Re: Does Video Processing Always Take Longer Than Audio?

Del Mibbler wrote:

Unfortunately, people are much more sensitive to errors where video
lags audio since that is the reverse of our normal experience. There
are sveral "standards for what is an acceptable range of error, but
one common one is that audio should not lead video by more than 15 ms
or lag it by more than 45 ms.

The OP can learn more than he probably cares to know about the topic
at http://www.lipfix.com/cln_000001_lip_sync_error_.html. One
paragraph in the article, "Solving Lip-Sync Problems in a Hybrid
Analog-Digital Television Plant" by Steven A. Smith provides a sad
commentary on the state of the art when it was written (there's no
date):

"Today, not a single vendor builds a production switcher that
compensates for audio delay. Nor is there any test and measurement
equipment available to evaluate sync errors in a hybrid broadcast
plant. Our engineers note errors simply by looking at lips. We use a
high resolution monitor, wait for the right shot, and eyeball the
delay. Not very high-tech, but we've found no better measurement
tool."

HDMI 1.3 includes lip-sync correction. How it is implemented, I don't
know. I have had a lip-sync problems once in over a year of digital/HD
viewing. It was a problem on the network end of the NBC nightly news.
.

Relevant Pages

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