I have a BenqW1200 video projector. This projector adds a significant delay on the display of video (perhaps 200 to 300 ms). In general , there are many different video display devices and many input sources which may have inherent sync problems.
Some AV receivers have the ability to add an audio delay, but many folks will be using an ordinary home hifi with no such delay facility.
What would be GREAT, would be if AppleTV could add an audio delay (to all of its outputs). This delay needs to be adjustable whilst viewing and listening to program material so you can easily make the adjustment until the lib-sync issue disappears.
Since different sources and programs also can have their own inherent and different sync delays, it would be useful to be able to name and save differing amounts of delay as preferences.
Although far less common, there are circumstances where the audio might be delayed more than the video, so adding a delay to the video (more usefully presented as a negative delay on the audio) would also be useful.
About +/-3000ms would be ideal and solve just about everyones lip-sync problems!
My BenQW1200 project appears to suffer with about 300ms of video delay, that's too much for some AV receivers to cope with.
As a final bells and whistles approach the iPhone and Mac both have ability to watch and listen (i.e. they have microphone and camera) An app that could present a flashing/ticking metronome andwatch and listen to the TV/Projector/Hifi and then measure the delay and configure the Apple TV to set the correct compensating delay would be amazing!
-- Michael Ellis