[FFmpeg-devel] manually hacked configure options increase h264 decoding speed significantly

Michael Niedermayer michaelni at gmx.at
Thu Oct 20 11:20:38 CEST 2011

On Thu, Oct 20, 2011 at 10:41:11AM +0200, madshi wrote:
> Hey guys,
> recently I've noticed that ffdshow decodes faster than my
> own ffmpeg dlls. After some digging I found out that ffdshow
> uses a couple of custom configure settings that noticably
> improve h264 decoding performance. So now I'm wondering
> why these options are not activated by default. Is there a
> good reason for that?
> I'm testing on win32, using MingW/GCC for compiling.
> Here's the list of changes I'm currently doing manually to
> config.h:
> #define HAVE_CMOV 1
> #define HAVE_FAST_CLZ 0
> #define HAVE_FAST_CMOV 1

> #define HAVE_ISATTY 0

This one should not make a meassureable difference with current git
how old was the checkout you used for testing ?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
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