Converting WAV to any compressed audio format in client-side JavaScript

Question

I am recording audio from getUserMedia({audio:true}); in the browser using Recorder.js and then exporting it as a WAV file because that\'s the only option the l

Answer 1

I had a similar issue (also using recorder.js) and have managed to resolve using the superb videoconverter.js project which includes a port of ffmpeg to Javascript using emscripen. Downside to this is the ffmpeg.js file is about 25Mb.

I modified the existing exportWAV function in recorderWorker.js to return both a WAV (for HTML5 playback) and a Blob containing an encoded MP2 file:

function encodeWAV(samples) {

  var buffer = new ArrayBuffer(44 + samples.length * 2);
  var view = new DataView(buffer);

  /* ... various writing methods */

  return { wavdata: new Blob([buffer], { type: "audio/wav" }), mp2data: ffmpeg_convert(buffer) };
}

function ffmpeg_convert(buffer) {
    console.log("starting mp2 conversion");
    var args = "-i input -f mp2 output.mp2";
    var results = ffmpeg_run({
        arguments: args.split(" "),
        files: [
          {
              data: new Uint8Array(buffer),
              "name": "input"
          }
        ]
    });
    if (results) {
        var file = results[0];
        console.log("File recieved", file.name, file.data);
        return new Blob([file.data], { type: "audio/mpeg" });
    }
    return null;
}

This method can be used to encode the WAV to any codec suppored by ffmpeg's libavcodec