third_party/WebKit/LayoutTests/webaudio/resources/late-start-testing.js

   1 function runLateStartTest(audit, context, node) {
   2
   3   // Set up a dummy signal path to keep the audio context running and spend
   4   // processing time before calling start(0).
   5   var osc = context.createOscillator();
   6   var silent = context.createGain();
   7
   8   osc.connect(silent);
   9   silent.connect(context.destination);
  10   silent.gain.setValueAtTime(0.0, 0);
  11   osc.start();
  12
  13   node.connect(context.destination);
  14
  15   // Task: define |onstatechange| and start rendering.
  16   audit.defineTask('test-late-start', function (done) {
  17
  18     // Trigger playback at 0 second. The assumptions are:
  19     //
  20     // 1) The specified timing of start() call is already passed in terms of
  21     // the context time. So the argument |0| will be clamped to the current
  22     // context time.
  23     // 2) The |onstatechange| event will be fired later than the 0 second
  24     // context time.
  25     //
  26     // See issue: crbug.com/462167
  27     context.onstatechange = function () {
  28       if (context.state === 'running') {
  29         node.start(0);
  30       }
  31     };
  32
  33     // Start rendering and verify result: this verifies if 1) the rendered
  34     // buffer contains at least one non-zero value and 2) the non-zero value is
  35     // found later than the first output sample.
  36     context.startRendering().then(function (buffer) {
  37
  38       var nonZeroValueIndex = -1;
  39       var channelData = buffer.getChannelData(0);
  40       for (var i = 0; i < channelData.length; i++) {
  41         if (channelData[i] !== 0) {
  42           nonZeroValueIndex = i;
  43           break;
  44         }
  45       }
  46
  47       if (nonZeroValueIndex === -1) {
  48         testFailed('The rendered buffer was all zeros.');
  49       } else if (nonZeroValueIndex === 0) {
  50         testFailed('The first sample was non-zero value. It should be zero.');
  51       } else {
  52         testPassed('The rendered buffer contains non-zero values after the first sample.');
  53       }
  54
  55       done();
  56     });
  57   });
  58
  59   audit.defineTask('finish-test', function (done) {
  60     done();
  61     finishJSTest();
  62   });
  63
  64   audit.runTasks(
  65     'test-late-start',
  66     'finish-test'
  67   );
  68
  69 }