test_audioParamGain.html

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<!DOCTYPE HTML>

<html>

<head>

  <title>Test AudioParam with pre-gain </title>

  <script src="/tests/SimpleTest/SimpleTest.js"></script>

  <script type="text/javascript" src="webaudio.js"></script>

  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />

</head>

<body>

<pre id="test">

<script class="testbody" type="text/javascript">

SimpleTest.waitForExplicitFinish();

var ctx = new AudioContext();

var source = ctx.createOscillator();

var lfo = ctx.createOscillator();

var lfoIntensity = ctx.createGain();

var effect = ctx.createGain();

var sp = ctx.createScriptProcessor(2048, 1);

source.frequency.value = 440;

lfo.frequency.value = 2;

// Very low gain, so the LFO should have very little influence

// on the source, its RMS value should be close to the nominal value

// for a sine wave.

lfoIntensity.gain.value = 0.0001;

lfo.connect(lfoIntensity);

lfoIntensity.connect(effect.gain);

source.connect(effect);

effect.connect(sp);

sp.onaudioprocess = function(e) {

  var buffer = e.inputBuffer.getChannelData(0);

  var rms = 0;

  for (var i = 0; i < buffer.length; i++) {

    rms += buffer[i] * buffer[i];

  rms /= buffer.length;

  rms = Math.sqrt(rms);

  // 1 / Math.sqrt(2) is the theoretical RMS value for a sine wave.

  ok(fuzzyCompare(rms, 1 / Math.sqrt(2)),

      "Gain correctly applied to the AudioParam.");

  ctx = null;

  sp.onaudioprocess = null;

  lfo.stop(0);

  source.stop(0);

  SimpleTest.finish();

lfo.start(0);

source.start(0);

</script>

</pre>

</body>