Option to run 2 conversions simultaneously

[luttrell1962]

On a 4 core machine ffmpeg only uses about utilizes 25-30% of the cpu's. I've looked at recompiling with pthreads, but that does not help. If we could run 2 conversions at the same time we could better utilize the power of a 4 core machine.

[gEd]

well if you are rolling your own ffmpeg you know a heck of a lot more than me so this is a long shot ...but does your ffmpeg command line use -threads n ??

processexplorer can verify the actual number of threads that are running.

[luttrell1962]

Yes I have threads 8 the max. I've tried to look at ffmpeg documentation to see if I can compile one that supports more threads but have not come across anything on the net yet that references that.

[gEd]

I doubt that you would actually want more than 2 threads running per core as you would run into cache contention and context switching overhead. If your cpu load is only 30% with 8 threads running, I would venture that you have contention elsewhere (i/o or ram) and increasing threads won't help.

[luttrell1962]

I can run 3 ffmpeg sessions at the same time. Then I get 75% utilization, no slow down in framerate conversions either. So my computer can handle at least 24 threads through ffmpeg.

My friends computer at 8 threads hits 80% but it's just a dual core 512meg cache 3ghz