[mythtv-users] video/audio sync

[Brian Wood]

Robert Koblish wrote:

> I cannot believe when I see my local TV station broadcast 
> locally-originated programming (the evening news) out of sync. Remote 
> pickups can be particularly bad. OTA analog NTSC. Don't blame it all on 
> your cable operator.

Believe it.

One of the biggest causes of that sort of thing is running the video 
through a frame synchronizer without running the audio through a delay 
line that equals the video delay through the F/S. Since any remote 
source has to be frame-synced to be in time with the station facility 
this makes remote broadcasts more susceptible to this problem, as you 
have noticed.

Of course multiple frame syncs make the problem even worse. Digital 
effects units, keyers and even the units that put the "bug" in the lower 
right can cause this problem as well.

It's more of a problem in the smaller markets, where they are less 
likely to have the budget for the proper gear, and, frankly, less 
competent technical people, and less observant audiences.

Generally the problem will show up as late video, because video is 
usually more processed than the audio.

beww