third_party/WebKit/LayoutTests/webaudio/biquad-tail.html

   1 <!doctype html>
   2 <html>
   3   <head>
   4     <title>Test Biquad Tail Output</title>
   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("Test Biquad Tail Output");
  13       window.jsTestIsAsync = true;
  14
  15       // A high sample rate shows the issue more clearly.
  16       var sampleRate = 192000;
  17       // Some short duration because we don't need to run the test for very long.
  18       var testDurationSec = 0.5;
  19       var testDurationFrames = testDurationSec * sampleRate;
  20
  21       // Amplitude experimentally determined to give a biquad output close to 1. (No attempt was
  22       // made to produce exactly 1; it's not needed.)
  23       var sourceAmplitude = 100;
  24
  25       // The output of the biquad filter should not change by more than this much between output
  26       // samples.  Threshold was determined experimentally.
  27       var glitchThreshold = 0.0129;
  28
  29       // Test that a Biquad filter doesn't have it's output terminated because the input has gone
  30       // away.  Generally, when a source node is finished, it disconnects itself from any downstream
  31       // nodes.  This is the correct behavior.  Nodes that have no inputs (disconnected) are
  32       // generally assumed to output zeroes.  This is also desired behavior.  However, biquad
  33       // filters have memory so they should not suddenly output zeroes when the input is
  34       // disconnected.  This test checks to see if the output doesn't suddenly change to zero.
  35       function runTest() {
  36         var context = new OfflineAudioContext(1, testDurationFrames, sampleRate);
  37
  38         // Create an impulse source.
  39         var buffer = context.createBuffer(1, 1, context.sampleRate);
  40         buffer.getChannelData(0)[0] = sourceAmplitude;
  41         var source = context.createBufferSource();
  42         source.buffer = buffer;
  43
  44         // Create the biquad filter. It doesn't really matter what kind, so the default filter type
  45         // and parameters is fine.  Connect the source to it.
  46         var biquad = context.createBiquadFilter();
  47         source.connect(biquad);
  48         biquad.connect(context.destination);
  49
  50         source.start();
  51
  52         context.startRendering().then(function(result) {
  53           // There should be no large discontinuities in the output
  54           var success = true;
  55           success = success && Should("Biquad output", result.getChannelData(0)).notGlitch(glitchThreshold);
  56           if (success)
  57             testPassed("Biquad tail output correctly completed.");
  58           else
  59             testFailed("Biquad tail output not correctly completed.");
  60         }).then(finishJSTest);
  61       }
  62
  63       runTest();
  64       successfullyParsed = true;
  65     </script>
  66   </body>
  67 </html>