third_party/WebKit/LayoutTests/webaudio/audiobuffersource-playbackrate-zero.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: test the "zero" playbackRate.');
  13     window.jsTestIsAsync = true;
  14
  15     // Sample rate should be power of 128 to observe the change of AudioParam at
  16     // the beginning of rendering quantum. (playbackRate is k-rate) This is the
  17     // minimum sample rate in the valid sample rate range.
  18     var sampleRate = 4096;
  19
  20     // The render duration in seconds, and the length in samples.
  21     var renderDuration = 1.0;
  22     var renderLength = renderDuration * sampleRate;
  23
  24     var context = new OfflineAudioContext(1, renderLength, sampleRate);
  25     var audit = Audit.createTaskRunner();
  26
  27
  28     // Task: Render the actual buffer and compare with the reference.
  29     audit.defineTask('synthesize-verify', function (done) {
  30       var ramp = context.createBufferSource();
  31       var rampBuffer = createLinearRampBuffer(context, renderLength);
  32       ramp.buffer = rampBuffer;
  33
  34       ramp.connect(context.destination);
  35       ramp.start();
  36
  37       // Leave the playbackRate as 1 for the first half, then change it
  38       // to zero at the exact half. The zero playback rate should hold the
  39       // sample value of the buffer index at the moment. (sample-and-hold)
  40       ramp.playbackRate.setValueAtTime(1.0, 0.0);
  41       ramp.playbackRate.setValueAtTime(0.0, renderDuration / 2);
  42
  43       context.startRendering().then(function (renderedBuffer) {
  44         var data = renderedBuffer.getChannelData(0);
  45         var rampData = rampBuffer.getChannelData(0);
  46         var half = rampData.length / 2;
  47         var passed = true;
  48
  49         for (var i = 1; i < rampData.length; i++) {
  50           if (i < half) {
  51             // Before the half position, the actual should match with the
  52             // original ramp data.
  53             if (data[i] !== rampData[i]) {
  54               passed = false;
  55               break;
  56             }
  57           } else {
  58             // From the half position, the actual value should not change.
  59             if (data[i] !== rampData[half]) {
  60               passed = false;
  61               break;
  62             }
  63           }
  64         }
  65
  66         if (passed) {
  67           testPassed('The zero playbackRate held the sample value correctly.');
  68         } else {
  69           testFailed('The zero playbackRate should hold the sample value. ' +
  70             'Expected ' + rampData[half] + ' but got ' + data[i] + ' at the index ' +
  71             i + '.');
  72         }
  73       }).then(done);
  74     });
  75
  76     audit.defineTask('finish', function (done) {
  77       finishJSTest();
  78       done();
  79     });
  80
  81     audit.runTasks(
  82       'synthesize-verify',
  83       'finish'
  84     );
  85
  86     successfullyParsed = true;
  87   </script>
  88 </body>
  89
  90 </html>