VRR customisation

[imkebe]

I have external display cappable of VRR. I can set constant resolution (48,60,75,120) and user variable one f(48-144Hz). It is possible to set using system preferences and app also. However custom resolutions menu also contain other (48-60Hz) options.
I'm wondering if it is possible to set custom range ? 48-120Hz? This is important since over 120Hz screen change chroma subsampling from 4:4:4 to lower ones. When I use my default native resolution 3840x1600 having HDR and 120Hz everything is fine. When swtched to VRR (48-144Hz) or set constant 144Hz it loses quality.
Is VRR range obtained from the screen/protocol or can be altered?

[imkebe]

@waydabber I want to discus this. I changed EDID to limit my screen from 144 to 120Hz. As I can tell VRR rate changes described on the web refer to changing Block 2 Range Limits. However for Windows there is need for changing drivers .inf files in addition. When new EDID file is uploaded and enabled in app I can see in details that screen is now 120Hz max, however the Refresh Rates still show old ranges. There is static 144Hz and VRR 48-144Hz. I can enable both and it works up to 144Hz. Where is the refresh range coming from? Shouldn't it be read from EDID ? Is MacOS reading it directly from the screen using DDC ?

https://www.reddit.com/r/Amd/comments/5iux1q/updated_tutorial_on_increasing_and_decreasing/
https://wccftech.com/amd-freesync-hack-expands-refresh-rate-range/

[waydabber]

afaik the EDID is interpreted by the DCP (which is a low level process and has a separate chip and custom real time OS) and the available modes are then communicated to the OS. I am not sure how well actual VRR modes work, I have a display that can show the current refresh rate and even on VRR modes it never went below the maximum (unlike on Windows). I think using fixed 120Hz (to match ProMotion for which Apple optimized its UI quite well) is the most sensible option for a high refresh rate third party external display in macOS.

[imkebe]

OK. Then middle chip is a blocker. I use 120Hz to send HDR in 4:4:4 mode. I was hopping to limit power usage in long term by using VRR - when you use screen for 12h daily it will sum up. In my case I saw changes in refresh rate when using VRR - even tiny like 139Hz.

[waydabber]

If you are using EDID override anyway, you can enable 120Hz VRR - I am not saying it does not work ever - it might be my display or something wrong with my setup. :)

[imkebe]

I'm jus saying that VRR is scaling in my case. However override doesn't work. That's why i'm asking.

[waydabber]

I am not sure I fully understand what "VRR is scaling" means. :)