[mythtv-users] ffmpeg and multiple CPUs. Was: Should I be switching to 0.21?
Tom Dexter
digitalaudiorock at gmail.com
Mon Apr 14 20:12:40 UTC 2008
On Mon, Apr 14, 2008 at 3:58 PM, Jay R. Ashworth <jra at baylink.com> wrote:
> On Mon, Apr 14, 2008 at 01:07:39PM -0400, Tom Dexter wrote:
> > However...and this is the interesting part...if I use ffmpeg but
> > switch the number of CPUs to 1 instead of 2 the performance of the two
> > is virtually identical. It seems that, at least with my
> > hyper-threaded 3 Ghz P4, ffmpeg works much better with a single core.
>
> Since, with Hyperthreading, you only actually *have* one processor, I
> would expect it even to be a little more efficient with 1 instead of 2,
> since you save the labor of partitioning the task.
>
> Cheers,
> -- jra
> --
> Jay R. Ashworth Baylink jra at baylink.com
> Designer The Things I Think RFC 2100
> Ashworth & Associates http://baylink.pitas.com '87 e24
> St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274
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Actually after re-reading your post I think you misunderstood my
original post there. When I referred to the performance being
'virtually identical', I meant the performance of ffmpeg with one cpu
was the same as the performance I was getting with libmpeg2.
The difference in performance between ffmpeg with 2 cpus and ffmpeg
with 1 was an improvement from 50% cpu to 30%...so the overhead
incurred by all the partitioning is apparently huge.
Tom
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