Newbie- Where do I start?

Jl1994

ASUS ProArt PA278CGV Monitor

The ASUS ProArt PA278CGV monitor, according to https://www.displayspecifications.com/en/model/53fc33b6, supports true 8-bit color, but uses FRC (temporal dithering) for 10-bit. You should ensure that the graphics card control panel is set to 8-bit to avoid engaging the FRC module.

PowerColor Radeon RX 7800 XT 16GB Red Devil

I'm sure the RX 7800 XT uses dithering when the AMD driver is loaded at any bit depth except the maximum value, which should be 12-bit, just like my former RX 6600. However, in Linux, starting from kernel v6.8-rc1, it should be 10-bit (?) according to this commit: https://github.com/torvalds/linux/commit/d5df648ec830cfd775bdacb3a3640c1e16de90f2. Try using ColorControl to disable dithering on the RX 7800 XT in Windows (https://github.com/Maassoft/ColorControl) and set the color depth to 8-bit in the graphics card control panel.

Jl1994

Gyazo Link to the settings in advanced display. Sorry if links are not allowed. It says Bit depth 10-bit. So I guess that means I have dithering.

The FRC module of the monitor is enabled for displaying 10-bit color. You have temporal dithering.

KM

My hypothesis is that the code is shared across several generations of GPU architectures. In the comment, Vega, Polaris, and Navi are mentioned. When Navi was released, spatial dithering was accidentally forced at 10-bit in this function. However, it was later set to truncation because this function is also used for other architectures where spatial dithering may not be acceptable at 10-bit.

I can't find where temporal dithering is forced on for Navi in the amdgpu kernel module. I mean where the options for temporal dithering are set; I only see where they are checked. But I'm not very familiar with the module's code, so I might be missing something.

Because it almost sounds like by default the amdgpu driver uses spatial dithering (not temporal dithering) regardless of the GPU type.

Judging by the code, if we reach the switch statement mentioned in the comment in the commit where the fix was made, the temporal dithering is not enabled in the same method: https://github.com/torvalds/linux/blob/11066801dd4b7c4d75fce65c812723a80c1481ae/drivers/gpu/drm/amd/display/dc/core/dc_resource.c#L4667. But how it works in reality remains a question.

Jl1994

Could you try using this guide: https://www.amd.com/en/resources/support-articles/faqs/DH3-008.html ?

But this might not have the desired effect, because the video card itself might still apply dithering. Additionally, try disabling dithering on the video card through ColorControl.

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Jl1994

The main goal right now is to eliminate dithering on your graphics cards and ensure that your monitor works well at 8-bit color depth. If you find that working becomes comfortable during any of these tests, your monitor should be fine.

Here are your options:

1. Ubuntu 18: This version likely doesn't support your graphics cards because it's quite old (?). That's why it's recommended for testing. Without support, the driver shouldn't initialize the card or enable dithering. However, there's always a risk that the card might default to dithering. This is the main concern with these step. Start testing with the UHD 770, and if it causes eye strain, switch to the RX 7800 for broader test coverage.

2. Latest Ubuntu: The newest version supports both of your graphics cards, meaning the driver will recognize and initialize them. It's been found that the driver for the UHD 770 doesn't enable dithering at 8-bit or higher, making it potentially safe. However, the situation with the RX 7800 is unclear and depends on the driver. Set the color depth to 8-bit.

3. Windows 10/11: You can use the Microsoft Basic Adapter Driver, which won't enable dithering on the graphics card. You can test here too, but be aware of the same risk mentioned in step 1.

4. Native Driver for UHD 770: Install the native driver instead of the Microsoft Basic Adapter Driver and test again, ensuring that the color depth is set to 8-bit. Use the Ditherig app to disable a dithering on the UHD 770, if eye strain is present. https://kawamoto.no-ip.org/henteko/myapp_en.html

5. Native Driver for RX 7800: Install the native driver instead of the Microsoft Basic Adapter Driver and test again. Use ColorControl to disable dithering on the card. Ensure that the color depth is set to 8-bit.

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