[Ffmpeg-devel] [PATCH] h264 - loopify some get_cabac calls

Alexander Strange astrange
Sun Mar 25 03:02:18 CEST 2007


On Mar 24, 2007, at 7:40 PM, Trent Piepho wrote:

> On Sat, 24 Mar 2007, Alexander Strange wrote:
>> This changes two series of straight-line get_cabac calls to loops.
>>
>> Not a big win, but there is a definite one.
>
> Not definite at all:
>
>         Wilcoxon rank sum test
>
> data: before and after
> W = 58, p-value = 0.5787
> alternative hypothesis: true mu is not equal to 0
>
> The p-value should be less than .05 to even consider rejecting the  
> null
> hypothesis.

Hm, that certainly isn't much of a change.
The numbers are very small, and I wouldn't have sent it if it was a  
major change to produce this.
It also reduces the size of the function by 105 insns, though.

It's really annoying that CABAC is so hard to optimize. Is CoreAVC  
actually much faster with CABAC vs. VLC with the SMP disabled? I  
wonder if most of its speed comes from doing motion compensation  on  
a seperate thread from bitstream parsing.




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