M4 Max & Asus DC500 Dock – Can't get 10bit RGB

[zs180951]

I have: an M4 Max MBP, Asus DC500 40Gbps/HDMI2.1 Thunderbolt-4 dock & an LG CX TV.

If I plug my HDMI cable directly into the laptop I get 4k/120Hz/10bit without needing BetterDisplay.

When using the dock, I don't have the option for 120Hz until I use BetterDisplay to override the EDID (changing the format to V1.4). However if I set my refresh rate in this way above 60Hz my color options are limited to a single option of YCbCr 4:2:0. I've tried a few different EDID modifications to get more color options to show, but nothing seems to do the trick. Even at 60Hz when using the dock I am missing the 10bit RGB option.

I would really appreciate any insight into how I can get better color at 120Hz with this dock :), or maybe I need to replace it with something else to get what I want.

Plugged into dock, at 30Hz (identical options to if I am plugged in directly without the dock):

Plugged into dock, at 60Hz:

Plugged into dock, above 60Hz:

Display modes:

[waydabber]

Hi there - you apparently bump into some kind of bandwidth issue. 10-bit require more bandwidth than 8-bit so the Mac compensates with reduced color resolution (4:2:0 chroma-subsampling). For higher refresh rates even with 8-bit the system must resort to this.

This might be a dock specific limitation.