[FFmpeg-user] -threads option has no effect

Claudiu Rad-Lohanel jazzman at misalpina.net
Tue Aug 12 14:40:04 CEST 2014

On 8/12/2014 2:23 PM, Carl Eugen Hoyos wrote:
> Claudiu Rad-Lohanel <jazzman <at> misalpina.net> writes:
>> ffmpeg -i <my file.avi> -threads <number of threads> ... <output>
> This is of course not sufficient since for decoding,
> threads also defaults to the number of cores and
> decoding can be the more time-consuming factor
> (depending on codecs and settings):
> $ ffmpeg -threads 1 -i input -threads 1 ... output
> Carl Eugen
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> ffmpeg-user at ffmpeg.org
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this is indeed arguable, because usually the encoding process is 
significantly more consuming than decoding, but yes, a good point: you 
want to make sure you use the minimum number of cores? apply -threads 1 
for both input AND output.
however i am inclined to think that decoder/encoder are independent in 
this matter, thus, one thread would go for decoding, one for encoding, 
thus, at the minimum you are still using two cores and in the worst case 
scenario, if the CPU requirement is about the same, you are eating a 
whole dual-core CPU and can't do anything about it.
please correct me if i'm wrong.


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