56 CET 2006


On Mon, Jan 16, 2006 at 03:32:08PM -0800, Loren Merritt wrote:
> On Mon, 16 Jan 2006, Guillaume POIRIER wrote:
> >On 1/8/06, Michael Niedermayer <michaelni at gmx.at> wrote:
> >>
> >>Snow currently uses the h.264 luma MC functions if possible and if not
> >>(1/8 pel) then its own MC functions (mc_block())
> >>the result is that mc_block() is only used for some chroma blocks if qpel 
> >>is
> >>enabled, so it would be nice if we could et rid of it, the attached patch
> >>does that, but it needs testing (encode stuff with and without and view 
> >>with
> >>the respective player with and without the patch)
> >>if anyone has other ideas on how this can be simplified then dont hesitate
> >>to reply ...
> >
> >I don't know if that was intended, but that patch fixed a chroma bug,
> >as you may notice it on those 2 screenshots:
> >
> >vanilla version:
> >http://tuxrip.free.fr/transperl/MPlayer/The%20Player%20-%20vanilla.png
> >
> >snow_MC_simplification patched version:
> >http://tuxrip.free.fr/transperl/MPlayer/The%20Player%20snow_MC_simplification.png
> >
> >So either a recent commit broke snow, or just just fixed a
> >longstanding bug... Anyway, that's good stuff!
> I see such artifacts when mixing an encode with the patch and mplayer 
> without it, or vice versa.
> My results:
> vcodec=snow:vstrict=-2:cmp=1:mbcmp=1:subcmp=1:v4mv:qpel:vme=8:vqscale=<1..4>
> patch adds an average of +.7% bitrate, -.08 dB chroma
> decoding speed +24% (athlon-xp)
> no visible difference

if noone can see a difference then iam in favor of the simpler chroma MC code
after all humans watch videos not PSNR evaluating computers ...

btw, we should maybe implement chroma ME and retest this ...



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