Most of this information is directly from brad-x.com
When “putting it all together”, Brad opted to copy and alter an existing unit-file.
My primary issue with this approach is that I am not a fan of depending on a non-associative copy of a vendor-configured unit-file.
Instead, we will create a unit file specifically to configure the gpu output.
Take it away Brad!
Some televisions and monitors are limited to the “broadcast RGB” color range. This is a subset of an 8-bit range of levels from 0-255 – in this case, 16-235. You’ll find this referred to as 16:235 in some cases.
You can find a lot more on this here: http://kodi.wiki/view/Video_levels_and_color_space
If you’re using Xorg this can be adjusted using the xrandr with something along the lines of:
xrandr --output HDMI-0 --set output_csc tvrgb (Radeon)
or
xrandr --output HDMI-0 --set "Broadcast RGB" "Limited 16:235" (Intel)
So – if you’ve noticed your colors are washed out and were wondering why, the above is a good starting point for you.
But wait! There’s more.
Maybe you’re like me, and you switched to Wayland. You had solved the above problem in Xorg, but you can’t find a way to do the same thing with Wayland.
The short answer: Wayland protocol itself doesn’t provide a facility for this, and the developers are leaving that up to the compositor to manage[1], and this hasn’t been implemented yet[2].
The way to do this is with the proptest utility, a test suite built with libdrm.
Brad builds libdrm, but we can get it from libdrm-tools
zypper in libdrm-tools
Back to you, Brad.
If you run the proptest command without arguments you’ll receive a list of connectors and properties.
Usage:
/root/libdrm-2.4.82/tests/proptest/.libs/proptest [options]
/root/libdrm-2.4.82/tests/proptest/.libs/proptest [options] [obj id] [obj type] [prop id] [value]
options:
-D DEVICE use the given device
-M MODULE use the given driver
The first form just prints all the existing properties. The second one is
used to set the value of a specified property. The object type can be one of
the following strings:
connector crtc
Example:
proptest 7 connector 2 1
will set property 2 of connector 7 to 1
Among these properties will be the specific one controlling output colorspace.
For Intel cards this will be Broadcast RGB and for Radeon it will be output_csc.
Nouveau may or may not have a property for this, don’t know.
Sample output from my laptop below:
trying to open device 'i915'...done
Connector 48 (eDP-1)
1 EDID:
flags: immutable blob
blobs:
value:
00ffffffffffff004d103e1400000000
28190104a52313780effb3a85334b825
0c4d5500000001010101010101010101
0101010101014dd000a0f0703e803020
35005ac2100000180000000000000000
00000000000000000000000000fe0037
50485054824c51313536443100000000
0002410328001200000b010a20200019
2 DPMS:
flags: enum
enums: On=0 Standby=1 Suspend=2 Off=3
value: 0
5 link-status:
flags: enum
enums: Good=0 Bad=1
value: 0
52 audio:
flags: enum
enums: force-dvi=18446744073709551614 off=18446744073709551615 auto=0 on=1
value: 0
53 Broadcast RGB:
flags: enum
enums: Automatic=0 Full=1 Limited 16:235=2
value: 0
54 scaling mode:
flags: enum
enums: None=0 Full=1 Center=2 Full aspect=3
value: 3
In my case, property 53 is the Broadcast RGB property. These numbers will vary on your own system.
Based on all of the above, you’d need to run:
proptest -M i915 -D /dev/dri/card0 48 connector 53 2
This doesn’t seem to take effect while Wayland is running, it has to be run beforehand.
Thank you Brad! This has been marvelously helpful.
I also found that the proptest command seems to conflict with the plymouth boot splash sequence, and would fail if the boot-animation was running during startup.
So I edited my grub sequence to NOT have splash=silent quiet in the grub entry.
This results in some verbose reboots and shutdowns, just in case that offends you.
Create a systemd-unit that executes your proptest command automatically on-boot
The unit file, tvRGB.service, in /etc/systemd/system/
[Unit]
Description=Force tv-RGB (16:235) output
DefaultDependencies=no
After=sysinit.target
[Service]
Type=oneshot
ExecStart=/usr/bin/proptest -M radeon 48 connector 40 1
[Install]
WantedBy=sysinit.target
To explain each line:
DefaultDependencies=no - Removes some un-needed dependencies so that the ExecStart line can be run/completed sooner than later
After=sysinit.target - Orders the ExecStart line to be run only after sysinit.target has completed
Type=oneshot - Defines the expectations of the process so that systemd can treat/report the unit appropriately
ExecStart=/usr/bin/proptest -M radeon 48 connector 40 1 - Upon the start of this unit, this command will be executed
WantedBy=sysinit.target - Defines the unit that will trigger tvRGB.service to be run.
Remember to enable your unit
systemctl enable tvRGB.service