[Ffmpeg-cvslog] CVS: ffmpeg/libavcodec mpegvideo.c,1.511,1.512

[Loren Merritt]

On Thu, 23 Mar 2006, Jeff Clagg wrote:

> On Fri, Mar 24, 2006 at 12:53:35AM +0200, Jan Knutar wrote:
>> On Friday 24 March 2006 00:43, Diego Biurrun wrote:
>>> On Thu, Mar 23, 2006 at 10:54:50PM +0100, Loren Merritt CVS wrote:
>>>>
>>>> Modified Files:
>>>>  mpegvideo.c
>>>> Log Message:
>>>> prefetch pixels for future motion compensation. 4-10% faster mpeg1/2/4.
>>>
>>> Have you benchmarked FFmpeg against libmpeg2 after the change?  Would be
>>> very interesting...
>>
>> As would benchmarks comparing ffmpeg before prefetch, with ffmpeg after
>> prefetch, on other CPUs than Loren's.
>
> I tried on one machine (not my own) and got mixed results, mostly
> unfavorable.
>
> The machine is a dual core 3.2ghz p4. I compared cvs from 3-21 (just
> prior to Loren's last bunch of mmx commits) with cvs from after the
> prefetch change, using GCC 4.0.3. In a nutshell, mpeg4 ASP is about 8%
> slower, mpeg2 is 10%-20% slower, but H.264 speed improved by less than
> 2%. Below is a summary of the results. Maybe sometime later on, I'll try
> these tests at home, using my Athlon 64 in 32-bit mode, with an older
> GCC. Though maybe Loren's already done exactly this test.

I found a P4 2.8GHz with gcc 4.0.3, and compared current cvs vs cvs with 
the prefetches commented out. Result: with prefetches gave 4% faster 
mpeg4asp, 1.5% faster h264.

--Loren Merritt