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originally https://greasyfork.org/en/scripts/8128-youtube-h-264 (https://github.com/erkserkserks/h264ify) and https://github.com/Shimmermare/NotYetAV1
< Youtube H.264 (updated 2020)についてのフィードバック
doesn't always work
need to change @match
http://youtube.com/*
https://youtube.com/*
http://www.youtube.com/*
https://www.youtube.com/*
to
*://*.youtube.com/*
Sadly it doesn't seem to work anymore.