[mythtv-users] 0.19, XvMC, and Prebuffer pause

[Joe Silver]

I'm a little late to this thread, but I've got similar issues here and
wanted to share my experiences with the list.  Since 0.19 I've been trying
to playback and watch live more hdtv programs.  My setup is:

FC3 per Jarod's Guide
Most recent Myth 0.19 from ATRPMS
P4 2.6 GHz
Soyo P4RC350 Motherboard, onboard video disabled.
512 MB
HD3000 QAM capture of 1080i
Kernel 2.6.12-1.1381_FC3
NVidia FX5200 driver 7676
Standard XVMC playback enabled
1280x768 LCD Monitor connected via VGA

HDTV playback isn't possible without XVMC (CPU ~99%), but since mythtv 0.19,
its acceptable to use it now that the OSD doesn't flicker all over (CPU
~45-50%).

I've varied all the tv playback settings I could think of and the only thing
I have found that helps the issue of many
NVP: prebuffering pause
followed by
WriteAudio: buffer underrun
and so on...

is to disable deinterlacing.  It doesn't matter which form of deinterlacing
I use, kernel, bob, linear, one field, whatever, I still get the audio
buffer underruns which are clearly audible and noticeable during playback as
audio glitches.  CPU is always 45-50% with or without deinterlacing.  With
deinterlacing disabled, the playback is perfect, and the
prebuffering/underrun messages are absent from the log, but since I have a
progressive display, interlacing artifacts are present (and obnoxious for a
stickler like me).  I think someone else mentioned this but I've found this
is consistent for live tv and for recordings, whether or not the recording
is finished or not.  I tried to carefully check the playback of a recorded
program, and find that the underruns don't happen at the same place
everytime.  When I disable deinterlacing they are gone.  These are the
experiences for 1080i source material.

For 720p source material, I find something strange.  For live TV, when
deinterlacing is enabled, playback is smooth and perfect, and I do not see
prebuffering pauses and no underruns/no audio glitches.  When it's disabled,
I get both prebuffering pauses and underruns/audio glitches.  For recorded
720p playback, I find pretty much the opposite:  deinterlacing enabled,
prebuffering pauses/underruns/audio glitches; deinterlacing disabled,
perfect playback, but lots of prebuffering pauses and no underruns/audio
glitches.  Strange behavior indeed.
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