[FFmpeg-user] -threads 1 seems not work
Cecil at decebal.nl
Mon Sep 12 16:00:03 EEST 2022
Paul B Mahol <onemda at gmail.com> writes:
> On 9/12/22, Cecil Westerhof via ffmpeg-user <ffmpeg-user at ffmpeg.org> wrote:
>> Paul B Mahol <onemda at gmail.com> writes:
>>> On 9/12/22, Cecil Westerhof via ffmpeg-user <ffmpeg-user at ffmpeg.org>
>>>> For a certain conversion I use '-threads 1'. As I understand it ffmpeg
>>>> should then only use one CPU. I see that the CPU usage is lower as
>>>> without this parameter, but it goes up to 180%. So clearly it is using
>>>> at least two CPU's.
>>>> Or am I understanding this parameter wrongly?
>>>> I am using ffmpeg version 4.3.4-0+deb11u1. (Debian always lags a
>>>> little bit behind to be more stable.)
>>> threads can be used for input decoding, output encoding and filtering.
>>> You need to use threads = 1 for all 3 of them.
>> I see:
>> But nothing for input decoding and output decoding.
>> By the way: does this mean that ffmpeg can always use 4 CPU's?
>> (input, output, filtering and complex filtering)
> No, ffmpeg may use sometimes only 1 or sometimes all available CPUs.
> That depends on many factors.
OK. But that still means it can use three CPU's if it wants to if I
have set all three to one?
> -threads is both input and output option.
Senior Software Engineer
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