Potential corner case HDR bug in Windows 10.

I noticed last week that one of my portable monitors has HDR so I enabled it and enabled HDR in Windows. It does seem to improve the quality of contrast, especially for videos.

This system is set to turn monitors off after 30 minutes. When they wake back up the HDR seems to be disabled (image looks very dim and dull) but in windows display setting HDR shows as enabled. If I turn it off and then back on HDR returns to normal.

I don't know how much of this matters but this system has 2 monitors (main is the HDR one), is on a Nvidia 2060 and is on Windows build 20H2 488. I am about to check 508 but I don't expect that to matter.

To reproduce this you would need to have HDR enabled and your system set to turn monitors off (but not sleep) after inactivity. When the monitors turn back on HDR will show enabled but be disabled, if you can confirm this bug.

 

Still happening on 508, as expected. Looks like a real bug.

 

Sleep is disabled, this is not a sleep issue. In power setting monitors are turned off after 30 minutes but the system does not sleep.

HDR on the monitor is on auto. Both the monitor and Windows show HDR as enabled when I wake the monitors up but it is clearly off. All I need to do is turn it off and then back on in Windows and everything is fine.

To repro this disable sleep but set monitors to turn off after 1 minute.

 

BTW, I suspect this has something to do with either having 2 monitors or using both monitors attached via USB C/Thunderbolt.

This is a portable workstation with all portable parts. The core system is a NUC9i9QNX and the 2 monitors have data and power over USB C/Thunderbolt.

I use 'monitors off' instead of sleep due to the portable monitors glitching out when the PC sleeps. They continuously turn on and off, probably due to power and data coming on the same port.

I use this for dev work and didn't even notice that I had HDR until a few days ago. This is a minor nuisance and probably a corner case bug but it is a bug none the less as I can reproduce it 100% of the time.

 

I'm not switching anything and USB C is awesome for what I use it for, powering and driving 2 portable monitors with just 2 cables. This is a dual monitor system.

I could just as easily hook 2 HDMI/DP cables up but then I still need to add power so that solution is useless to me.

I did some more testing and this is definitely a bug in the 'monitors off' function and HDR. If I reboot the system the problem does not happen, HDR functions normally.

 

Nvidia and integrated are on latest builds. I am not bothered by this minor bug but it would be interesting to see if anyone can reproduce it.

I assume that this a corner case that involves 3 factors:

1. HDR on
2. The system is set to turn monitors off but not sleep
3. Monitor(s) attached via USB C/Thunderbolt.

Not 100% sure about #3 but it seems like it must be the case otherwise I would not be the only one reporting the issue. I can't imagine that portable monitors using HDR is a common thing,

 

Windows is showing that HDR is enabled when it is disabled, it is their bug. I would need to contact Microsoft and doing that for a corner case is going to be pointless.

 

I noticed one more odd thing. After waking the monitors and HDR is in its glitched state, when you disable HDR it turns on first and then turns back off.

 

Did some more testing and found that pretty much anything that makes a change to the display will trigger HDR is switch from 'fake' on to actually on.

For example if the bug is in effect, changing scaling will trigger HDR to turn back on.

 

This bug has one more very strange feature. When the bug is in effect, the mouse pointer seems to be still in HDR mode, it is very bright compared to literally everything else.

 

This happened on both 19042.488 and 19042.508.

This bug is super easy to test for anyone that uses HDR.

Go to screen saver, make sure its off. Go to power settings and disable sleep but set "Turn off the display" to 1 minute. Wait 1 minute and then move the mouse to wake the monitor back up.

If you have the bug, display settings will show HDR still on but it will clearly be off. Turn off HDR and you will see it turn on and then instantly back off. Turning it back on will work as it should at this point.

With the bug in effect changing screen resolution or font scaling will also make the bug go away.

 

I was kind of hoping to get some testers to confirm this first. I suspect that this is a corner case related to my monitors connected via USB C. If people that use HDR tried the above steps (literally takes 1 minute and is 100% harmless) I'd have a better idea of what is actually going on here.

Eventually someone will read this and try it. The bug itself is not even worth reporting if it impacts a very small percentage of users and MS would just ignore me in that case anyway.

 

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