third_party/WebKit/LayoutTests/webaudio/audioparam-connect-audioratesignal.html

   1 <!DOCTYPE html>
   2
   3 <!--
   4 Tests that an audio-rate signal (AudioNode output) can be connected to an AudioParam.
   5 Specifically, this tests that an audio-rate signal coming from an AudioBufferSourceNode
   6 playing an AudioBuffer containing a specific curve can be connected to an AudioGainNode's
   7 .gain attribute (an AudioParam).  Another AudioBufferSourceNode will be the audio source
   8 having its gain changed.  We load this one with an AudioBuffer containing a constant value of 1.
   9 Thus it's easy to check that the resultant signal should be equal to the gain-scaling curve.
  10 -->
  11
  12 <html>
  13 <head>
  14 <script src="resources/compatibility.js"></script>
  15 <script src="resources/audio-testing.js"></script>
  16 <script src="../resources/js-test.js"></script>
  17
  18 </head>
  19 <body>
  20
  21 <script>
  22
  23 var sampleRate = 44100.0;
  24 var lengthInSeconds = 1;
  25
  26 var context = 0;
  27 var constantOneBuffer = 0;
  28 var linearRampBuffer = 0;
  29
  30 function checkResult(event) {
  31     var renderedBuffer = event.renderedBuffer;
  32     var renderedData = renderedBuffer.getChannelData(0);
  33     var expectedData = linearRampBuffer.getChannelData(0);
  34     var n = renderedBuffer.length;
  35
  36     if (n == linearRampBuffer.length) {
  37         testPassed("Rendered signal is of correct length.");
  38     } else {
  39         testFailed("Rendered signal is not of correct length.");
  40     }
  41
  42     // Check that the rendered result exactly matches the buffer used to control gain.
  43     // This is because we're changing the gain of a signal having constant value 1.
  44     var success = true;
  45     for (var i = 0; i < n; ++i) {
  46         if (renderedData[i] != expectedData[i]) {
  47             success = false;
  48             break;
  49         }
  50     }
  51
  52     if (success) {
  53         testPassed("Rendered signal exactly matches the audio-rate gain changing signal.");
  54     } else {
  55         testFailed("Rendered signal differs from the audio-rate gain changing signal.");
  56     }
  57
  58     finishJSTest();
  59 }
  60
  61 function runTest() {
  62     if (window.testRunner) {
  63         testRunner.dumpAsText();
  64         testRunner.waitUntilDone();
  65     }
  66
  67     window.jsTestIsAsync = true;
  68
  69     var sampleFrameLength = sampleRate * lengthInSeconds;
  70
  71     // Create offline audio context.
  72     context = new OfflineAudioContext(1, sampleFrameLength, sampleRate);
  73
  74     // Create buffer used by the source which will have its gain controlled.
  75     constantOneBuffer = createConstantBuffer(context, sampleFrameLength, 1);
  76
  77     // Create buffer used to control gain.
  78     linearRampBuffer = createLinearRampBuffer(context, sampleFrameLength);
  79
  80     // Create the two sources.
  81
  82     var constantSource = context.createBufferSource();
  83     constantSource.buffer = constantOneBuffer;
  84
  85     var gainChangingSource = context.createBufferSource();
  86     gainChangingSource.buffer = linearRampBuffer;
  87
  88     // Create a gain node controlling the gain of constantSource and make the connections.
  89     var gainNode = context.createGain();
  90
  91     // Intrinsic baseline gain of zero.
  92     gainNode.gain.value = 0;
  93
  94     constantSource.connect(gainNode);
  95     gainNode.connect(context.destination);
  96
  97     // Connect an audio-rate signal to control the .gain AudioParam.
  98     // This is the heart of what is being tested.
  99     gainChangingSource.connect(gainNode.gain);
 100
 101     // Start both sources at time 0.
 102     constantSource.start(0);
 103     gainChangingSource.start(0);
 104
 105     context.oncomplete = checkResult;
 106     context.startRendering();
 107 }
 108
 109 runTest();
 110 successfullyParsed = true;
 111
 112 </script>
 113
 114 </body>
 115 </html>