Cyril

Picture (colorspace):

Set up for desktop use or for kodi (video appliance) have different approaches.
The colorspace of the display decides whether we are trying to scale to rgb full, or rgb limited.
The Vizio FV551XVT displays a limited spectrum, so that is what we want to send from the PC.

AVR/TV:

kodi 18 > Denon 1911 > Vizio FV551XVT
TV: turn off the effects & color shaping & stuff. The PC will drive the bus.
AVR: Video Mode: Auto: Process video automatically based on the HDMI content
information. (p.47)

PC:

GPU set to bypass/passthrough
The GPU is set to pass the full color range from the application to the display, which avoids unecessary manipulation of the video levels. The disadvantage is that desktop applications which do NOT manage the colorspace correctly (or at all), end up being displayed incorrectly.

GPU output set to match the display The GPU is set to map the full color range of all applications to a specific range (whether larger or more limited), which ensures that ALL color levels (desktop environment, apps, etc) are displayed consistently, and closer to how they were intended. The disadvantage is that some color-levels will be scaled/manipulated multiple times prior to being displayed, which may result in poorer gradients in the form of lines or banding.

For a more detailed explanation, see how kodi addresses colorspace.

App-managed colorspace:

app(kodi) gpu display
full limited limited

advantage: correct levels displayed for both player and desktop
disadvantage: video levels are scaled twice (banding likely).

GPU-managed colorspace

app(kodi) gpu display
limited full limited

advantage: color-range preserved, zero scaling
disadvantage: incorrect color display of desktop content (crushed blacks and whites)

interestingly, despite kodi’s recommendation to avoid the extra scaling by leaving the gpu as pass-through,openelec’s colorspace recommendation seems to be to have the gpu do the scaling. The recommendation of app vs. OS control seems to follow that kodi is an app (that can also operate as it’s own DE), and openelec is an OS.

Wayland

Brad x tells us how (and reddit helps us out), starting with proptest output, ending with an altered gdm.service unit.

Instead of an altered unit, we will instead create a custom unit to configure the GPU output during boot (prior to login).

  1. Gather hardware info
  2. Compose command
  3. Generate systemd-unit
dubFam@kodi12:/home/cyril> proptest
trying to open device 'i915'...failed
trying to open device 'amdgpu'...failed
trying to open device 'radeon'...done
Connector 46 (DP-1)
		[ ... ]
	40 output_csc:
		flags: enum
		enums: bypass=0 tvrgb=1 ycbcr601=2 ycbcr709=3
		value: 0
Connector 48 (DVI-I-1)
		[ ... ]
	40 output_csc:
		flags: enum
		enums: bypass=0 tvrgb=1 ycbcr601=2 ycbcr709=3
		value: 0

Module = radeon
connector = 48 #DVI-I-1
device = /dev/dri/card0
property = 40 #output_csc
value = 1 #tvrgb=1

proptest -M radeon -D dev/dri/card0 48 connector 40 1

/etc/systemd/system/tvRGB.service

[Unit]
Description=Force tv-RGB (16-235) output
DefaultDependencies=no
After=sysinit.target

[Service]
Type=oneshot
ExecStart=/usr/bin/proptest -M radeon -D /dev/dri/card0 48 connector 40 1

[Install]
WantedBy=sysinit.target

** NOTE ** proptest command conflicts with plymouth boot-splash animation, so
spash=silent quiet must be removed from grub kernel command line for this unit to function properly.

built using: https://www.freedesktop.org/software/systemd/man/systemd.service.html#Examples
with input from: [https://forums.opensuse.org/showthread.php/537877…]https://forums.opensuse.org/showthread.php/537877-There-is-no-gdm-service-so-where-to-add-gdm-session-exec-line?p=2917186#post2917186

Xorg

(nvidia/nouveau):

Nvidia via the nouveau driver doesn’t seem to respond to xorg.conf.d colorspace entries, so we use the intel method: « untested » [[ ~/.config/autostart/ ]] [[ /etc/xdg/autostart ]] all users

remember to make executable

set-colorspace.sh

#!/bin/sh
xrandr --output HDMIx --set "Broadcast RGB" "Limited 16:235"

#!/bin/sh  
xrandr --output HDMIx --set "Broadcast RGB" "Full"

(replace HDMIx with the appropriate output device, verify by running xrandr).

ref-openelec :: ref-archwiki :: ref-kodiwiki :: kodi addresses colorspace

(nvidia/nvidia);

/etc/X11/xorg.conf.d/20-nvidia.conf (sets ColorRange for the specified device)

Section "Device"
	Identifier "Device0"
	Driver "nvidia"
	VendorName "NVIDIA Corporation"
	BoardName "GeForce GT 730"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device "Device0"
#	Option "ColorRange" "Full"
	Option "ColorRange" "Limited"
#	Option "ColorSpace" "YCbCr444"
#	Option "ColorSpace" "RGB"
EndSection

Notes:

kodi addresses colorspace

test images
http://www.lagom.nl/lcd-test/ https://ndimitrov.com/wp-content/uploads/2010/07/ndimitrov_calibration_chart.jpg