root/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java

DEFINITIONS

1. JNINamespace
2. calledOnValidThread
3. runningOnJellyBeanOrHigher
4. runningOnJellyBeanMR1OrHigher
5. runningOnJellyBeanMR2OrHigher
6. CalledByNative
7. id
8. CalledByNative
9. name
10. createAudioManagerAndroid
11. init
12. close
13. setCommunicationAudioModeOn
14. setDevice
15. getAudioInputDeviceNames
16. getNativeOutputSampleRate
17. getMinInputFrameSize
18. getMinOutputFrameSize
19. isAudioLowLatencySupported
20. getAudioLowLatencyOutputFrameSize
21. shouldUseAcousticEchoCanceler
22. checkIfCalledOnValidThread
23. registerBluetoothIntentsIfNeeded
24. unregisterBluetoothIntentsIfNeeded
25. setSpeakerphoneOn
26. setMicrophoneMute
27. isMicrophoneMute
28. hasEarpiece
29. hasWiredHeadset
30. hasBluetoothPermission
31. hasBluetoothHeadset
32. registerForWiredHeadsetIntentBroadcast
33. unregisterForWiredHeadsetIntentBroadcast
34. registerForBluetoothHeadsetIntentBroadcast
35. unregisterForBluetoothHeadsetIntentBroadcast
36. registerForBluetoothScoIntentBroadcast
37. unregisterForBluetoothScoIntentBroadcast
38. startBluetoothSco
39. stopBluetoothSco
40. setAudioDevice
41. selectDefaultDevice
42. deviceHasBeenRequested
43. updateDeviceActivation
44. getNumOfAudioDevices
45. reportUpdate
46. logDeviceInfo
47. logd
48. loge
49. startObservingVolumeChanges
50. stopObservingVolumeChanges
51. nativeSetMute

// 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.

package org.chromium.media;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothManager;
import android.content.BroadcastReceiver;
import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.database.ContentObserver;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioRecord;
import android.media.AudioTrack;
import android.media.audiofx.AcousticEchoCanceler;
import android.os.Build;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Process;
import android.provider.Settings;
import android.util.Log;

import org.chromium.base.CalledByNative;
import org.chromium.base.JNINamespace;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

@JNINamespace("media")
class AudioManagerAndroid {
    private static final String TAG = "AudioManagerAndroid";

    // Set to true to enable debug logs. Avoid in production builds.
    // NOTE: always check in as false.
    private static final boolean DEBUG = false;

    /**
     * NonThreadSafe is a helper class used to help verify that methods of a
     * class are called from the same thread.
     * Inspired by class in package com.google.android.apps.chrome.utilities.
     * Is only utilized when DEBUG is set to true.
     */
    private static class NonThreadSafe {
        private final Long mThreadId;

        public NonThreadSafe() {
            if (DEBUG) {
                mThreadId = Thread.currentThread().getId();
            } else {
                // Avoids "Unread field" issue reported by findbugs.
                mThreadId = 0L;
            }
        }

        /**
         * Checks if the method is called on the valid thread.
         * Assigns the current thread if no thread was assigned.
         */
        public boolean calledOnValidThread() {
            if (DEBUG) {
                return mThreadId.equals(Thread.currentThread().getId());
            }
            return true;
        }
    }

    private static boolean runningOnJellyBeanOrHigher() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN;
    }

    private static boolean runningOnJellyBeanMR1OrHigher() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1;
    }

    private static boolean runningOnJellyBeanMR2OrHigher() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2;
    }

    /** Simple container for device information. */
    private static class AudioDeviceName {
        private final int mId;
        private final String mName;

        private AudioDeviceName(int id, String name) {
            mId = id;
            mName = name;
        }

        @CalledByNative("AudioDeviceName")
        private String id() { return String.valueOf(mId); }

        @CalledByNative("AudioDeviceName")
        private String name() { return mName; }
    }

    // List if device models which have been vetted for good quality platform
    // echo cancellation.
    // NOTE: only add new devices to this list if manual tests have been
    // performed where the AEC performance is evaluated using e.g. a WebRTC
    // audio client such as https://apprtc.appspot.com/?r=<ROOM NAME>.
    private static final String[] SUPPORTED_AEC_MODELS = new String[] {
         "GT-I9300",  // Galaxy S3
         "GT-I9500",  // Galaxy S4
         "GT-N7105",  // Galaxy Note 2
         "Nexus 4",   // Nexus 4
         "Nexus 5",   // Nexus 5
         "Nexus 7",   // Nexus 7
         "SM-N9005",  // Galaxy Note 3
         "SM-T310",   // Galaxy Tab 3 8.0 (WiFi)
    };

    // Supported audio device types.
    private static final int DEVICE_DEFAULT = -2;
    private static final int DEVICE_INVALID = -1;
    private static final int DEVICE_SPEAKERPHONE = 0;
    private static final int DEVICE_WIRED_HEADSET = 1;
    private static final int DEVICE_EARPIECE = 2;
    private static final int DEVICE_BLUETOOTH_HEADSET = 3;
    private static final int DEVICE_COUNT = 4;

    // Maps audio device types to string values. This map must be in sync
    // with the device types above.
    // TODO(henrika): add support for proper detection of device names and
    // localize the name strings by using resource strings.
    // See http://crbug.com/333208 for details.
    private static final String[] DEVICE_NAMES = new String[] {
        "Speakerphone",
        "Wired headset",      // With or without microphone.
        "Headset earpiece",   // Only available on mobile phones.
        "Bluetooth headset",  // Requires BLUETOOTH permission.
    };

    // List of valid device types.
    private static final Integer[] VALID_DEVICES = new Integer[] {
        DEVICE_SPEAKERPHONE,
        DEVICE_WIRED_HEADSET,
        DEVICE_EARPIECE,
        DEVICE_BLUETOOTH_HEADSET,
    };

    // Bluetooth audio SCO states. Example of valid state sequence:
    // SCO_INVALID -> SCO_TURNING_ON -> SCO_ON -> SCO_TURNING_OFF -> SCO_OFF.
    private static final int STATE_BLUETOOTH_SCO_INVALID = -1;
    private static final int STATE_BLUETOOTH_SCO_OFF = 0;
    private static final int STATE_BLUETOOTH_SCO_ON = 1;
    private static final int STATE_BLUETOOTH_SCO_TURNING_ON = 2;
    private static final int STATE_BLUETOOTH_SCO_TURNING_OFF = 3;

    // Use 44.1kHz as the default sampling rate.
    private static final int DEFAULT_SAMPLING_RATE = 44100;
    // Randomly picked up frame size which is close to return value on N4.
    // Return this value when getProperty(PROPERTY_OUTPUT_FRAMES_PER_BUFFER)
    // fails.
    private static final int DEFAULT_FRAME_PER_BUFFER = 256;

    private final AudioManager mAudioManager;
    private final Context mContext;
    private final long mNativeAudioManagerAndroid;

    // Enabled during initialization if BLUETOOTH permission is granted.
    private boolean mHasBluetoothPermission = false;

    private int mSavedAudioMode = AudioManager.MODE_INVALID;

    // Stores the audio states related to Bluetooth SCO audio, where some
    // states are needed to keep track of intermediate states while the SCO
    // channel is enabled or disabled (switching state can take a few seconds).
    private int mBluetoothScoState = STATE_BLUETOOTH_SCO_INVALID;

    private boolean mIsInitialized = false;
    private boolean mSavedIsSpeakerphoneOn;
    private boolean mSavedIsMicrophoneMute;

    // Id of the requested audio device. Can only be modified by
    // call to setDevice().
    private int mRequestedAudioDevice = DEVICE_INVALID;

    // This class should be created, initialized and closed on the audio thread
    // in the audio manager. We use |mNonThreadSafe| to ensure that this is
    // the case. Only active when |DEBUG| is set to true.
    private final NonThreadSafe mNonThreadSafe = new NonThreadSafe();

    // Lock to protect |mAudioDevices| and |mRequestedAudioDevice| which can
    // be accessed from the main thread and the audio manager thread.
    private final Object mLock = new Object();

    // Contains a list of currently available audio devices.
    private boolean[] mAudioDevices = new boolean[DEVICE_COUNT];

    private final ContentResolver mContentResolver;
    private ContentObserver mSettingsObserver = null;
    private HandlerThread mSettingsObserverThread = null;
    private int mCurrentVolume;

    // Broadcast receiver for wired headset intent broadcasts.
    private BroadcastReceiver mWiredHeadsetReceiver;

    // Broadcast receiver for Bluetooth headset intent broadcasts.
    // Utilized to detect changes in Bluetooth headset availability.
    private BroadcastReceiver mBluetoothHeadsetReceiver;

    // Broadcast receiver for Bluetooth SCO broadcasts.
    // Utilized to detect if BT SCO streaming is on or off.
    private BroadcastReceiver mBluetoothScoReceiver;

    /** Construction */
    @CalledByNative
    private static AudioManagerAndroid createAudioManagerAndroid(
            Context context,
            long nativeAudioManagerAndroid) {
        return new AudioManagerAndroid(context, nativeAudioManagerAndroid);
    }

    private AudioManagerAndroid(Context context, long nativeAudioManagerAndroid) {
        mContext = context;
        mNativeAudioManagerAndroid = nativeAudioManagerAndroid;
        mAudioManager = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);
        mContentResolver = mContext.getContentResolver();
    }

    /**
     * Saves the initial speakerphone and microphone state.
     * Populates the list of available audio devices and registers receivers
     * for broadcast intents related to wired headset and Bluetooth devices.
     */
    @CalledByNative
    private void init() {
        checkIfCalledOnValidThread();
        if (DEBUG) logd("init");
        if (DEBUG) logDeviceInfo();
        if (mIsInitialized)
            return;

        // Initialize audio device list with things we know is always available.
        mAudioDevices[DEVICE_EARPIECE] = hasEarpiece();
        mAudioDevices[DEVICE_WIRED_HEADSET] = hasWiredHeadset();
        mAudioDevices[DEVICE_SPEAKERPHONE] = true;

        // Register receivers for broadcast intents related to Bluetooth device
        // and Bluetooth SCO notifications. Requires BLUETOOTH permission.
        registerBluetoothIntentsIfNeeded();

        // Register receiver for broadcast intents related to adding/
        // removing a wired headset (Intent.ACTION_HEADSET_PLUG).
        registerForWiredHeadsetIntentBroadcast();

        mIsInitialized = true;

        if (DEBUG) reportUpdate();
    }

    /**
     * Unregister all previously registered intent receivers and restore
     * the stored state (stored in {@link #init()}).
     */
    @CalledByNative
    private void close() {
        checkIfCalledOnValidThread();
        if (DEBUG) logd("close");
        if (!mIsInitialized)
            return;

        stopObservingVolumeChanges();
        unregisterForWiredHeadsetIntentBroadcast();
        unregisterBluetoothIntentsIfNeeded();

        mIsInitialized = false;
    }

    /**
     * Saves current audio mode and sets audio mode to MODE_IN_COMMUNICATION
     * if input parameter is true. Restores saved audio mode if input parameter
     * is false.
     */
    @CalledByNative
    private void setCommunicationAudioModeOn(boolean on) {
        if (DEBUG) logd("setCommunicationAudioModeOn(" + on + ")");

        if (on) {
            if (mSavedAudioMode != AudioManager.MODE_INVALID) {
                Log.wtf(TAG, "Audio mode has already been set!");
                return;
            }

            // Store the current audio mode the first time we try to
            // switch to communication mode.
            try {
                mSavedAudioMode = mAudioManager.getMode();
            } catch (SecurityException e) {
                Log.wtf(TAG, "getMode exception: ", e);
                logDeviceInfo();
            }

            // Store microphone mute state and speakerphone state so it can
            // be restored when closing.
            mSavedIsSpeakerphoneOn = mAudioManager.isSpeakerphoneOn();
            mSavedIsMicrophoneMute = mAudioManager.isMicrophoneMute();

            try {
                mAudioManager.setMode(AudioManager.MODE_IN_COMMUNICATION);
            } catch (SecurityException e) {
                Log.wtf(TAG, "setMode exception: ", e);
                logDeviceInfo();
            }

            // Start observing volume changes to detect when the
            // voice/communication stream volume is at its lowest level.
            // It is only possible to pull down the volume slider to about 20%
            // of the absolute minimum (slider at far left) in communication
            // mode but we want to be able to mute it completely.
            startObservingVolumeChanges();

        } else {
            if (mSavedAudioMode == AudioManager.MODE_INVALID) {
                Log.wtf(TAG, "Audio mode has not yet been set!");
                return;
            }

            stopObservingVolumeChanges();

            // Restore previously stored audio states.
            setMicrophoneMute(mSavedIsMicrophoneMute);
            setSpeakerphoneOn(mSavedIsSpeakerphoneOn);

            // Restore the mode that was used before we switched to
            // communication mode.
            try {
                mAudioManager.setMode(mSavedAudioMode);
            } catch (SecurityException e) {
                Log.wtf(TAG, "setMode exception: ", e);
                logDeviceInfo();
            }
            mSavedAudioMode = AudioManager.MODE_INVALID;
        }
    }

    /**
     * Activates, i.e., starts routing audio to, the specified audio device.
     *
     * @param deviceId Unique device ID (integer converted to string)
     * representing the selected device. This string is empty if the so-called
     * default device is requested.
     */
    @CalledByNative
    private boolean setDevice(String deviceId) {
        if (DEBUG) logd("setDevice: " + deviceId);
        if (!mIsInitialized)
            return false;
        int intDeviceId = deviceId.isEmpty() ?
            DEVICE_DEFAULT : Integer.parseInt(deviceId);

        if (intDeviceId == DEVICE_DEFAULT) {
            boolean devices[] = null;
            synchronized (mLock) {
                devices = mAudioDevices.clone();
                mRequestedAudioDevice = DEVICE_DEFAULT;
            }
            int defaultDevice = selectDefaultDevice(devices);
            setAudioDevice(defaultDevice);
            return true;
        }

        // A non-default device is specified. Verify that it is valid
        // device, and if so, start using it.
        List<Integer> validIds = Arrays.asList(VALID_DEVICES);
        if (!validIds.contains(intDeviceId) || !mAudioDevices[intDeviceId]) {
            return false;
        }
        synchronized (mLock) {
            mRequestedAudioDevice = intDeviceId;
        }
        setAudioDevice(intDeviceId);
        return true;
    }

    /**
     * @return the current list of available audio devices.
     * Note that this call does not trigger any update of the list of devices,
     * it only copies the current state in to the output array.
     */
    @CalledByNative
    private AudioDeviceName[] getAudioInputDeviceNames() {
        if (DEBUG) logd("getAudioInputDeviceNames");
        if (!mIsInitialized)
            return null;
        boolean devices[] = null;
        synchronized (mLock) {
            devices = mAudioDevices.clone();
        }
        List<String> list = new ArrayList<String>();
        AudioDeviceName[] array =
            new AudioDeviceName[getNumOfAudioDevices(devices)];
        int i = 0;
        for (int id = 0; id < DEVICE_COUNT; ++id) {
            if (devices[id]) {
                array[i] = new AudioDeviceName(id, DEVICE_NAMES[id]);
                list.add(DEVICE_NAMES[id]);
                i++;
            }
        }
        if (DEBUG) logd("getAudioInputDeviceNames: " + list);
        return array;
    }

    @CalledByNative
    private int getNativeOutputSampleRate() {
        if (runningOnJellyBeanMR1OrHigher()) {
            String sampleRateString = mAudioManager.getProperty(
                    AudioManager.PROPERTY_OUTPUT_SAMPLE_RATE);
            return (sampleRateString == null ?
                    DEFAULT_SAMPLING_RATE : Integer.parseInt(sampleRateString));
        } else {
            return DEFAULT_SAMPLING_RATE;
        }
    }

  /**
   * Returns the minimum frame size required for audio input.
   *
   * @param sampleRate sampling rate
   * @param channels number of channels
   */
    @CalledByNative
    private static int getMinInputFrameSize(int sampleRate, int channels) {
        int channelConfig;
        if (channels == 1) {
            channelConfig = AudioFormat.CHANNEL_IN_MONO;
        } else if (channels == 2) {
            channelConfig = AudioFormat.CHANNEL_IN_STEREO;
        } else {
            return -1;
        }
        return AudioRecord.getMinBufferSize(
                sampleRate, channelConfig, AudioFormat.ENCODING_PCM_16BIT) / 2 / channels;
    }

  /**
   * Returns the minimum frame size required for audio output.
   *
   * @param sampleRate sampling rate
   * @param channels number of channels
   */
    @CalledByNative
    private static int getMinOutputFrameSize(int sampleRate, int channels) {
        int channelConfig;
        if (channels == 1) {
            channelConfig = AudioFormat.CHANNEL_OUT_MONO;
        } else if (channels == 2) {
            channelConfig = AudioFormat.CHANNEL_OUT_STEREO;
        } else {
            return -1;
        }
        return AudioTrack.getMinBufferSize(
                sampleRate, channelConfig, AudioFormat.ENCODING_PCM_16BIT) / 2 / channels;
    }

    @CalledByNative
    private boolean isAudioLowLatencySupported() {
        return mContext.getPackageManager().hasSystemFeature(
                PackageManager.FEATURE_AUDIO_LOW_LATENCY);
    }

    @CalledByNative
    private int getAudioLowLatencyOutputFrameSize() {
        String framesPerBuffer =
                mAudioManager.getProperty(AudioManager.PROPERTY_OUTPUT_FRAMES_PER_BUFFER);
        return (framesPerBuffer == null ?
                DEFAULT_FRAME_PER_BUFFER : Integer.parseInt(framesPerBuffer));
    }

    @CalledByNative
    private static boolean shouldUseAcousticEchoCanceler() {
        // AcousticEchoCanceler was added in API level 16 (Jelly Bean).
        if (!runningOnJellyBeanOrHigher()) {
            return false;
        }

        // Verify that this device is among the supported/tested models.
        List<String> supportedModels = Arrays.asList(SUPPORTED_AEC_MODELS);
        if (!supportedModels.contains(Build.MODEL)) {
            return false;
        }
        if (DEBUG && AcousticEchoCanceler.isAvailable()) {
            logd("Approved for use of hardware acoustic echo canceler.");
        }

        // As a final check, verify that the device supports acoustic echo
        // cancellation.
        return AcousticEchoCanceler.isAvailable();
    }

    /**
     * Helper method for debugging purposes. Logs message if method is not
     * called on same thread as this object was created on.
     */
    private void checkIfCalledOnValidThread() {
        if (DEBUG && !mNonThreadSafe.calledOnValidThread()) {
            Log.wtf(TAG, "Method is not called on valid thread!");
        }
    }

    /**
     * Register for BT intents if we have the BLUETOOTH permission.
     * Also extends the list of available devices with a BT device if one exists.
     */
    private void registerBluetoothIntentsIfNeeded() {
        // Check if this process has the BLUETOOTH permission or not.
        mHasBluetoothPermission = hasBluetoothPermission();

        // Add a Bluetooth headset to the list of available devices if a BT
        // headset is detected and if we have the BLUETOOTH permission.
        // We must do this initial check using a dedicated method since the
        // broadcasted intent BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED
        // is not sticky and will only be received if a BT headset is connected
        // after this method has been called.
        if (!mHasBluetoothPermission) {
            return;
        }
        mAudioDevices[DEVICE_BLUETOOTH_HEADSET] = hasBluetoothHeadset();

        // Register receivers for broadcast intents related to changes in
        // Bluetooth headset availability and usage of the SCO channel.
        registerForBluetoothHeadsetIntentBroadcast();
        registerForBluetoothScoIntentBroadcast();
    }

    /** Unregister for BT intents if a registration has been made. */
    private void unregisterBluetoothIntentsIfNeeded() {
        if (mHasBluetoothPermission) {
            mAudioManager.stopBluetoothSco();
            unregisterForBluetoothHeadsetIntentBroadcast();
            unregisterForBluetoothScoIntentBroadcast();
        }
    }

    /** Sets the speaker phone mode. */
    private void setSpeakerphoneOn(boolean on) {
        boolean wasOn = mAudioManager.isSpeakerphoneOn();
        if (wasOn == on) {
            return;
        }
        mAudioManager.setSpeakerphoneOn(on);
    }

    /** Sets the microphone mute state. */
    private void setMicrophoneMute(boolean on) {
        boolean wasMuted = mAudioManager.isMicrophoneMute();
        if (wasMuted == on) {
            return;
        }
        mAudioManager.setMicrophoneMute(on);
    }

    /** Gets  the current microphone mute state. */
    private boolean isMicrophoneMute() {
        return mAudioManager.isMicrophoneMute();
    }

    /** Gets the current earpiece state. */
    private boolean hasEarpiece() {
        return mContext.getPackageManager().hasSystemFeature(
            PackageManager.FEATURE_TELEPHONY);
    }

    /**
     * Checks whether a wired headset is connected or not.
     * This is not a valid indication that audio playback is actually over
     * the wired headset as audio routing depends on other conditions. We
     * only use it as an early indicator (during initialization) of an attached
     * wired headset.
     */
    @Deprecated
    private boolean hasWiredHeadset() {
        return mAudioManager.isWiredHeadsetOn();
    }

    /** Checks if the process has BLUETOOTH permission or not. */
    private boolean hasBluetoothPermission() {
        boolean hasBluetooth = mContext.checkPermission(
            android.Manifest.permission.BLUETOOTH,
            Process.myPid(),
            Process.myUid()) == PackageManager.PERMISSION_GRANTED;
        if (DEBUG && !hasBluetooth) {
            logd("BLUETOOTH permission is missing!");
        }
        return hasBluetooth;
    }

    /**
     * Gets the current Bluetooth headset state.
     * android.bluetooth.BluetoothAdapter.getProfileConnectionState() requires
     * the BLUETOOTH permission.
     */
    private boolean hasBluetoothHeadset() {
        if (!mHasBluetoothPermission) {
            Log.wtf(TAG, "hasBluetoothHeadset() requires BLUETOOTH permission!");
            return false;
        }

        // To get a BluetoothAdapter representing the local Bluetooth adapter,
        // when running on JELLY_BEAN_MR1 (4.2) and below, call the static
        // getDefaultAdapter() method; when running on JELLY_BEAN_MR2 (4.3) and
        // higher, retrieve it through getSystemService(String) with
        // BLUETOOTH_SERVICE.
        BluetoothAdapter btAdapter = null;
        if (runningOnJellyBeanMR2OrHigher()) {
            // Use BluetoothManager to get the BluetoothAdapter for
            // Android 4.3 and above.
            try {
                BluetoothManager btManager =
                        (BluetoothManager)mContext.getSystemService(
                                Context.BLUETOOTH_SERVICE);
                btAdapter = btManager.getAdapter();
            } catch (Exception e) {
                Log.wtf(TAG, "BluetoothManager.getAdapter exception", e);
                return false;
            }
        } else {
            // Use static method for Android 4.2 and below to get the
            // BluetoothAdapter.
            try {
                btAdapter = BluetoothAdapter.getDefaultAdapter();
            } catch (Exception e) {
                Log.wtf(TAG, "BluetoothAdapter.getDefaultAdapter exception", e);
                return false;
            }
        }

        int profileConnectionState;
        try {
            profileConnectionState = btAdapter.getProfileConnectionState(
                android.bluetooth.BluetoothProfile.HEADSET);
        } catch (Exception e) {
            Log.wtf(TAG, "BluetoothAdapter.getProfileConnectionState exception", e);
            profileConnectionState =
                android.bluetooth.BluetoothProfile.STATE_DISCONNECTED;
        }

        // Ensure that Bluetooth is enabled and that a device which supports the
        // headset and handsfree profile is connected.
        // TODO(henrika): it is possible that btAdapter.isEnabled() is
        // redundant. It might be sufficient to only check the profile state.
        return btAdapter.isEnabled() && profileConnectionState ==
            android.bluetooth.BluetoothProfile.STATE_CONNECTED;
    }

    /**
     * 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. */
        mWiredHeadsetReceiver = 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);
                if (DEBUG) {
                    int microphone = intent.getIntExtra("microphone", HAS_NO_MIC);
                    String name = intent.getStringExtra("name");
                    logd("BroadcastReceiver.onReceive: a=" + intent.getAction() +
                        ", s=" + state +
                        ", m=" + microphone +
                        ", n=" + name +
                        ", sb=" + isInitialStickyBroadcast());
                }
                switch (state) {
                    case STATE_UNPLUGGED:
                        synchronized (mLock) {
                            // Wired headset and earpiece are mutually exclusive.
                            mAudioDevices[DEVICE_WIRED_HEADSET] = false;
                            if (hasEarpiece()) {
                                mAudioDevices[DEVICE_EARPIECE] = true;
                            }
                        }
                        break;
                    case STATE_PLUGGED:
                        synchronized (mLock) {
                            // Wired headset and earpiece are mutually exclusive.
                            mAudioDevices[DEVICE_WIRED_HEADSET] = true;
                            mAudioDevices[DEVICE_EARPIECE] = false;
                        }
                        break;
                    default:
                        loge("Invalid state!");
                        break;
                }

                // Update the existing device selection, but only if a specific
                // device has already been selected explicitly.
                if (deviceHasBeenRequested()) {
                    updateDeviceActivation();
                } else if (DEBUG) {
                    reportUpdate();
                }
            }
        };

        // Note: the intent we register for here is sticky, so it'll tell us
        // immediately what the last action was (plugged or unplugged).
        // It will enable us to set the speakerphone correctly.
        mContext.registerReceiver(mWiredHeadsetReceiver, filter);
    }

    /** Unregister receiver for broadcasted ACTION_HEADSET_PLUG intent. */
    private void unregisterForWiredHeadsetIntentBroadcast() {
        mContext.unregisterReceiver(mWiredHeadsetReceiver);
        mWiredHeadsetReceiver = null;
    }

    /**
     * Registers receiver for the broadcasted intent related to BT headset
     * availability or a change in connection state of the local Bluetooth
     * adapter. Example: triggers when the BT device is turned on or off.
     * BLUETOOTH permission is required to receive this one.
     */
    private void registerForBluetoothHeadsetIntentBroadcast() {
        IntentFilter filter = new IntentFilter(
            android.bluetooth.BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED);

        /** Receiver which handles changes in BT headset availability. */
        mBluetoothHeadsetReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                // A change in connection state of the Headset profile has
                // been detected, e.g. BT headset has been connected or
                // disconnected. This broadcast is *not* sticky.
                int profileState = intent.getIntExtra(
                    android.bluetooth.BluetoothHeadset.EXTRA_STATE,
                    android.bluetooth.BluetoothHeadset.STATE_DISCONNECTED);
                if (DEBUG) {
                    logd("BroadcastReceiver.onReceive: a=" + intent.getAction() +
                        ", s=" + profileState +
                        ", sb=" + isInitialStickyBroadcast());
                }

                switch (profileState) {
                    case android.bluetooth.BluetoothProfile.STATE_DISCONNECTED:
                        // We do not have to explicitly call stopBluetoothSco()
                        // since BT SCO will be disconnected automatically when
                        // the BT headset is disabled.
                        synchronized (mLock) {
                            // Remove the BT device from the list of devices.
                            mAudioDevices[DEVICE_BLUETOOTH_HEADSET] = false;
                        }
                        break;
                    case android.bluetooth.BluetoothProfile.STATE_CONNECTED:
                        synchronized (mLock) {
                            // Add the BT device to the list of devices.
                            mAudioDevices[DEVICE_BLUETOOTH_HEADSET] = true;
                        }
                        break;
                    case android.bluetooth.BluetoothProfile.STATE_CONNECTING:
                        // Bluetooth service is switching from off to on.
                        break;
                    case android.bluetooth.BluetoothProfile.STATE_DISCONNECTING:
                        // Bluetooth service is switching from on to off.
                        break;
                    default:
                        loge("Invalid state!");
                        break;
                }

                // Update the existing device selection, but only if a specific
                // device has already been selected explicitly.
                if (deviceHasBeenRequested()) {
                    updateDeviceActivation();
                } else if (DEBUG) {
                    reportUpdate();
                }
           }
        };

        mContext.registerReceiver(mBluetoothHeadsetReceiver, filter);
    }

    private void unregisterForBluetoothHeadsetIntentBroadcast() {
        mContext.unregisterReceiver(mBluetoothHeadsetReceiver);
        mBluetoothHeadsetReceiver = null;
    }

    /**
     * Registers receiver for the broadcasted intent related the existence
     * of a BT SCO channel. Indicates if BT SCO streaming is on or off.
     */
    private void registerForBluetoothScoIntentBroadcast() {
        IntentFilter filter = new IntentFilter(
            AudioManager.ACTION_SCO_AUDIO_STATE_UPDATED);

        /** BroadcastReceiver implementation which handles changes in BT SCO. */
        mBluetoothScoReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                int state = intent.getIntExtra(
                    AudioManager.EXTRA_SCO_AUDIO_STATE,
                    AudioManager.SCO_AUDIO_STATE_DISCONNECTED);
                if (DEBUG) {
                    logd("BroadcastReceiver.onReceive: a=" + intent.getAction() +
                        ", s=" + state +
                        ", sb=" + isInitialStickyBroadcast());
                }

                switch (state) {
                    case AudioManager.SCO_AUDIO_STATE_CONNECTED:
                        mBluetoothScoState = STATE_BLUETOOTH_SCO_ON;
                        break;
                    case AudioManager.SCO_AUDIO_STATE_DISCONNECTED:
                        mBluetoothScoState = STATE_BLUETOOTH_SCO_OFF;
                        break;
                    case AudioManager.SCO_AUDIO_STATE_CONNECTING:
                        // do nothing
                        break;
                    default:
                        loge("Invalid state!");
                }
                if (DEBUG) {
                    reportUpdate();
                }
           }
        };

        mContext.registerReceiver(mBluetoothScoReceiver, filter);
    }

    private void unregisterForBluetoothScoIntentBroadcast() {
        mContext.unregisterReceiver(mBluetoothScoReceiver);
        mBluetoothScoReceiver = null;
    }

    /** Enables BT audio using the SCO audio channel. */
    private void startBluetoothSco() {
        if (!mHasBluetoothPermission) {
            return;
        }
        if (mBluetoothScoState == STATE_BLUETOOTH_SCO_ON ||
            mBluetoothScoState == STATE_BLUETOOTH_SCO_TURNING_ON) {
            // Unable to turn on BT in this state.
            return;
        }

        // Check if audio is already routed to BT SCO; if so, just update
        // states but don't try to enable it again.
        if (mAudioManager.isBluetoothScoOn()) {
            mBluetoothScoState = STATE_BLUETOOTH_SCO_ON;
            return;
        }

        if (DEBUG) logd("startBluetoothSco: turning BT SCO on...");
        mBluetoothScoState = STATE_BLUETOOTH_SCO_TURNING_ON;
        mAudioManager.startBluetoothSco();
    }

    /** Disables BT audio using the SCO audio channel. */
    private void stopBluetoothSco() {
        if (!mHasBluetoothPermission) {
            return;
        }
        if (mBluetoothScoState != STATE_BLUETOOTH_SCO_ON &&
            mBluetoothScoState != STATE_BLUETOOTH_SCO_TURNING_ON) {
            // No need to turn off BT in this state.
            return;
        }
        if (!mAudioManager.isBluetoothScoOn()) {
            // TODO(henrika): can we do anything else than logging here?
            loge("Unable to stop BT SCO since it is already disabled!");
            return;
        }

        if (DEBUG) logd("stopBluetoothSco: turning BT SCO off...");
        mBluetoothScoState = STATE_BLUETOOTH_SCO_TURNING_OFF;
        mAudioManager.stopBluetoothSco();
    }

    /**
     * Changes selection of the currently active audio device.
     *
     * @param device Specifies the selected audio device.
     */
    private void setAudioDevice(int device) {
        if (DEBUG) logd("setAudioDevice(device=" + device + ")");

        // Ensure that the Bluetooth SCO audio channel is always disabled
        // unless the BT headset device is selected.
        if (device == DEVICE_BLUETOOTH_HEADSET) {
            startBluetoothSco();
        } else {
            stopBluetoothSco();
        }

        switch (device) {
            case DEVICE_BLUETOOTH_HEADSET:
                break;
            case DEVICE_SPEAKERPHONE:
                setSpeakerphoneOn(true);
                break;
            case DEVICE_WIRED_HEADSET:
                setSpeakerphoneOn(false);
                break;
            case DEVICE_EARPIECE:
                setSpeakerphoneOn(false);
                break;
            default:
                loge("Invalid audio device selection!");
                break;
        }
        reportUpdate();
    }

    /**
     * Use a special selection scheme if the default device is selected.
     * The "most unique" device will be selected; Wired headset first,
     * then Bluetooth and last the speaker phone.
     */
    private static int selectDefaultDevice(boolean[] devices) {
        if (devices[DEVICE_WIRED_HEADSET]) {
            return DEVICE_WIRED_HEADSET;
        } else if (devices[DEVICE_BLUETOOTH_HEADSET]) {
            // TODO(henrika): possibly need improvements here if we are
            // in a state where Bluetooth is turning off.
            return DEVICE_BLUETOOTH_HEADSET;
        }
        return DEVICE_SPEAKERPHONE;
    }

    /** Returns true if setDevice() has been called with a valid device id. */
    private boolean deviceHasBeenRequested() {
        synchronized (mLock) {
            return (mRequestedAudioDevice != DEVICE_INVALID);
        }
    }

    /**
     * Updates the active device given the current list of devices and
     * information about if a specific device has been selected or if
     * the default device is selected.
     */
    private void updateDeviceActivation() {
        boolean devices[] = null;
        int requested = DEVICE_INVALID;
        synchronized (mLock) {
            requested = mRequestedAudioDevice;
            devices = mAudioDevices.clone();
        }
        if (requested == DEVICE_INVALID) {
            loge("Unable to activate device since no device is selected!");
            return;
        }

        // Update default device if it has been selected explicitly, or
        // the selected device has been removed from the list.
        if (requested == DEVICE_DEFAULT || !devices[requested]) {
            // Get default device given current list and activate the device.
            int defaultDevice = selectDefaultDevice(devices);
            setAudioDevice(defaultDevice);
        } else {
            // Activate the selected device since we know that it exists in
            // the list.
            setAudioDevice(requested);
        }
    }

    /** Returns number of available devices */
    private static int getNumOfAudioDevices(boolean[] devices) {
        int count = 0;
        for (int i = 0; i < DEVICE_COUNT; ++i) {
            if (devices[i])
                ++count;
        }
        return count;
    }

    /**
     * For now, just log the state change but the idea is that we should
     * notify a registered state change listener (if any) that there has
     * been a change in the state.
     * TODO(henrika): add support for state change listener.
     */
    private void reportUpdate() {
        synchronized (mLock) {
            List<String> devices = new ArrayList<String>();
            for (int i = 0; i < DEVICE_COUNT; ++i) {
                if (mAudioDevices[i])
                    devices.add(DEVICE_NAMES[i]);
            }
            if (DEBUG) {
                logd("reportUpdate: requested=" + mRequestedAudioDevice +
                    ", btSco=" + mBluetoothScoState +
                    ", devices=" + devices);
            }
        }
    }

    /** Information about the current build, taken from system properties. */
    private void logDeviceInfo() {
        logd("Android SDK: " + Build.VERSION.SDK_INT + ", " +
            "Release: " + Build.VERSION.RELEASE + ", " +
            "Brand: " + Build.BRAND + ", " +
            "CPU_ABI: " + Build.CPU_ABI + ", " +
            "Device: " + Build.DEVICE + ", " +
            "Id: " + Build.ID + ", " +
            "Hardware: " + Build.HARDWARE + ", " +
            "Manufacturer: " + Build.MANUFACTURER + ", " +
            "Model: " + Build.MODEL + ", " +
            "Product: " + Build.PRODUCT);
    }

    /** Trivial helper method for debug logging */
    private static void logd(String msg) {
        Log.d(TAG, msg);
    }

    /** Trivial helper method for error logging */
    private static void loge(String msg) {
        Log.e(TAG, msg);
    }

    /** Start thread which observes volume changes on the voice stream. */
    private void startObservingVolumeChanges() {
        if (DEBUG) logd("startObservingVolumeChanges");
        if (mSettingsObserverThread != null)
            return;
        mSettingsObserverThread = new HandlerThread("SettingsObserver");
        mSettingsObserverThread.start();

        mSettingsObserver = new ContentObserver(
            new Handler(mSettingsObserverThread.getLooper())) {

                @Override
                public void onChange(boolean selfChange) {
                    if (DEBUG) logd("SettingsObserver.onChange: " + selfChange);
                    super.onChange(selfChange);

                    // Ensure that the observer is activated during communication mode.
                    if (mAudioManager.getMode() != AudioManager.MODE_IN_COMMUNICATION) {
                        Log.wtf(TAG, "Only enable SettingsObserver in COMM mode!");
                        return;
                    }

                    // Get stream volume for the voice stream and deliver callback if
                    // the volume index is zero. It is not possible to move the volume
                    // slider all the way down in communication mode but the callback
                    // implementation can ensure that the volume is completely muted.
                    int volume = mAudioManager.getStreamVolume(
                        AudioManager.STREAM_VOICE_CALL);
                    if (DEBUG) logd("nativeSetMute: " + (volume == 0));
                    nativeSetMute(mNativeAudioManagerAndroid, (volume == 0));
                }
        };

        mContentResolver.registerContentObserver(
            Settings.System.CONTENT_URI, true, mSettingsObserver);
    }

    /** Quit observer thread and stop listening for volume changes. */
    private void stopObservingVolumeChanges() {
        if (DEBUG) logd("stopObservingVolumeChanges");
        if (mSettingsObserverThread == null)
            return;

        mContentResolver.unregisterContentObserver(mSettingsObserver);
        mSettingsObserver = null;

        mSettingsObserverThread.quit();
        try {
            mSettingsObserverThread.join();
        } catch (InterruptedException e) {
            Log.wtf(TAG, "Thread.join() exception: ", e);
        }
        mSettingsObserverThread = null;
    }

    private native void nativeSetMute(long nativeAudioManagerAndroid, boolean muted);
}