Audio and Video don’t match up (out of synch) in High Definition

Response courtesy of Doug Finck (WPXT, WPME) - explanation of "out of synch" voice issues I pointed out to them by writing to the station. Keep in mind that this is a technical explanation but the bottom line is that when the audio and video is out of synch, it is not your television, it is the broadcaster. So your best bet is to call the station to let them know.

We have a digital processor that feeds the encoder. In the
digital processor we have a number of cards that upconvert non-high definition
signals, or pass through legitimate high definition signals, depending upon what
we are feeding.

Our engineers check out the system and we were off by 9 frames. In other words, our audio was 9 frames ahead of our video (the sound was coming before the mouths were moving). Given the fact that there are 30 frames per second, we were off by a about a third of a second. I appreciate you bringing it to our attention. We're a little baffled about how it could have gotten "out of sync."

We haven't added any new equipment or made any adjustments and it was perfectly sync-ed up the last time we tested. The one thing we wonder about is the PSIP data. That information is injected into our signal (as required by law) but we don't control it. We pay an outside company to create and deliver the data
stream to us, then we inject it into our system.

If they added (or deleted) a large amount of data, that may have had an impact on the timing of the audio and video.My question to our engineers is, "why did we not observe what you observed…the fact that the sound and the lips were out of
sync?" The answer is interesting.

We are currently broadcasting in both analog and digital. Each of our control rooms has a video monitor for the respective signals. The nature of analog is that whatever we do is seen immediately. In the digital world, however, everything is delayed by a few seconds. We fed our analog signal into the digital processor and it takes a second or two to convert the 525i, 4:3 analog image, into a 1080i, 16:9
digital image.

That delay causes both audio and video digital signals to be "behind" our analog signal. When the Master Control operators watch our monitors, they see both signals, but they only listen to the analog. The digital audio is several seconds behind the analog. The solution seems simply, watch and listen in digital to see if the sound and mouth movement is in sync. The problem with that is the delay would cause a problem whenever we went to a commercial, had to superimpose some information, or tried to start a new program. Because we would be watching a delayed feed, we would start the next element based on what we were watching…but that would have ended a few seconds before we saw it…so by watching the delayed digital feed, we would always have 2-3 seconds of black silence between any ad, show or event. The long-term answer is to say goodbye to analog. Once we are in a pure digital realm, we will no longer be upconverting (which is where the delay occurs) and the digital feed will be in "real time" and we can monitor and switch off of that. In the meantime, we'll keep an eye on things and I would ask that you do the same…and keep us honest!One final request.

We have adjusted the timing so everything is in sync right now. That's fine
because everything we're broadcasting is being upconverted. Our next
network high definition program will be on Sunday night. Do me a favor,
take a look and make sure that the network high definition is in sync. It
doesn't get converted and I hope that the adjustments we made to the processor
don't have any impact on the network high definition broadcasts! Thanks and have great weekend,