test_oscillatorNodeNegativeFrequency.html

Enable keyboard shortcuts

<!DOCTYPE HTML>

<html>

<head>

  <title>Test the OscillatorNode when the frequency is negative</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();

addLoadEvent(function() {

  var types = ["sine",

               "square",

               "sawtooth",

               "triangle"];

  var finished = 0;

  function finish() {

    if (++finished == types.length) {

      SimpleTest.finish();

  types.forEach(function(t) {

    var context = new OfflineAudioContext(1, 256, 44100);

    var osc = context.createOscillator();

    osc.frequency.value = -440;

    osc.type = t;

    osc.connect(context.destination);

    osc.start();

    context.startRendering().then(function(buffer) {

      var samples = buffer.getChannelData(0);

      // This samples the wave form in the middle of the first period, the value

      // should be negative.

      ok(samples[Math.floor(44100 / 440 / 4)] < 0., "Phase should be inverted when using a " + t + " waveform");

      finish();

});

});

});

</script>

</pre>

</body>

</html>