Which HDMI cable?
A few more things:
I only have two HDMI 2.1 cables and they are the same brand and cable. I do not have another Mac. The video route is:
Unfortunately the Windows PC is miles away. I went there to burn the firmware. It's not mine.
Yeah that 2560x1440 max means you still have a problem.
On the same Mac M1 thunderbolt/usb-c output, I am connected into my Dell AW3420DW monitor with DisplayPort at 4k120Hz10bpc. So I believe that my Mac M1 video signal performs as expected. I tried a different TV port and a different HDMI 2.1 cable between the TV and the Mac. No luck.
Have you tried the EDID file uploaded by OP? The modified EDID doesn't work on my TCL TV either, but OP's EDID do the magic for me.
Wow! I used the EDID in the instructions rather than using my own edits. Now I am at 3840x2160 120Hz, 8bpc. Not sure why others have 10 bpc, but THANK YOU!!!
Could it be 8bpc framebuffer being output as 10bpc HDMI? I think the Graphics/Displays tab in System Information.app will show framebuffer info. SwitchResX will show output timing. AllRez will show output bpc for Intel Macs that are using modern GPU drivers. Older GPUs on Intel Macs require a kext to get output bpc (my Lilu/WhateverGreen for example - though I want to try to make a kext that doesn't require Lilu/WhateverGreen). It's good to have a display that shows timing and color info.
CGDisplayCurrentMode always seems to report 8bpc so it should be ignored if the other methods are available.64bpp 16bpc but it also shows encoding --------RRRRRRRRGGGGGGGGBBBBBBBB which is 8bpc. Probably the former is true.
This is also present on my Pro Display XDR showing in SRX and BD 8b. On my LG C2 OLED some time it shows 10b but most of time 8b. I dont know what this issue in Display Color Depth is. I also ask some time ago @stevemr123 but he says that this information comes from MacOS. But it is 100% 10b because a lot of people, like me, test some patters and can confirm it's 10b. I report this also to apple, but nothing happened. But ure informations are very interesting.
Hi guys, BetterDisplay will show 10bpc if `samplesPerPixel` is 10 - for all other occurrences (even though the reported value is sometimes 16) the app will show 8bpc as I believe the latter result (16) is not real and I did not want to confuse anybody by showing 16bpc - but I did not investigate this further. The 8 vs 10 is solely about the framebuffer - the connection might as be as well 10bits especially as the dongle can do whatever it wants, the app won't take that into account. If the framebuffer depth is 8bpc then the TV showing 10bits is irrelevant, will not make the image any better.
(+ note: I think it is really difficult to discern the difference between 8 and 10 bits in any real life setting + I never saw anything else other than 8bit on my mini-LED 4K display@120Hz with direct displayPort or USB-C connection either - 10 bits shows up on my QHD test displays usually - so I'd be surprised if this would be any different for the LG TVs)