[FFmpeg-user] ffmpeg x265 on multi-cpus

Reindl Harald h.reindl at thelounge.net
Mon Apr 10 16:05:51 EEST 2017

Am 10.04.2017 um 14:59 schrieb fred fred:
> hello Harald, it is not a conclusion, it's an expectation ! and a question : for one file from some format to x265, what it the best efficient way to use my 24 cores ? can you contribute ?BestFred

parallelization depends on a lot of things and you always have sharded 
ressources like memory, IO, thread-synchronisation - for one video task 
probably there is just no way to get 24 core to 100% CPU usage

with 3 different parallel tasks each using 8 cores probably better 
because each one has it's own thread-synchronisation and so on

you just can't expect that throwing enough CPU cores on a problem will 
solve it faster the same as 9 girls can't make a child in one month :-)

>      Le Lundi 10 avril 2017 14h54, Reindl Harald <h.reindl at thelounge.net> a écrit :
> Am 10.04.2017 um 14:43 schrieb fred fred:
>> thank you Moritz !
>> anyway, even with -threads 0
>> x265 [info]: Thread pool created using 24 threadsx265
>> I see with top command between 400% - 500% CPU on ffmpeg ...
>> I was expected like 2400% or 24 ffmpeg workers with 100%
> how did you come to the conclusion that parallelization scales magically
> and with no limits? if that would be realistic just throwing enough CPU
> cores on whatever problem would be the soplution - but that is not how
> computers are working

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