Cannot turn off Dolby Vision HDR mode after calling NvAPI_Disp_HdrColorControl with NV_HDR_MODE_DOLBY_VISION

Hi, I’m working with Dolby to implement Dolby Vision HDMI pass-through on the Nvidia cards. In their sample code, it uses NvAPI_Disp_HdrColorControl function with the .hdrMode field set to NV_HDR_MODE_DOLBY_VISION and that works, but to turn it off, it calls NvAPI_Disp_HdrColorControl with the NV_HDR_MODE_OFF value. This does not work and the attached TV remains in Dolby Vision mode with a black screen. Does anyone know how to reset or force the adapter back to the Windows desktop without HDR programmatically? Of course I have asked Dolby about this issue but they have referred me back to NVidia since it seems to be a driver issue. Already tried the latest driver.

Dear @chilongtsang

Thank you for contacting NVIDIA developer forum.
We have sent your query to the respective team for details and we will get back to you on same.

NVAPI Forum Moderator

Yes, only reboot helps. It is just funny! Xbox gaming NOT COMING ANYTIME soon I see! Mass Effect Andromeda is STILL BROKEN!

Ask Battlefield 1 with APItrace. They correctly exit it. Frostbite, AM I right?

Is this going to get fixed??

Dear @chilongtsang

Sorry for the delay from our side on attending this. We will do initial scrutiny of the concerned API and if required, we will ask you to file a support ticket.

Thank you.
NVAPI Forum Moderator

Don’t you want Xbox Dolby Vision Gaming working on windows 11?? You can search through normal nvidia forums or through Internet and see how many people complain that Mass Effect Andromeda Next Generation of Gaming | 4k Dolby Vision on PC tutorial 2020 - YouTube

It was removed from Anthem though.

You can still force Andromeda to work but it is hard, you need to select RGB full and then load in HDR10 but then switch to Dolby Vision.

Still, when you exit Mass effect you will get black screen which you can only fix while rebooting.

Yes, I would like Dolby Vision working on Windows.
@agokhale please look into this as I have contacted Dolby to push this too. Switching to Dolby Vision works, its the exiting back to standard SDR Windows that does not.

Need for speed heat also has working dolby vision. Dolby Vision Working PC Game Settings Need For Speed Heat 12900K Overclock 5400Mhz - YouTube

It triggers Dolby Vision for me, but it does not work. And on exit Dolby Vision is not exiting.

Here is a comment about how when you exit, it stops working.

For those who got the black screen problem, you can ssh to your cmd, then type “powershell” there, after which this will work (those are 3 lines, not one):

$d = Get-PnpDevice| where {$_.class -like "Display*"}

 $d  | Disable-PnpDevice -Confirm:$false

 $d  | Enable-PnpDevice -Confirm:$false

It will restart your display driver device and fix it (not Dolby Vision, just the display).

Hello @val.zapod.vz , @chilongtsang

Our HDR expert from the dev team was OOTO last week. I’ll follow up with them this week. Please allow us some more time till he goes through the query and determines next steps. I’ll post the intermediate updates for you.

Thank you.
NVAPI Forum Moderator

Actually I just installed Mass Effect Andromeda and it also does not work anymore, just causes black screen on start. It does trigger dolby vision symbol on my TV though.

Hello @val.zapod.vz

As discussed with the HDR experts from our development team, the NvAPI_Disp_HdrColorControl() only supports the legacy Dolby Vision (DV) spec. Dolby has moved to a new DV scheme which does not necessarily need NVIDIA Graphics Driver involvement. The new TVs are not likely going to support old DV. We request you to kindly check about the new DV spec, which is the best way to go forward if you are writing a new game/app. Since you are already trying with the NvAPI, to disable the DV HDR mode, you may want to try a workaround by sending couple of extra NV_HDR_MODE_OFF calls.

Thank you.
NVAPI Forum Moderator

Actually if you are talking about Standard vs Low latency dolby vision Sony TV added support for Standard too. Or are you talking about new 120 fps DoVi mode since LG CX? Anyway, you cannot remove this API, since it breaks Need For speed HEAT, unless you remove DoVi block from EDID.

The fact of the matter I played Mass Effect in Dolby Vision but now it does not work.

HI @agokhale
That’s not really the point. There are millions of legacy DV TVs out there and our app has to support all the versions of DV TVs that users may attach to the Nvidia card.
We are not asking for any upgrades to the DV signalling, just that it switches OFF when NV_HDR_MODE_OFF is called. It should be fundamental that the API can switch off Dolby Vision, HDR10, HLG or whatever HDR mode back to standard SDR and ultimately back to the Windows desktop.

Hello @val.zapod.vz , @chilongtsang

Thank you for the prompt responses. Let me relay your points to the development team and I’ll get back to you when I hear from them.

Warm regards,
NVAPI Forum Moderator

You can also make microsoft to support Dolby Vision on desktop. That would also fix this issue, obviously.