[mythtv-users] Occasional jerkiness during DVD playback

Juergen Botz jurgen at botz.org
Sat Jun 23 21:37:15 UTC 2007


Brian Wood wrote:
>> But when playing DVDs, once in a while, usually on scene changes
>> where the whole field is different, I get a few seconds of jerky
>> video and stuttering sound.
> 
> If you are getting your "20%" CPU load number from top, remember that it
> is an average, and the peak usage might be well in excess of that.

Yeah... right after I sent that message I played a DVD and watched
top carefully and noticed something peculiar...

The CPU usage seems to follow a kind of reverse sawtooth pattern,
I.e. it's low for a while (15%-20%) then jumps up to something like
60% around the time of the jerkiness.  Then it slowly goes back
down.

Looks like a bug, either in in Mythtv or in the XvMC library or
openchrome driver.

> How fast is your CPU?

It's an EPIA SP 13000 board... so the CPU is slow, maybe equivalent
to a P3 800 at most.  Before I got XvMC working video was frequently
jerky and the CPU was usually at 70-80%.

> I'd start by playing the DVD outside of Myth,

I'll try mplayer (if I can verify that it works with XvMC)... that
way I can eliminate or verify Mythtv as being the source of the
problem.

> with as little else
> running as possible, and see if you get the same problem. If it's OK,
> and re-appears as you add more running apps, you might need to think
> about a lighter-weight window manager (or no window manager) or
> otherwise reducing resource load.

There's nothing other than Mythtv using resources on that box right now. 
  I run mythfrontend directly from xinit.

:j




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