XDR values range

[piskov]

The range of values for Apple Studio Display is 400 to 60000. The range of values for Apple XDR Display is still untested.

For XDR the range is 400 ... 50_000.

For 400 in a completely dark room the brightness starts to change with increments of just 20. Though, of course, +20 will feel like nothing at higher brightness

[piskov]

Also, thank you for this product!

(If only I could make XDR output to 6k with Nvidia in Ubuntu like I can in Windows -- dreams, ah dreams; alas seems need to switch to Radeon for that)

[nikosdion]

Thank you! I updated the README to reflect this information.

FWIW< I have not used either the XDR display, or an NVIDIA card. I have only used the Apple Studio Display on various Linux distros (Ubuntu and many of its derivatives, as well as Arch Linux) with Intel integrated graphics, and AMD Radeon discrete graphics. I could get the full 5k resolution of my display with zero configuration on my part.

[piskov]

Probably needs percentage logic updated to accommodate both 50k and 60k max?

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As for Nvidia and XDR: it works at 5k out of the box — it’s the 6k that is an issue (outside of normal display port bandwidth and needs hacks like compression or stitching multiple virtual displays, that just wasn't implemented in nvidia drivers on linux for apple's special case)

[nikosdion]

That's a sensible request. My C is very rusty – I can read a lot of it, and tinker, but I am not sure how I'd go about what you proposed. If you could update the logic and make a PR I would be very happy to include it.

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About Nvidia and XDR: Right! The display is driven using the DisplayPort alt-mode. DisplayPort 1.4a only goes up to 5K at 60Hz with 30 bit/pixel RGB. Going beyond that requires dropping the refresh rate, or color width, or enable stream compression. Having a 6K HDR10 display at 60Hz requires DisplayPort 2.0 which is not supported in the 40-series Nvidia cards.