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     this.audioContext_ = new window.webkitAudioContext();
  28     this.audioProc_ = null;
  29     this.state = AudioState.STOPPED;
  30   };
  31
  32   AudioManager.prototype.__proto__ = cr.EventTarget.prototype;
  33
  34   /**
  35    * Called when the audio data arrives.
  36    *
  37    * @param {Event} audioEvent The audio event.
  38    * @private
  39    */
  40   AudioManager.prototype.onAudioProcess_ = function(audioEvent) {
  41     var data = audioEvent.inputBuffer.getChannelData(0);
  42     var intData = new Int16Array(data.length);
  43     for (var i = 0; i < data.length; ++i)
  44       intData[i] = Math.round(data[i] * 32767);
  45     var event = new Event('audio');
  46     event.data = intData;
  47     this.dispatchEvent(event);
  48   };
  49
  50   /**
  51    * Called when the audio stream is ready.
  52    *
  53    * @param {MediaStream} stream The media stream which is now available.
  54    * @private
  55    */
  56   AudioManager.prototype.onAudioReady_ = function(stream) {
  57     var audioIn = this.audioContext_.createMediaStreamSource(stream);
  58     this.audioProc_ = this.audioContext_.createScriptProcessor(
  59         4096 /* buffer size */, 1 /* channels */, 1 /* channels */);
  60     this.audioProc_.onaudioprocess = this.onAudioProcess_.bind(this);
  61
  62     audioIn.connect(this.audioProc_);
  63     this.audioProc_.connect(this.audioContext_.destination);
  64     this.state = AudioState.LISTENING;
  65   };
  66
  67   /**
  68    * Returns the sampling rate of the current audio context.
  69    * @return {number} The sampling rate.
  70    */
  71   AudioManager.prototype.getSampleRate = function() {
  72     return this.audioContext_.sampleRate;
  73   };
  74
  75   /**
  76    * Starts the audio processing.
  77    */
  78   AudioManager.prototype.start = function() {
  79     if (this.state == AudioState.LISTENING)
  80       return;
  81
  82     if (this.audioProc_) {
  83       this.audioProc_.connect(this.audioContext_.destination);
  84       this.state = AudioState.LISTENING;
  85       return;
  86     }
  87
  88     navigator.webkitGetUserMedia(
  89         {audio: true},
  90         this.onAudioReady_.bind(this),
  91         function(msg) { console.error('Failed to getUserMedia: ' + msg); });
  92   };
  93
  94   /**
  95    * Stops the audio processing.
  96    */
  97   AudioManager.prototype.stop = function() {
  98     if (this.state != AudioState.LISTENING)
  99       return;
 100     this.audioProc_.disconnect();
 101     this.state = AudioState.STOPPED;
 102   };
 103
 104   return {
 105     AudioManager: AudioManager,
 106     AudioState: AudioState
 107   };
 108 });