Tiens, il est interessant de constater chez Youtube qu'en 3840x2160 le fichier VP9 est plus lourd que le H264.
Je ne suis pas en mesure de juger de la différence de qualité entre les deux, je ne suis pas équipé.
C:\youtube-dl>youtube-dl.exe -F https://www.youtube.com/watch?v=gEnkA5jR410
[youtube] gEnkA5jR410: Downloading webpage
[youtube] gEnkA5jR410: Downloading video info webpage
[youtube] gEnkA5jR410: Extracting video information
[youtube] gEnkA5jR410: Downloading MPD manifest
[info] Available formats for gEnkA5jR410:
format code extension resolution note
249 webm audio only DASH audio 56k , opus @ 50k (48000Hz), 2.85MiB
250 webm audio only DASH audio 78k , opus @ 70k (48000Hz), 3.62MiB
171 webm audio only DASH audio 121k , vorbis@128k (44100Hz), 6.38MiB
140 m4a audio only DASH audio 128k , m4a_dash container, mp4a.40.2@128k (44100Hz), 7.69MiB
251 webm audio only DASH audio 150k , opus @160k (48000Hz), 7.40MiB
278 webm 256x144 DASH video 117k , webm container, vp9, 30fps, video only, 5.64MiB
160 mp4 256x144 DASH video 123k , avc1.4d400c, 30fps, video only, 6.55MiB
133 mp4 426x240 DASH video 256k , avc1.4d4015, 30fps, video only, 14.51MiB
242 webm 426x240 DASH video 272k , vp9, 30fps, video only, 9.44MiB
243 webm 640x360 DASH video 493k , vp9, 30fps, video only, 17.69MiB
134 mp4 640x360 DASH video 640k , avc1.4d401e, 30fps, video only, 18.05MiB
244 webm 854x480 DASH video 960k , vp9, 30fps, video only, 31.01MiB
135 mp4 854x480 DASH video 1170k , avc1.4d401f, 30fps, video only, 38.10MiB
247 webm 1280x720 DASH video 1923k , vp9, 30fps, video only, 62.48MiB
136 mp4 1280x720 DASH video 2342k , avc1.4d401f, 30fps, video only, 75.52MiB
248 webm 1920x1080 DASH video 3383k , vp9, 30fps, video only, 111.43MiB
137 mp4 1920x1080 DASH video 4359k , avc1.640028, 30fps, video only, 141.98MiB
264 mp4 2560x1440 DASH video 10591k , avc1.640032, 30fps, video only, 351.25MiB
271 webm 2560x1440 DASH video 11802k , vp9, 30fps, video only, 308.19MiB
313 webm 3840x2160 DASH video 21217k , vp9, 30fps, video only, 794.71MiB
266 mp4 3840x2160 DASH video 23364k , avc1.640033, 30fps, video only, 752.21MiB
17 3gp 176x144 small , mp4v.20.3, mp4a.40.2@ 24k
36 3gp 320x180 small , mp4v.20.3, mp4a.40.2
5 flv 426x240 small , h263, mp3 @ 64k
43 webm 640x360 medium , vp8.0, vorbis@128k
18 mp4 640x360 medium , avc1.42001E, mp4a.40.2@ 96k
22 mp4 1280x720 hd720 , avc1.64001F, mp4a.40.2@192k (best)