[mythtv] A/V Sync problem only on some PBS Hi-def shows
R. G. Newbury
newbury at mandamus.org
Wed Apr 16 16:23:27 UTC 2008
DaveD 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. They are all recorded over cable (QAM), some times with a
> PC-HD3000, some times with a Fusion 5 Gold. Same problem in playback on
> two different systems that have no trouble with any 1080i shows from
> commercial stations. One user on the list replied that he has identical
> problems. He also has Comcast in Seattle. He noticed changing frame
> rates when watching problem shows in Mplayer. I got an answer from the
> engineer at our PBS station who said all their shows use the same
> compression algorithm. I have had this problem for some time. It seems
> to have started in between Myth upgrades, while using a stable version
> (0.20, I think) so I assume it's something that has changed in the way
> they are broadcast and not due to any changes in Myth, although I can't
> be certain of that. No upgrade (0.21 trunk or 0.21 release) has
> affected it. All shows play fine in Mplayer and Xine.
> Any ideas?
I noticed this last night while watching an HD recording of "Emma" on
Masterpiece Theatre. In the course of fiddling with some things earlier,
I had unchecked "Use Video as Timebase" in Settings->Settings
->TV-Settings->Playback.
Without that set, the Audio was up to 2 seconds out of sync. With it
checked the Audio was spot on the PBS HD programs. I did not notice it
on recordings of "Dexter" or "Lost", both of which are broadcast as
1080i while PBS is 720p...which may have something to do with it..
Geoff
I did some checking later and interestingly, this defect was only
noticeable on
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