Arbitrary scaling and HDR limitations on M4 Max MBP on high refresh monitor on HDMI 2.1.

[madihy]

Hi all,

Just wanted to document some strangeness I'm sure Apple hardcoded as a limitation. I have a 4k 240HZ HDR monitor with HDMI 2.1 (https://www.displayspecifications.com/en/model/62d1378a).

For native 4k and resolution scales up to 130%, 2496x1404, I am able to enable "HDR Mode". Any other resolution past that its not available. This issue is the same for 120hz and 240hz so it doesn't seem like something that is calculated based on available bandwidth or resources.

Just mildly annoying for a $4k laptop but hoping it's addressed in the future.

BetterDisplay is amazing though!

[waydabber]

Interesting, this is the same limit as with the entry level M4 and some older Macs.

[madihy]

After some experimentation I found forcing the resolution to a round number and doing an exact 1.2x upscale enabled HDR Mode with high refresh rates. 3200x1800 is actually perfect for me for 4k.

Maybe there is some higher computation overhead when working with scales that require a high floating point precision. Hopefully this will help other M4 users