This is a fork of ekisu's mpv-webm that adds several new settings, while removing unneeded or broken ones.
Simply put the script into your scripts folder. By default, the script is activated with the e key.
Follow the on-screen instructions. Video files will have audio/subs based on the current playback options (i.e. will be muted if no audio, won't have hardcoded subs if subs aren't visible).
Currently not supported, due to me being too lazy to update the files needed for it.