Sure, but most YouTube streams aren’t delivered as a single webm or mp4 file, and the language & subtitle selection you’re referring to aren’t implemented by the browser (but instead by a JavaScript application downloaded from Google). So it’s not what OP asked about.
Sure, but most YouTube streams aren’t delivered as a single webm or mp4 file, and the language & subtitle selection you’re referring to aren’t implemented by the browser (but instead by a JavaScript application downloaded from Google). So it’s not what OP asked about.