[Direct3D 12 HDR sample] Metadata not forwarded in windowed mode

[mitzsch]

I just got a question regarding the Direct3D 12 HDR sample app.
Actual metadata is only transmitted when the app is in fullscreen. I confirmed this with a hdfury arcana that shows the HDMI stream information. Is this behavior intended, where metadata is only forwarded in fullscreen mode, or is this a bug? Or to ask it differently what is needed for the windows compositor to actually forward HDR metadata?

This behavior is also present in other apps, like the video player mpv, that rely on the same api calls (like IDXGISwapChain4_SetHDRMetaData). The mpv video player transmits metadata only in fullscreen mode, like the HDR samples app.

(tested on Windows 10 21H2, with a RTX3050 and a RX 580)

[kpsam2000Intel]

As I know, for KMD it's always scRGB (709 FP16 linear with higher extends) with the fixed static metadata - ideally will be the same as that the display EDID indicate back to OS.