Originally Posted by SyncSyncHalt
There are others here with far more knowledge and experience than I, but, to provide one user's experience....
In terms of actual disc playing (DVD and Blu-ray only since I have no UHDs yet), I have, as, apparently many others, zero problems.
The primary issue I have experienced has been, again as reported by others, loss of synchronization at various times. These seem sporadic, but I've seen it with both disc play and network (local DLNA) streaming. I originally thought this was only related to the HDMI input, but, alas, it appears otherwise as well. It only seems to occur after an extended period of play (essentially the whole movie; happened a couple of nights ago at the end of Ex Machina).
. . . .
What have you done to verify the correctness of A/V Sync in your setup?
The reason I ask is that MOST movies have some sync error -- and it usually varies by scenes. There are lots of reasons for this, but it often goes back to the way the original theatrical release was made.
Now most of the time, such inherent sync error is small enough that you won't notice it. But if you've got some sync error in your setup, and if it happens to be in the same direction, the combo can make the inherent error in the movie noticeable. And since the inherent error in the movie likely varies by scenes, the error will become noticeable only in some scenes. Indeed in some scenes, the error in the movie might counter the error in your setup.
So you want to get sync "right" in your setup, which maximizes the chances that the (usually small) inherent error in the movies you watch won't be noticeable -- regardless of the direction.
To do that, you have to test with content of known sync "correctness". Which means a calibration disc. There are good A/V Sync charts on Disney's "WOW World of Wonder", Blu-ray, and on "Spears & Munsil v2", Blu-ray.
Sync error happens due to video processing time. (Audio processing takes no time at all in comparison.) What THIS means is that when checking/adjusting A/V Sync in your setup you need to be sure you are sending the same type of video down your video chain that you'll actually be using when viewing.
For example, it's actually quite common for a TV to take more time to process /24 video than /60 video. And it wouldn't be surprising for a TV to take more time processing 4K video than 1080p video. So if you are going to use 4K/24 video to your TV for movie watching, then that's also what you want to use when checking/adjusting A/V Sync with the calibration disc.