vp9 encoding

https://trac.ffmpeg.org/wiki/Encode/VP9

Constant quality

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 10 -b:v 0 -c:a libvorbis output.webm

p.s. Yeah stick with Vorbis which seems to be decently supported on Android (Opus isn’t).

http://caniuse.com/#search=opus

p.s.2. Global all browsers included % support (full + partical)

h.264       88.98%
vp9         70.42%

Probably not even worth bothering with vp9 at this point.