[Ffmpeg-devel] snow MC simplification

[Loren Merritt]

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

--Loren Merritt