[FFmpeg-devel] [PATCH 0/2] Fix strict aliasing violations in AAC and AC3 parsers
Mon Dec 15 13:59:50 CET 2008
On 12/15/2008 10:35 AM, M?ns Rullg?rd wrote:
> M?ns Rullg?rd <mans at mansr.com> writes:
>> "Jason Garrett-Glaser" <darkshikari at gmail.com> writes:
>>>> am i interperting this correctly, that the code is hugely faster with
>>>> 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%
> BTW, that was with codesourcery gcc 4.2.1.
>> I will test with Jason's sample on Core2 and see if I get anything
>> resembling his results.
> Tested on Core2, and I get no such numbers:
> vanilla 203.7867 s
> -fno-strict-aliasing 204.2257 s
> This was with gcc 4.2.4.
same with gcc 4.3.2 on a Core2:
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