Ah, you’re totally right, I missed that DXGI min luminance levels were also different… ref: dxgi docs. Looks like Mesa just doesn’t send the metadata if it’s invalid and will result in proto error.
I guess this is fixable on either dxvk/vkd3d or driver level? vkd3d fix might make more sense since it really should be the clients not violating the protocol… although Nvidia side fix would be more catch all, and I guess there’s no harm in the fix so maybe it’s less overall “work” for the driver to handle it like Mesa does.
I wonder how Windows deals with this? Looks like Microsoft now recommends that apps do not send HDR metadata anymore, but I’m not sure what it does for still sent invalid metadata (I guess it might just internally discard it like Mesa, probably for similar reasons).