...which Firefox supports. You already properly cross-origin isolate your website, so it is already available on it.
Does not work in Firefox 79+ because SharedArrayBuffer is undefined - https://github.com/ffmpegwasm/ffmpeg.wasm/issues/106
Edit: limitation is gone, it should work 100% now
To me, that is an obvious contradiction.
It should instead keep the name of the video file, and just have the mp3 extension. It looks like you already have this filename in the preview audio player widget.
Also, there doesn't seem to be any caching of the files. Might be good to look in to something for that as well.
What do you mean by file caching?
Technically speaking, ffmpeg could accomplish 99% of what I'm building at https://mastershot.app/, but GUI > CLI for most people.