[mythtv] Need help diagnosing slow XvMC problem

Rob R rob.r at plutohome.com
Sat Jan 14 18:39:14 UTC 2006

What does the console output/frontend log show while it's playing in slow

I get that exact behavior when "extra audio buffering" is disabled.   My log
shows a ton of "prebuffering pauses".  With extra audio buffering enabled,
it works correctly *most* of the time but I haven't been able to totally
solve it.

-----Original Message-----
From: mythtv-dev-bounces at mythtv.org [mailto:mythtv-dev-bounces at mythtv.org]
On Behalf Of Jerry Rubinow
Sent: Tuesday, January 10, 2006 5:10 PM
To: mythtv-dev at mythtv.org
Subject: [mythtv] Need help diagnosing slow XvMC problem

When I play back content using XvMC, it plays back slower than real
time, both HD and SD, cpu is not maxed out.  I haven't been able to
figure out why, but it seems like it might be a Myth problem (but
maybe not?).

Here's what I have:

Separate front end/back end.  Front end is a 2.8Ghz P4 with a GeForce 5200
Running FC4 setup per Jarod's guide.
Myth SVN as of about a week ago.
Nvidia driver version 7667.

Here's what I've tried:

Tried with and without OpenGL sync.
Tried Various Nvidia drivers up the the current 81xx.
Tried playing same video files over nfs using mplayer with xvmc and
they have no problem, so that seems to eliminate disk, network, or
graphics card bandwidth problems.
No deinterlacing going on.

When it plays inside myth, everything is slow-mo.  Not a stuttering
problem.  CPU usage is down below 20%.  If I turn off XvMC, SD plays
back fine, but HD maxes out the CPU.  However, I hadn't been
optimizing for P4 (d'oh), so that can probably be improved somewhat. 
But if I could get the XvMC thing working that would be a much better
solution, since I'd have room to spare for deinterlacing and whatnot.

All suggestions welcome.  I'll post whatever logs would be most
helpful to diagnose this, just let me know which ones.

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