chrome/test/data/extensions/api_test/tabs/basics/sinewave.js

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 window.sinewave = {
   6   play: function(win, frequency) {
   7     win.sinewaveData_ = win.sinewaveData_ || {};
   8     data = win.sinewaveData_;
   9
  10     if (!data.audioContext) {
  11       data.audioContext = new AudioContext();
  12       data.gainNode = data.audioContext.createGain();
  13       data.gainNode.gain.value = 0.5;
  14       data.gainNode.connect(data.audioContext.destination);
  15     }
  16     if (!data.oscillator ||
  17         data.oscillator.frequency.value != frequency) {
  18
  19       // Note: We recreate the oscillator each time because this switches the
  20       // audio frequency immediately.  Re-using the same oscillator tends to
  21       // take several hundred milliseconds to ramp-up/down the frequency.
  22       if (data.oscillator) {
  23         data.oscillator.stop();
  24         data.oscillator.disconnect();
  25       }
  26       data.oscillator = data.audioContext.createOscillator();
  27       data.oscillator.type = OscillatorNode.SINE;
  28       data.oscillator.frequency.value = frequency;
  29       data.oscillator.connect(data.gainNode);
  30     }
  31     data.oscillator.start();
  32   },
  33
  34   stop: function(win) {
  35     if (win.sinewaveData_)
  36       win.sinewaveData_.oscillator.stop();
  37   }
  38 };