The macOS screen recording tool doesn't appear to support recording HDR content (f.e. in QuickTime player). This tool can record from the camera using various YCbCr 422 and 420 formats needed for HVEC and ProRes HDR10 recording, but doesn't offer any options for screen recording HDR.
So that leaves in-game screen recording with AVFoundation. Without any YCbCr formats exposed in Metal api, how do we use CVPixelBuffer with Metal, and then send these formats off to the video codes directly? Can we send Rec2020 RGB10A2Unorm data directly? I'd like the fewest conversions possible.