I no longer see the warning on the readme, but, this relies on SharedArrayBuffer, so it is not currently supported on mobile
(except Firefox for android) and some other browsers: https://caniuse.com/sharedarraybuffer
> Your browser doesn't support SharedArrayBuffer, thus ffmpeg.wasm cannot execute. Please use latest version of Chromium or any other browser supports SharedArrayBuffer.
> Your browser doesn't support SharedArrayBuffer, thus ffmpeg.wasm cannot execute. Please use latest version of Chromium or any other browser supports SharedArrayBuffer.