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Sound sync problems

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Don Stauffer

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Oct 22, 2009, 10:00:36 AM10/22/09
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My wife worries a lot about maintaining the sound sync in her desktop
video work. But then I show her the stuff I watch on broadcast (and
cable) TV and she thinks it is ridiculous that folks put that stuff out.

My set has a setting for delay, but it is useless. The setting has to
change for each channel, and, for instance, on a news broadcast, the
tape segments seem to have a different delay for each tape segment
(which of course does not match the live "talking heads".

Was this sound sync problem not anticipated?

What would it take to actually sync the sound and video? Couldn't some
sort of time code be written into both the sound and video so that
playback could automatically sync things up?

No Spam

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Oct 22, 2009, 2:19:11 PM10/22/09
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Most broadcasters and cable networks are able to keep the lipsync issue
in check. In fact, there is a timestamp (timecode) on each packet of
video and audio for the decoder to utilize. The real main issue is that
cable and DBS companies re-encode or bit rate shape the video without
much care to the timestamps in the pass-though audio and it's effect on
lipsync as they claim it's "close enough".

Other issues are that some older motorola STB ignore the PTS/DTS
timestamp on the audio. Other cheap asian decoders have the same issue
and need to be reset every few hours to bring the lipsync back as the
audio and video decoder are working without looking at the reference
clock.

With the exception of breaking news, no producer will let their
production release with bad lipsync. It's very easy to resolve in the
edit suite. No network will let such an issue leave their facility. They
hire QC people to watch for just this type of problem. The problem you
seek is really in the distribution network and bandwidth greedy program
distributors.

Don Stauffer

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Oct 23, 2009, 11:09:48 AM10/23/09
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No Spam wrote:
>
> With the exception of breaking news, no producer will let their
> production release with bad lipsync. It's very easy to resolve in the
> edit suite. No network will let such an issue leave their facility. They
> hire QC people to watch for just this type of problem. The problem you
> seek is really in the distribution network and bandwidth greedy program
> distributors.
>
I do notice that it is primarily local news and not network news. And,
of course the cable is terrible.
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