[chupasaurus]

> Small note. There are methods of compression and encoding that allow for scalability. There's some fancy signal processing you can do to encode multiple <framerates / resolutions / compression qualities> into a single bitstream without necessarily storing redundant data.

A big note. All of this wasn't used by YT because they've always used a widely used standard codecs and media containers. All the lower qualities of videos they provide use storage nearly the same as the highest one (so 2x total), all bitrates are the same for all videos. As for download part, the players in auto quality would get first a maximum quality they can for current download speed, if there's a room or connection isn't stable - also 480p version, and if the speed was enough to download current and next chunk in lower quality it would download the best and switch to it over on completion (there were a times when player was downloading the whole video in the best quality after it had finished in an optimal).

> the sort of awful, buggy things (formatting/file wise) that people try to upload that break everything.

YT has very narrow list of formats allowed to upload with hard breaks in converting process, especially for the audio.