My input setup:
- RTX3070 > HDMI 2.1 cable > LG C9 65"
- Chromecast > LG C9 65"
My output setup:
LG C9 65" > HDMI 2.1 cable via eARC > Samsung Q850t
TV is set to passthrough any audio with no processing, no AI Sound etc.
For my PC, I have it set to output PCM 5.1 at the highest bitrate and bit depth possible, in this mode there is no perceivable AV sync issues with a 4k 120hz 10bit video signal in 4:4:4 RGB. I can also output Atmos and the AV sync is fine but there is an annoying bug where the first 1s or so of any new Atmos audio stream is silent so you miss all notification sounds on windows, that forced me back to PCM 5.1 to avoid the silence issue.
If any internal apps (Netflix, Disney+, etc) output atmos there is an unbearably bad audio delay that is unfixable from the soundbar or TV settings. The delay is reduced if you can select a non-atmos sound stream but sadly in some apps there is no option to select a "lower quality" audio source. I tried to watch a Dolby Vision + Dolby Atmos Moon Knight episode on Disney+ and the AV sync was awful so I
aquired a non-atmos copy to watch directly from my PC and had to sacrifice Dolby Vision in the process.
Seeing as LG have not fixed this issue and have essentially no communication about it I will never be buying a LG TV again. Waiting on the new Sony QD-OLED, once it's out I'll sell my C9to someone and never have to deal with LG again.
Class Action against LG anyone?