I am trying to use MediaRecorder in a way that it outputs a format that can be played back on all major browsers (Chrome-based, Firefox, Safari) without server-side re-encoding.

Here's what I have been scratching my head on:

• What format/codec should I use so that MediaRecorder outputs the most compatible output that can be natively played back by major browsers in a simple <audio src=...> tag?

• How can I configure MediaRecorder to record with that format and codec?

In the MediaRecorder1 documentation, they configure the format this way:

      var blob = new Blob(chunks, { 'type' : 'audio/ogg; codecs=opus' });

But it looks like tagging an already-recorded blob with a audio/ogg MIME i.e. if I replace with audio/mpeg I don't actually get a mpeg-encoded output.