[FFmpeg-user] -threads 1 seems not work

[Cecil Westerhof]

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>
>>> wrote:
>>>> 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:
>>     -filter_threads
>>     -filter_complex_threads
>>
>> 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.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof