[Ffmpeg-devel] [PATCH] h264.c faster decode_residual

[diane_cartman at gmx.de]

Hi all,

this patch addresses two FIXMEs that are in the code for decoding of
residual blocks in CAVLC mode.
1. seperated code for first coefficient level (after the trailing ones) and
subsequent coefficient levels.
2. merged decode of runs with dequantisation

I timed the function from the handling of trailing ones down to the end with
START_TIMER and
STOP_TIMER. This showed an improvement of almost 20% for the Apple Trailer
"Batman Begins"
in 1080p for that function.
Overall, when decoding the clip with "mplayer batman_begins_1080p.mov -vo
null -ao dummy"
on my P4 with 3GHz I get
V: 144.3 3460/3460 100%  0%  0.0% 0 0
before applying the patch and
V: 144.3 3460/3460 97%  0%  0.0% 0 0
after.
Maybe not that much of an improvement, but I guess it's worth it.

P.S. please cc me as I am not subscribed. And show some mercy, this is my
first patch :)

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