[mythtv] A/V Sync problem only on some PBS Hi-def shows

DaveD mythtv at guiplot.com
Wed Apr 16 04:12:26 UTC 2008

Steve Wilson wrote:
> --- DaveD <mythtv at guiplot.com> wrote:
>> I've posted this problem a couple of times to the
>> users list, so far no 
>> solutions.  I have bad (unwatchable) A/V sync on
>> some of our 720p HD PBS 
>> shows.  Some shows (Desert Speaks) always work, some
>> shows (e2) never 
>> work. ...
> === message truncated ===
> I had that problem and it was only on the high-def PBS
> channel as the sound would wobble really bad and that
> was the only channel. I either turned on or off
> Aggressive Sound Card buffering under Setup -> General
> and the problem went away. I can't remember which way
> since I built a new system.
Thanks for the response.  I'm not sure I got the right setting, but I 
tried turning TV Settings / Playback / Extra Audio Buffering off and it 
broke ALL 720p playback, not just the problem shows.  Interesting that 
1080i works fine with this setting on or off, as does SD.  I'm wondering 
what, exactly, that setting does.  720p playback works fine on some 
shows with it on but has a completely different symptom (or maybe 
greatly exaggerated) on all shows when it is off.  It's not just sync 
issues when it's off, but playback barely happens; it moves slowly and 
the sound sort of motorboats.  BTW, CPU is < 50% on 720p, no matter what 
the buffering setting is and whether shows play properly or not.  
Horsepower doesn't seem to be the issue.  1080i uses about 65% CPU and 
plays just fine.

I'm still wondering what's causing the extra database connection during 
playback when the problem occurs?


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