chrome/test/data/third_party/spaceport/js/tests/audioLatency.js

   1 define([ 'util/ensureCallback', 'util/cacheBust', 'util/timeout' ], function (ensureCallback, cacheBust, timeout) {
   2     var MAX_LATENCY = 20;
   3
   4     function getPlayLatency(audio, callback) {
   5         callback = ensureCallback(callback);
   6
   7         var startTime;
   8
   9         function update() {
  10             var endTime = Date.now();
  11
  12             audio.removeEventListener('play', update, false);
  13             audio.removeEventListener('timeupdate', update, false);
  14             audio.pause();
  15
  16             callback(null, endTime - startTime);
  17         }
  18
  19         audio.addEventListener('play', update, false);
  20         audio.addEventListener('timeupdate', update, false);
  21
  22         startTime = Date.now();
  23         audio.play();
  24     }
  25
  26     function audioLatency(callback) {
  27         callback = ensureCallback(callback);
  28
  29         if (!window.Audio) {
  30             callback(new Error('Audio not supported'));
  31             return;
  32         }
  33
  34         var audio = new window.Audio();
  35
  36         function onCanPlayThrough() {
  37             audio.removeEventListener('canplaythrough', onCanPlayThrough, false);
  38
  39             // Run the test twice: once for "cold" time, once for "warm" time.
  40             getPlayLatency(audio, function (err, coldTime) {
  41                 if (err) {
  42                     callback(err);
  43                     return;
  44                 }
  45
  46                 getPlayLatency(audio, function (err, warmTime) {
  47                     if (err) {
  48                         callback(err);
  49                         return;
  50                     }
  51
  52                     callback(null, {
  53                         pass: coldTime <= MAX_LATENCY && warmTime <= MAX_LATENCY,
  54                         coldLatency: coldTime,
  55                         warmLatency: warmTime
  56                     });
  57                 });
  58             });
  59         }
  60
  61         function onError() {
  62             callback(new Error('Failed to load audio'));
  63         }
  64
  65         var source = document.createElement('source');
  66         source.src = cacheBust.url('assets/silence.wav');
  67         source.addEventListener('error', onError, false);
  68
  69         audio.addEventListener('canplaythrough', onCanPlayThrough, false);
  70         audio.addEventListener('error', onError, false);
  71         audio.appendChild(source);
  72         audio.play();
  73
  74         // Work around Webkit bug (present in Chrome <= 15, Safari <= 5, at
  75         // time of writing) where the browser will decide it doesn't /need/
  76         // to download all these pesky audio files.
  77         window['audio__' + Math.random()] = audio;
  78     }
  79
  80     return function (callback) {
  81         callback = ensureCallback(callback);
  82
  83         timeout(5000, audioLatency, callback);
  84     };
  85 });