You also only really need the video to push the browser to do things in HDR. You can’t express a CSS colour way outside the normal range, but blending calculations are not clamped so can be used to get the colour. https://github.com/kiding/wanna-see-a-whiter-white was posted here a while ago and demonstrated the technique.

I'm not sure why you're being downvoted when that's exactly what's happening. The QR code comes from the mask-image in the inline-style, not the video.

The 1.19 KB video file itself has been created "manually" using a video editor. See https://github.com/dtinth/superwhite#creating-the-video

We can expect it is possible to create a much more compact video file with the same features.

Sure, I totally agree with that. Though not too much smaller: there's >500 bytes of required headers in an MP4 file encapsulating video.

In any case, that's not what the person I was replying to was talking about.