Cannot have HDR enabled at 165hz and full RGB (AW3423DWF)

[mrashed-dev]

Hey! Was trying your app as I just got a brand new monitor (AW3423DWF) but I seem to be running an issue, I'm wondering if I can get some clarification. So my monitor supports up to 165hz and HDR as well (out of the box only 8-bit HDR) at the 3440x1440 resolution. On Windows I can clearly see that, using the included DP -> DP cable I can get 165hz at the native resolution with 8bit HDR and with full RGB. On MacOS though there seems to always be a sacrifice. Note I'm using the included DP -> USB-C cable, not a poor/aftermarket cable so I don't think it's the cable.

From my testing I have come to the conclusion that these are the 'sacrifices' I must make:

• 1440p + 165hz (variable) + HDR ON => Forced to use 10 bit with YCbCr limited (bad colours) also no HiDPI setting
  
• 1440p + 165hz (variable) + HiDPI + 8-bit Full RGB => No HDR option

• 1440p + 100hz + HDR On + HDR10 full RGB => No HiDPI and also not using the full refresh rate of the monitor

In the last case, it seems like I can only choose one of HiDPI and HDR, they're interchangeable and the rest stays the same.

Also here's the output from the -connectionModeListAll flag for my monitor at the native resolution:

Right now, the most acceptable tradeoff seems to be 100hz & HDR vs. 165hz & HiDPI. It's just odd though because if I just change the input to my windows PC I get 165hz with HDR 8-bit Full RGB @ 1440p without any configuration. Is this just down to MacOS? Or am I doing something wrong maybe? Thank you!

Edit: Played around some more and I found that setting it to 89% resolution HiDPI (3062x1282) allows me to enable both HiDPI and HDR. However, at 165hz I only see HDR 12 bit and HDR 10 bit both at the limited YCbCr colour space.

Still, at 100hz @ 3062x1282 I'm able to get HiDPI & HDR 10-bit working with full RGB, so that's a better trade-off to me than the above scenarios.

Would love to have the full 165hz working with HDR 8-bit like Windows though.

[marcebdev]

Adding a data point as I was just searching this topic after trying to finally fix some monitor issues on Mac and trying this tool out. Some things to note:

1. It's def not the DP cable. I have a Club3D C to DP cable plugged directly into my Thunderbolt port. FWIW the cables in the box aren't always reliable though
2. As far as I can tell BetterDisplay seems it can do HiDPi (I'm running 99% res, not sure if you still have to do that to get supersampling), 8bit RGB and 165hz. But if I look at the native settings I notice it only shows 100hz. So I'm guessing BD is forcing something in the EDID or how MacOS reads it, but it's unclear if the result actually is 165hz.
3. Unlike Windows I can instantly see VRR flicker with it turned on, I'd suggest to just keep a static 165hz, shouldn't really matter for most typical use cases on Mac unlike gaming on Windows (where it's actually useful)
4. I had a similar issue with Mac and YCbCr on another Dell UW, I can't remember what I had done but I believe I had fixed it by just forcing RGB mode in the OSD, I'll have to give a further look tomorrow to see if this can change anything. But I did notice that this monitor had the same issue where MacOS is defaulting it to YCbCr just like it did on my old one.

DSC has had a bumpy road, but double checking as of Sonoma it seems like it does work and doing some quick research it seems anything past an M1 Pro at least has it.

Maybe some DSC negotiation issue, as I also witness the same where with HDR I get res cuts between native straight down to 88%

Edit: Apparently the AW3423DWF doesn't even support or at least use/need DSC for 3440x1440@165hz HDR so don't think that's the issue. Seems either a MacOS bug or some negotiation issue/maybe EDID issue in regards to BD with this monitor?

[mrashed-dev]

Ditto on the VRR issue, I too had the same experience on black and grey colours until I turned on static 165hz. Regarding the monitor's OSD, I can alter the RGB settings on non-HDR presets only, I don't have control over what colour space to use in HDR using the Monitor's OSD.

I don't think the 'full RGB HDR @ 165hz not showing up' is specifically a BD issue, unless BD is reading the EDID wrong. I posted a screenshot in my post of my terminal window getting the supported modes at 3440x1440. There's no intersection between 3440x1440, 165hz, HDR and RGB. I do know that it's possible because on Windows I'm getting all of that on 8-bit (there's a 'hack' to get 10-bit working on the monitor but it's not supported out of the box). I didn't install any software on my Windows machine either like a driver or anything Dell/monitor-specific, it's just what my GPU settings are reading.

I'm mostly either looking for a tip or maybe an easier way in BD to override/force specific settings. I know you can edit EDIDs in an external program but none of the programs I found had a way to enable full RGB in HDR at 165hz, the closest I found is disabling YCbCr entirely but that just takes away the HDR option completely in BD. That also doesn't explain why HDR (even with limited YCbCr) can't run alongside HiDPI at full resolution, that might be a BD issue, but I'm really not well versed about this.