[FFmpeg-devel] [PATCH 0/2] Fix strict aliasing violations in AAC and AC3 parsers

Måns Rullgård mans
Mon Dec 15 04:48:32 CET 2008

"Jason Garrett-Glaser" <darkshikari at gmail.com> writes:

>> am i interperting this correctly, that the code is hugely faster with
>> -fno-strict-aliasing
>> ?
>> and iam of course in favor of the faster variant for h264.c
> Yes, but it makes absolutely no sense why it would be faster--the
> oprofile says even the asm functions are faster which of course makes
> no sense at all.
> Others in #ffmpeg-devel have reported small speed increases or
> decreases, but nothing like what I posted.

Changes in decoding time after adding -fno-strict-aliasing on ARM:

H.264   -2.4%
MPEG4   +0.14%
MPEG2   -2.3%
Vorbis  +0.08%
Flac    +3.6%
MP3     +2.6%
AC3     +0.83%
DTS     +0.81%

I will test with Jason's sample on Core2 and see if I get anything
resembling his results.

M?ns Rullg?rd
mans at mansr.com

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