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WavEncoder

WavEncoder is a fast cross-browser riff wave encoder for real-time audio synthesis in HTML5. Works in Web Workers and in the main window (in contrast to encoders using window.btoa).

Dual licensed under the MIT or GPL Version 2 licenses.

Examples

To play 1 sec of noise in the main window, we can

<script type='text/javascript' src='wavencoder.js'></script>
<script type='text/javascript'>

  var samples = [];
  for (var t = 0; t < 22050; ++t) {
    samples[t] = 2 * Math.random() - 1;  // in the interval [-1,1]
  }

  var datauri = WavEncoder.encode(samples);
  var audio = new Audio(datauri);

  document.onload(function(){ audio.play(); });

</script>

WavEncoder objects are optimized to create many samples of the same length. A typical use case is to generate a set of tones, say in a web worker

includeScripts('wavencoder.js');

var sampleRateHz = 44100;
var numSamples = 1 * sampleRateHz;                 // 1 sec
var baseFreq = 2 * Math.PI * 27.5 / sampleRateHz;  // A0

var wavEncoder = new WavEncoder(numSamples, {sampleRateHz: sampleRateHz});

var tones = [];
var samples = [];
for (var n = 0; n < 88; ++n) {

  var freq = baseFreq * Math.pow(2, n/12);
  for (var t = 0; t < numSamples; ++t) {
    samples[t] = Math.sin(freq * t);
  }

  tones[n] = wavEncoder.encode(samples);
}

postMessage(tones);
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