testing/web-platform/tests/webaudio/the-audio-api/the-audiobuffersourcenode-interface/sample-accurate-scheduling.html

   1 <!DOCTYPE html>
   2 <!--
   3 Tests that we are able to schedule a series of notes to playback with sample-accuracy.
   4 We use an impulse so we can tell exactly where the rendering is happening.
   5 -->
   6 <html>
   7   <head>
   8     <title>
   9       sample-accurate-scheduling.html
  10     </title>
  11     <script src="/resources/testharness.js"></script>
  12     <script src="/resources/testharnessreport.js"></script>
  13     <script src="/webaudio/resources/audit-util.js"></script>
  14     <script src="/webaudio/resources/audit.js"></script>
  15     <script src="/webaudio/resources/buffer-loader.js"></script>
  16   </head>
  17   <body>
  18     <script id="layout-test-code">
  19       let audit = Audit.createTaskRunner();
  20
  21       let sampleRate = 44100.0;
  22       let lengthInSeconds = 4;
  23
  24       let context = 0;
  25       let bufferLoader = 0;
  26       let impulse;
  27
  28       // See if we can render at exactly these sample offsets.
  29       let sampleOffsets = [0, 3, 512, 517, 1000, 1005, 20000, 21234, 37590];
  30
  31       function createImpulse() {
  32         // An impulse has a value of 1 at time 0, and is otherwise 0.
  33         impulse = context.createBuffer(2, 512, sampleRate);
  34         let sampleDataL = impulse.getChannelData(0);
  35         let sampleDataR = impulse.getChannelData(1);
  36         sampleDataL[0] = 1.0;
  37         sampleDataR[0] = 1.0;
  38       }
  39
  40       function playNote(time) {
  41         let bufferSource = context.createBufferSource();
  42         bufferSource.buffer = impulse;
  43         bufferSource.connect(context.destination);
  44         bufferSource.start(time);
  45       }
  46
  47       function checkSampleAccuracy(buffer, should) {
  48         let bufferDataL = buffer.getChannelData(0);
  49         let bufferDataR = buffer.getChannelData(1);
  50
  51         let impulseCount = 0;
  52         let badOffsetCount = 0;
  53
  54         // Left and right channels must be the same.
  55         should(bufferDataL, 'Content of left and right channels match and')
  56             .beEqualToArray(bufferDataR);
  57
  58         // Go through every sample and make sure it's 0, except at positions in
  59         // sampleOffsets.
  60         for (let i = 0; i < buffer.length; ++i) {
  61           if (bufferDataL[i] != 0) {
  62             // Make sure this index is  in sampleOffsets
  63             let found = false;
  64             for (let j = 0; j < sampleOffsets.length; ++j) {
  65               if (sampleOffsets[j] == i) {
  66                 found = true;
  67                 break;
  68               }
  69             }
  70             ++impulseCount;
  71             should(found, 'Non-zero sample found at sample offset ' + i)
  72                 .beTrue();
  73             if (!found) {
  74               ++badOffsetCount;
  75             }
  76           }
  77         }
  78
  79         should(impulseCount, 'Number of impulses found')
  80             .beEqualTo(sampleOffsets.length);
  81
  82         if (impulseCount == sampleOffsets.length) {
  83           should(badOffsetCount, 'bad offset').beEqualTo(0);
  84         }
  85       }
  86
  87       audit.define(
  88           {label: 'test', description: 'Test sample-accurate scheduling'},
  89           function(task, should) {
  90
  91             // Create offline audio context.
  92             context = new OfflineAudioContext(
  93                 2, sampleRate * lengthInSeconds, sampleRate);
  94             createImpulse();
  95
  96             for (let i = 0; i < sampleOffsets.length; ++i) {
  97               let timeInSeconds = sampleOffsets[i] / sampleRate;
  98               playNote(timeInSeconds);
  99             }
 100
 101             context.startRendering().then(function(buffer) {
 102               checkSampleAccuracy(buffer, should);
 103               task.done();
 104             });
 105           });
 106
 107       audit.run();
 108     </script>
 109   </body>
 110 </html>