A simple JavaScript sound recorder and editor
JavaScript HTML CSS

README.md

JSSoundRecorder

Record sounds / noises around you and turn them into music.

It’s a work in progress, at the moment it enables you to record live audio straight from your browser, edit it and save these sounds as a WAV file.

There's also a sequencer part where you can create small loops using these sounds with a drone synth overlaid on them.

See it working: http://daaain.github.com/JSSoundRecorder

Technology

No servers involved, only Web Audio API with binary sound Blobs passed around!

Web Audio API

GetUserMedia audio for live recording

Experimental API to record any system audio input (including USB soundcards, musical instruments, etc).

// shim and create AudioContext
window.AudioContext = window.AudioContext || window.webkitAudioContext || window.mozAudioContext;
var audio_context = new AudioContext();

// shim and start GetUserMedia audio stream
navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia;
navigator.getUserMedia({audio: true}, startUserMedia, function(e) {
  console.log('No live audio input: ' + e);
});

Audio nodes for routing

You can route audio stream around, with input nodes (microphone, synths, etc), filters (volume / gain, equaliser, low pass, etc) and outputs (speakers, binary streams, etc).

function startUserMedia(stream) {
  // create MediaStreamSource and GainNode
  var input = audio_context.createMediaStreamSource(stream);
  var volume = audio_context.createGain();
  volume.gain.value = 0.7;

  // connect them and pipe output
  input.connect(volume);
  volume.connect(audio_context.destination);

  // connect recorder as well - see below
  var recorder = new Recorder(input);
}

WebWorker

Processing (interleaving) record buffer is done in the background to not block the main thread and the UI.

Also WAV conversion for export is also quite heavy for longer recordings, so best left to run in the background.

this.context = input.context;
this.node = this.context.createScriptProcessor(4096, 2, 2);
this.node.onaudioprocess = function(e){
  worker.postMessage({
   command: 'record',
   buffer: [
     e.inputBuffer.getChannelData(0),
     e.inputBuffer.getChannelData(1)
   ]
  });
}
function record(inputBuffer){
  var bufferL = inputBuffer[0];
  var bufferR = inputBuffer[1];
  var interleaved = interleave(bufferL, bufferR);
  recBuffers.push(interleaved);
  recLength += interleaved.length;
}

function interleave(inputL, inputR){
  var length = inputL.length + inputR.length;
  var result = new Float32Array(length);

  var index = 0,
      inputIndex = 0;

  while (index < length){
    result[index++] = inputL[inputIndex];
    result[index++] = inputR[inputIndex];
    inputIndex++;
  }
  return result;
}
function encodeWAV(samples){
  var buffer = new ArrayBuffer(44 + samples.length * 2);
  var view = new DataView(buffer);

  /* RIFF identifier */
  writeString(view, 0, 'RIFF');
  /* file length */
  view.setUint32(4, 32 + samples.length * 2, true);
  /* RIFF type */
  writeString(view, 8, 'WAVE');
  /* format chunk identifier */
  writeString(view, 12, 'fmt ');
  /* format chunk length */
  view.setUint32(16, 16, true);
  /* sample format (raw) */
  view.setUint16(20, 1, true);
  /* channel count */
  view.setUint16(22, 2, true);
  /* sample rate */
  view.setUint32(24, sampleRate, true);
  /* byte rate (sample rate * block align) */
  view.setUint32(28, sampleRate * 4, true);
  /* block align (channel count * bytes per sample) */
  view.setUint16(32, 4, true);
  /* bits per sample */
  view.setUint16(34, 16, true);
  /* data chunk identifier */
  writeString(view, 36, 'data');
  /* data chunk length */
  view.setUint32(40, samples.length * 2, true);

  floatTo16BitPCM(view, 44, samples);

  return view;
}

Binary Blob

Instead of file drag and drop interface this binary blob is passed to editor.

Note: BlobBuilder deprecated (but a lot of examples use it), you should use Blob constructor instead!

var f = new FileReader();
f.onload = function(e) {
  audio_context.decodeAudioData(e.target.result, function(buffer) {
      $('#audioLayerControl')[0].handleAudio(buffer);
    }, function(e) {
      console.warn(e);
    });
  };
f.readAsArrayBuffer(blob);
function exportWAV(type){
  var buffer = mergeBuffers(recBuffers, recLength);
  var dataview = encodeWAV(buffer);
  var audioBlob = new Blob([dataview], { type: type });

  this.postMessage(audioBlob);
}

Virtual File – URL.createObjectURL

You can create file download link pointing to WAV blob, but also set it as the source of an Audio element.

var url = URL.createObjectURL(blob);
var audioElement = document.createElement('audio');
var downloadAnchor = document.createElement('a');

audioElement.controls = true;
audioElement.src = url;

downloadAnchor.href = url;

TODO

  • Sequencer top / status row should be radio buttons :)
  • Code cleanup / restructuring
  • Enable open / drag and drop files for editing
  • Visual feedback (levels) for live recording
  • Sequencer UI (and separation to a different module)

Credits / license

Live recording code adapted from: http://www.phpied.com/files/webaudio/record.html

Editor code adapted from: https://github.com/plucked/html5-audio-editor

Copyright (c) 2012 Daniel Demmel

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.