HDR support in Wayland/Weston

Graeme Gill graeme2 at argyllcms.com
Mon Mar 4 10:30:55 UTC 2019

Chris Murphy wrote:

Hi Chris,

> Well you need a client to do display calibration which necessarily
> means altering the video LUT (to linear) in order to do the
> measurements from which a correction curve is computed, and then that
> client needs to install that curve into the video LUT. Now, colord
> clearly has such capability, as it's applying vcgt tags in ICC
> profiles now. If colord can do it, then what prevents other clients
> from doing it?

my suggestion is not to make the profiling application deal in
these sort of nuts and bolts. If there is an API to install
a profile for a particular output, then the Compositor can
take responsibility for implementing the ICC 'vcgt' tag.
It can choose to implement it in hardware (CRTC), or any other
way it wants, as long as it is implemented so that it
doesn't disadvantage the result compared to implementing it in hardware.


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