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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* @fileoverview The manager of audio streams.
*/
cr.define('speech', function() {
'use strict';
/**
* The enum of the status of hotword audio recognition.
*
* @enum {number}
*/
var AudioState = {
STOPPED: 0,
LISTENING: 1
};
/**
* @constructor
* @extends {cr.EventTarget}
*/
function AudioManager() {
this.audioContext_ = new window.webkitAudioContext();
this.audioProc_ = null;
this.state = AudioState.STOPPED;
};
AudioManager.prototype.__proto__ = cr.EventTarget.prototype;
/**
* Called when the audio data arrives.
*
* @param {Event} audioEvent The audio event.
* @private
*/
AudioManager.prototype.onAudioProcess_ = function(audioEvent) {
var data = audioEvent.inputBuffer.getChannelData(0);
var intData = new Int16Array(data.length);
for (var i = 0; i < data.length; ++i)
intData[i] = Math.round(data[i] * 32767);
var event = new Event('audio');
event.data = intData;
this.dispatchEvent(event);
};
/**
* Called when the audio stream is ready.
*
* @param {MediaStream} stream The media stream which is now available.
* @private
*/
AudioManager.prototype.onAudioReady_ = function(stream) {
var audioIn = this.audioContext_.createMediaStreamSource(stream);
this.audioProc_ = this.audioContext_.createScriptProcessor(
4096 /* buffer size */, 1 /* channels */, 1 /* channels */);
this.audioProc_.onaudioprocess = this.onAudioProcess_.bind(this);
audioIn.connect(this.audioProc_);
this.audioProc_.connect(this.audioContext_.destination);
this.state = AudioState.LISTENING;
};
/**
* Returns the sampling rate of the current audio context.
* @return {number} The sampling rate.
*/
AudioManager.prototype.getSampleRate = function() {
return this.audioContext_.sampleRate;
};
/**
* Starts the audio processing.
*/
AudioManager.prototype.start = function() {
if (this.state == AudioState.LISTENING)
return;
if (this.audioProc_) {
this.audioProc_.connect(this.audioContext_.destination);
this.state = AudioState.LISTENING;
return;
}
navigator.webkitGetUserMedia(
{audio: true},
this.onAudioReady_.bind(this),
function(msg) { console.error('Failed to getUserMedia: ' + msg); });
};
/**
* Stops the audio processing.
*/
AudioManager.prototype.stop = function() {
if (this.state != AudioState.LISTENING)
return;
this.audioProc_.disconnect();
this.state = AudioState.STOPPED;
};
return {
AudioManager: AudioManager,
AudioState: AudioState
};
});
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