test_waveShaperGain.html

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<head>

<meta charset="utf-8">

  <title>Test that WaveShaperNode doesn't corrupt its inputs when the gain is !=

    1.0 (bug 1203616)</title>

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

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

</head>

<body>

<pre>

</pre>

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

SimpleTest.waitForExplicitFinish();

var samplerate = 44100;

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

var dc = context.createBufferSource();

var buffer = context.createBuffer(1, 1, samplerate);

buffer.getChannelData(0)[0] = 1.0;

dc.buffer = buffer;

var gain = context.createGain();

var ws2 = context.createWaveShaper();

var ws = [];

// No-op waveshaper curves.

for (var i = 0; i < 2; i++) {

  ws[i] = context.createWaveShaper();

  var curve = new Float32Array(2);

  curve[0] = -1.0;

  curve[1] = 1.0;

  ws[i].curve = curve;

  ws[i].connect(context.destination);

  gain.connect(ws[i]);

dc.connect(gain);

dc.start();

gain.gain.value = 0.5;

context.startRendering().then(buffer => {

  document.querySelector("pre").innerHTML = buffer.getChannelData(0)[0];

  ok(buffer.getChannelData(0)[0] == 1.0, "Volume was handled properly");

  context = new OfflineAudioContext(1, 100, samplerate);

  var oscillator = context.createOscillator();

  var gain = context.createGain();

  var waveShaper = context.createWaveShaper();

  oscillator.start(0);

  oscillator.connect(gain);

  // to silence

  gain.gain.value = 0;

  gain.connect(waveShaper);

  // convert all signal into 1.0. The non unity values are to detect the use

  // of uninitialized buffers (see Bug 1283910).

  waveShaper.curve = new Float32Array([ 0.5, 0.5, 0.5, 0.5, 0.5, 1, 1, 0.5, 0.5, 0.5, 0.5, 0.5 ]);

  waveShaper.connect(context.destination);

  context.startRendering().then((buffer) => {

    var result = buffer.getChannelData(0);

    ok(result.every(x => x === 1), "WaveShaper handles zero gain properly");

    SimpleTest.finish();

});

});

</script>

</body>