anotherim/src/main/java/eu/siacs/conversations/services/AppRTCAudioManager.java

/*
 *  Copyright 2014 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 eu.siacs.conversations.services;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.media.AudioDeviceInfo;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.os.Build;
import androidx.annotation.Nullable;
import android.util.Log;

import org.webrtc.ThreadUtils;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.CountDownLatch;

import eu.siacs.conversations.Config;
import eu.siacs.conversations.utils.AppRTCUtils;

/**
 * AppRTCAudioManager manages all audio related parts of the AppRTC demo.
 */
public class AppRTCAudioManager {

    private static CountDownLatch microphoneLatch;

    private final Context apprtcContext;
    // Contains speakerphone setting: auto, true or false
    @Nullable
    private final SpeakerPhonePreference speakerPhonePreference;
    // Handles all tasks related to Bluetooth headset devices.
    private final AppRTCBluetoothManager bluetoothManager;
    @Nullable
    private AudioManager audioManager;
    @Nullable
    private AudioManagerEvents audioManagerEvents;
    private AudioManagerState amState;
    private boolean savedIsSpeakerPhoneOn;
    private boolean savedIsMicrophoneMute;
    private boolean hasWiredHeadset;
    // 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;
    // Proximity sensor object. It measures the proximity of an object in cm
    // relative to the view screen of a device and can therefore be used to
    // assist device switching (close to ear <=> use headset earpiece if
    // available, far from ear <=> use speaker phone).
    @Nullable
    private AppRTCProximitySensor proximitySensor;
    // Contains a list of available audio devices. A Set collection is used to
    // avoid duplicate elements.
    private Set<AudioDevice> audioDevices = new HashSet<>();
    // Broadcast receiver for wired headset intent broadcasts.
    private BroadcastReceiver wiredHeadsetReceiver;
    // Callback method for changes in audio focus.
    @Nullable
    private AudioManager.OnAudioFocusChangeListener audioFocusChangeListener;

    private AppRTCAudioManager(Context context, final SpeakerPhonePreference speakerPhonePreference) {
        Log.d(Config.LOGTAG, "ctor");
        ThreadUtils.checkIsOnMainThread();
        apprtcContext = context;
        audioManager = ((AudioManager) context.getSystemService(Context.AUDIO_SERVICE));
        bluetoothManager = AppRTCBluetoothManager.create(context, this);
        wiredHeadsetReceiver = new WiredHeadsetReceiver();
        amState = AudioManagerState.UNINITIALIZED;
        this.speakerPhonePreference = speakerPhonePreference;
        if (speakerPhonePreference == SpeakerPhonePreference.EARPIECE && hasEarpiece()) {
            defaultAudioDevice = AudioDevice.EARPIECE;
        } else {
            defaultAudioDevice = AudioDevice.SPEAKER_PHONE;
        }
        // Create and initialize the proximity sensor.
        // Tablet devices (e.g. Nexus 7) does not support proximity sensors.
        // Note that, the sensor will not be active until start() has been called.
        proximitySensor = AppRTCProximitySensor.create(context,
                // This method will be called each time a state change is detected.
                // Example: user holds his hand over the device (closer than ~5 cm),
                // or removes his hand from the device.
                this::onProximitySensorChangedState);
        Log.d(Config.LOGTAG, "defaultAudioDevice: " + defaultAudioDevice);
        AppRTCUtils.logDeviceInfo(Config.LOGTAG);
    }

    /**
     * Construction.
     */
    public static AppRTCAudioManager create(Context context, SpeakerPhonePreference speakerPhonePreference) {
        return new AppRTCAudioManager(context, speakerPhonePreference);
    }

    public static boolean isMicrophoneAvailable() {
        microphoneLatch = new CountDownLatch(1);
        AudioRecord audioRecord = null;
        boolean available = true;
        try {
            final int sampleRate = 44100;
            final int channel = AudioFormat.CHANNEL_IN_MONO;
            final int format = AudioFormat.ENCODING_PCM_16BIT;
            final int bufferSize = AudioRecord.getMinBufferSize(sampleRate, channel, format);
            audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleRate, channel, format, bufferSize);
            audioRecord.startRecording();
            final short[] buffer = new short[bufferSize];
            final int audioStatus = audioRecord.read(buffer, 0, bufferSize);
            if (audioStatus == AudioRecord.ERROR_INVALID_OPERATION || audioStatus == AudioRecord.STATE_UNINITIALIZED)
                available = false;
        } catch (Exception e) {
            available = false;
        } finally {
            release(audioRecord);

        }
        microphoneLatch.countDown();
        return available;
    }

    private static void release(final AudioRecord audioRecord) {
        if (audioRecord == null) {
            return;
        }
        try {
            audioRecord.release();
        } catch (Exception e) {
            //ignore
        }
    }

    /**
     * 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 (speakerPhonePreference != SpeakerPhonePreference.AUTO) {
            return;
        }
        // The proximity sensor should only be activated when there are exactly two
        // available audio devices.
        if (audioDevices.size() == 2 && audioDevices.contains(AppRTCAudioManager.AudioDevice.EARPIECE)
                && audioDevices.contains(AppRTCAudioManager.AudioDevice.SPEAKER_PHONE)) {
            if (proximitySensor.sensorReportsNearState()) {
                // Sensor reports that a "handset is being held up to a person's ear",
                // or "something is covering the light sensor".
                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".
                setAudioDeviceInternal(AppRTCAudioManager.AudioDevice.SPEAKER_PHONE);
            }
        }
    }

    @SuppressWarnings("deprecation")
    public void start(AudioManagerEvents audioManagerEvents) {
        Log.d(Config.LOGTAG, AppRTCAudioManager.class.getName() + ".start()");
        ThreadUtils.checkIsOnMainThread();
        if (amState == AudioManagerState.RUNNING) {
            Log.e(Config.LOGTAG, "AudioManager is already active");
            return;
        }
        awaitMicrophoneLatch();
        this.audioManagerEvents = audioManagerEvents;
        amState = AudioManagerState.RUNNING;
        // Store current audio state so we can restore it when stop() is called.
        savedIsSpeakerPhoneOn = audioManager.isSpeakerphoneOn();
        savedIsMicrophoneMute = audioManager.isMicrophoneMute();
        hasWiredHeadset = hasWiredHeadset();
        // Create an AudioManager.OnAudioFocusChangeListener instance.
        audioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
            // Called on the listener to notify if the audio focus for this listener has been changed.
            // The |focusChange| value indicates whether the focus was gained, whether the focus was lost,
            // and whether that loss is transient, or whether the new focus holder will hold it for an
            // unknown amount of time.
            // TODO(henrika): possibly extend support of handling audio-focus changes. Only contains
            // logging for now.
            @Override
            public void onAudioFocusChange(int focusChange) {
                final String typeOfChange;
                switch (focusChange) {
                    case AudioManager.AUDIOFOCUS_GAIN:
                        typeOfChange = "AUDIOFOCUS_GAIN";
                        break;
                    case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT:
                        typeOfChange = "AUDIOFOCUS_GAIN_TRANSIENT";
                        break;
                    case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE:
                        typeOfChange = "AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE";
                        break;
                    case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK:
                        typeOfChange = "AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK";
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS:
                        typeOfChange = "AUDIOFOCUS_LOSS";
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                        typeOfChange = "AUDIOFOCUS_LOSS_TRANSIENT";
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
                        typeOfChange = "AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK";
                        break;
                    default:
                        typeOfChange = "AUDIOFOCUS_INVALID";
                        break;
                }
                Log.d(Config.LOGTAG, "onAudioFocusChange: " + typeOfChange);
            }
        };
        // Request audio playout focus (without ducking) and install listener for changes in focus.
        int result = audioManager.requestAudioFocus(audioFocusChangeListener,
                AudioManager.STREAM_VOICE_CALL, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
        if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
            Log.d(Config.LOGTAG, "Audio focus request granted for VOICE_CALL streams");
        } else {
            Log.e(Config.LOGTAG, "Audio focus request failed");
        }
        // 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.
        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 BT or wired headset or by covering/uncovering
        // the proximity sensor.
        updateAudioDeviceState();
        // Register receiver for broadcast intents related to adding/removing a
        // wired headset.
        registerReceiver(wiredHeadsetReceiver, new IntentFilter(Intent.ACTION_HEADSET_PLUG));
        Log.d(Config.LOGTAG, "AudioManager started");
    }

    private void awaitMicrophoneLatch() {
        final CountDownLatch latch = microphoneLatch;
        if (latch == null) {
            return;
        }
        try {
            latch.await();
        } catch (InterruptedException e) {
            //ignore
        }
    }

    @SuppressWarnings("deprecation")
    public void stop() {
        Log.d(Config.LOGTAG, AppRTCAudioManager.class.getName() + ".stop()");
        ThreadUtils.checkIsOnMainThread();
        if (amState != AudioManagerState.RUNNING) {
            Log.e(Config.LOGTAG, "Trying to stop AudioManager in incorrect state: " + amState);
            return;
        }
        amState = AudioManagerState.UNINITIALIZED;
        unregisterReceiver(wiredHeadsetReceiver);
        bluetoothManager.stop();
        // Restore previously stored audio states.
        setSpeakerphoneOn(savedIsSpeakerPhoneOn);
        setMicrophoneMute(savedIsMicrophoneMute);
        audioManager.setMode(AudioManager.MODE_NORMAL);
        // Abandon audio focus. Gives the previous focus owner, if any, focus.
        audioManager.abandonAudioFocus(audioFocusChangeListener);
        audioFocusChangeListener = null;
        Log.d(Config.LOGTAG, "Abandoned audio focus for VOICE_CALL streams");
        if (proximitySensor != null) {
            proximitySensor.stop();
            proximitySensor = null;
        }
        audioManagerEvents = null;
    }

    /**
     * Changes selection of the currently active audio device.
     */
    private void setAudioDeviceInternal(AudioDevice device) {
        Log.d(Config.LOGTAG, "setAudioDeviceInternal(device=" + device + ")");
        AppRTCUtils.assertIsTrue(audioDevices.contains(device));
        switch (device) {
            case SPEAKER_PHONE:
                setSpeakerphoneOn(true);
                break;
            case EARPIECE:
            case WIRED_HEADSET:
            case BLUETOOTH:
                setSpeakerphoneOn(false);
                break;
            default:
                Log.e(Config.LOGTAG, "Invalid audio device selection");
                break;
        }
        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(Config.LOGTAG, "Invalid default audio device selection");
                break;
        }
        Log.d(Config.LOGTAG, "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(Config.LOGTAG, "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<>(audioDevices));
    }

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

    /**
     * Helper method for receiver registration.
     */
    private void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
        apprtcContext.registerReceiver(receiver, filter);
    }

    /**
     * Helper method for unregistration of an existing receiver.
     */
    private void unregisterReceiver(BroadcastReceiver receiver) {
        apprtcContext.unregisterReceiver(receiver);
    }

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

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

    /**
     * Gets the current earpiece state.
     */
    private boolean hasEarpiece() {
        return apprtcContext.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() {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            return audioManager.isWiredHeadsetOn();
        } else {
            final AudioDeviceInfo[] devices = audioManager.getDevices(AudioManager.GET_DEVICES_ALL);
            for (AudioDeviceInfo device : devices) {
                final int type = device.getType();
                if (type == AudioDeviceInfo.TYPE_WIRED_HEADSET) {
                    Log.d(Config.LOGTAG, "hasWiredHeadset: found wired headset");
                    return true;
                } else if (type == AudioDeviceInfo.TYPE_USB_DEVICE) {
                    Log.d(Config.LOGTAG, "hasWiredHeadset: found USB audio device");
                    return true;
                }
            }
            return false;
        }
    }

    /**
     * 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(Config.LOGTAG, "--- updateAudioDeviceState: "
                + "wired headset=" + hasWiredHeadset + ", "
                + "BT state=" + bluetoothManager.getState());
        Log.d(Config.LOGTAG, "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.
            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).
            newAudioDevices.add(AudioDevice.SPEAKER_PHONE);
            if (hasEarpiece()) {
                newAudioDevices.add(AudioDevice.EARPIECE);
            }
        }
        // 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;
        }
        // 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(Config.LOGTAG, "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.
        final AudioDevice newAudioDevice;
        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 {
            // 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(Config.LOGTAG, "New device status: "
                    + "available=" + audioDevices + ", "
                    + "selected=" + newAudioDevice);
            if (audioManagerEvents != null) {
                // Notify a listening client that audio device has been changed.
                audioManagerEvents.onAudioDeviceChanged(selectedAudioDevice, audioDevices);
            }
        }
        Log.d(Config.LOGTAG, "--- updateAudioDeviceState done");
    }

    /**
     * AudioDevice is the names of possible audio devices that we currently
     * support.
     */
    public enum AudioDevice {SPEAKER_PHONE, WIRED_HEADSET, EARPIECE, BLUETOOTH, NONE}

    /**
     * AudioManager state.
     */
    public enum AudioManagerState {
        UNINITIALIZED,
        PREINITIALIZED,
        RUNNING,
    }

    public enum SpeakerPhonePreference {
        AUTO, EARPIECE, SPEAKER
    }

    /**
     * Selected audio device change event.
     */
    public interface AudioManagerEvents {
        // Callback fired once audio device is changed or list of available audio devices changed.
        void onAudioDeviceChanged(
                AudioDevice selectedAudioDevice, Set<AudioDevice> availableAudioDevices);
    }

    /* 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(Config.LOGTAG, "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();
        }
    }
}