On Sat, 29 Jan 2011 11:22:19 -0800, David Nebenzahl wrote:

On 1/29/2011 11:03 AM Fred McKenzie spake thus:

In article m,
David Nebenzahl wrote:

Question is about DTV sound synchronization in the United States (the
only DTV I have any experience of). Seems to me that since it replaced
analog, the synchronization of sound to picture is, at best, variable,
and sometimes it's absolutely ****-poor.

I'm surprised there aren't more complaints about this. Two HD
television sets connected to the same antenna system can have an audio
difference between the two. Weak signal conditions seem to be the
worst, with very obvious delay just before the picture breaks up.

There are probably several reasons for the discrepancy, but there is no
excuse. Audio-video sync shouldn't be a problem with a digital system,
but the current HD system is obviously weak in this area. Perhaps
there is a delay due to the need for error correction when signals are
poor. If so, why isn't one delayed so both audio and video are
presented at the same time? It might take some extra memory to hold
delayed data, and maybe an algorithm to shed an occasional video frame.
Or is it the other way around, with audio leading the video?

Judging by the behavior of my system (set-top DTV box, Zenith DTT901),
I'd say that the audio is simply sacrificed for the sake of displaying
video. When there's a marginal signal coming in, the video will continue
to be displayed, albeit with some break-up and possible freezing, while
the audio simply drops out.

Newest Sci-Atlanta DTVHD-DVR, TWC here. Don't notice a lot of sync
problems. Being a musician I would notice even a few milliseconds.

More problems with picture fizzle-out accompanied by audio drops and buzz
on HD channels. Signal tested recently. Found to be high-normal in the HD
range. Nothing to bitch about except when Discovery-HD fizzed and buzzed
every 10 seconds. A new DVR fixed that.



--
Live Fast, Die Young and Leave a Pretty Corpse