(In reply to Mike Lothian from comment #13) > I know my SkyQ box outputs at 2160@60Hz in 10bit colour https://en.wikipedia.org/wiki/HDMI#Refresh_frequency_limits_for_HDR10_video 4k@60@10bpc needs YUV 4:2:2 for HDMI 2.0, so it can't handle RGB (or YUV 4:4:4). That's probably the discrepancy - there's currently no great way for userspace to select which encoding variant is to be used (or what bpc to send it at).