Embeds offline voice recognizer plugin and its manager to app-list start page.

chrome/browser/resources/app_list/audio_manager.js

+// 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 and interaction with the plugin.
+ */
+
+cr.define('speech', function() {
+  'use strict';
+
+  /**
+   * The enum of the status of hotword audio recognition.
+   *
+   * @enum {number}
+   */
+  var AudioState = {
+    UNINITIALIZED: 0,
+    READY: 1,
+    RECOGNIZING: 2
+  };
+
+  /**
+   * @constructor
+   */
+  function AudioManager(onReady, onRecognizing, onRecognized) {
+    this.state = AudioState.UNINITIALIZED;
+    if (!speech.isPluginAvailable())
+      return;
+    this.onReady_ = onReady;
+    this.onRecognizing_ = onRecognizing;
+    this.pluginManager_ = new speech.PluginManager(
+        this.onPluginReady_.bind(this), onRecognized);
+    this.audioContext_ = new window.webkitAudioContext();
+    this.audioProc_ = null;
+    this.pluginManager_.scheduleInitialize(
+        this.audioContext_.sampleRate,
+        'chrome://app-list/okgoogle_hotword.config');
+  };
+
+  /**
+   * Called when the plugin is ready.
+   *
+   * @private
+   */
+  AudioManager.prototype.onPluginReady_ = function() {
+    this.state = AudioState.READY;
+    this.onReady_();
+  };
+
+  /**
+   * 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);
+    this.pluginManager_.sendAudioData(intData.buffer);
+  };
+
+  /**
+   * 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.RECOGNIZING;
+    this.onRecognizing_();
+  };
+
+  /**
+   * Starts the audio recognition with the plugin.
+   */
+  AudioManager.prototype.start = function() {
+    // Not yet initialized.
+    if (this.state != AudioState.READY)
+      return;
+    if (this.pluginManager_.state < speech.PluginState.READY)
+      return;
+
+    if (this.pluginManager_.state == speech.PluginState.READY)
+      this.pluginManager_.startRecognizer();
+
+    if (this.audioProc_) {
+      this.audioProc_.connect(this.audioContext_.destination);
+      this.state = AudioState.RECOGNIZING;
+      this.onRecognizing_();
+      return;
+    }
+
+    navigator.webkitGetUserMedia(
+        {audio: true},
+        this.onAudioReady_.bind(this),
+        function(msg) { console.error('Failed to getUserMedia: ' + msg); });
+  };
+
+  /**
+   * Stops the audio recognition.
+   */
+  AudioManager.prototype.stop = function() {
+    if (this.state <= AudioState.READY)
+      return;
+    this.audioProc_.disconnect();
+    this.pluginManager_.stopRecognizer();
+    this.state = AudioState.READY;
+  };
+
+  return {
+    AudioManager: AudioManager
+  };
+});