third_party/WebKit/ManualTests/webaudio/multichannel.html

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   2 <html>
   3   <head>
   4     <title>Test multichannel support.</title>
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   6       body {
   7         margin: 2em;
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   9       .manual-test-ui {
  10         font-family: Arial;
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  14       .manual-test-ui button {
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  20
  21   <body>
  22     <h1>Test Multichannel Audio Output</h1>
  23
  24     <p>Tests that multichannel audio output (> 8 channels) is working correctly.
  25       This test cannot be run with an offline audio context because it requires
  26       an actual audio hardware with the multichannel capability.</p>
  27
  28     <p>Press "Start Test Tone" to run the test. You should hear an one-second
  29       sine tone from all the available audio output channels from the channel 1
  30       to the last channel.</p>
  31
  32     <p>Note that this test only works on OSX because CoreAudio driver supports
  33       the multichannel streams (more than 2) on a single audio device whereas
  34       other platforms do not.</p>
  35
  36     <p>CRBUG issue: <a href="https://code.google.com/p/chromium/issues/detail?id=424795" target="_blank">
  37       424795</a></p>
  38
  39     <div class="manual-test-ui">
  40       <p>Max Channel Count: <span id="eMaxChannelCount">2</span></p>
  41       <p>Currently playing: <span id="eChannelIndex">NONE</span></p>
  42       <button id="eButton" onclick="startTestTones()">Start Test Tone</button>
  43     </div>
  44
  45     <script type="text/javascript">
  46       // Silent interval between the test tones.
  47       var testToneInterval = 0.1;
  48
  49       // The safe range for the equal loudness of sinusoid is roughly between
  50       // 200 ~ 1000Hz, which is A3(57) ~ C6(84). In this test, the starting
  51       // pitch is 220Hz and the interval is the whole tone. (2 MIDI pitch)
  52       // With 16 speakers, the last test tone will play the MIDI pitch of
  53       // F6(89), which is 1396Hz.
  54       var startMIDIPitch = 57;
  55
  56       var eMaxChannelCount = document.querySelector('#eMaxChannelCount');
  57       var eButton = document.querySelector('#eButton');
  58       var eChannelIndex = document.querySelector('#eChannelIndex');
  59
  60       var context = new AudioContext();
  61       var maxChannelCount = context.destination.maxChannelCount;
  62
  63       // Sets the destination properties for multichannel access.
  64       context.destination.channelCount = maxChannelCount;
  65       context.destination.channelCountMode = 'explicit';
  66       context.destination.channelInterpretation = 'discrete';
  67
  68       // The ChannelMerger for the individual channel access.
  69       var merger = context.createChannelMerger(maxChannelCount);
  70       merger.channelCountMode = 'explicit';
  71       merger.channelInterpretation = 'discrete';
  72       merger.connect(context.destination);
  73
  74       eMaxChannelCount.textContent = maxChannelCount;
  75
  76       // Convert the MIDI pitch to frequency.
  77       function midi2freq(midiPitch) {
  78         return 440 * Math.pow(2, (midiPitch - 69) / 12);
  79       }
  80
  81       // Play a test tone for the specified amount of duration at the channel.
  82       function playTestToneAtChannel(channelIndex, gain, duration) {
  83         var osc = context.createOscillator();
  84         var amp = context.createGain();
  85         osc.connect(amp);
  86         amp.connect(merger, 0, channelIndex);
  87
  88         osc.onended = function () {
  89           var nextChannelIndex = channelIndex + 1;
  90           if (nextChannelIndex < maxChannelCount)
  91             playTestToneAtChannel(nextChannelIndex, gain, duration);
  92           else
  93             endTestTone();
  94         };
  95
  96         // The pitch for each speaker goes up as the channel index increases.
  97         // Note that the interval is 2, whole tone.
  98         osc.frequency.value = midi2freq(startMIDIPitch + channelIndex * 2);
  99
 100         // The channel index starts from 1.
 101         eChannelIndex.textContent = 'Channel #' + (channelIndex + 1);
 102
 103         var now = context.currentTime;
 104         var toneDuration = duration - testToneInterval;
 105
 106         // Add fade in and out to avoid the click noise.
 107         amp.gain.setValueAtTime(0.0, now);
 108         amp.gain.linearRampToValueAtTime(gain, now + toneDuration * 0.1);
 109         amp.gain.setValueAtTime(gain, now + toneDuration * 0.9);
 110         amp.gain.linearRampToValueAtTime(0.0, now + toneDuration);
 111
 112         osc.start(now);
 113         osc.stop(now + duration);
 114       }
 115
 116       // When the button is clicked the button to produce the test sound,
 117       // the button is grayed out so one cannot press again until the tone is
 118       // over. (producing sounds multiple times in a short period time will
 119       // hurt the speaker).
 120       function startTestTones() {
 121         eButton.disabled = true;
 122
 123         // Math.SQRT1_2(=0.707..) is -3dB. This is necessary because 1.0
 124         // amplitude can cause overload/distortion on some speakers.
 125         playTestToneAtChannel(0, Math.SQRT1_2, 1.0);
 126       }
 127
 128       // The button needs to be active back again when the test tone is over.
 129       // The index number in DIV should also be reset.
 130       function endTestTone() {
 131         eButton.disabled = false;
 132         eChannelIndex.textContent = 'NONE';
 133       }
 134     </script>
 135   </body>
 136 </html>