third_party/WebKit/LayoutTests/webaudio/waveshaper.html

   1 <!DOCTYPE html>
   2
   3 <html>
   4 <head>
   5 <script src="../resources/js-test.js"></script>
   6 <script src="resources/compatibility.js"></script>
   7 <script type="text/javascript" src="resources/audio-testing.js"></script>
   8 <script type="text/javascript" src="resources/buffer-loader.js"></script>
   9 </head>
  10
  11 <body>
  12
  13 <div id="description"></div>
  14 <div id="console"></div>
  15
  16 <script>
  17 description("Tests that WaveShaperNode applies proper non-linear distortion.");
  18
  19 var sampleRate = 44100;
  20 var lengthInSeconds = 4;
  21 var numberOfRenderFrames = sampleRate * lengthInSeconds;
  22 var numberOfCurveFrames = 65536;
  23 var inputBuffer;
  24 var waveShapingCurve;
  25
  26 var context;
  27
  28 function generateInputBuffer() {
  29     // Create mono input buffer.
  30     var buffer = context.createBuffer(1, numberOfRenderFrames, context.sampleRate);
  31     var data = buffer.getChannelData(0);
  32
  33     // Generate an input vector with values from -1 -> +1 over a duration of lengthInSeconds.
  34     // This exercises the full nominal input range and will touch every point of the shaping curve.
  35     for (var i = 0; i < numberOfRenderFrames; ++i) {
  36         var x = i / numberOfRenderFrames; // 0 -> 1
  37         x = 2 * x - 1; // -1 -> +1
  38         data[i] = x;
  39     }
  40
  41     return buffer;
  42 }
  43
  44 // Generates a symmetric curve: Math.atan(5 * x) / (0.5 * Math.PI)
  45 // (with x == 0 corresponding to the center of the array)
  46 // This curve is arbitrary, but would be useful in the real-world.
  47 // To some extent, the actual curve we choose is not important in this test,
  48 // since the input vector walks through all possible curve values.
  49 function generateWaveShapingCurve() {
  50     var curve = new Float32Array(numberOfCurveFrames);
  51
  52     var n = numberOfCurveFrames;
  53     var n2 = n / 2;
  54
  55     for (var i = 0; i < n; ++i) {
  56         var x = (i - n2) / n2;
  57         var y = Math.atan(5 * x) / (0.5 * Math.PI);
  58     }
  59
  60     return curve;
  61 }
  62
  63 function checkShapedCurve(event) {
  64     var buffer = event.renderedBuffer;
  65
  66     var inputData = inputBuffer.getChannelData(0);
  67     var outputData = buffer.getChannelData(0);
  68
  69     var success = true;
  70
  71     // Go through every sample and make sure it has been shaped exactly according to the shaping curve we gave it.
  72     for (var i = 0; i < buffer.length; ++i) {
  73         var input = inputData[i];
  74
  75         // Calculate an index based on input -1 -> +1 with 0 being at the center of the curve data.
  76         var index = Math.floor(numberOfCurveFrames * 0.5 * (input + 1));
  77
  78         // Clip index to the input range of the curve.
  79         // This takes care of input outside of nominal range -1 -> +1
  80         index = index < 0 ? 0 : index;
  81         index = index > numberOfCurveFrames - 1 ? numberOfCurveFrames - 1 : index;
  82
  83         var expectedOutput = waveShapingCurve[index];
  84
  85         var output = outputData[i];
  86
  87         if (output != expectedOutput) {
  88             success = false;
  89             break;
  90         }
  91     }
  92
  93     if (success) {
  94         testPassed("WaveShaperNode properly applied non-linear distortion.");
  95     } else {
  96         testFailed("WaveShaperNode did not properly apply non-linear distortion.");
  97     }
  98
  99     finishJSTest();
 100 }
 101
 102 function runTest() {
 103     if (window.testRunner) {
 104         testRunner.dumpAsText();
 105         testRunner.waitUntilDone();
 106     }
 107
 108     window.jsTestIsAsync = true;
 109
 110     // Create offline audio context.
 111     context = new OfflineAudioContext(1, numberOfRenderFrames, sampleRate);
 112
 113     // source -> waveshaper -> destination
 114     var source = context.createBufferSource();
 115     var waveshaper = context.createWaveShaper();
 116     source.connect(waveshaper);
 117     waveshaper.connect(context.destination);
 118
 119     // Create an input test vector.
 120     inputBuffer = generateInputBuffer();
 121     source.buffer = inputBuffer;
 122
 123     // We'll apply non-linear distortion according to this shaping curve.
 124     waveShapingCurve = generateWaveShapingCurve();
 125     waveshaper.curve = waveShapingCurve;
 126
 127     source.start(0);
 128
 129     context.oncomplete = checkShapedCurve;
 130     context.startRendering();
 131 }
 132
 133 runTest();
 134
 135 </script>
 136
 137 </body>
 138 </html>