Originally Posted by wxman
Do you have yours setup with audio from player to AVR and video from player to tv using 2 HDMI cables? If you do, then SDR, HDR and DV should all have the exact same offset. Mine are all 80 ms, and not one format has lip sync issues. The fact that I do not have issues tells me it is not a disc issue with regards to lip sync, but either an AVR or player issue and I have a 5 year old cheap Onkyo 5.1 AVR.
That simply isn't the case here. Lionsgate and Paramount DV discs behave differently than Warner discs. The former cause the TV to freak out and have more input lag. It really doesn't matter if you split the audio and video or if you have them go straight through the receiver.
It happened with the X700, it happens with the UB820. I've seen people mention it happens with the LG players as well. There's a lot of evidence that the TV behaves differently depending on how the source is authored.
Dolby Vision has several profiles. More specifically, there's "Full Enhancement Layer" and "Minimum Enhancement Layer". Full Enhancement Layer is a diff against the 10bit HDR10 base layer to reconstruct a full 12bit output with dynamic metadata. MEL is really a very minimum DV layer that allows for dynamic metadata, but isn't enough information to reconstruct full 12 bit output. The difference in data rates is rather large. MEL is only around 60kbps while FEL is 5-7mbps. MEL was created to allow a software upgrade solution for TVs and not require specific hardware. This is also what they refer to as a the "low latency" dolby vision profile. Latency, input lag, I think you can see where I'm going with this.
FEL is original profile. Our TVs support FEL since they are chipset based.
So, here's the fun bit. MEL discs (like The Matrix) are the ones that play with no lipsync issues. FEL discs (Braveheart) are the ones that require delay compensation. All that tracks too. FEL is a much more intensive operation. Our TVs can do it, but it takes more processing. The metadata is much higher bitrate and you are converting from 10bit to 12 bit on top of the dynamic metadata. MEL discs don't include the 10bit to 12bit diff data, it's simply including scene by scene metadata. The interesting thing is the TV is apparently aware of the processing overhead because if you bypass the AVR altogether, audio plays out of the TV in sync with the video. Also, if you force output to be 1080p rather than 4k (but keep BT.2020 and DV), suddenly everything is in sync again. Again, the TV has less processing to do, so input lag is lower and AV sync is maintained.
So, speculation time. If I were to guess, Oppo isn't properly identifying if a display is FEL capable and always doing a FEL to MEL conversion before output and outputting JUST the minimum enhancement layer. There's really no way to verify outside of gear capable of debugging Dolby Vision signals, but Occam's Razor applies. The quality difference between FEL and MEL would probably require VERY specific circumstances to uncover and likely can't be seen on our TVs since they are 10bit panels anyways.
So, basically, my guess is there's a bug in Oppo's DV implementation that's allowing you to play all discs without display latency issues due to it always outputting the "low latency" DV profile or something similar that's stripping out the 12 bit data, giving the TV less to process.
All speculation, but it all fits the evidence. Regardless, it's frustrating for a lot of people. I wonder if there's something that could be put in the HDMI chain to alter the reporting of the TVs capabilities to force the low latency profile all the time.