[FFmpeg-user] Turn Off Multi-Threading

James Board jpboard2 at yahoo.com
Wed Jul 31 15:34:30 CEST 2013

>> I'm not using any other filters.  Anyway, does anyone know
>> how to turn off multi-threading?  I tried "-threads 1" and
>> I see see CPU usage at almost 200 percent for ffmpeg

>please post complete command line if you
>want help instead "i did this and that"

Here is an example command
    ffmpeg -i IN.avi -threads 1 -vf select='-between(n, 1, 1000)',setpts=N/FRAME_RATE/TB -c:v ffvhuff -af aselect='-between(n, 1, 1000)',asetpts=N/SR/TB -c:a wmav2 OUT.avi
There are several more between(n, x, y) segments.  I'm thinking that the select filter is using a single thread and
the ffvhuff is using a thread, but that's only a guess.  Also, I typed that command into this email (not cut and paste)
so it's possible I'm off by one or two characters.
Why do I want to do this?  My machine has 6 cores and I have dozens of segments to encode.  I tried
setting -threads 6 for the mpeg4 encoding and it only improved by 2x the overall run time.  However, if I
encode 6 segments at a time on 6 different cores, I think I can get closer to 6x speedup.  But the current 
problem is that's it's spawning so many threads, the process slows to a halt, runs out of memory and that's
Thank you for helping.

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