dwm_lut
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lauralex
10-bit SDR Output
When SDR LUTs are applied to 10bpc displays, colour banding occurs in applications that support 10-bit output such as Adobe suite & BlackMagic Davinci Resolve. I'm wondering if this is a bug, a current limitation with dwm_lut, or a limitation of Windows DWM.
For some information, the displays are driven by an nvidia GPU through DisplayPorts. When LUTs are disabled, the banding issue goes away and the displays with LUTs assigned present smooth gradients again.
I've once met banding on Quadro cards, but new 3xxx-4xxx cards make smooth gradients.
I believe the limitation lies within DWM, dwm_lut creates an overlay using DWM and DWM only works in 8bit with SDR mode, also as seen here, https://learn.microsoft.com/en-us/windows/win32/direct3darticles/high-dynamic-range
The article also mentions the new Windows ACM, which might mitigate this issue, the feature is already available on 22H2 if you have an SDR monitor.
Meanwhile, I got an HDR monitor running in SDR mode, and only the latest insider build supports that config with ACM, but the latest dwm_lut doesn't work on the insider build, so I can't test it myself.
Do you have an information about 10 bit displays support on 22H2? Unfortunately can't check it myself.
It is mentioned inside the article I linked above, but its said the monitor has to be specially provisioned.
Advanced Color capabilities were first introduced ... for specially provisioned SDR displays with the Windows 11, version 22H2 (10.0; Build 22621) release.
AFAIK you could add entries to the registry to tell Windows your monitor is provisioned, I have googled and tried but it didn't work with my HDR monitor.