Just been looking at the available playback options for this video <https://www.youtube.com/watch?v=_u7d1wNDOyc> (“Casanova” by L.A.B.,
if you don’t want to have to click to find out ;)). youtube-dl†’s “-F”
option reports, among other things, the following:

248 webm 1920x1080 25 │ 26.86MiB 1019k https │ vp09.00.40.08 1019k video only 1080p, webm_dash
313 webm 3840x2160 25 │ 263.14MiB 9986k https │ vp09.00.50.08 9986k video only 2160p, webm_dash
571 mp4 7680x4320 25 │ 316.53MiB 12013k https │ av01.0.16M.08 12013k video only 4320p, mp4_dash

That’s 2K, 4K and 8K video options.

Note the 10× jump in the video bitrate going from 2K to 4K, for only a
4× jump in the number of pixels. Then 8K (another 4× increase in
pixels) is only about another 20% on top of that.

OK, so the 8K version is using a different codec. But it seems to me
either the 4K one is at a needlessly high bitrate, or alternatively
the 2K one is set too low. I suspect the former.

†yt-dlp, actually, since the original youtube-dl is now defunct. But I
have it aliased to the command “youtube-dl”, for old time’s sake. ;)

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