[MPlayer-users] mp3lib/ffmp3 performance issues on via c7

Robert Henney robh at rut.org
Fri Jun 20 00:33:03 CEST 2008

I have recently noticed that both mp3lib and ffmp3 consume a lot more
of the cpu on my via c7 machine than on my other machines.  several 
times more cpu in fact.

so I benchmarked some aspects of mplayer between the via c7 machine 
and an old pII, both with clocks fixed at 400MHz.  both ffodivx and 
ffh264 on the c7 slightly edged out the pII in performance, which was 
to be expected but makes it even more puzzling as to why the audio
codec performance is falling far in the other direction.

next I played a 256.0 kbit mp3 using mp3lib, ffmp3, and ffvorbis.
mp3lib on the pII barely registered in the top output, with cpu
staying up at 99% idle.  on the c7 however, mplayer consumed much more
cpu, with the cpu hovering at 91% idle.

        mp3lib ffmp3 ffvorbis
pII cpu  1%     5%    5%
c7 cpu   9%    15%    8%

at first I thought it might be a FPU issue, but doesn't ffmp3 use fixed

compiling was done using gcc 4.2.4 on the c7, and 4.1.2 on the pII.
latest cvs was used.

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