[FFmpeg-devel] [PATCH] VP8 coeff decoding optimizations

[Pascal Massimino]

Jason,

On Mon, Aug 2, 2010 at 1:32 AM, Jason Garrett-Glaser
<darkshikari at gmail.com>wrote:

> Attached are two mutually exclusive VP8 optimization patches.
>
> Approach in #1 (test.diff): simplify addressing by eliminating
> vp8_coeff_band
> Advantage: one less dereference, seems to be slightly faster, but
> might depend on the mood of gcc
>

+1 here. Seems to be a tad faster than test3.diff (gcc 4.2.4 x86-64):

current (timing decode_mb_coeffs()):
47533 dezicycles in dec, 131005 runs, 67 skips
47594 dezicycles in dec, 130977 runs, 95 skips
47681 dezicycles in dec, 131003 runs, 69 skips
47503 dezicycles in dec, 130997 runs, 75 skips

test.diff
46065 dezicycles in dec, 131004 runs, 68 skips
46009 dezicycles in dec, 130996 runs, 76 skips
46119 dezicycles in dec, 131035 runs, 37 skips
46226 dezicycles in dec, 131000 runs, 72 skips

test3.diff:
46255 dezicycles in dec, 131003 runs, 69 skips
46156 dezicycles in dec, 131009 runs, 63 skips
46263 dezicycles in dec, 131017 runs, 55 skips


> Disadvantage: more cache usage
>
> Approach in #2 (test3.diff): simplify addressing by making the
> probability table single-dimensional and merging the complex
> addressing logic into vp8_coeff_band
> Advantage: trivial addressing
> Disadvantage: still has the dereference, and a bit ugly (probably fixable)
>
> Thoughts?
>
> Dark Shikari
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
> https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
>