[FFmpeg-devel] [PATCH] faster vp6 decoding
Thu Feb 12 00:29:26 CET 2009
Zuxy Meng wrote:
> 2009/2/9 Jason Garrett-Glaser <darkshikari at gmail.com>:
> > + "punpcklbw %%mm7, %%mm0\n\t" \
> > + "punpcklbw %%mm7, %%mm1\n\t" \
> > + "punpckhbw %%mm7, %%mm3\n\t" \
> > + "punpckhbw %%mm7, %%mm4\n\t" \
> > + "pmullw 0(%2), %%mm0\n\t" /* src[x-8 ] * biweight  */ \
> > + "pmullw 8(%2), %%mm1\n\t" /* src[x ] * biweight  */ \
> > + "pmullw 0(%2), %%mm3\n\t" /* src[x-8 ] * biweight  */ \
> > + "pmullw 8(%2), %%mm4\n\t" /* src[x ] * biweight  */ \
> > + "paddw %%mm1, %%mm0\n\t" \
> > + "paddw %%mm4, %%mm3\n\t" \
> > This can be done faster with pmaddubsw (SSSE3-only, but worth making
> > another version surely).
> Sure but that would require weights to be stored as arrays of int8_t
> instead of int16_t?
> > Worthwhile if you make an SSE version.
> > Works by interleaving the weights, allowing you to avoid the unpacks,
> > use only two multiplies, and avoid the adds, too, I think. If I'm
> > right, that makes the entire thing quite a bit less than half the
> > instructions.
> I tried something like below and it's about 15% faster on my Pentium
> M. The speed up should be more prominent on modern CPUs with 128 bit
> FADD unit:
> [...some asm code...]
Nice. I fixed it so that it works on x86_64 and I cleaned it up.
It works but has some small visible artifacts.
It would be great if you could fix attached patch so that it gives
bitexact result with:
ffmpeg -i sample.flv -f framecrc out.crc
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