[mythtv-users] PBS HD lip-sync problem solution causes FE failure

[finlay]

I have a Vizio 42 LCD tv that has a problem with some broadcast PBS HD 
programs. The picture seems to briefly freeze every second or so and 
audio is out of sync with the video sometimes for a significant time 
period. Vizio points the finger at PBS and PBS claims the tv is not 
decoding properly. My neighbor with a different set and similar setup 
gets a perfect picture for the same channels. I even went to far as to 
set up my set next to his to see if his antenna signal was better - same 
problem.

After recording the some of the problem programs using mythtv I found 
that I could make the program playback perfectly if I set both "Use 
video as timebase" and "Enable OpenGL vertical sync for timing". I'm not 
sure how this works but it seems to clear up my sync and freeze 
problems. This works fine on one FE but one FE seems to quit every few 
minutes while playing back. Relevent portions of the FE log:

2008-05-22 20:15:36.243 TV: Attempting to change from None to 
WatchingPreRecorded
2008-05-22 20:15:36.988 AFD: Opened codec 0xaeef1dc0, id(MPEG2VIDEO) 
type(Video)
2008-05-22 20:15:36.988 AFD: codec AC3 has 6 channels
2008-05-22 20:15:36.989 AFD: Opened codec 0xb2e95c70, id(AC3) type(Audio)
2008-05-22 20:15:36.998 Opening audio device 'default'. ch 2(2) sr 48000
2008-05-22 20:15:36.998 Opening ALSA audio device 'default'.
2008-05-22 20:15:37.040 mixer unable to find control Master 1
2008-05-22 20:15:37.232 VideoOutputXv: XVideo Adaptor Name: 'NV17 Video 
Texture'
2008-05-22 20:15:37.797 OSD Theme Dimensions W: 640 H: 480
2008-05-22 20:15:38.246 TV: Changing from None to WatchingPreRecorded
2008-05-22 20:15:38.247 The realtime priority setting is not enabled.
2008-05-22 20:15:38.351 OpenGLVideoSync()
2008-05-22 20:15:38.395 Video timing method: SGI OpenGL
2008-05-22 20:19:29.390 NVP: prebuffering pause
2008-05-22 20:19:30.770 NVP: Prebuffer wait timed out 10 times.
2008-05-22 20:19:32.205 NVP: Prebuffer wait timed out 10 times.
2008-05-22 20:19:32.437 
RingBuf(myth://172.20.2.3:6543/1071_20080504200100.mpg): Waited 4.0 
seconds for data to become available...
2008-05-22 20:19:33.657 NVP: Prebuffer wait timed out 10 times.
2008-05-22 20:19:35.091 NVP: Prebuffer wait timed out 10 times.
2008-05-22 20:19:36.437 
RingBuf(myth://172.20.2.3:6543/1071_20080504200100.mpg): Waited 8.0 
seconds for data to become available...
2008-05-22 20:19:36.476 NVP: Prebuffer wait timed out 10 times.
2008-05-22 20:19:36.748 
RingBuf(myth://172.20.2.3:6543/1071_20080504200100.mpg) Error: 
RingBuffer::safe_read(RemoteFile* ...): read failed
2008-05-22 20:19:36.944 ~OpenGLVideoSync() -- begin
2008-05-22 20:19:36.944 ~OpenGLVideoSync() -- middle
2008-05-22 20:19:36.944 ~OpenGLVideoSync() -- end

The FE runs mythbuntu 8.04 and uses an nividia 8500gt. If I unset 
"Enable OpenGL vertical sync for timing" the problem doesn't occur. Any 
ideas how to fix this?

Thanks

John