[FFmpeg-user] ffmpeg x265 on multi-cpus

Carl Eugen Hoyos ceffmpeg at gmail.com
Fri Apr 14 08:40:01 EEST 2017

2017-04-10 14:43 GMT+02:00 fred fred <fr1d_mail-at-yahoo.fr at ffmpeg.org>:

> anyway, even with -threads 0
> x265 [info]: Thread pool created using 24 threadsx265 [info]: Slices                              : 1x265 [info]: frame threads / pool features       : 5 / wpp(5 rows)
> I see with top command between 400% - 500% CPU on ffmpeg ...

> I was expected like 2400% or 24 ffmpeg workers with 100%

It is possible to change the x265 code so that you get something like
2400% - the disadvantage is that encoding takes longer in that case
compared to the 500% you see now;-(

You have to understand that for "real" (not intra-only) codecs
performance cannot be increased by simply adding more cpu cores.

> what it the best efficient way to use my 24 cores ?

That is easy to answer: If there are no other bottlenecks (harddisk
and memory come to mind), starting 24 transcoding processes
with -threads 1 each is most efficient.

Carl Eugen

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