HDR and color management in KWin, part 3
zamundaaa.github.io
Since the last two posts about this topic (part one, part two) there has been some more progress, so let’s take a look.

Part one: https://zamundaaa.github.io/wayland/2023/05/18/hdr-and-color-management-in-kwin.html

Part two: https://zamundaaa.github.io/wayland/2023/12/18/update-on-hdr-and-colormanagement-in-plasma.html

  • Zamundaaa@discuss.tchncs.de
    ·
    4 months ago

    That has pretty much nothing to do with the color profile, when colors look very desaturated on HDR screens, that's the driver messing up the colorspace signaling.

    What GPU do you have? Both Intel and NVidia still have major problems with this.

    Many displays (but not all, which is why it's not exposed in the GUI) also support doing HDR without additional colorspace signaling, you could try enabling only hdr and disabling wcg with kscreen-doctor. IMO the color part is the more noticeable benefit of HDR, but you could at least have functional HDR until your GPU driver is fixed.

    • Lojcs@lemm.ee
      ·
      4 months ago

      I had thought it was about the color profile because with hdr disabled from system settings, enabling the built in color profile desaturates colors quite a bit and does some kind of perceived brightness to luminosity mapping that desaturates bright / dark hdr content even more. Although I don't think that's the cause of my problems anymore.

      Thanks to your tip about kscreen-doctor, I could try different combinations of hdr / wcg / edid and see how the colors look with different combinations:

      Show

      I think there must be something wrong with my screen since the hdr reduces saturation more than anything else. Anyways, thanks for the good work

      Edit: Tried this with an amd gpu. hdr+wcg works as expected without muted colors. hdr without wcg still significantly desaturates colors, so I guess that's a monitor bug. Now to figure out gpu passthrough.. (Edit 2: It seems to just work??)

      Side note, when I turn off hdr only from kscreendoctor the display stays in hdr mode until it turns off and on again, that didn't happen with nvidia

      Edit 3: Found something weirder... Hdr colors are muted on nvidia gpu and seems vibrant with the amd igpu. If I plug the monitor to the motherboard (amd), enable hdr, then unplug and plug it into the nvidia gpu, the colors are still vibrant??? I can disable and enable hdr again and again and they aren't affected. They're even fine when hdr is enabled without wcg???? But if I fully turn off the monitor and back on they once again become muted with hdr. Weird ass behavior

      • Zamundaaa@discuss.tchncs.de
        ·
        4 months ago

        enabling the built in color profile desaturates colors quite a bit and does some kind of perceived brightness to luminosity mapping that desaturates bright / dark hdr content even more

        It maps the colors to be more correct, and it does use the brightness info from the EDID for HDR content, so that checks out.

        I think there must be something wrong with my screen since the hdr reduces saturation more than anything else

        It might enable some sort of gamut mapping on the display side... HDR on monitors is really weird sometimes.

        Side note, when I turn off hdr only from kscreendoctor the display stays in hdr mode until it turns off and on again, that didn't happen with nvidia

        I think that's a bug in amdgpu. It should force a modeset on hdr change, but it doesn't.