There are some devices out there which claim to lock the audio/video
sync from beginning to end but they require a totally digital plant and
path in between. Any analog device in the chain breaks the lock. It will
be years before all analog equipment is removed from the chain/path.
Richard P.
Unfortunately, the digital lip sync issue is more complicated than it
would appear. In analog transmissions, the video and audio get processed
and transmitted at the same rates. With digital, video takes longer to
process than audio, and the delay is compensated for by most responsible
editors/engineers. But as soon as it hits the transmitter, a whole new
set of problems are introduced. Most broadcast transmissions are via
satellite and the number of hops that a signal takes is variable. Each
hop creates delays, usually with the video...
This suggests that the designers of the DTV formats were not thinking
about this problem at the time the standard was developed.
The multiple hop/transmission path problem was thought of when IP was
designed. The Internet sends data in packets and there is nothing in the
system that assures all packets in a stream are sent by the same route or
even that all the sent packets arrive. So packets are numbered
sequentially and when they get to your computer they are put in proper
order. Missing packets may be requested and resent (or not).
Looks like DTV is based on a more optimistic view of the world.
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