HDR Option Not Available at all Resolutions & Refresh Rate M1 Mac Pro

[HXavS]

Just to track as known issue caused by Mac OS and discussed in Better Display Discord

There is a bug in Sonoma 14.1 that will limit HDR availability depending on resolution and refresh rate.

• https://www.reddit.com/r/MacOS/comments/17hh371/hdr_option_is_not_available_on_macos_141_for_m1/

This issue is caused by Sonoma 14.0 and was fixed for M2 in 14.1.

M1 Still have the bug as of 14.3

[waydabber]

Hi there,

The limitation is refresh rate and framebuffer size dependent (so what seems to matter is the framebuffer pixel clock). Not sure why Apple did it especially as everything seemingly worked just fine for 2+ years and everybody was happy (except for some people complained about a 8bit reported framebuffer color depth but that was a small minority, most ppl did not care). This same limitation applied to M2 initially (probably due to the M2 green screen of death bug) while M1 was unlimited (which was awkward as the older chip seemingly did better than the new one). When they fixed the M2 they also limited M1 (in the same move) - this indicates that probably the same engineer (or maybe a group of engineers) made the changes to both chip firmwares (the capabilities should depend on the rtOS - firmware - version running in a dedicated component of the Apple Silicon chip called "DCP").

Multiple (rather vague) replies from Apple support clarifies that the limitation is intentional and is here to stay. It would be great if the guys actually making the change explained things a bit better though. :)

One can make 120Hz HDR work up to 2432x1368 HiDPI (you can use BetterDisplay to unlock that resolution) which is slightly higher than the stock 2304x1296 mentioned here. Would have been better if the engineers pushed a bit harder and allow 2560x1440@120Hz HiDPI for HDR. :)

Note regarding the DCP firmware: this firmware is loaded at boot time and is macOS version specific - each macOS version has its own build. It's not the usual firmware in the typical sense that it is somehow permanently stored inside the chip itself in some kind of eprom. It's actually a separate real time operating system (called rtOS) that runs inside this specific part of the Apple Silicon chip called DCP (Display Coprocessor probably) - a chip inside the chip. Each macOS has build has its own matching build for the DCP firmware (OS) and the two work together as the functionality is divided up between them - some stuff is handled by macOS, some by rtOS and they interface with each other in a specific way - neither of them can operate properly without the other. DCP handles display modes, all negotiations with displays (and among other things manages also the built-in DP2HDMI hardware for first gen Apple Silicon Macs) and also manages video memory bandwidth stuff (this is probably where the limitation of modes come).

---

Since there is nothing I can do to fix this with BetterDisplay (the limitation is at DCP firmware level), I'll move this over to discussions.

[CorgFather]

@waydabber is there any way to force detected HDR content to auto disable HiDPI and enable HDR, so I don't have to do manually to watch a video? I have Pro if it matters.

If not, it looks like Apple will be forcing me to upgrade earlier than expected.

[waydabber]

Unfortunately no, there is no mechanism to detect HDR content on an SDR screen (as by definition no app will render HDR content onto it).

You can easily create a script and use the Shortcuts app to tie it to a keyboard combo that does all you need when watching 4K HDR video:

• enables HDR
• turns off night shift
• sets the native resolution for perfect pixel mapping
• blanks unneeded other displays

See more here: https://github.com/waydabber/BetterDisplay/wiki/Integration-features,-CLI

If you can't figure out how to make this script, let me know, I can help.

[CorgFather]

Thank you. With the link and GPT, I got the below (written in Script Editor and saved as .app).

repeat
	set infuseIsRunning to application "Infuse" is running
	if infuseIsRunning then
		do shell script "/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set --name=LG TV SSCR2 --hidpi off --resolution 3840X2160 --hdr on --nightshift off"
		exit repeat
	end if
	delay 5 -- Check every 5 seconds
end repeat

However, I get

error "Failed." number 1. 

I also tried using quotes around the name, but that didn't work either.

[waydabber]

Hmm. You should first make sure the shell script part actually works when simply called from Terminal.

Here is the fixed version:

/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set --namelike=lg --hidpi=off --resolution=3840x2160 --hdr=on --nightshift=off

If you installed betterdisplaycli, it's similar:

betterdisplaycli set --namelike=lg --hidpi=off --resolution=3840x2160 --hdr=on --nightshift=off

If you want to use the full name with --name, then don't forget you need to escape the spaces in parameters in shell commands (like \ ).

[ErinPo]

I can't get HDR support to show up in macos settings > display for any resolution / hz combo on my M1 mba connected to a TV with HDR support. Is it possible that the USB-C to HDMI adapter I use does not support HDR? (It does support 1440p@120HZ and 2160p@60Hz.)

[waydabber]

It is (there all kinds of adapters out there) - but a HDM 2.0 adapter should normally support HDR.

[CorgFather]

@ErinPo Is HiDPI off?

@waydabber

/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set --namelike=lg --hidpi=off --resolution=3840x2160 --hdr=on --nightshift=off

Awesome, thanks! My final script (save as .app in Script Editor and add to Login Items) which is working in case anyone else wants to do this:

repeat
	set infuseIsRunning to application "Infuse" is running
	if infuseIsRunning then
		do shell script "/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set --namelike=lg --hidpi=off --resolution=3840x2160 --hdr=on --nightshift=off"
		repeat until application "Infuse" is not running
			delay 5 -- Check every 5 seconds to see if Infuse is still running
		end repeat
		-- When Infuse is quit, revert settings here
		do shell script "/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set --namelike=lg --hidpi=on --resolution=3840x2160 --hdr=off --nightshift=on"
	end if
	delay 5 -- Check every 5 seconds for Infuse to start
end repeat

[ErinPo]

I keep HiDPI on usually to improve text legibility below native 4K resolutions, but even when I turn it off, turn night shift off and use the native 4k resolution, there is no option to enable HDR in MacOS display settings. Are you saying that HiDPI and HDR are generally mutually exclusive? I didn't realize that.

[CorgFather]

Is this for the external display or built-in? It won’t appear for built-in. If external, is the display HDR10 compatible?

See here for more details.

[ErinPo]

I was talking about the MacOS settings for the external display which is a TV. The TV supports HDR10 according to its specs. When I connect a cheap Windows PC using an HDMI to HDMI cable to it and activate HDR on it the PC recognizes the source as HDR and I can tell the difference on the screen as well. It really seems to be an issue with the particular USB-C to HDMI adapter that I am using for the Mac. I will look into switching it.

Can you confirm if HiDPI is incompatible with HDR or are you just turning HiDPI off in your script because it's not needed for movies or because your movies are all 4k?

[waydabber]

HiDPI is compatible with HDR. Some Macs however limit HDMR beyond a certain framebuffer resolution and refresh rate (framebuffer pixel clock).