Incorrect clamped colors

[meidoqt]

When clamping colors to sRGB/BT.709 from native (dci-p3) something weird is happening, it's hard to explain but they just look darker and still oversaturated. The old version of novideo_srgb "correctly" desaturated them instead. I'm saying "correctly" here with the understanding that I actually have no idea which method is technically correct. But with this fork the color still look oversaturated on my display, they're just darker.

I'm on Windows 11. ACM is disabled.

[ItsPasi]

Same thing happening for me. My monitor has colors far outside of sRGB and even outside of DCI-P3 and clamping them makes them definitely too dark. I can confirm this since my 2nd monitor that is close to sRGB has brighter and less saturated colors when calibrated.

[hadoooooouken]

I encountered the same issue. I tried the following driver versions:
595.79 - wrong colors (darker than should);
591.86 - wrong colors (darker than should) ;
591.74 - wrong colors (darker than should) ;
591.44 - good colors but very noticable banding is everywhere with any combination;
581.57 - all good.

So for me, version 581.57 remains the best option for now.

I reported the bug about 595.79 driver to NVIDIA using this feedback form:
https://forms.gle/kJ9Bqcaicvjb82SdA

They even replied to my email and asked for some additional details specific to my case. I recommend that you submit a bug report as well so they can confirm the issue is affecting multiple users.

[guzenco]

What you see is most likely the result of using a gamma setting different from sRGB, most likely Absolute/Relative with a 100% black output offset. This comes from limitations of MHC2, which ignores profile TRCs and treats them as sRGB instead.

In version 1.3.0, the "Optimize CSC matrix for gamma" option was added to mitigate this.

[meidoqt]

1.3.0 did not fix this issue with the new option, and this happens even without using a different gamma. I can't post high quality comparisons but will try taking some pictures later to show what I mean exactly.

[ItsPasi]

Yeah I also still have the issue. The colors only get dark when I actually clamp down the color gamut. When I keep it at native it looks correct.

[Carl-Robert]

The original novideo had broken gamma calibration/correction due to Nvidia drivers (one of the main reasons this fork exists). So if you are comparing this msovideo and the original novideo head-to-head on recent Nvidia drivers then of course any "darker" gamma in msovideo makes the colours look darker compared to the washed out/not "darkened" gamma in novideo. Same thing with comparing monitor native gamma and corrected gamma in msovideo. It is supposed to look "darker" if you are calibrating to a "darker" gamma than your native one.

Colours aren't the same at different gamma targets. If you want hard data to check if there actually is unnecessary "darkening" going on: profile with a colorimeter with the clamp active against an artificial profile with the gamma value you are targeting and check for deltaE.

[ItsPasi]

I am using ICC profiles I measured myself and my high gammut monitor when calibrated to sRGB is way darker than my already sRGB 2nd Monitor. The colors get darker, not the gamma. It's clearly a bug with the nvidia drivers like stated above.

[guzenco]

1. Does issue occur with R580 drivers?
2. Does issue occur when ACM is enabled?
3. Does issue occur with this build? (I used the novideo matrix calculation method for this build. I changed it earlier(before 1.0.0) because it produced incorrect results (visually and in measurements) compared to novideo and ACM in my tests.)

[meidoqt]

@guzenco 1, Yet to test it with old drivers, but realistically I'm not going back to older drivers just for this. 3, this build clearly shifts the white balance for me so I'm assuming it has some other issues.

Pics:

msovideo/novideo settings: EDID, BT.709 gamut. No gamma options selected.

• ACM Off (Native Monitor colors, 95% DCI-P3)

• ACM On
• Note: ACM On without any msovideo/novideo is visually consistent with the legacy version of novideo.

• ACM off (msovideo 1.3)
• Note: msovideo 1.3 is the only one here with the visibly darkened colors, especially noticeable on reds. This is not a grayscale gamma issue, as the grayscale gamma is visibly identical on all four images, and no gamma options were selected anyway.

• ACM off (novideo_srgb fork)
• Note: A fork of the legacy novideo, visually consistent with just using ACM On.

edit: replaced the images with slightly better ones, rewording

[ItsPasi]

1. Does issue occur with R580 drivers?
   I don't want to downgrade either right now, but I am going to assume that it would fix the issue
2. Does issue occur when ACM is enabled?
   No, it does not happen with ACM. For additional context, after disabling ACM it did stay looking correct for about 10 seconds and then by itself got darker again with the colors. It must definitely be a GPU Driver bug.
3. Does issue occur with the build that was linked?
   Yes

[deniscfd-cmyk]

Good suggestion is to uninstall driver with DDU and install again. Check weather it will be the same.

[ItsPasi]

Good suggestion is to uninstall driver with DDU and install again. Check weather it will be the same.

I already had issues with the colors when I applied the original novideo_srgb when I tried doing as comparison, but the original sRGb actually somehow broke the monitors color info and permanently clamped down the colors, which only using DDU fixed. I also already tried DDU yesterday and that doesn't fix this darkening issue. Idk why nvidia has to constantly change things that worked before.

[NS-6]

as far as I can tell, the clamp only briefly applies but then turns off and you can test this by turning HDR or ACM on and off. you'll see the clamp apply properly and then about 30 seconds later you see the colors revert to pre clamp even if the clamped option stays on in msovideo app.

you still see some changes with the clamp checkbox because it just applies or turns off the color profile, which you can also check with the color management window, unchecking and checking the "Use my settings for this device" box.

I've just been using it with ACM on, the clamp stays applied with it. I'm on nvidia driver version 591.74 - Jan 5th if it helps, can't use the latest one as it causes some issues with some games I'm playing.

[ItsPasi]

Well using ACM isn't the solution because on my device in some applications ACM makes the screen randomly flicker and it happens every minute or so.