Audio/Video Sync on Apple TV 4

Channels Apple TV
#1

I have two setups that are very similar and exhibit the same problem:

Apple TV 4K HDR -> TCL 55 6-Series -> Optical Cable -> Onkyo S3500 Home Theatre System
Apple TV 4K HDR -> TCL 49 5-Series -> Optical Cable -> Vizio SB3651 Home Theatre System

In both cases, the audio lags slightly behind the video when set to output surround sound. If I change anything - so it's just stereo or receiving PCM audio from the Apple TV it goes away. On the 55 inch TV I have a splitter that creates dedicated HDMI Audio channel and that works fine, but the loop thru from the TV there's a lag. This only happens inside of Channels - Netflix, etc are all fine using the TV's optical out.

There are workarounds, but any of the workarounds ends up losing the 5.1 Surround Sound. Thoughts?

#2

This is a common issue with some TVs which introduce lag on the optical ARC. There may be some settings hidden in your TVs menus which can reduce or eliminate the latency.

See for example http://forums.roku.com/viewtopic.php?t=110877