chrome/browser/resources/app_list/audio_manager.js

   1 // Copyright 2013 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 /**
   6  * @fileoverview The manager of audio streams.
   7  */
   8
   9 cr.define('speech', function() {
  10   'use strict';
  11
  12   /**
  13    * The enum of the status of hotword audio recognition.
  14    *
  15    * @enum {number}
  16    */
  17   var AudioState = {
  18     STOPPED: 0,
  19     LISTENING: 1
  20   };
  21
  22   /**
  23    * @constructor
  24    * @extends {cr.EventTarget}
  25    */
  26   function AudioManager() {
  27     var audioContext = new window.AudioContext();
  28     this.sampleRate = audioContext.sampleRate;
  29     this.audioProc_ = null;
  30     this.audioIn_ = null;
  31     this.stream_ = null;
  32     this.state = AudioState.STOPPED;
  33   };
  34
  35   AudioManager.prototype.__proto__ = cr.EventTarget.prototype;
  36
  37   /**
  38    * Called when the audio data arrives.
  39    *
  40    * @param {Event} audioEvent The audio event.
  41    * @private
  42    */
  43   AudioManager.prototype.onAudioProcess_ = function(audioEvent) {
  44     var data = audioEvent.inputBuffer.getChannelData(0);
  45     var intData = new Int16Array(data.length);
  46     for (var i = 0; i < data.length; ++i)
  47       intData[i] = Math.round(data[i] * 32767);
  48     var event = new Event('audio');
  49     event.data = intData;
  50     this.dispatchEvent(event);
  51   };
  52
  53   /**
  54    * Called when the audio stream is ready.
  55    *
  56    * @param {MediaStream} stream The media stream which is now available.
  57    * @private
  58    */
  59   AudioManager.prototype.onAudioReady_ = function(stream) {
  60     var audioContext = new window.AudioContext();
  61     this.stream_ = stream;
  62     this.audioIn_ = audioContext.createMediaStreamSource(stream);
  63     this.audioProc_ = audioContext.createScriptProcessor(
  64         4096 /* buffer size */, 1 /* channels */, 1 /* channels */);
  65     this.audioProc_.onaudioprocess = this.onAudioProcess_.bind(this);
  66
  67     this.audioIn_.connect(this.audioProc_);
  68     this.audioProc_.connect(audioContext.destination);
  69     this.state = AudioState.LISTENING;
  70   };
  71
  72   /**
  73    * Starts the audio processing.
  74    */
  75   AudioManager.prototype.start = function() {
  76     if (this.state == AudioState.LISTENING)
  77       return;
  78
  79     navigator.webkitGetUserMedia(
  80         {audio: true},
  81         this.onAudioReady_.bind(this),
  82         function(msg) { console.error('Failed to getUserMedia: ' + msg); });
  83   };
  84
  85   /**
  86    * Stops the audio processing.
  87    */
  88   AudioManager.prototype.stop = function() {
  89     if (this.state != AudioState.LISTENING)
  90       return;
  91     this.audioProc_.disconnect();
  92     this.audioIn_.disconnect();
  93     var audioTracks = this.stream_.getAudioTracks();
  94     for (var i = 0; i < audioTracks.length; ++i) {
  95       audioTracks[i].stop();
  96     }
  97     this.audioProc_ = null;
  98     this.audioIn_ = null;
  99     this.stream_ = null;
 100     this.state = AudioState.STOPPED;
 101   };
 102
 103   return {
 104     AudioManager: AudioManager,
 105     AudioState: AudioState
 106   };
 107 });