Author says that it can’t be represented with css, but I think HDR is supported in Safari within Display P3 I believe, you can give a value higher than 1.0?
"HDR" contains multiple components:
- Electro-Optical Transfer Function. That's the famous "gamma" of the display which is no longer a gamma
- color space (which real-life color does RGB = 100%, 0%, 0% match)
- Absolute brightness. There are metadata in the video files that say that RGB=100%, 100%, 100% mean 2000cd/m2 (and gives the average frame brightness like 10%, which helps scales for displays not capable of 2000cd/m2 everywhere)
- Increased bit depth
Display-P3 is only the color space (and maybe the EOTF). This video uses the "absolute brightness" feature of HDR to increase brightness.