[FFmpeg-devel] [PATCH] Optimize QTRLE encoding

[Malcolm Bechard]

On Thu, Feb 14, 2013 at 12:35 PM, Alexis Ballier
<alexis.ballier at gmail.com>wrote:

> 2013/2/12 Malcolm Bechard <malcolm.bechard at gmail.com>:
> > I don't think we can assume all compilers will optimize that. The fact
> that
> > this code runs 2x-3x faster when compiled with VS2010 vs. gcc shows how
> > much optimization can be missed (although I'm hoping it's something I'm
> > doing wrong with the gcc compile).
> > The goal of the patch is to speed up that loop so while it may be a small
> > or even immeasurable speedup I think it's valid portion of the work
> without
> > adding any complexity to the code.
>
> I was only asking if you _did_ see an improvement with that change
> alone; you should still probably submit two patches: a first one for
> this change alone, and a second one for the algorithm change.
>
> btw I'm not sure how you compile this code, the 2x-3x difference seems
> huge, if you compile with ffmpeg build system it should be done
> automatically but if you compile by hand be sure to use gcc -O2 so
> that it optimizes it.
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I'm re-compiling every time with a full remake under Ubuntu, cross
compiling for Windows, debug off and optimizations on. I agree it's a
surprising difference. Now that I've got ffmpeg building natively under
VS2010 I see other cases where VS2010 is slower (decoding some formats,
sws_scale). So neither is the clear winner.