test_audioBufferSourceNodeRate.html

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<head>

  <title>Test AudioBufferSourceNode</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 rate = 44100;

var off = new OfflineAudioContext(1, rate, rate);

var off2 = new OfflineAudioContext(1, rate, rate);

var source = off.createBufferSource();

var source2 = off2.createBufferSource();

// a buffer of a 440Hz at half the length. If we detune by -1200 or set the

// playbackRate to 0.5, we should get 44100 samples back with a sine at 220Hz.

var buf = off.createBuffer(1, rate / 2, rate);

var bufarray = buf.getChannelData(0);

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

  bufarray[i] = Math.sin(i * 440 * 2 * Math.PI / rate);

source.buffer = buf;

source.playbackRate.value = 0.25; // slowdown to 25% speed

source.connect(off.destination);

source.start(0);

source2.buffer = buf;

source2.detune.value = -2400; // two octaves -> slowdown to 25% speed

source2.connect(off2.destination);

source2.start(0);

off.startRendering().then((renderedPlaybackRate) => {

  // we don't care about comparing the value here, we just want to know whether

  // the second part is noisy.

  var rmsValue = rms(renderedPlaybackRate, 0, 22050);

  ok(rmsValue != 0, "Resampling happened (rms of the second part " + rmsValue + ")");

  off2.startRendering().then((renderedDetune) => {

    var rmsValue = rms(renderedDetune, 0, 22050);

    ok(rmsValue != 0, "Resampling happened (rms of the second part " + rmsValue + ")");

    // The two buffers should be the same: detune of -2400 is a slowdown to 25% speed

    compareBuffers(renderedPlaybackRate, renderedDetune);

    SimpleTest.finish();

});

});

</script>

</pre>

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