Originally Posted by TVOD
I was thinking that too, but display delay stays consistent with a given setting. Rather than signatures, it would be nice with handshaking if the display conveyed its delay.
It seems to me that display lag is dependent both on the settings of the display and the format of the content. I could be mistaken, but I seem to need different amounts of audio delay depending on whether the source is 480p, 720p, 1080i, or 1080p. I think I have also noticed it more with higher native framerates (e.g. 60 fps) than with lower ones (e.g. 24 fps) or possibly the other way around. This could just be issues with the lip sync in the source but, judging from the way my screen goes black for about a half second every time I switch from a 720p channel to a 1080i channel, I suspect that my TV has a noticeable amount of display lag in it and that the lag might just vary a good bit depending on how much upscaling and/or de-interlacing the TV has to do for a given format, even with the same TV settings.
The issue is that, again, we are separating the audio from the video when we use a surround sound system. And, as things are now, the audio isn't even being sent to the TV, so it is not possible to do another analysis after the video processing is complete but before the image is displayed. It seems there are three possible solutions for this...
1) Start passing the audio to the display before it is sent to the speakers and do one final analysis of lip sync in the TV after the video processing is done, but before the image is displayed. Adjust the lip sync one last time and use the audio return channel to tell the AVR when to play the audio. For this to work TV's would have to be compatible with all of the same audio formats used by your AVR in order to prevent your audio from being gimped. This would add to the cost of TV's since they would have to pay the licensing for all of those formats in order to ensure compatibility.
2) Do a better job of establishing and holding to a specific amount of display lag in a particular TV, regardless of the TV settings and the format of the content. Once you know what the highest amount of display lag will be for a given display for the worst possible combination of TV settings and content format, set that as the universal display lag and buffer everything else to match that. Once you have a constant display lag, all you would need to do is have the display report that to the AVR so it can automatically delay the audio by the correct amount, as TVOD suggested. This would ensure that whatever comes in, goes out as far as lip sync is involved. So, if the Blu-Ray player/AVR can do the finger print analysis and autocorrect the lip sync before the video signal leaves the AVR on the way to the display then everything should be in sync. The only place where you might need to disable this feature would be for gaming, since reduced lag is more important than proper AV-sync.
3) Stop using a TV to process video. Use an external video processor that handles all of the video processing and the lip syncing in coordination with the AVR. At this point your TV is nothing more than a monitor. The problem with this solution is the cost of the additional video processor.
would be the cheapest for the consumer. Solution #1
is probably unlikely any time soon, but may come about as a result of streaming and the fact that they want the TV's to be able to use their own built-in streaming apps, which means the TV's have to support all of those audio formats for an optimal experience anyways. Solution #3
is the most expensive, but it's main advantage is that you can pretty much do that with today's equipment if you are willing to pay for it.