[mythtv-users] Possible XvMC prebuffering issues solution?

[Steven Adeff]

On 11/29/06, Michael Tiller <michael.tiller at gmail.com> wrote:
> On 11/29/06, Alex Halovanic <halovanic at gmail.com> wrote:
> > 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
> Thanks for the info.  I'm outputing to a normal TV-out (composite).  I'm not
> sure what modeline to specify for that?!? Isn't the refresh rate of the NTSC
> signal fixed?  What does changing the modeling do in that case?!?

its fixed, but has some float to it. Plus with tv output chips, they
don't care about the float, so playing with the modeline frequency
will help. I think "720x480_30" should work with the nvidia drivers
for NTSC output without overscan compensation.

-- 
Steve
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