[opus] port Opus to Javascript using Emscripten

[Timothy B. Terriberry]

Wu, Rachel wrote:
> We are interested in adopting Opus into our web based application for
> speech recording. I’m wondering if there is a plan to port Opus encoder
> and decoder to Javascript using Emscripten in the near future?

libopus compiles with Emscripten without any problems.

Early work on a full player can be found here: 
https://github.com/maikmerten/ogv.js/tree/opus

A live example of that code is here: http://maikmerten.de/opus-demo/

Be cautioned that that code doesn't work particularly well in Firefox at 
the moment because of 
<https://bugzilla.mozilla.org/show_bug.cgi?id=970773> (though of course 
Firefox has native Opus support).

No one has done any work on an encoder in JS that I know of, but Firefox 
at least supports the Media Recorder API: 
<https://developer.mozilla.org/en-US/docs/Web/API/MediaRecorder_API>. I 
don't know if or when other browsers plan to add support for this API.