[mythtv] Audio sync problem with recent CVS build

Terry Barnaby terry1 at beam.ltd.uk
Sun Apr 10 21:25:29 UTC 2005

Ed W wrote:
>>> I've attached the frontend log output in case it helps - the only
>>> thing in there that I noticed that is new is the use of OpenGL vsync
>>> support. Previous ATrpms builds have not had that and so RTC timing
>>> has been used.
>> There's a reason that that defaults to off.
> FYI: I get lots of segfaults with ogl sync.  I haven't had time to debug 
> it, but I did do some backtraces a month or two back.   Actually, for me 
> the RTC is not smooth either - I think it's because the 1024 interval is 
> not perfect for 50Hz PAL.  I did some experimentation with other freqs, 
> but couldn't really make it smooth, have manually patched to force 
> usleep which is "smoother".  I still get occasionaly situations where it 
> jitters, but pausing and unpausing fixes it (ie it's jittering around a 
> frame redraw interval).
> Anyone else got any notes on PAL?
> Ed W
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I think you have interlace sync issues. If you are running MythTv with 
25Hz output frame rate the 50Hz fields can be either in sync or out of
sync. When there is motion in the picture all is smooth when the fields
are in sync. If they go out of sync you will ge a lot of motion jitter.
If you are able to set "Bob" de-interlacing, this may fix the issue for

See my info at:


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