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

Loren Merritt lorenm
Fri Apr 20 12:56:43 CEST 2007

On Thu, 19 Apr 2007, Alexander Strange wrote:
> It skips once whenever it handles a skip macroblock. Probably it should skip 
> START_TIMER as well, but I did it a while ago and the numbers should be the 
> same.

Skips in the timer macro have nothing to do with the skip macroblock type.
The timer assumes that any run which takes more than 8x longer than the 
average so far is not real cpu-time but instead is due to a context 
switch. That heuristic improves the benchmarking precision on functions 
whose expected run time is constant, but fails on functions that do 
varying amount of work. deblocking varies. (and skip macroblocks tend to 
have the fastest deblocking, so they're the ones that aren't skips in 
the timer.)

--Loren Merritt

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