[mythtv-users] Possible XvMC prebuffering issues solution?

[Alex Halovanic]

Just posting this, hoping it will help someone else :)
I was having lots of problems with XvMC playback of HD streams from my
HDHomerun, with prebuffering pauses causing skips in sound and
messages that the video was 4 or 5 frames ahead of the audio ever few
seconds.  After trying every possible combination of settings possible
(and realizing that the problem also existed in Xine), I think I've
finally found the real solution.  I had been using a modeline with a
vertical refresh of 59.94 hz in an attempt to keep it as close to the
framerate of the videos and official specs.  Increasing this to about
60.92 hz (That's a dotclock of 74.9 for my 720p modeline) has gotten
rid of nearly all of the pauses.  There's still some prebuffering for
a few seconds after the channel is tuned, and when the program
changes, especially when one commercial changes to another, but then
it will "settle down" for the program, even when skipping about in it.
 Sometimes there are a couple of messages that the video is now ahead
of the audio, but these too go away within a few seconds.  Total cpu
usage for my wimpy little machine: 50-60%!
Note: I take no responsibility if you try this and the higher refresh
rate causes your tv to burst into flames

My set-up:
1.6 ghz Duron KM400, 512 mb RAM
Geforce 5200 FX, vga thru component converter at 720p to cheap Walmart Sanyo CRT
Nvidia binary driver 1.0-9625
Modeline "720p" 74.9 1144 1320 1376 1650 696 722 728 750 +hsync +vsync
(actually 1144x696, adjusted for overscan)
Myth SVN 11828 compiled for athlon-xp
audio output device-ALSA:default, deinterlace Bob2x, Use Realtime
Priority Threads, Extra Audio Buffering, UseChromaKeyOSD,
UseXvMCForHDOnly