[mythtv-users] CPU load when watching TV

Brian Wood beww at beww.org
Sun Dec 13 00:07:18 UTC 2009

On Saturday 12 December 2009 04:54:09 pm lee wrote:
> On Sat, Dec 12, 2009 at 04:23:52PM -0700, Brian Wood wrote:
> Debian testing, amd64, Phenom 965, GeForce GT 240

Is this a combined backend/frontend?

> Xosview shows from 20% to 40% on the four processor cores when
> watching live tv with mythtvfrontend. When not watching (and not much
> else is going on), it shows between 0% and 12%.
> That way, it's hard to tell what load mythtvfrontend actually
> causes. But kaffeine, for example, doesn't cause a load like
> mythtvfrontend does.
> > > > VDPAU will drop your CPU load, assuming the load is from decoding 
> > > > video and not something else.
> How can I tell if VDPAU is used?

You need to:

Have a VDPAU-capable video card (you do)

Use the latest nVidia drivers

Select or create a playback profile that uses VDPAU.

> > > Another observation: In my experience, misconfiguring X can result in 
> > >  heavy CPU load from X, vs. from the MythTV frontend.
> Well, I haven't had this problem yet. But mythtvfrontend as well as
> mythtv-setup make the mouse pointer invisible once it enters the
> window. Is there a way to change that?

I'm not sure why you'd want to do that, Myth swallows the mouse cursor 
intentionally, who wants that on screen when watching TV? Myth is not 
designed for mouse control, it expects you to use a remote.

> > > One other point: Even if the CPU load is high, that's not necessarily a
> > > problem, so long as video playback is still smooth. If the high load is
> > > causing pauses, stuttering, sluggish responses to remote commands,
> > > etc., then it's a real problem.
> >
> > I agree, you buy a CPU to use, not to sit around idle. If you are running
> > 5% all the time you wasted your money.
> The harder the CPU has to work, the more power it consumes. Anyway,
> getting 20--40% load just from watching TV is quite a lot, considering
> the hardware I have. In a way it doesn't really matter since it's
> running smoothly, but it eventually blocks resources that could be
> used for something else instead. And I haven't tried yet to watch
> while other things put some load on the CPU, maybe it won't so smooth
> anymore ...
> Compared to other programs, the load is too high. Maybe I still have a
> problem with the configuration?

I'd expect Myth to use more CPU than Kaffeine, since it's doing a lot more, 
like running a database, but I agree pulling that much on 4 cores is too 

Top will show you what's using what, start with that.

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