For you guys who are having LIP sync issues, I've solved it by connecting my Blu-ray player direct to the Soundbar, rather than the TV.
Blu-ray player = LG UBK90
TV = LG OLED55C9PLA
Soundbar = HW-Q90R
Initial connections. Blu-ray to HDMI-1 on the TV, and TV HDMI ARC to HDMI Arc on the Soundbar.
All sound types other than Dolby Atmos have NO delay problems. When DOLBY Atmos used, i.e. using bitstream input, and auto decode, or any other option to enable Dolby Atmos you get a delay or around 120ms between screen and sound.
Intuitively you would think this should be the connected setup, so with all delay options on soundbar and TV set to Zero, you can't go negative numbers, you will always get a delay. Obviously decode processing times cause a delay within the soundbar.
Changing setup of Blu-ray to HDMI-2 on the soundbar, and keep HDMI ARC on soundbar to HDMI ARC on TV, you get NO delay with Dolby Atmos, as the Soundbar is doing the decoding and sending the video data at the correct time, in this case again with a Zero delay setting on the soundbar.
You are losing Blu-ray to tv connectivity, but most systems can communicate fine through the soundbar with CEC codes anyway, and picture quality should be the same. It's digital init ?
Ideally, I'd want the Blu-ray player connected directly to the TV, but until Samsung sort out delay processing issues, then outputing directly to soundbar is the only work around.
I have never had lip sync issues on my Q90r tv and Q90r sound bar and xbox, tv and nvida shield all are running on Dolby atmos using the netflix app on any of these 3. Even playing games no lip sync issues.
I have ever cannot get Xbox X running atmos directly plugged into hdmi on tv but get it through soundbar.
Yet tv and shield get atmos using netflix directly in hdmi on tv.
Dont know why people are lip sync issues. Never had that issue
A couple things. The lip sync problems with Dolby on the cable box isn't on every channel. It's channels that broadcast in surround sound, like our local NBC station. This could be why you don't encounter it. Dolby Atmos won't transmit any other way than through bitstream. If your Xbox isn't transmitting it, maybe it's using linear PCM? PCM can still transmit 5.1 Dolby, but not anything above it. I still had audio lag this way though without the tv pass through.
I have now solved my lip Samsung Q90r, Q7f Samsung TV and Sky Q.
Sky Q to Soundbar HDMI Arc. Soundbar HDMI 1 or 2 to Samsung TV any HDMI port (not arc) on TV, set delay to 100 (maybe different on other TV's) my HDMI cables are both 8K.
The only problem is that the TV does not recognise the TV and soundbar individually but only as soundbar.
Why it works I have not got a clue, possibly sound and light travel at different speeds and reversing the set up equalises them both, 5.1 works perfectly.
I hope this helps from the annoyance of the lip sync syndrome.