[mythtv-users] How to minimize CPU usage

Jerry Rubinow jerrymr at gmail.com
Sat Jan 28 22:55:07 UTC 2006


On 1/28/06, Kevin Kuphal <kuphal at dls.net> wrote:
> Jerry Rubinow wrote:
> > I'm running myth with separate front/back end computers.  The frontend
> > is a 2.8GHz P4 with 512MB ram, trying to display 720p HD, but I'm
> > maxing out the CPU - myth ~65+%, X around 30+%.  The video is at times
> > choppy when there's a lot of stuff changing in the frame.  What can I
> > do to reduce CPU usage?
> >
> > Here's what I've done so far:
> > -compiled myth with --enable-proc-opt (using SVN from less than a week ago)
> > -using ratpoison for window manager
> > -not using any deinterlacing
> >
> > Note: XvMC is not an option.
> >
> > I'm running FC4.
> >
> > mythfrontend -v playback reports that it's using Xvideo, format I420,
> > using realtime priority, video timing method: RTC (glx vsync not
> > supported in my driver).  Then I get a lot of video ahead of audio
> > dropping frames messages, and then a lot of audio ahead of video
> > messages.
> >
> > /proc/meminfo says there's 100MB free while running myth, so I guess
> > it's not swapping.
> >
> > What might be causing the high CPU?  I've read about people with
> > 2.4Ghz P4s not having a problem with HD, so it seems like there should
> > be something I can do.  Would compiling my own kernel help?  With what
> > options?  Anything else I can try first?
> >
> Try using libmpeg2 for your playback.  I'd suggest looking into
> hyperthreading support in your kernel to see if it is enabled.  I
> believe this means using an SMP kernel.  I'm not sure if that will make
> a difference but it might.  And lastly, your video card and drivers do
> help alot.  I've struggled with my choice of ATI on one of my frontends
> and as I'm moving to HD, I'm biting the bullet and spending the $40 on
> an Nvidia FX card and it will be one of the best $40 I've spent on my
> system as it means HD playback on my 2.4ghz Celeron with XvMC.
>
> Kevin

Sorry, I left out that I'm using libmpeg2.  Hyperthreading - hmm,
unfortunately I just checked and my CPU doesn't support hyperthreading
(it's a 533MHz bus 2.8GHz P4).  I tried going the FX 5200 route, only
to discover that I I can't achieve the transfer speeds I need over PCI
(my motherboard only has two slots, both PCI).  1280x720x(24 or 32)
bits, 30 frames a second (or 60, even worse) - PCI's max throughput is
600 to 700 Mbits/sec.  I tried XvMC on the 5200 but it was always a
bit glitchy.  The onboard graphics is AGP, but now instead of being
limited by bus speed, it's by CPU speed.  Very frustrating, since it's
soooo close to working properly.

-Jerry


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