On 2025-01-15 03:00, Simon Ser wrote: > Is this 125 magic number something we can expect other hardware to > implement as well? > It's based on MS's CCCS interpretation of 80 nits as 1.0f [1]. Based on this definition one needs to use 125.0f to represent 10,000 nits, the maximum value PQ can represent. It's hard to say whether other HW will implement it the same way, though most drivers for HW that supports HDR on Windows might have a similar concept somewhere. > Could AMD use the HDR multiplier or another block to behave as if > the multiplier didn't exist? > Gamescope makes use of this scaled PQ EOTF and its inverse, so I'd like to expose at least one color pipeline that we can use to move gamescope from the AMD-private color properties to the color pipeline API. We only have a single HDR multiplier but three curves (1 and 3 are EOTF, curve 2 is the inverse). We could only mode a PQ curve in the range of 0 to MAX_VALUE (1.0, 255, 1024, etc.) for the 1st EOTF, not for the 2nd or 3rd curves. I'm not sure how useful that would be. [1] https://learn.microsoft.com/en-us/windows/win32/direct3darticles/high-dynamic-range#system-composition-using-a-high-bit-depth-canonical-color-space-1 Harry > Note, I am no HDR expert. Maybe others have a better idea whether this > makes sense or not.
