third_party/WebKit/LayoutTests/webaudio/audiobuffersource-detune-modulated-impulse.html

   1 <!DOCTYPE html>
   2 <html>
   3
   4 <head>
   5   <script src="../resources/js-test.js"></script>
   6   <script src="resources/compatibility.js"></script>
   7   <script src="resources/audio-testing.js"></script>
   8 </head>
   9
  10 <body>
  11   <script>
  12     description('AudioBufferSourceNode: DC-driven detune modulation.');
  13     window.jsTestIsAsync = true;
  14
  15     var sampleRate = 44100;
  16
  17     // To get an observable change on detune modulation, the minimum
  18     // rendering length should greater than the rendering quantum.
  19     var renderLength = 256;
  20     var half = renderLength / 2;
  21
  22     // With the detune of 0, the duration of impulse buffer should be 4
  23     // samples (which means the interval between impulses is 4). Increasing
  24     // detune to 1200 (1 octave) decrease the interval to 2 samples.
  25     var impulseLength = 4;
  26
  27     var context = new OfflineAudioContext(1, renderLength, sampleRate);
  28     var impulseBuffer, dcOffsetBuffer;
  29
  30     var audit = Audit.createTaskRunner();
  31
  32
  33     // Task: build an impulse and DC-offset buffers for testing.
  34     audit.defineTask('build-buffers', function (done) {
  35       // 4-sample impulse sample.
  36       impulseBuffer = createImpulseBuffer(context, impulseLength);
  37
  38       // Create a DC offset buffer with 2 values [0, 1200] for modulating
  39       // detune. The first half of buffer is 0 and the rest is 1200.
  40       dcOffsetBuffer = context.createBuffer(1, renderLength, sampleRate);
  41       var dcOffsetArray = dcOffsetBuffer.getChannelData(0);
  42       for (i = 0; i < dcOffsetArray.length; i++) {
  43
  44         // Note that these values will be added to the detune AudioParam
  45         // value. For example, 1 DC offset value will result detune of 1200.
  46         dcOffsetArray[i] = i < half ? 0 : 1200;
  47       }
  48
  49       done();
  50     });
  51
  52
  53     // Task: Render the actual buffer and compare with the reference.
  54     audit.defineTask('synthesize-verify', function (done) {
  55       var impulse = context.createBufferSource();
  56       var dcOffset = context.createBufferSource();
  57
  58       impulse.buffer = impulseBuffer;
  59       dcOffset.buffer = dcOffsetBuffer;
  60       impulse.loop = true;
  61
  62       impulse.connect(context.destination);
  63       dcOffset.connect(impulse.detune);
  64
  65       impulse.start();
  66       dcOffset.start();
  67
  68       context.startRendering().then(function (renderedBuffer) {
  69         var data = renderedBuffer.getChannelData(0);
  70         var passed = true, i = 0;
  71         var nextImpulseIndex = 0;
  72
  73         while (i < renderLength) {
  74           if (i === nextImpulseIndex && data[i] === 1) {
  75             // From 0 to 127th element, the interval between impulses is 4. On the other
  76             // hand, the interval is 2 between 128th and 255th element.
  77             nextImpulseIndex += (i < half) ? impulseLength : impulseLength / 2;
  78           } else if (data[i] !== 0) {
  79             // If a value is neither 0 or 1, break the loop and fail the test.
  80             passed = false;
  81             break;
  82           }
  83
  84           i++;
  85         }
  86
  87         if (passed) {
  88           testPassed('Increasing detune to 1200 decreased the interval between impulses to half.');
  89         } else {
  90           testFailed('Increasing detune produced the incorrect result' +
  91             'at the index ' + i + '.');
  92         }
  93       }).then(done);
  94     });
  95
  96     audit.defineTask('finish', function (done) {
  97       finishJSTest();
  98       done();
  99     });
 100
 101     audit.runTasks(
 102       'build-buffers',
 103       'synthesize-verify',
 104       'finish'
 105     );
 106
 107     successfullyParsed = true;
 108   </script>
 109 </body>
 110
 111 </html>