Black screen issue if attached two HDMI device on NUC8i7HVK with WIN10

[Alexiss]

Hello,

 Recently, I've used my NUC to connect my sound bar(sony z9f). Z9f also connects a projector.

 If z9f+projector+monitor are power on, two display are working as normal. Then once I power off the projector, the monitor will just show black screen(no signal). However, if I turn off the monitor and keep the projector on, the projector still  works fine. A weird thing is that the windows still detect two displays on system even monitor are power off.

I feel annoyed about this problem, because it is inconvenient. After watching movie with projector, I want to use the computer. However, no video on monitor. I have to remove HDMI cable from the NUC. Then monitor shows image.

I've used my Macbook Air(intel chip) to do the same test, no problem at all. The only different is that MAC_Air has internal LCD.  Also, I found AIR can recognize AV receiver after power off the projector.

It seems a intel graphic driver issue. Has anyone  ever meet this issue? any suggestion? please advice.

system: NUC8i7HVK

BIOS: HNKBLi70.86A.0064.2020.1028.1438

video driver:  intel 63027.20.100.8681

                         AMD radeon rx  vega M Adrenalin 2020 Edition 20.2.2 or 25.20.15002.58

OS: Win10 20H2

Repro:

scenario A
1. Attaching one HDMI cable with HDMI monitor on one of NUC's HDMI ports.

2. Attaching another HDMI cable with sony z9f on the other NUC's HDMI ports.

3. Attaching another HDMI cable with sony z9f output port with a projecter

4. power on z9f+monitor+projector, boot into windows, two displays works normal

5. power off the projector, the monitor is black screen.

6.remove HDMI cable which connect to z9f form NUC's HDMI ports, monitor are normal again.

scenario B

1. Attaching one HDMI cable with HDMI monitor on one of NUC's HDMI ports.

2. Attaching another HDMI cable with sony z9f on the other NUC's HDMI ports.

3. Attaching another HDMI cable with sony z9f output port with a projecter

4. power on monitor+z9f, power on NUC. Before entering into windows, you'll see nuc logo.

5.after entering into windows, monitor has video one or two seconds. Then black screen.

[Alexiss]

Hi, all

  The issue should be caused by graphic driver.  System think z9f is second monitor, but didn't get any response. That's why caused the issue.  After google, I find one workaround. You need to edit some registry keys. I share this inform for people who meet same problem.

First, use RegEdit to delete all the registry keys inside these 3 folders (not the folders themselves, just the keys inside):
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers\Configuration >>

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers\Connectivity >>

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers\ScaleFactors >>

Then if I attach two HDMI with z9f and monitor, Win10 think there has two monitors on system.(original states is black screen). The only trouble is even I turn off the z9f, win10 still think two monitors on system. However, I think it's better than you  have to always remove HDMI cable from system.

PS: I got idea from this link as below:

https://forums.tomshardware.com/threads/sticky-problem-with-hdmi-soundbar-and-windows-10.3615867/

Finally, I still hope intel can fix this issue in the future of AMD radeon rx vega m  driver.

[Maria_R_Intel]

Hello Alexiss,

Thank you for posting on the Intel* Community.

We are glad to know you found a workaround, thank you for taking the time to share this fix, and hopefully, it may help other community members experiencing similar behavior. Since the thread is now solved, we will proceed to close it.

However, I will share your feedback with the proper team so they can take this into consideration in case they are planning future releases, at the meantime, I cannot promise a fix. Thank you for your understanding.

If you need any additional information, please submit a new question as this thread will no longer be monitored.

Best regards,

Maria R.

Intel Customer Support Technician