Not that she has to, but my wife does a decent job of reading lips. And for some reason she's always looking at the actor's lips on TV and audio sync is always a problem. It varies from source to source & from program to program. It was a minor issue when we had a 27" CRT TV. But as TV's have gotten larger the lip movements have become larger & therefore more noticeable.
When we got our first HDTV I had to get a new A/V receiver with audio delay in order to get things reasonable correct & I only had to change the delay once in a while. We recently got a bigger TV & the delay never seemed to be enough, so I got a new AVR which goes up to a 400ms delay. Now matter what I set the delay to it's never correct for her. If I start with a 100ms delay & increase in 10 or 20ms steps to 150ms it makes things worse. If I decrease down to 50ms it also makes things worse.
The TV does not have an auto lip sync function but the AVR does. But I have tried all possible setting combinations. Have also tried HDMI to AVR to TV, HDMI to TV but SPDIF to AVR, and also using just the TV speakers. Nothing gets it right for her. It's difficult to comprehend that she can be so sensitive to sync when I don't notice any problem unless the delay is way far off.
Is it possible that sync can vary from scene to scene in a TV program or movie? IOW maybe a series of shots have the audio delayed 10ms and another series of shots has the audio delayed 30ms. And when the scenes are cut & spliced together in an interleaved pattern the delay keeps changing from 10 to 30 to 10 to 30, etc. Does that or can that happen?