Adds basic Bluetooth support to AppRTCMobile

BUG=webrtc:6649 - Supports Bluetooth Headset profile. - Detects new BT headset: + enabled at start, and + powered on during active call. - Enables/disables BT SCO channel when BT device is selected. - Removes proximity sensor usage to avoid conflicts (will be added again later). - Adds new (unused) APIs to explicitly select audio device. - Starts routing audio to BT headset when enabled, i.e, BT is default. Review-Url: https://codereview.webrtc.org/2501983002 Cr-Commit-Position: refs/heads/master@{#15610}
2016-12-14 07:36:56 -08:00
parent db8af2a953
commit c3c2f31852
7 changed files with 1106 additions and 144 deletions
--- a/webrtc/BUILD.gn
+++ b/webrtc/BUILD.gn
@ -704,6 +704,7 @@ if (rtc_include_tests) {
        "androidjunit/src/org/webrtc/CameraEnumerationTest.java",
        "examples/androidjunit/src/org/appspot/apprtc/DirectRTCClientTest.java",
        "examples/androidjunit/src/org/appspot/apprtc/TCPChannelClientTest.java",
+        "examples/androidjunit/src/org/appspot/apprtc/BluetoothManagerTest.java",
      ]

      deps = [
--- a/webrtc/examples/BUILD.gn
+++ b/webrtc/examples/BUILD.gn
@ -65,6 +65,7 @@ if (is_android) {
  android_library("AppRTCMobile_javalib") {
    java_files = [
      "androidapp/src/org/appspot/apprtc/AppRTCAudioManager.java",
+      "androidapp/src/org/appspot/apprtc/AppRTCBluetoothManager.java",
      "androidapp/src/org/appspot/apprtc/AppRTCClient.java",
      "androidapp/src/org/appspot/apprtc/AppRTCProximitySensor.java",
      "androidapp/src/org/appspot/apprtc/CallActivity.java",
--- a/webrtc/examples/androidapp/AndroidManifest.xml
+++ b/webrtc/examples/androidapp/AndroidManifest.xml
@ -13,6 +13,7 @@
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
--- a/webrtc/examples/androidapp/src/org/appspot/apprtc/AppRTCAudioManager.java
+++ b/webrtc/examples/androidapp/src/org/appspot/apprtc/AppRTCAudioManager.java
@ -22,8 +22,11 @@ import android.media.AudioManager;
 import android.preference.PreferenceManager;
 import android.util.Log;

+import org.webrtc.ThreadUtils;
+
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;

 /**
@ -39,22 +42,48 @@ public class AppRTCAudioManager {
   * AudioDevice is the names of possible audio devices that we currently
   * support.
   */
-  // TODO(henrika): add support for BLUETOOTH as well.
-  public enum AudioDevice {
-    SPEAKER_PHONE,
-    WIRED_HEADSET,
-    EARPIECE,
+  public enum AudioDevice { SPEAKER_PHONE, WIRED_HEADSET, EARPIECE, BLUETOOTH, NONE }
+
+  /** AudioManager state. */
+  public enum AudioManagerState {
+    UNINITIALIZED,
+    PREINITIALIZED,
+    RUNNING,
+  }
+
+  /** Selected audio device change event. */
+  public static interface AudioManagerEvents {
+    // Callback fired once audio device is changed or list of available audio devices changed.
+    void onAudioDeviceChanged(
+        AudioDevice selectedAudioDevice, Set<AudioDevice> availableAudioDevices);
  }

  private final Context apprtcContext;
-  private final Runnable onStateChangeListener;
-  private boolean initialized = false;
  private AudioManager audioManager;
+
+  private AudioManagerEvents audioManagerEvents;
+  private AudioManagerState amState;
  private int savedAudioMode = AudioManager.MODE_INVALID;
  private boolean savedIsSpeakerPhoneOn = false;
  private boolean savedIsMicrophoneMute = false;
+  private boolean hasWiredHeadset = false;

-  private final AudioDevice defaultAudioDevice;
+  // Default audio device; speaker phone for video calls or earpiece for audio
+  // only calls.
+  private AudioDevice defaultAudioDevice;
+
+  // Contains the currently selected audio device.
+  // This device is changed automatically using a certain scheme where e.g.
+  // a wired headset "wins" over speaker phone. It is also possible for a
+  // user to explicitly select a device (and overrid any predefined scheme).
+  // See |userSelectedAudioDevice| for details.
+  private AudioDevice selectedAudioDevice;
+
+  // Contains the user-selected audio device which overrides the predefined
+  // selection scheme.
+  // TODO(henrika): always set to AudioDevice.NONE today. Add support for
+  // explicit selection based on choice by userSelectedAudioDevice.
+  private AudioDevice userSelectedAudioDevice;

  // Contains speakerphone setting: auto, true or false
  private final String useSpeakerphone;
@ -65,12 +94,12 @@ public class AppRTCAudioManager {
  // available, far from ear <=> use speaker phone).
  private AppRTCProximitySensor proximitySensor = null;

-  // Contains the currently selected audio device.
-  private AudioDevice selectedAudioDevice;
+  // Handles all tasks related to Bluetooth headset devices.
+  private final AppRTCBluetoothManager bluetoothManager;

  // Contains a list of available audio devices. A Set collection is used to
  // avoid duplicate elements.
-  private final Set<AudioDevice> audioDevices = new HashSet<AudioDevice>();
+  private Set<AudioDevice> audioDevices = new HashSet<AudioDevice>();

  // Broadcast receiver for wired headset intent broadcasts.
  private BroadcastReceiver wiredHeadsetReceiver;
@ -78,8 +107,10 @@ public class AppRTCAudioManager {
  // Callback method for changes in audio focus.
  private AudioManager.OnAudioFocusChangeListener audioFocusChangeListener;

-  // This method is called when the proximity sensor reports a state change,
-  // e.g. from "NEAR to FAR" or from "FAR to NEAR".
+  /**
+   * This method is called when the proximity sensor reports a state change,
+   * e.g. from "NEAR to FAR" or from "FAR to NEAR".
+   */
  private void onProximitySensorChangedState() {
    if (!useSpeakerphone.equals(SPEAKERPHONE_AUTO)) {
      return;
@ -92,29 +123,55 @@ public class AppRTCAudioManager {
      if (proximitySensor.sensorReportsNearState()) {
        // Sensor reports that a "handset is being held up to a person's ear",
        // or "something is covering the light sensor".
-        setAudioDevice(AppRTCAudioManager.AudioDevice.EARPIECE);
+        setAudioDeviceInternal(AppRTCAudioManager.AudioDevice.EARPIECE);
      } else {
        // Sensor reports that a "handset is removed from a person's ear", or
        // "the light sensor is no longer covered".
-        setAudioDevice(AppRTCAudioManager.AudioDevice.SPEAKER_PHONE);
+        setAudioDeviceInternal(AppRTCAudioManager.AudioDevice.SPEAKER_PHONE);
      }
    }
  }

-  /** Construction */
-  static AppRTCAudioManager create(Context context, Runnable deviceStateChangeListener) {
-    return new AppRTCAudioManager(context, deviceStateChangeListener);
+  /* Receiver which handles changes in wired headset availability. */
+  private class WiredHeadsetReceiver extends BroadcastReceiver {
+    private static final int STATE_UNPLUGGED = 0;
+    private static final int STATE_PLUGGED = 1;
+    private static final int HAS_NO_MIC = 0;
+    private static final int HAS_MIC = 1;
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+      int state = intent.getIntExtra("state", STATE_UNPLUGGED);
+      int microphone = intent.getIntExtra("microphone", HAS_NO_MIC);
+      String name = intent.getStringExtra("name");
+      Log.d(TAG, "WiredHeadsetReceiver.onReceive" + AppRTCUtils.getThreadInfo() + ": "
+              + "a=" + intent.getAction() + ", s="
+              + (state == STATE_UNPLUGGED ? "unplugged" : "plugged") + ", m="
+              + (microphone == HAS_MIC ? "mic" : "no mic") + ", n=" + name + ", sb="
+              + isInitialStickyBroadcast());
+      hasWiredHeadset = (state == STATE_PLUGGED);
+      updateAudioDeviceState();
+    }
+  };
+
+  /** Construction. */
+  static AppRTCAudioManager create(Context context) {
+    return new AppRTCAudioManager(context);
  }

-  private AppRTCAudioManager(Context context, Runnable deviceStateChangeListener) {
+  private AppRTCAudioManager(Context context) {
+    Log.d(TAG, "ctor");
+    ThreadUtils.checkIsOnMainThread();
    apprtcContext = context;
-    onStateChangeListener = deviceStateChangeListener;
    audioManager = ((AudioManager) context.getSystemService(Context.AUDIO_SERVICE));
+    bluetoothManager = AppRTCBluetoothManager.create(context, this);
+    wiredHeadsetReceiver = new WiredHeadsetReceiver();
+    amState = AudioManagerState.UNINITIALIZED;

    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
    useSpeakerphone = sharedPreferences.getString(context.getString(R.string.pref_speakerphone_key),
        context.getString(R.string.pref_speakerphone_default));
-
+    Log.d(TAG, "useSpeakerphone: " + useSpeakerphone);
    if (useSpeakerphone.equals(SPEAKERPHONE_FALSE)) {
      defaultAudioDevice = AudioDevice.EARPIECE;
    } else {
@ -132,19 +189,29 @@ public class AppRTCAudioManager {
        onProximitySensorChangedState();
      }
    });
+
+    Log.d(TAG, "defaultAudioDevice: " + defaultAudioDevice);
    AppRTCUtils.logDeviceInfo(TAG);
  }

-  public void init() {
-    Log.d(TAG, "init");
-    if (initialized) {
+  public void start(AudioManagerEvents audioManagerEvents) {
+    Log.d(TAG, "start");
+    ThreadUtils.checkIsOnMainThread();
+    if (amState == AudioManagerState.RUNNING) {
+      Log.e(TAG, "AudioManager is already active");
      return;
    }
+    // TODO(henrika): perhaps call new method called preInitAudio() here if UNINITIALIZED.

-    // Store current audio state so we can restore it when close() is called.
+    Log.d(TAG, "AudioManager starts...");
+    this.audioManagerEvents = audioManagerEvents;
+    amState = AudioManagerState.RUNNING;
+
+    // Store current audio state so we can restore it when stop() is called.
    savedAudioMode = audioManager.getMode();
    savedIsSpeakerPhoneOn = audioManager.isSpeakerphoneOn();
    savedIsMicrophoneMute = audioManager.isMicrophoneMute();
+    hasWiredHeadset = hasWiredHeadset();

    // Create an AudioManager.OnAudioFocusChangeListener instance.
    audioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
@ -199,31 +266,43 @@ public class AppRTCAudioManager {
    // Start by setting MODE_IN_COMMUNICATION as default audio mode. It is
    // required to be in this mode when playout and/or recording starts for
    // best possible VoIP performance.
-    // TODO(henrika): we migh want to start with RINGTONE mode here instead.
    audioManager.setMode(AudioManager.MODE_IN_COMMUNICATION);

    // Always disable microphone mute during a WebRTC call.
    setMicrophoneMute(false);

+    // Set initial device states.
+    userSelectedAudioDevice = AudioDevice.NONE;
+    selectedAudioDevice = AudioDevice.NONE;
+    audioDevices.clear();
+
+    // Initialize and start Bluetooth if a BT device is available or initiate
+    // detection of new (enabled) BT devices.
+    bluetoothManager.start();
+
    // Do initial selection of audio device. This setting can later be changed
-    // either by adding/removing a wired headset or by covering/uncovering the
-    // proximity sensor.
-    updateAudioDeviceState(hasWiredHeadset());
+    // either by adding/removing a BT or wired headset or by covering/uncovering
+    // the proximity sensor.
+    updateAudioDeviceState();

    // Register receiver for broadcast intents related to adding/removing a
-    // wired headset (Intent.ACTION_HEADSET_PLUG).
-    registerForWiredHeadsetIntentBroadcast();
-
-    initialized = true;
+    // wired headset.
+    registerReceiver(wiredHeadsetReceiver, new IntentFilter(Intent.ACTION_HEADSET_PLUG));
+    Log.d(TAG, "AudioManager started");
  }

-  public void close() {
-    Log.d(TAG, "close");
-    if (!initialized) {
+  public void stop() {
+    Log.d(TAG, "stop");
+    ThreadUtils.checkIsOnMainThread();
+    if (amState != AudioManagerState.RUNNING) {
+      Log.e(TAG, "Trying to stop AudioManager in incorrect state: " + amState);
      return;
    }
+    amState = AudioManagerState.UNINITIALIZED;

-    unregisterForWiredHeadsetIntentBroadcast();
+    unregisterReceiver(wiredHeadsetReceiver);
+
+    bluetoothManager.stop();

    // Restore previously stored audio states.
    setSpeakerphoneOn(savedIsSpeakerPhoneOn);
@ -240,94 +319,90 @@ public class AppRTCAudioManager {
      proximitySensor = null;
    }

-    initialized = false;
+    audioManagerEvents = null;
+    Log.d(TAG, "AudioManager stopped");
  }

  /** Changes selection of the currently active audio device. */
-  public void setAudioDevice(AudioDevice device) {
-    Log.d(TAG, "setAudioDevice(device=" + device + ")");
+  private void setAudioDeviceInternal(AudioDevice device) {
+    Log.d(TAG, "setAudioDeviceInternal(device=" + device + ")");
    AppRTCUtils.assertIsTrue(audioDevices.contains(device));

    switch (device) {
      case SPEAKER_PHONE:
        setSpeakerphoneOn(true);
-        selectedAudioDevice = AudioDevice.SPEAKER_PHONE;
        break;
      case EARPIECE:
        setSpeakerphoneOn(false);
-        selectedAudioDevice = AudioDevice.EARPIECE;
        break;
      case WIRED_HEADSET:
        setSpeakerphoneOn(false);
-        selectedAudioDevice = AudioDevice.WIRED_HEADSET;
+        break;
+      case BLUETOOTH:
+        setSpeakerphoneOn(false);
        break;
      default:
        Log.e(TAG, "Invalid audio device selection");
        break;
    }
-    onAudioManagerChangedState();
+    selectedAudioDevice = device;
+  }
+
+  /**
+   * Changes default audio device.
+   * TODO(henrika): add usage of this method in the AppRTCMobile client.
+   */
+  public void setDefaultAudioDevice(AudioDevice defaultDevice) {
+    ThreadUtils.checkIsOnMainThread();
+    switch (defaultDevice) {
+      case SPEAKER_PHONE:
+        defaultAudioDevice = defaultDevice;
+        break;
+      case EARPIECE:
+        if (hasEarpiece()) {
+          defaultAudioDevice = defaultDevice;
+        } else {
+          defaultAudioDevice = AudioDevice.SPEAKER_PHONE;
+        }
+        break;
+      default:
+        Log.e(TAG, "Invalid default audio device selection");
+        break;
+    }
+    Log.d(TAG, "setDefaultAudioDevice(device=" + defaultAudioDevice + ")");
+    updateAudioDeviceState();
+  }
+
+  /** Changes selection of the currently active audio device. */
+  public void selectAudioDevice(AudioDevice device) {
+    ThreadUtils.checkIsOnMainThread();
+    if (!audioDevices.contains(device)) {
+      Log.e(TAG, "Can not select " + device + " from available " + audioDevices);
+    }
+    userSelectedAudioDevice = device;
+    updateAudioDeviceState();
  }

  /** Returns current set of available/selectable audio devices. */
  public Set<AudioDevice> getAudioDevices() {
+    ThreadUtils.checkIsOnMainThread();
    return Collections.unmodifiableSet(new HashSet<AudioDevice>(audioDevices));
  }

  /** Returns the currently selected audio device. */
  public AudioDevice getSelectedAudioDevice() {
+    ThreadUtils.checkIsOnMainThread();
    return selectedAudioDevice;
  }

-  /**
-   * Registers receiver for the broadcasted intent when a wired headset is
-   * plugged in or unplugged. The received intent will have an extra
-   * 'state' value where 0 means unplugged, and 1 means plugged.
-   */
-  private void registerForWiredHeadsetIntentBroadcast() {
-    IntentFilter filter = new IntentFilter(Intent.ACTION_HEADSET_PLUG);
-
-    /** Receiver which handles changes in wired headset availability. */
-    wiredHeadsetReceiver = new BroadcastReceiver() {
-      private static final int STATE_UNPLUGGED = 0;
-      private static final int STATE_PLUGGED = 1;
-      private static final int HAS_NO_MIC = 0;
-      private static final int HAS_MIC = 1;
-
-      @Override
-      public void onReceive(Context context, Intent intent) {
-        int state = intent.getIntExtra("state", STATE_UNPLUGGED);
-        int microphone = intent.getIntExtra("microphone", HAS_NO_MIC);
-        String name = intent.getStringExtra("name");
-        Log.d(TAG, "BroadcastReceiver.onReceive" + AppRTCUtils.getThreadInfo() + ": "
-                + "a=" + intent.getAction() + ", s="
-                + (state == STATE_UNPLUGGED ? "unplugged" : "plugged") + ", m="
-                + (microphone == HAS_MIC ? "mic" : "no mic") + ", n=" + name + ", sb="
-                + isInitialStickyBroadcast());
-
-        boolean hasWiredHeadset = (state == STATE_PLUGGED);
-        switch (state) {
-          case STATE_UNPLUGGED:
-            updateAudioDeviceState(hasWiredHeadset);
-            break;
-          case STATE_PLUGGED:
-            if (selectedAudioDevice != AudioDevice.WIRED_HEADSET) {
-              updateAudioDeviceState(hasWiredHeadset);
-            }
-            break;
-          default:
-            Log.e(TAG, "Invalid state");
-            break;
-        }
-      }
-    };
-
-    apprtcContext.registerReceiver(wiredHeadsetReceiver, filter);
+  /** Helper method for receiver registration. */
+  private void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
+    apprtcContext.registerReceiver(receiver, filter);
  }

-  /** Unregister receiver for broadcasted ACTION_HEADSET_PLUG intent. */
-  private void unregisterForWiredHeadsetIntentBroadcast() {
-    apprtcContext.unregisterReceiver(wiredHeadsetReceiver);
-    wiredHeadsetReceiver = null;
+  /** Helper method for unregistration of an existing receiver. */
+  private void unregisterReceiver(BroadcastReceiver receiver) {
+    apprtcContext.unregisterReceiver(receiver);
  }

  /** Sets the speaker phone mode. */
@ -365,55 +440,139 @@ public class AppRTCAudioManager {
    return audioManager.isWiredHeadsetOn();
  }

-  /** Update list of possible audio devices and make new device selection. */
-  private void updateAudioDeviceState(boolean hasWiredHeadset) {
-    // Update the list of available audio devices.
-    audioDevices.clear();
+  /**
+   * Updates list of possible audio devices and make new device selection.
+   * TODO(henrika): add unit test to verify all state transitions.
+   */
+  public void updateAudioDeviceState() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "--- updateAudioDeviceState: "
+            + "wired headset=" + hasWiredHeadset + ", "
+            + "BT state=" + bluetoothManager.getState());
+    Log.d(TAG, "Device status: "
+            + "available=" + audioDevices + ", "
+            + "selected=" + selectedAudioDevice + ", "
+            + "user selected=" + userSelectedAudioDevice);
+
+    // Check if any Bluetooth headset is connected. The internal BT state will
+    // change accordingly.
+    // TODO(henrika): perhaps wrap required state into BT manager.
+    if (bluetoothManager.getState() == AppRTCBluetoothManager.State.HEADSET_AVAILABLE
+        || bluetoothManager.getState() == AppRTCBluetoothManager.State.HEADSET_UNAVAILABLE
+        || bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_DISCONNECTING) {
+      bluetoothManager.updateDevice();
+    }
+
+    // Update the set of available audio devices.
+    Set<AudioDevice> newAudioDevices = new HashSet<>();
+
+    if (bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTED
+        || bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTING
+        || bluetoothManager.getState() == AppRTCBluetoothManager.State.HEADSET_AVAILABLE) {
+      newAudioDevices.add(AudioDevice.BLUETOOTH);
+    }
+
    if (hasWiredHeadset) {
      // If a wired headset is connected, then it is the only possible option.
-      audioDevices.add(AudioDevice.WIRED_HEADSET);
+      newAudioDevices.add(AudioDevice.WIRED_HEADSET);
    } else {
      // No wired headset, hence the audio-device list can contain speaker
      // phone (on a tablet), or speaker phone and earpiece (on mobile phone).
-      audioDevices.add(AudioDevice.SPEAKER_PHONE);
+      newAudioDevices.add(AudioDevice.SPEAKER_PHONE);
      if (hasEarpiece()) {
-        audioDevices.add(AudioDevice.EARPIECE);
+        newAudioDevices.add(AudioDevice.EARPIECE);
      }
    }
-    Log.d(TAG, "audioDevices: " + audioDevices);
+    // Store state which is set to true if the device list has changed.
+    boolean audioDeviceSetUpdated = !audioDevices.equals(newAudioDevices);
+    // Update the existing audio device set.
+    audioDevices = newAudioDevices;
+    // Correct user selected audio devices if needed.
+    if (bluetoothManager.getState() == AppRTCBluetoothManager.State.HEADSET_UNAVAILABLE
+        && userSelectedAudioDevice == AudioDevice.BLUETOOTH) {
+      // If BT is not available, it can't be the user selection.
+      userSelectedAudioDevice = AudioDevice.NONE;
+    }
+    if (hasWiredHeadset && userSelectedAudioDevice == AudioDevice.SPEAKER_PHONE) {
+      // If user selected speaker phone, but then plugged wired headset then make
+      // wired headset as user selected device.
+      userSelectedAudioDevice = AudioDevice.WIRED_HEADSET;
+    }
+    if (!hasWiredHeadset && userSelectedAudioDevice == AudioDevice.WIRED_HEADSET) {
+      // If user selected wired headset, but then unplugged wired headset then make
+      // speaker phone as user selected device.
+      userSelectedAudioDevice = AudioDevice.SPEAKER_PHONE;
+    }

-    // Switch to correct audio device given the list of available audio devices.
-    if (hasWiredHeadset) {
-      setAudioDevice(AudioDevice.WIRED_HEADSET);
+    // Need to start Bluetooth if it is available and user either selected it explicitly or
+    // user did not select any output device.
+    boolean needBluetoothAudioStart =
+        bluetoothManager.getState() == AppRTCBluetoothManager.State.HEADSET_AVAILABLE
+        && (userSelectedAudioDevice == AudioDevice.NONE
+               || userSelectedAudioDevice == AudioDevice.BLUETOOTH);
+
+    // Need to stop Bluetooth audio if user selected different device and
+    // Bluetooth SCO connection is established or in the process.
+    boolean needBluetoothAudioStop =
+        (bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTED
+            || bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTING)
+        && (userSelectedAudioDevice != AudioDevice.NONE
+               && userSelectedAudioDevice != AudioDevice.BLUETOOTH);
+
+    if (bluetoothManager.getState() == AppRTCBluetoothManager.State.HEADSET_AVAILABLE
+        || bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTING
+        || bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTED) {
+      Log.d(TAG, "Need BT audio: start=" + needBluetoothAudioStart + ", "
+              + "stop=" + needBluetoothAudioStop + ", "
+              + "BT state=" + bluetoothManager.getState());
+    }
+
+    // Start or stop Bluetooth SCO connection given states set earlier.
+    if (needBluetoothAudioStop) {
+      bluetoothManager.stopScoAudio();
+      bluetoothManager.updateDevice();
+    }
+
+    if (needBluetoothAudioStart && !needBluetoothAudioStop) {
+      // Attempt to start Bluetooth SCO audio (takes a few second to start).
+      if (!bluetoothManager.startScoAudio()) {
+        // Remove BLUETOOTH from list of available devices since SCO failed.
+        audioDevices.remove(AudioDevice.BLUETOOTH);
+        audioDeviceSetUpdated = true;
+      }
+    }
+
+    // Update selected audio device.
+    AudioDevice newAudioDevice = selectedAudioDevice;
+
+    if (bluetoothManager.getState() == AppRTCBluetoothManager.State.SCO_CONNECTED) {
+      // If a Bluetooth is connected, then it should be used as output audio
+      // device. Note that it is not sufficient that a headset is available;
+      // an active SCO channel must also be up and running.
+      newAudioDevice = AudioDevice.BLUETOOTH;
+    } else if (hasWiredHeadset) {
+      // If a wired headset is connected, but Bluetooth is not, then wired headset is used as
+      // audio device.
+      newAudioDevice = AudioDevice.WIRED_HEADSET;
    } else {
-      setAudioDevice(defaultAudioDevice);
+      // No wired headset and no Bluetooth, hence the audio-device list can contain speaker
+      // phone (on a tablet), or speaker phone and earpiece (on mobile phone).
+      // |defaultAudioDevice| contains either AudioDevice.SPEAKER_PHONE or AudioDevice.EARPIECE
+      // depending on the user's selection.
+      newAudioDevice = defaultAudioDevice;
+    }
+    // Switch to new device but only if there has been any changes.
+    if (newAudioDevice != selectedAudioDevice || audioDeviceSetUpdated) {
+      // Do the required device switch.
+      setAudioDeviceInternal(newAudioDevice);
+      Log.d(TAG, "New device status: "
+              + "available=" + audioDevices + ", "
+              + "selected=" + newAudioDevice);
+      if (audioManagerEvents != null) {
+        // Notify a listening client that audio device has been changed.
+        audioManagerEvents.onAudioDeviceChanged(selectedAudioDevice, audioDevices);
      }
    }
-
-  /** Called each time a new audio device has been added or removed. */
-  private void onAudioManagerChangedState() {
-    Log.d(TAG, "onAudioManagerChangedState: devices=" + audioDevices + ", selected="
-            + selectedAudioDevice);
-
-    // Enable the proximity sensor if there are two available audio devices
-    // in the list. Given the current implementation, we know that the choice
-    // will then be between EARPIECE and SPEAKER_PHONE.
-    if (audioDevices.size() == 2) {
-      AppRTCUtils.assertIsTrue(audioDevices.contains(AudioDevice.EARPIECE)
-          && audioDevices.contains(AudioDevice.SPEAKER_PHONE));
-      // Start the proximity sensor.
-      proximitySensor.start();
-    } else if (audioDevices.size() == 1) {
-      // Stop the proximity sensor since it is no longer needed.
-      proximitySensor.stop();
-    } else {
-      Log.e(TAG, "Invalid device list");
-    }
-
-    if (onStateChangeListener != null) {
-      // Run callback to notify a listening client. The client can then
-      // use public getters to query the new state.
-      onStateChangeListener.run();
-    }
+    Log.d(TAG, "--- updateAudioDeviceState done");
  }
 }
--- a/webrtc/examples/androidapp/src/org/appspot/apprtc/AppRTCBluetoothManager.java
+++ b/webrtc/examples/androidapp/src/org/appspot/apprtc/AppRTCBluetoothManager.java
@ -0,0 +1,521 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.appspot.apprtc;
+
+import org.appspot.apprtc.util.AppRTCUtils;
+
+import android.bluetooth.BluetoothAdapter;
+import android.bluetooth.BluetoothDevice;
+import android.bluetooth.BluetoothHeadset;
+import android.bluetooth.BluetoothProfile;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.pm.PackageManager;
+import android.media.AudioManager;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Process;
+import android.util.Log;
+
+import org.webrtc.ThreadUtils;
+
+import java.util.List;
+import java.util.Set;
+
+/**
+ * AppRTCProximitySensor manages functions related to Bluetoth devices in the
+ * AppRTC demo.
+ */
+public class AppRTCBluetoothManager {
+  private static final String TAG = "AppRTCBluetoothManager";
+
+  // Timeout interval for starting or stopping audio to a Bluetooth SCO device.
+  private static final int BLUETOOTH_SCO_TIMEOUT_MS = 4000;
+  // Maximum number of SCO connection attempts.
+  private static final int MAX_SCO_CONNECTION_ATTEMPTS = 2;
+
+  // Bluetooth connection state.
+  public enum State {
+    // Bluetooth is not available; no adapter or Bluetooth is off.
+    UNINITIALIZED,
+    // Bluetooth error happened when trying to start Bluetooth.
+    ERROR,
+    // Bluetooth proxy object for the Headset profile exists, but no connected headset devices,
+    // SCO is not started or disconnected.
+    HEADSET_UNAVAILABLE,
+    // Bluetooth proxy object for the Headset profile connected, connected Bluetooth headset
+    // present, but SCO is not started or disconnected.
+    HEADSET_AVAILABLE,
+    // Bluetooth audio SCO connection with remote device is closing.
+    SCO_DISCONNECTING,
+    // Bluetooth audio SCO connection with remote device is initiated.
+    SCO_CONNECTING,
+    // Bluetooth audio SCO connection with remote device is established.
+    SCO_CONNECTED
+  }
+
+  private final Context apprtcContext;
+  private final AppRTCAudioManager apprtcAudioManager;
+  private final AudioManager audioManager;
+  private final Handler handler;
+
+  int scoConnectionAttempts;
+  private State bluetoothState;
+  private final BluetoothProfile.ServiceListener bluetoothServiceListener;
+  private BluetoothAdapter bluetoothAdapter;
+  private BluetoothHeadset bluetoothHeadset;
+  private BluetoothDevice bluetoothDevice;
+  private final BroadcastReceiver bluetoothHeadsetReceiver;
+
+  // Runs when the Bluetooth timeout expires. We use that timeout after calling
+  // startScoAudio() or stopScoAudio() because we're not guaranteed to get a
+  // callback after those calls.
+  private final Runnable bluetoothTimeoutRunnable = new Runnable() {
+    @Override
+    public void run() {
+      bluetoothTimeout();
+    }
+  };
+
+  /**
+   * Implementation of an interface that notifies BluetoothProfile IPC clients when they have been
+   * connected to or disconnected from the service.
+   */
+  private class BluetoothServiceListener implements BluetoothProfile.ServiceListener {
+    @Override
+    // Called to notify the client when the proxy object has been connected to the service.
+    // Once we have the profile proxy object, we can use it to monitor the state of the
+    // connection and perform other operations that are relevant to the headset profile.
+    public void onServiceConnected(int profile, BluetoothProfile proxy) {
+      if (profile != BluetoothProfile.HEADSET || bluetoothState == State.UNINITIALIZED) {
+        return;
+      }
+      Log.d(TAG, "BluetoothServiceListener.onServiceConnected: BT state=" + bluetoothState);
+      // Android only supports one connected Bluetooth Headset at a time.
+      bluetoothHeadset = (BluetoothHeadset) proxy;
+      updateAudioDeviceState();
+      Log.d(TAG, "onServiceConnected done: BT state=" + bluetoothState);
+    }
+
+    @Override
+    /** Notifies the client when the proxy object has been disconnected from the service. */
+    public void onServiceDisconnected(int profile) {
+      if (profile != BluetoothProfile.HEADSET || bluetoothState == State.UNINITIALIZED) {
+        return;
+      }
+      Log.d(TAG, "BluetoothServiceListener.onServiceDisconnected: BT state=" + bluetoothState);
+      stopScoAudio();
+      bluetoothHeadset = null;
+      bluetoothDevice = null;
+      bluetoothState = State.HEADSET_UNAVAILABLE;
+      updateAudioDeviceState();
+      Log.d(TAG, "onServiceDisconnected done: BT state=" + bluetoothState);
+    }
+  }
+
+  // Intent broadcast receiver which handles changes in Bluetooth device availability.
+  // Detects headset changes and Bluetooth SCO state changes.
+  private class BluetoothHeadsetBroadcastReceiver extends BroadcastReceiver {
+    @Override
+    public void onReceive(Context context, Intent intent) {
+      if (bluetoothState == State.UNINITIALIZED) {
+        return;
+      }
+      final String action = intent.getAction();
+      // Change in connection state of the Headset profile. Note that the
+      // change does not tell us anything about whether we're streaming
+      // audio to BT over SCO. Typically received when user turns on a BT
+      // headset while audio is active using another audio device.
+      if (action.equals(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED)) {
+        final int state =
+            intent.getIntExtra(BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_DISCONNECTED);
+        Log.d(TAG, "BluetoothHeadsetBroadcastReceiver.onReceive: "
+                + "a=ACTION_CONNECTION_STATE_CHANGED, "
+                + "s=" + stateToString(state) + ", "
+                + "sb=" + isInitialStickyBroadcast() + ", "
+                + "BT state: " + bluetoothState);
+        if (state == BluetoothHeadset.STATE_CONNECTED) {
+          scoConnectionAttempts = 0;
+          updateAudioDeviceState();
+        } else if (state == BluetoothHeadset.STATE_CONNECTING) {
+          // No action needed.
+        } else if (state == BluetoothHeadset.STATE_DISCONNECTING) {
+          // No action needed.
+        } else if (state == BluetoothHeadset.STATE_DISCONNECTED) {
+          // Bluetooth is probably powered off during the call.
+          stopScoAudio();
+          updateAudioDeviceState();
+        }
+        // Change in the audio (SCO) connection state of the Headset profile.
+        // Typically received after call to startScoAudio() has finalized.
+      } else if (action.equals(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED)) {
+        final int state = intent.getIntExtra(
+            BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_AUDIO_DISCONNECTED);
+        Log.d(TAG, "BluetoothHeadsetBroadcastReceiver.onReceive: "
+                + "a=ACTION_AUDIO_STATE_CHANGED, "
+                + "s=" + stateToString(state) + ", "
+                + "sb=" + isInitialStickyBroadcast() + ", "
+                + "BT state: " + bluetoothState);
+        if (state == BluetoothHeadset.STATE_AUDIO_CONNECTED) {
+          cancelTimer();
+          if (bluetoothState == State.SCO_CONNECTING) {
+            Log.d(TAG, "+++ Bluetooth audio SCO is now connected");
+            bluetoothState = State.SCO_CONNECTED;
+            scoConnectionAttempts = 0;
+            updateAudioDeviceState();
+          } else {
+            Log.w(TAG, "Unexpected state BluetoothHeadset.STATE_AUDIO_CONNECTED");
+          }
+        } else if (state == BluetoothHeadset.STATE_AUDIO_CONNECTING) {
+          Log.d(TAG, "+++ Bluetooth audio SCO is now connecting...");
+        } else if (state == BluetoothHeadset.STATE_AUDIO_DISCONNECTED) {
+          Log.d(TAG, "+++ Bluetooth audio SCO is now disconnected");
+          if (isInitialStickyBroadcast()) {
+            Log.d(TAG, "Ignore STATE_AUDIO_DISCONNECTED initial sticky broadcast.");
+            return;
+          }
+          updateAudioDeviceState();
+        }
+      }
+      Log.d(TAG, "onReceive done: BT state=" + bluetoothState);
+    }
+  };
+
+  /** Construction. */
+  static AppRTCBluetoothManager create(Context context, AppRTCAudioManager audioManager) {
+    Log.d(TAG, "create" + AppRTCUtils.getThreadInfo());
+    return new AppRTCBluetoothManager(context, audioManager);
+  }
+
+  protected AppRTCBluetoothManager(Context context, AppRTCAudioManager audioManager) {
+    Log.d(TAG, "ctor");
+    ThreadUtils.checkIsOnMainThread();
+    apprtcContext = context;
+    apprtcAudioManager = audioManager;
+    this.audioManager = getAudioManager(context);
+    bluetoothState = State.UNINITIALIZED;
+    bluetoothServiceListener = new BluetoothServiceListener();
+    bluetoothHeadsetReceiver = new BluetoothHeadsetBroadcastReceiver();
+    handler = new Handler(Looper.getMainLooper());
+  }
+
+  /** Returns the internal state. */
+  public State getState() {
+    ThreadUtils.checkIsOnMainThread();
+    return bluetoothState;
+  }
+
+  /**
+   * Activates components required to detect Bluetooth devices and to enable
+   * BT SCO (audio is routed via BT SCO) for the headset profile. The end
+   * state will be HEADSET_UNAVAILABLE but a state machine has started which
+   * will start a state change sequence where the final outcome depends on
+   * if/when the BT headset is enabled.
+   * Example of state change sequence when start() is called while BT device
+   * is connected and enabled:
+   *   UNINITIALIZED --> HEADSET_UNAVAILABLE --> HEADSET_AVAILABLE -->
+   *   SCO_CONNECTING --> SCO_CONNECTED <==> audio is now routed via BT SCO.
+   * Note that the AppRTCAudioManager is also involved in driving this state
+   * change.
+   */
+  public void start() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "start");
+    if (!hasPermission(apprtcContext, android.Manifest.permission.BLUETOOTH)) {
+      Log.w(TAG, "Process (pid=" + Process.myPid() + ") lacks BLUETOOTH permission");
+      return;
+    }
+    if (bluetoothState != State.UNINITIALIZED) {
+      Log.w(TAG, "Invalid BT state");
+      return;
+    }
+    bluetoothHeadset = null;
+    bluetoothDevice = null;
+    scoConnectionAttempts = 0;
+    // Get a handle to the default local Bluetooth adapter.
+    bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
+    if (bluetoothAdapter == null) {
+      Log.w(TAG, "Device does not support Bluetooth");
+      return;
+    }
+    // Ensure that the device supports use of BT SCO audio for off call use cases.
+    if (!audioManager.isBluetoothScoAvailableOffCall()) {
+      Log.e(TAG, "Bluetooth SCO audio is not available off call");
+      return;
+    }
+    logBluetoothAdapterInfo(bluetoothAdapter);
+    // Establish a connection to the HEADSET profile (includes both Bluetooth Headset and
+    // Hands-Free) proxy object and install a listener.
+    if (!getBluetoothProfileProxy(
+            apprtcContext, bluetoothServiceListener, BluetoothProfile.HEADSET)) {
+      Log.e(TAG, "BluetoothAdapter.getProfileProxy(HEADSET) failed");
+      return;
+    }
+    // Register receivers for BluetoothHeadset change notifications.
+    IntentFilter bluetoothHeadsetFilter = new IntentFilter();
+    // Register receiver for change in connection state of the Headset profile.
+    bluetoothHeadsetFilter.addAction(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED);
+    // Register receiver for change in audio connection state of the Headset profile.
+    bluetoothHeadsetFilter.addAction(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED);
+    registerReceiver(bluetoothHeadsetReceiver, bluetoothHeadsetFilter);
+    Log.d(TAG, "HEADSET profile state: "
+            + stateToString(bluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEADSET)));
+    Log.d(TAG, "Bluetooth proxy for headset profile has started");
+    bluetoothState = State.HEADSET_UNAVAILABLE;
+    Log.d(TAG, "start done: BT state=" + bluetoothState);
+  }
+
+  /** Stops and closes all components related to Bluetooth audio. */
+  public void stop() {
+    ThreadUtils.checkIsOnMainThread();
+    unregisterReceiver(bluetoothHeadsetReceiver);
+    Log.d(TAG, "stop: BT state=" + bluetoothState);
+    if (bluetoothAdapter != null) {
+      // Stop BT SCO connection with remote device if needed.
+      stopScoAudio();
+      // Close down remaining BT resources.
+      if (bluetoothState != State.UNINITIALIZED) {
+        cancelTimer();
+        if (bluetoothHeadset != null) {
+          bluetoothAdapter.closeProfileProxy(BluetoothProfile.HEADSET, bluetoothHeadset);
+          bluetoothHeadset = null;
+        }
+        bluetoothAdapter = null;
+        bluetoothDevice = null;
+        bluetoothState = State.UNINITIALIZED;
+      }
+    }
+    Log.d(TAG, "stop done: BT state=" + bluetoothState);
+  }
+
+  /**
+   * Starts Bluetooth SCO connection with remote device.
+   * Note that the phone application always has the priority on the usage of the SCO connection
+   * for telephony. If this method is called while the phone is in call it will be ignored.
+   * Similarly, if a call is received or sent while an application is using the SCO connection,
+   * the connection will be lost for the application and NOT returned automatically when the call
+   * ends. Also note that: up to and including API version JELLY_BEAN_MR1, this method initiates a
+   * virtual voice call to the Bluetooth headset. After API version JELLY_BEAN_MR2 only a raw SCO
+   * audio connection is established.
+   * TODO(henrika): should we add support for virtual voice call to BT headset also for JBMR2 and
+   * higher. It might be required to initiates a virtual voice call since many devices do not
+   * accept SCO audio without a "call".
+   */
+  public boolean startScoAudio() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "startSco: BT state=" + bluetoothState + ", "
+            + "attempts: " + scoConnectionAttempts + ", "
+            + "SCO is on: " + isScoOn());
+    if (scoConnectionAttempts >= MAX_SCO_CONNECTION_ATTEMPTS) {
+      Log.e(TAG, "BT SCO connection fails - no more attempts");
+      return false;
+    }
+    if (bluetoothState != State.HEADSET_AVAILABLE) {
+      Log.e(TAG, "BT SCO connection fails - no headset available");
+      return false;
+    }
+    // Start BT SCO channel and wait for ACTION_AUDIO_STATE_CHANGED.
+    Log.d(TAG, "Starting Bluetooth SCO and waits for ACTION_AUDIO_STATE_CHANGED...");
+    // The SCO connection establishment can take several seconds, hence we cannot rely on the
+    // connection to be available when the method returns but instead register to receive the
+    // intent ACTION_SCO_AUDIO_STATE_UPDATED and wait for the state to be SCO_AUDIO_STATE_CONNECTED.
+    bluetoothState = State.SCO_CONNECTING;
+    audioManager.startBluetoothSco();
+    scoConnectionAttempts++;
+    startTimer();
+    Log.d(TAG, "startScoAudio done: BT state=" + bluetoothState);
+    return true;
+  }
+
+  /** Stops Bluetooth SCO connection with remote device. */
+  public void stopScoAudio() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "stopScoAudio: BT state=" + bluetoothState + ", "
+            + "SCO is on: " + isScoOn());
+    if (bluetoothState != State.SCO_CONNECTING && bluetoothState != State.SCO_CONNECTED) {
+      return;
+    }
+    cancelTimer();
+    audioManager.stopBluetoothSco();
+    bluetoothState = State.SCO_DISCONNECTING;
+    Log.d(TAG, "stopScoAudio done: BT state=" + bluetoothState);
+  }
+
+  /**
+   * Use the BluetoothHeadset proxy object (controls the Bluetooth Headset
+   * Service via IPC) to update the list of connected devices for the HEADSET
+   * profile. The internal state will change to HEADSET_UNAVAILABLE or to
+   * HEADSET_AVAILABLE and |bluetoothDevice| will be mapped to the connected
+   * device if available.
+   */
+  public void updateDevice() {
+    if (bluetoothState == State.UNINITIALIZED || bluetoothHeadset == null) {
+      return;
+    }
+    Log.d(TAG, "updateDevice");
+    // Get connected devices for the headset profile. Returns the set of
+    // devices which are in state STATE_CONNECTED. The BluetoothDevice class
+    // is just a thin wrapper for a Bluetooth hardware address.
+    List<BluetoothDevice> devices = bluetoothHeadset.getConnectedDevices();
+    if (devices.isEmpty()) {
+      bluetoothDevice = null;
+      bluetoothState = State.HEADSET_UNAVAILABLE;
+      Log.d(TAG, "No connected bluetooth headset");
+    } else {
+      // Always use first device is list. Android only supports one device.
+      bluetoothDevice = devices.get(0);
+      bluetoothState = State.HEADSET_AVAILABLE;
+      Log.d(TAG, "Connected bluetooth headset: "
+              + "name=" + bluetoothDevice.getName() + ", "
+              + "state=" + stateToString(bluetoothHeadset.getConnectionState(bluetoothDevice))
+              + ", SCO audio=" + bluetoothHeadset.isAudioConnected(bluetoothDevice));
+    }
+    Log.d(TAG, "updateDevice done: BT state=" + bluetoothState);
+  }
+
+  /**
+   * Stubs for test mocks.
+   */
+  protected AudioManager getAudioManager(Context context) {
+    return (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
+  }
+
+  protected void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
+    apprtcContext.registerReceiver(receiver, filter);
+  }
+
+  protected void unregisterReceiver(BroadcastReceiver receiver) {
+    apprtcContext.unregisterReceiver(receiver);
+  }
+
+  protected boolean getBluetoothProfileProxy(
+      Context context, BluetoothProfile.ServiceListener listener, int profile) {
+    return bluetoothAdapter.getProfileProxy(context, listener, profile);
+  }
+
+  protected boolean hasPermission(Context context, String permission) {
+    return apprtcContext.checkPermission(permission, Process.myPid(), Process.myUid())
+        == PackageManager.PERMISSION_GRANTED;
+  }
+
+  /** Logs the state of the local Bluetooth adapter. */
+  protected void logBluetoothAdapterInfo(BluetoothAdapter localAdapter) {
+    Log.d(TAG, "BluetoothAdapter: "
+            + "enabled=" + localAdapter.isEnabled() + ", "
+            + "state=" + stateToString(localAdapter.getState()) + ", "
+            + "name=" + localAdapter.getName() + ", "
+            + "address=" + localAdapter.getAddress());
+    // Log the set of BluetoothDevice objects that are bonded (paired) to the local adapter.
+    Set<BluetoothDevice> pairedDevices = localAdapter.getBondedDevices();
+    if (!pairedDevices.isEmpty()) {
+      Log.d(TAG, "paired devices:");
+      for (BluetoothDevice device : pairedDevices) {
+        Log.d(TAG, " name=" + device.getName() + ", address=" + device.getAddress());
+      }
+    }
+  }
+
+  /** Ensures that the audio manager updates its list of available audio devices. */
+  private void updateAudioDeviceState() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "updateAudioDeviceState");
+    apprtcAudioManager.updateAudioDeviceState();
+  }
+
+  /** Starts timer which times out after BLUETOOTH_SCO_TIMEOUT_MS milliseconds. */
+  private void startTimer() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "startTimer");
+    handler.postDelayed(bluetoothTimeoutRunnable, BLUETOOTH_SCO_TIMEOUT_MS);
+  }
+
+  /** Cancels any outstanding timer tasks. */
+  private void cancelTimer() {
+    ThreadUtils.checkIsOnMainThread();
+    Log.d(TAG, "cancelTimer");
+    handler.removeCallbacks(bluetoothTimeoutRunnable);
+  }
+
+  /**
+   * Called when start of the BT SCO channel takes too long time. Usually
+   * happens when the BT device has been turned on during an ongoing call.
+   */
+  private void bluetoothTimeout() {
+    ThreadUtils.checkIsOnMainThread();
+    if (bluetoothState == State.UNINITIALIZED || bluetoothHeadset == null) {
+      return;
+    }
+    Log.d(TAG, "bluetoothTimeout: BT state=" + bluetoothState + ", "
+            + "attempts: " + scoConnectionAttempts + ", "
+            + "SCO is on: " + isScoOn());
+    if (bluetoothState != State.SCO_CONNECTING) {
+      return;
+    }
+    // Bluetooth SCO should be connecting; check the latest result.
+    boolean scoConnected = false;
+    List<BluetoothDevice> devices = bluetoothHeadset.getConnectedDevices();
+    if (devices.size() > 0) {
+      bluetoothDevice = devices.get(0);
+      if (bluetoothHeadset.isAudioConnected(bluetoothDevice)) {
+        Log.d(TAG, "SCO connected with " + bluetoothDevice.getName());
+        scoConnected = true;
+      } else {
+        Log.d(TAG, "SCO is not connected with " + bluetoothDevice.getName());
+      }
+    }
+    if (scoConnected) {
+      // We thought BT had timed out, but it's actually on; updating state.
+      bluetoothState = State.SCO_CONNECTED;
+      scoConnectionAttempts = 0;
+    } else {
+      // Give up and "cancel" our request by calling stopBluetoothSco().
+      Log.w(TAG, "BT failed to connect after timeout");
+      stopScoAudio();
+    }
+    updateAudioDeviceState();
+    Log.d(TAG, "bluetoothTimeout done: BT state=" + bluetoothState);
+  }
+
+  /** Checks whether audio uses Bluetooth SCO. */
+  private boolean isScoOn() {
+    return audioManager.isBluetoothScoOn();
+  }
+
+  /** Converts BluetoothAdapter states into local string representations. */
+  private String stateToString(int state) {
+    switch (state) {
+      case BluetoothAdapter.STATE_DISCONNECTED:
+        return "DISCONNECTED";
+      case BluetoothAdapter.STATE_CONNECTED:
+        return "CONNECTED";
+      case BluetoothAdapter.STATE_CONNECTING:
+        return "CONNECTING";
+      case BluetoothAdapter.STATE_DISCONNECTING:
+        return "DISCONNECTING";
+      case BluetoothAdapter.STATE_OFF:
+        return "OFF";
+      case BluetoothAdapter.STATE_ON:
+        return "ON";
+      case BluetoothAdapter.STATE_TURNING_OFF:
+        // Indicates the local Bluetooth adapter is turning off. Local clients should immediately
+        // attempt graceful disconnection of any remote links.
+        return "TURNING_OFF";
+      case BluetoothAdapter.STATE_TURNING_ON:
+        // Indicates the local Bluetooth adapter is turning on. However local clients should wait
+        // for STATE_ON before attempting to use the adapter.
+        return  "TURNING_ON";
+      default:
+        return "INVALID";
+    }
+  }
+}
--- a/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
+++ b/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
@ -33,6 +33,9 @@ import java.io.IOException;
 import java.lang.RuntimeException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Set;
+import org.appspot.apprtc.AppRTCAudioManager.AudioDevice;
+import org.appspot.apprtc.AppRTCAudioManager.AudioManagerEvents;
 import org.appspot.apprtc.AppRTCClient.RoomConnectionParameters;
 import org.appspot.apprtc.AppRTCClient.SignalingParameters;
 import org.appspot.apprtc.PeerConnectionClient.DataChannelParameters;
@ -527,18 +530,19 @@ public class CallActivity extends Activity implements AppRTCClient.SignalingEven

    // Create and audio manager that will take care of audio routing,
    // audio modes, audio device enumeration etc.
-    audioManager = AppRTCAudioManager.create(this, new Runnable() {
-      // This method will be called each time the audio state (number and
-      // type of devices) has been changed.
-      @Override
-      public void run() {
-        onAudioManagerChangedState();
-      }
-    });
+    audioManager = AppRTCAudioManager.create(this);
    // Store existing audio settings and change audio mode to
    // MODE_IN_COMMUNICATION for best possible VoIP performance.
-    Log.d(TAG, "Initializing the audio manager...");
-    audioManager.init();
+    Log.d(TAG, "Starting the audio manager...");
+    audioManager.start(new AudioManagerEvents() {
+      // This method will be called each time the number of available audio
+      // devices has changed.
+      @Override
+      public void onAudioDeviceChanged(
+          AudioDevice audioDevice, Set<AudioDevice> availableAudioDevices) {
+        onAudioManagerDevicesChanged(audioDevice, availableAudioDevices);
+      }
+    });
  }

  // Should be called from UI thread
@ -555,9 +559,13 @@ public class CallActivity extends Activity implements AppRTCClient.SignalingEven
    peerConnectionClient.enableStatsEvents(true, STAT_CALLBACK_PERIOD);
  }

-  private void onAudioManagerChangedState() {
-    // TODO(henrika): disable video if AppRTCAudioManager.AudioDevice.EARPIECE
-    // is active.
+  // This method is called when the audio manager reports audio device change,
+  // e.g. from wired headset to speakerphone.
+  private void onAudioManagerDevicesChanged(
+      final AudioDevice device, final Set<AudioDevice> availableDevices) {
+    Log.d(TAG, "onAudioManagerDevicesChanged: " + availableDevices + ", "
+            + "selected: " + device);
+    // TODO(henrika): add callback handler.
  }

  // Disconnect from remote resources, dispose of local resources, and exit.
@ -584,7 +592,7 @@ public class CallActivity extends Activity implements AppRTCClient.SignalingEven
      remoteRenderScreen = null;
    }
    if (audioManager != null) {
-      audioManager.close();
+      audioManager.stop();
      audioManager = null;
    }
    if (iceConnected && !isError) {
--- a/webrtc/examples/androidjunit/src/org/appspot/apprtc/BluetoothManagerTest.java
+++ b/webrtc/examples/androidjunit/src/org/appspot/apprtc/BluetoothManagerTest.java
@ -0,0 +1,271 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.appspot.apprtc;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.doCallRealMethod;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.bluetooth.BluetoothAdapter;
+import android.bluetooth.BluetoothDevice;
+import android.bluetooth.BluetoothHeadset;
+import android.bluetooth.BluetoothProfile;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.media.AudioManager;
+import android.util.Log;
+import java.util.LinkedList;
+import java.util.List;
+import org.appspot.apprtc.AppRTCBluetoothManager.State;
+import org.chromium.testing.local.LocalRobolectricTestRunner;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.annotation.Config;
+import org.robolectric.shadows.ShadowApplication;
+import org.robolectric.shadows.ShadowLog;
+
+/**
+ * Verifies basic behavior of the AppRTCBluetoothManager class.
+ * Note that the test object uses an AppRTCAudioManager (injected in ctor),
+ * but a mocked version is used instead. Hence, the parts "driven" by the AppRTC
+ * audio manager are not included in this test.
+ */
+@RunWith(LocalRobolectricTestRunner.class)
+@Config(manifest = Config.NONE)
+public class BluetoothManagerTest {
+  private static final String TAG = "BluetoothManagerTest";
+  private static final String BLUETOOTH_TEST_DEVICE_NAME = "BluetoothTestDevice";
+
+  private BroadcastReceiver bluetoothHeadsetStateReceiver;
+  private BluetoothProfile.ServiceListener bluetoothServiceListener;
+  private BluetoothHeadset mockedBluetoothHeadset;
+  private BluetoothDevice mockedBluetoothDevice;
+  private List<BluetoothDevice> mockedBluetoothDeviceList;
+  private AppRTCBluetoothManager bluetoothManager;
+  private AppRTCAudioManager mockedAppRtcAudioManager;
+  private AudioManager mockedAudioManager;
+  private Context context;
+
+  @Before
+  public void setUp() {
+    ShadowLog.stream = System.out;
+    context = ShadowApplication.getInstance().getApplicationContext();
+    mockedAppRtcAudioManager = mock(AppRTCAudioManager.class);
+    mockedAudioManager = mock(AudioManager.class);
+    mockedBluetoothHeadset = mock(BluetoothHeadset.class);
+    mockedBluetoothDevice = mock(BluetoothDevice.class);
+    mockedBluetoothDeviceList = new LinkedList<BluetoothDevice>();
+
+    // Simulate that bluetooth SCO audio is available by default.
+    when(mockedAudioManager.isBluetoothScoAvailableOffCall()).thenReturn(true);
+
+    // Create the test object and override protected methods for this test.
+    bluetoothManager = new AppRTCBluetoothManager(context, mockedAppRtcAudioManager) {
+      @Override
+      protected AudioManager getAudioManager(Context context) {
+        Log.d(TAG, "getAudioManager");
+        return mockedAudioManager;
+      }
+
+      @Override
+      protected void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
+        Log.d(TAG, "registerReceiver");
+        if (filter.hasAction(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED)
+            && filter.hasAction(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED)) {
+          // Gives access to the real broadcast receiver so the test can use it.
+          bluetoothHeadsetStateReceiver = receiver;
+        }
+      }
+
+      @Override
+      protected void unregisterReceiver(BroadcastReceiver receiver) {
+        Log.d(TAG, "unregisterReceiver");
+        if (receiver == bluetoothHeadsetStateReceiver) {
+          bluetoothHeadsetStateReceiver = null;
+        }
+      }
+
+      @Override
+      protected boolean getBluetoothProfileProxy(
+          Context context, BluetoothProfile.ServiceListener listener, int profile) {
+        Log.d(TAG, "getBluetoothProfileProxy");
+        if (profile == BluetoothProfile.HEADSET) {
+          // Allows the test to access the real Bluetooth service listener object.
+          bluetoothServiceListener = listener;
+        }
+        return true;
+      }
+
+      @Override
+      protected boolean hasPermission(Context context, String permission) {
+        Log.d(TAG, "hasPermission(" + permission + ")");
+        // Ensure that the client asks for Bluetooth permission.
+        return (permission == android.Manifest.permission.BLUETOOTH);
+      }
+
+      @Override
+      protected void logBluetoothAdapterInfo(BluetoothAdapter localAdapter) {
+        // Do nothing in tests. No need to mock BluetoothAdapter.
+      }
+    };
+  }
+
+  // Verify that Bluetooth service listener for headset profile is properly initialized.
+  @Test
+  public void testBluetoothServiceListenerInitialized() {
+    bluetoothManager.start();
+    assertNotNull(bluetoothServiceListener);
+    verify(mockedAppRtcAudioManager, never()).updateAudioDeviceState();
+  }
+
+  // Verify that broadcast receivers for Bluetooth SCO audio state and Bluetooth headset state
+  // are properly registered and unregistered.
+  @Test
+  public void testBluetoothBroadcastReceiversAreRegistered() {
+    bluetoothManager.start();
+    assertNotNull(bluetoothHeadsetStateReceiver);
+    bluetoothManager.stop();
+    assertNull(bluetoothHeadsetStateReceiver);
+  }
+
+  // Verify that the Bluetooth manager starts and stops with correct states.
+  @Test
+  public void testBluetoothDefaultStartStopStates() {
+    bluetoothManager.start();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+    bluetoothManager.stop();
+    assertEquals(bluetoothManager.getState(), State.UNINITIALIZED);
+  }
+
+  // Verify correct state after receiving BluetoothServiceListener.onServiceConnected()
+  // when no BT device is enabled.
+  @Test
+  public void testBluetoothServiceListenerConnectedWithNoHeadset() {
+    bluetoothManager.start();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+    simulateBluetoothServiceConnectedWithNoConnectedHeadset();
+    verify(mockedAppRtcAudioManager, times(1)).updateAudioDeviceState();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+  }
+
+  // Verify correct state after receiving BluetoothServiceListener.onServiceConnected()
+  // when one emulated (test) BT device is enabled. Android does not support more than
+  // one connected BT headset.
+  @Test
+  public void testBluetoothServiceListenerConnectedWithHeadset() {
+    bluetoothManager.start();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+    simulateBluetoothServiceConnectedWithConnectedHeadset();
+    verify(mockedAppRtcAudioManager, times(1)).updateAudioDeviceState();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_AVAILABLE);
+  }
+
+  // Verify correct state after receiving BluetoothProfile.ServiceListener.onServiceDisconnected().
+  @Test
+  public void testBluetoothServiceListenerDisconnected() {
+    bluetoothManager.start();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+    simulateBluetoothServiceDisconnected();
+    verify(mockedAppRtcAudioManager, times(1)).updateAudioDeviceState();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+  }
+
+  // Verify correct state after BluetoothServiceListener.onServiceConnected() and
+  // the intent indicating that the headset is actually connected. Both these callbacks
+  // results in calls to updateAudioDeviceState() on the AppRTC audio manager.
+  // No BT SCO is enabled here to keep the test limited.
+  @Test
+  public void testBluetoothHeadsetConnected() {
+    bluetoothManager.start();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+    simulateBluetoothServiceConnectedWithConnectedHeadset();
+    simulateBluetoothHeadsetConnected();
+    verify(mockedAppRtcAudioManager, times(2)).updateAudioDeviceState();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_AVAILABLE);
+  }
+
+  // Verify correct state sequence for a case when a BT headset is available,
+  // followed by BT SCO audio being enabled and then stopped.
+  @Test
+  public void testBluetoothScoAudioStartAndStop() {
+    bluetoothManager.start();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_UNAVAILABLE);
+    simulateBluetoothServiceConnectedWithConnectedHeadset();
+    assertEquals(bluetoothManager.getState(), State.HEADSET_AVAILABLE);
+    bluetoothManager.startScoAudio();
+    assertEquals(bluetoothManager.getState(), State.SCO_CONNECTING);
+    simulateBluetoothScoConnectionConnected();
+    assertEquals(bluetoothManager.getState(), State.SCO_CONNECTED);
+    bluetoothManager.stopScoAudio();
+    simulateBluetoothScoConnectionDisconnected();
+    assertEquals(bluetoothManager.getState(), State.SCO_DISCONNECTING);
+    bluetoothManager.stop();
+    assertEquals(bluetoothManager.getState(), State.UNINITIALIZED);
+    verify(mockedAppRtcAudioManager, times(3)).updateAudioDeviceState();
+  }
+
+  /**
+   * Private helper methods.
+   */
+  private void simulateBluetoothServiceConnectedWithNoConnectedHeadset() {
+    mockedBluetoothDeviceList.clear();
+    when(mockedBluetoothHeadset.getConnectedDevices()).thenReturn(mockedBluetoothDeviceList);
+    bluetoothServiceListener.onServiceConnected(BluetoothProfile.HEADSET, mockedBluetoothHeadset);
+    // In real life, the AppRTC audio manager makes this call.
+    bluetoothManager.updateDevice();
+  }
+
+  private void simulateBluetoothServiceConnectedWithConnectedHeadset() {
+    mockedBluetoothDeviceList.clear();
+    mockedBluetoothDeviceList.add(mockedBluetoothDevice);
+    when(mockedBluetoothHeadset.getConnectedDevices()).thenReturn(mockedBluetoothDeviceList);
+    when(mockedBluetoothDevice.getName()).thenReturn(BLUETOOTH_TEST_DEVICE_NAME);
+    bluetoothServiceListener.onServiceConnected(BluetoothProfile.HEADSET, mockedBluetoothHeadset);
+    // In real life, the AppRTC audio manager makes this call.
+    bluetoothManager.updateDevice();
+  }
+
+  private void simulateBluetoothServiceDisconnected() {
+    bluetoothServiceListener.onServiceDisconnected(BluetoothProfile.HEADSET);
+  }
+
+  private void simulateBluetoothHeadsetConnected() {
+    Intent intent = new Intent();
+    intent.setAction(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED);
+    intent.putExtra(BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_CONNECTED);
+    bluetoothHeadsetStateReceiver.onReceive(context, intent);
+  }
+
+  private void simulateBluetoothScoConnectionConnected() {
+    Intent intent = new Intent();
+    intent.setAction(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED);
+    intent.putExtra(BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_AUDIO_CONNECTED);
+    bluetoothHeadsetStateReceiver.onReceive(context, intent);
+  }
+
+  private void simulateBluetoothScoConnectionDisconnected() {
+    Intent intent = new Intent();
+    intent.setAction(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED);
+    intent.putExtra(BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_AUDIO_DISCONNECTED);
+    bluetoothHeadsetStateReceiver.onReceive(context, intent);
+  }
+}