[fritsch]

still WIP

"Adding the support would involve several parts:

1) Add all the generic HDMI forum VSDB parsing and whatnot to the EDID parser

This is needed so that we'll know whether the sink supports YCbCr 4:2:0. There have been some patches towards HDMI 2.0 support for the EDID parser, but I can't recall how much was still missing from them. Not much merged so far.

3) Implement YCbCr 4:4:4 output support

This would involve doing RGB->YCbCr conversion with the pipe CSC. I started to implement this at some point, but got sidetracked and never actually finished. I should probably have a branch with some half finished code somewhere.

2) Extend out DP->HDMI dongle support to allow YCbCr 4:2:0 output.

Looking at the DP 1.4 spec, I see a PROTOCOL_CONVERTER_CONTROL_1 register that would allow you to enable YCbCr 4:2:0 conversion. If I'm reading things correctly we need to output YCbCr 4:4:4 to the dongle, and then dongle will downsample that to 4:2:0 when instructed to do so via this register. We probably have to parse a few other things from the DPCD as well so that we'll know whether the dongle even supports this."

So what is being output currently with Libreelec is it full or limited RGB?

Limited - No scale. It announces Limited, but does not scale nor clamp values. It's a special output patch I did some months ago to ease switching between full and limited.