third_party/WebKit/LayoutTests/webaudio/dynamicscompressor-simple.html

   1 <!DOCTYPE HTML>
   2 <html>
   3   <head>
   4     <script src="../resources/js-test.js"></script>
   5     <script src="resources/compatibility.js"></script>
   6     <script type="text/javascript" src="resources/audio-testing.js"></script>
   7   </head>
   8
   9   <body>
  10     <div id="description"></div>
  11     <div id="console"></div>
  12
  13     <script>
  14       description("Test pre-emphasis in DynamicsCompressor is removed");
  15       var context;
  16       var sampleRate = 44100;
  17       var lengthInSeconds = 1;
  18       var renderedData;
  19       // This threshold experimentally determined. It depends on the the gain value of the gain node
  20       // below and the dynamics compressor.  When the DynamicsCompressor had the pre-emphasis
  21       // filters, the peak value is about 0.21.  Without it, the peak is about 0.84.
  22       var peakThreshold = 0.83;
  23
  24       function checkResult(event) {
  25         var renderedBuffer = event.renderedBuffer;
  26         renderedData = renderedBuffer.getChannelData(0);
  27         // Search for a peak in the last part of the data.
  28         var startSample = sampleRate * (lengthInSeconds - .1);
  29         var endSample = renderedData.length;
  30         var k;
  31         var peak = -1;
  32
  33         for (k = startSample; k < endSample; ++k) {
  34           var sample = Math.abs(renderedData[k]);
  35           if (peak < sample)
  36              peak = sample;
  37         }
  38
  39         if (peak >= peakThreshold) {
  40           testPassed("Pre-emphasis effect not applied as expected..");
  41         } else {
  42           testFailed("Pre-emphasis caused output to be decreased to " + peak
  43                      + " (expected >= " + peakThreshold + ")");
  44         }
  45
  46         finishJSTest();
  47       }
  48
  49       function runTest() {
  50         if (!window.testRunner) {
  51           testRunner.dumpAsTest();
  52           testRunner.waitUntilDone();
  53         }
  54
  55         window.jsTestIsAsync = true;
  56
  57         context = new OfflineAudioContext(1, sampleRate * lengthInSeconds, sampleRate);
  58         // Connect an oscillator to a gain node to the compressor.  The
  59         // oscillator frequency is set to a high value for the (original)
  60         // emphasis to kick in. The gain is a little extra boost to get the
  61         // compressor enabled.
  62         //
  63         var osc = context.createOscillator();
  64         osc.frequency.value = 15000;
  65         var gain = context.createGain();
  66         gain.gain.value = 1.5;
  67         var compressor = context.createDynamicsCompressor();
  68         osc.connect(gain);
  69         gain.connect(compressor);
  70         compressor.connect(context.destination);
  71         osc.start();
  72         context.oncomplete = checkResult;
  73         context.startRendering();
  74       }
  75
  76       runTest();
  77       successfullyParsed = true;
  78
  79     </script>
  80
  81   </body>
  82 </html>