[FFmpeg-user] maximum CPU utilization with ffmpeg and libx264

Reindl Harald h.reindl at thelounge.net
Tue Mar 22 08:53:41 CET 2011

Am 22.03.2011 02:41, schrieb George D Pylant III:

> My understanding is that these cores support hyperthreading allowing two threads
> to run simultaneously on each core. 

yes and no
since it is not a full core / cpu you can not expect wonders
HT is using on non-ht-cpus wasted parts of the die (to say it simple)

> So why doesn't ffmpeg/libx264 use all "sixteen" cores, i.e. two threads 
> per core like handbrakecli does?  -

because you can not scale linear with more cpus and
not every operation can benefit from multithreading

who tells you that the 100% cpu from "handbrakecli" is not wasted
for useless thread-synchronisation, try it and reduce the software
to use only 8 threads, maybe it gets slightly faster than with 16


Mit besten Grüßen, Reindl Harald
the lounge interactive design GmbH
A-1060 Vienna, Hofmühlgasse 17
CTO / software-development / cms-solutions
p: +43 (1) 595 3999 33, m: +43 (676) 40 221 40
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