Apple colorimetry 1:3:5:1: bt709, but full color range?
When h264 video from Apple's Airplay-mirror streaming protocol is streamed to gstreamer, h264parse gets its colorimetry values as 1:3:5;1 which video4linux2 does not recognize and caps negotiations fail. Is there some known full-color-range variant of bt709 (bt709 colorimetry = 2:3:5:1)?
The workaround is to use capsetter to declare the colorimetry as bt709, and then things work (v4l2h264dec plugin on Raspberry Pi).
is there any recognized color scheme variant of h264 like this? or could h264parse be getting it wrong, and it is just bt709? Could this just be Apple doing its own thing?
I'm guessing that the values are taken from some parameters in the initial SPS and PPS NAL units that begin the first frame of the bitstream. All content streamed in the iOS/macOS client screen-mirroring protocol seems to be 1:3:5:1. Where to look?, I can read the SPS and PPS.
Its not really an issue, since the capsetter workaround in the pipeline (in between between h264parse and v4l2h264dec) works, but I would welcome any input on this, thanks.