So they serve two versions of every file, one for browsers using Widevine's scheme and another for everything else using their own scheme? And the benefit of Wi

So they serve two versions of every file, one for browsers using Widevine's scheme and another for everything else using their own scheme? And the benefit of Widevine is that it's a closed-source blob shipped with the browser itself (or not, as is the fundamental issue solved by the OP) rather than some obfuscated javascript, so you have zero access to it? At least until it ultimately writes PCM to the soundcard where you can then do what you want with it.