ljm_a0/modules/RTC/RTCUtils.js

/* global $,
          __filename,
          attachMediaStream,
          MediaStreamTrack,
          RTCIceCandidate: true,
          RTCPeerConnection,
          RTCSessionDescription: true,
          webkitMediaStream,
          webkitRTCPeerConnection,
          webkitURL
*/
import CameraFacingMode from '../../service/RTC/CameraFacingMode';
import EventEmitter from 'events';
import { getLogger } from 'jitsi-meet-logger';
import GlobalOnErrorHandler from '../util/GlobalOnErrorHandler';
import JitsiTrackError from '../../JitsiTrackError';
import Listenable from '../util/Listenable';
import * as MediaType from '../../service/RTC/MediaType';
import Resolutions from '../../service/RTC/Resolutions';
import RTCBrowserType from './RTCBrowserType';
import RTCEvents from '../../service/RTC/RTCEvents';
import ortcRTCPeerConnection from './ortc/RTCPeerConnection';
import screenObtainer from './ScreenObtainer';
import SDPUtil from '../xmpp/SDPUtil';
import Statistics from '../statistics/statistics';
import VideoType from '../../service/RTC/VideoType';

const logger = getLogger(__filename);

// XXX Don't require Temasys unless it's to be used because it doesn't run on
// React Native, for example.
const AdapterJS
    = RTCBrowserType.isTemasysPluginUsed()
        ? require('./adapter.screenshare')
        : undefined;

// Require adapter only for certain browsers. This is being done for
// react-native, which has its own shims, and while browsers are being migrated
// over to use adapter's shims.
if (RTCBrowserType.usesNewGumFlow()) {
    require('webrtc-adapter');
}

const eventEmitter = new EventEmitter();

const AVAILABLE_DEVICES_POLL_INTERVAL_TIME = 3000; // ms

// TODO (brian): Move this devices hash, maybe to a model, so RTCUtils remains
// stateless.
const devices = {
    audio: false,
    video: false
};

// Currently audio output device change is supported only in Chrome and
// default output always has 'default' device ID
let audioOutputDeviceId = 'default'; // default device
// whether user has explicitly set a device to use
let audioOutputChanged = false;

// Disables all audio processing
let disableAP = false;

// Disables Acoustic Echo Cancellation
let disableAEC = false;

// Disables Noise Suppression
let disableNS = false;

// Disables Automatic Gain Control
let disableAGC = false;

// Disables Highpass Filter
let disableHPF = false;

const featureDetectionAudioEl = document.createElement('audio');
const isAudioOutputDeviceChangeAvailable
    = typeof featureDetectionAudioEl.setSinkId !== 'undefined';

let currentlyAvailableMediaDevices;

/**
 * "rawEnumerateDevicesWithCallback" will be initialized only after WebRTC is
 * ready. Otherwise it is too early to assume that the devices listing is not
 * supported.
 */
let rawEnumerateDevicesWithCallback;

/**
 *
 */
function initRawEnumerateDevicesWithCallback() {
    rawEnumerateDevicesWithCallback
        = navigator.mediaDevices && navigator.mediaDevices.enumerateDevices
            ? function(callback) {
                navigator.mediaDevices.enumerateDevices().then(
                    callback,
                    () => callback([]));
            }

            // Safari:
            // "ReferenceError: Can't find variable: MediaStreamTrack" when
            // Temasys plugin is not installed yet, have to delay this call
            // until WebRTC is ready.
            : MediaStreamTrack && MediaStreamTrack.getSources
                ? function(callback) {
                    MediaStreamTrack.getSources(
                        sources =>
                            callback(
                                sources.map(convertMediaStreamTrackSource)));
                }
                : undefined;
}

// TODO: currently no browser supports 'devicechange' event even in nightly
// builds so no feature/browser detection is used at all. However in future this
// should be changed to some expression. Progress on 'devicechange' event
// implementation for Chrome/Opera/NWJS can be tracked at
// https://bugs.chromium.org/p/chromium/issues/detail?id=388648, for Firefox -
// at https://bugzilla.mozilla.org/show_bug.cgi?id=1152383. More information on
// 'devicechange' event can be found in spec -
// http://w3c.github.io/mediacapture-main/#event-mediadevices-devicechange
// TODO: check MS Edge
const isDeviceChangeEventSupported = false;

let rtcReady = false;

/**
 *
 * @param constraints
 * @param isNewStyleConstraintsSupported
 * @param resolution
 */
function setResolutionConstraints(
        constraints,
        isNewStyleConstraintsSupported,
        resolution) {
    if (Resolutions[resolution]) {
        if (isNewStyleConstraintsSupported) {
            constraints.video.width = {
                ideal: Resolutions[resolution].width
            };
            constraints.video.height = {
                ideal: Resolutions[resolution].height
            };
        }

        constraints.video.mandatory.minWidth = Resolutions[resolution].width;
        constraints.video.mandatory.minHeight = Resolutions[resolution].height;
    }

    if (constraints.video.mandatory.minWidth) {
        constraints.video.mandatory.maxWidth
            = constraints.video.mandatory.minWidth;
    }

    if (constraints.video.mandatory.minHeight) {
        constraints.video.mandatory.maxHeight
            = constraints.video.mandatory.minHeight;
    }
}

/**
 * @param {string[]} um required user media types
 *
 * @param {Object} [options={}] optional parameters
 * @param {string} options.resolution
 * @param {number} options.bandwidth
 * @param {number} options.fps
 * @param {string} options.desktopStream
 * @param {string} options.cameraDeviceId
 * @param {string} options.micDeviceId
 * @param {CameraFacingMode} options.facingMode
 * @param {bool} firefox_fake_device
 */
function getConstraints(um, options) {
    const constraints = { audio: false,
        video: false };

    // Don't mix new and old style settings for Chromium as this leads
    // to TypeError in new Chromium versions. @see
    // https://bugs.chromium.org/p/chromium/issues/detail?id=614716
    // This is a temporary solution, in future we will fully split old and
    // new style constraints when new versions of Chromium and Firefox will
    // have stable support of new constraints format. For more information
    // @see https://github.com/jitsi/lib-jitsi-meet/pull/136
    const isNewStyleConstraintsSupported
        = RTCBrowserType.isFirefox()
        || RTCBrowserType.isEdge()
        || RTCBrowserType.isReactNative()
        || RTCBrowserType.isTemasysPluginUsed();

    if (um.indexOf('video') >= 0) {
        // same behaviour as true
        constraints.video = { mandatory: {},
            optional: [] };

        if (options.cameraDeviceId) {
            if (isNewStyleConstraintsSupported) {
                // New style of setting device id.
                constraints.video.deviceId = options.cameraDeviceId;
            }

            // Old style.
            constraints.video.optional.push({
                sourceId: options.cameraDeviceId
            });
        } else {
            // Prefer the front i.e. user-facing camera (to the back i.e.
            // environment-facing camera, for example).
            // TODO: Maybe use "exact" syntax if options.facingMode is defined,
            // but this probably needs to be decided when updating other
            // constraints, as we currently don't use "exact" syntax anywhere.
            const facingMode = options.facingMode || CameraFacingMode.USER;

            if (isNewStyleConstraintsSupported) {
                constraints.video.facingMode = facingMode;
            }
            constraints.video.optional.push({
                facingMode
            });
        }

        if (options.minFps || options.maxFps || options.fps) {
            // for some cameras it might be necessary to request 30fps
            // so they choose 30fps mjpg over 10fps yuy2
            if (options.minFps || options.fps) {
                // Fall back to options.fps for backwards compatibility
                options.minFps = options.minFps || options.fps;
                constraints.video.mandatory.minFrameRate = options.minFps;
            }
            if (options.maxFps) {
                constraints.video.mandatory.maxFrameRate = options.maxFps;
            }
        }

        setResolutionConstraints(
            constraints, isNewStyleConstraintsSupported, options.resolution);
    }
    if (um.indexOf('audio') >= 0) {
        if (RTCBrowserType.isReactNative()) {
            // The react-native-webrtc project that we're currently using
            // expects the audio constraint to be a boolean.
            constraints.audio = true;
        } else if (RTCBrowserType.isFirefox()) {
            if (options.micDeviceId) {
                constraints.audio = {
                    mandatory: {},
                    deviceId: options.micDeviceId, // new style
                    optional: [ {
                        sourceId: options.micDeviceId // old style
                    } ] };
            } else {
                constraints.audio = true;
            }
        } else {
            // same behaviour as true
            constraints.audio = { mandatory: {},
                optional: [] };
            if (options.micDeviceId) {
                if (isNewStyleConstraintsSupported) {
                    // New style of setting device id.
                    constraints.audio.deviceId = options.micDeviceId;
                }

                // Old style.
                constraints.audio.optional.push({
                    sourceId: options.micDeviceId
                });
            }

            // if it is good enough for hangouts...
            constraints.audio.optional.push(
                { echoCancellation: !disableAEC && !disableAP },
                { googEchoCancellation: !disableAEC && !disableAP },
                { googAutoGainControl: !disableAGC && !disableAP },
                { googNoiseSupression: !disableNS && !disableAP },
                { googHighpassFilter: !disableHPF && !disableAP },
                { googNoiseSuppression2: !disableNS && !disableAP },
                { googEchoCancellation2: !disableAEC && !disableAP },
                { googAutoGainControl2: !disableAGC && !disableAP }
            );
        }
    }
    if (um.indexOf('screen') >= 0) {
        if (RTCBrowserType.isChrome()) {
            constraints.video = {
                mandatory: {
                    chromeMediaSource: 'screen',
                    maxWidth: window.screen.width,
                    maxHeight: window.screen.height,
                    maxFrameRate: 3
                },
                optional: []
            };
        } else if (RTCBrowserType.isTemasysPluginUsed()) {
            constraints.video = {
                optional: [
                    {
                        sourceId: AdapterJS.WebRTCPlugin.plugin.screensharingKey
                    }
                ]
            };
        } else if (RTCBrowserType.isFirefox()) {
            constraints.video = {
                mozMediaSource: 'window',
                mediaSource: 'window'
            };

        } else {
            const errmsg
                = '\'screen\' WebRTC media source is supported only in Chrome'
                    + ' and with Temasys plugin';

            GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
            logger.error(errmsg);
        }
    }
    if (um.indexOf('desktop') >= 0) {
        constraints.video = {
            mandatory: {
                chromeMediaSource: 'desktop',
                chromeMediaSourceId: options.desktopStream,
                maxWidth: window.screen.width,
                maxHeight: window.screen.height,
                maxFrameRate: 3
            },
            optional: []
        };
    }

    if (options.bandwidth) {
        if (!constraints.video) {
            // same behaviour as true
            constraints.video = { mandatory: {},
                optional: [] };
        }
        constraints.video.optional.push({ bandwidth: options.bandwidth });
    }

    // we turn audio for both audio and video tracks, the fake audio & video
    // seems to work only when enabled in one getUserMedia call, we cannot get
    // fake audio separate by fake video this later can be a problem with some
    // of the tests
    if (RTCBrowserType.isFirefox() && options.firefox_fake_device) {
        // seems to be fixed now, removing this experimental fix, as having
        // multiple audio tracks brake the tests
        // constraints.audio = true;
        constraints.fake = true;
    }

    return constraints;
}

/**
 * Default MediaStreamConstraints to use for calls to getUserMedia.
 *
 * @private
 */
const DEFAULT_CONSTRAINTS = {
    video: {
        aspectRatio: 16 / 9,
        height: {
            ideal: 1080,
            max: 1080,
            min: 240
        }
    }
};

/**
 * Creates a constraints object to be passed into a call to getUserMedia.
 *
 * @param {Array} um - An array of user media types to get. The accepted
 * types are "video", "audio", and "desktop."
 * @param {Object} options - Various values to be added to the constraints.
 * @param {string} options.cameraDeviceId - The device id for the video
 * capture device to get video from.
 * @param {Object} options.constraints - Default constraints object to use
 * as a base for the returned constraints.
 * @param {Object} options.desktopStream - The desktop source id from which
 * to capture a desktop sharing video.
 * @param {string} options.facingMode - Which direction the camera is
 * pointing to.
 * @param {string} options.micDeviceId - The device id for the audio capture
 * device to get audio from.
 * @private
 * @returns {Object}
 */
function newGetConstraints(um = [], options = {}) {
    // Create a deep copy of the constraints to avoid any modification of
    // the passed in constraints object.
    const constraints = JSON.parse(JSON.stringify(
        options.constraints || DEFAULT_CONSTRAINTS));

    if (um.indexOf('video') >= 0) {
        if (!constraints.video) {
            constraints.video = {};
        }

        if (options.cameraDeviceId) {
            constraints.video.deviceId = options.cameraDeviceId;
        } else {
            const facingMode = options.facingMode || CameraFacingMode.USER;

            constraints.video.facingMode = facingMode;
        }
    } else {
        constraints.video = false;
    }

    if (um.indexOf('audio') >= 0) {
        if (!constraints.audio || typeof constraints.audio === 'boolean') {
            constraints.audio = {};
        }

        // NOTE(brian): the new-style ('advanced' instead of 'optional')
        // doesn't seem to carry through the googXXX constraints
        // Changing back to 'optional' here (even with video using
        // the 'advanced' style) allows them to be passed through
        // but also requires the device id to capture to be set in optional
        // as sourceId otherwise the constraints are considered malformed.
        if (!constraints.audio.optional) {
            constraints.audio.optional = [];
        }

        constraints.audio.optional.push(
            { sourceId: options.micDeviceId },
            { echoCancellation: !disableAEC && !disableAP },
            { googEchoCancellation: !disableAEC && !disableAP },
            { googAutoGainControl: !disableAGC && !disableAP },
            { googNoiseSupression: !disableNS && !disableAP },
            { googHighpassFilter: !disableHPF && !disableAP },
            { googNoiseSuppression2: !disableNS && !disableAP },
            { googEchoCancellation2: !disableAEC && !disableAP },
            { googAutoGainControl2: !disableAGC && !disableAP }
        );
    } else {
        constraints.audio = false;
    }

    if (um.indexOf('desktop') >= 0) {
        if (!constraints.video || typeof constraints.video === 'boolean') {
            constraints.video = {};
        }

        constraints.video = {
            mandatory: {
                chromeMediaSource: 'desktop',
                chromeMediaSourceId: options.desktopStream,
                maxWidth: window.screen.width,
                maxHeight: window.screen.height,
                maxFrameRate: 3
            }
        };
    }

    return constraints;
}

/**
 * Sets the availbale devices based on the options we requested and the
 * streams we received.
 * @param um the options we requested to getUserMedia.
 * @param stream the stream we received from calling getUserMedia.
 */
function setAvailableDevices(um, stream) {
    const audioTracksReceived = stream && stream.getAudioTracks().length > 0;
    const videoTracksReceived = stream && stream.getVideoTracks().length > 0;

    if (um.indexOf('video') !== -1) {
        devices.video = videoTracksReceived;
    }
    if (um.indexOf('audio') !== -1) {
        devices.audio = audioTracksReceived;
    }

    eventEmitter.emit(RTCEvents.AVAILABLE_DEVICES_CHANGED, devices);
}

/**
 * Checks if new list of available media devices differs from previous one.
 * @param {MediaDeviceInfo[]} newDevices - list of new devices.
 * @returns {boolean} - true if list is different, false otherwise.
 */
function compareAvailableMediaDevices(newDevices) {
    if (newDevices.length !== currentlyAvailableMediaDevices.length) {
        return true;
    }

    /* eslint-disable newline-per-chained-call */

    return (
        newDevices.map(mediaDeviceInfoToJSON).sort().join('')
            !== currentlyAvailableMediaDevices
                .map(mediaDeviceInfoToJSON).sort().join(''));

    /* eslint-enable newline-per-chained-call */

    /**
     *
     * @param info
     */
    function mediaDeviceInfoToJSON(info) {
        return JSON.stringify({
            kind: info.kind,
            deviceId: info.deviceId,
            groupId: info.groupId,
            label: info.label,
            facing: info.facing
        });
    }
}

/**
 * Periodically polls enumerateDevices() method to check if list of media
 * devices has changed. This is temporary workaround until 'devicechange' event
 * will be supported by browsers.
 */
function pollForAvailableMediaDevices() {
    // Here we use plain navigator.mediaDevices.enumerateDevices instead of
    // wrapped because we just need to know the fact the devices changed, labels
    // do not matter. This fixes situation when we have no devices initially,
    // and then plug in a new one.
    if (rawEnumerateDevicesWithCallback) {
        rawEnumerateDevicesWithCallback(ds => {
            // We don't fire RTCEvents.DEVICE_LIST_CHANGED for the first time
            // we call enumerateDevices(). This is the initial step.
            if (typeof currentlyAvailableMediaDevices === 'undefined') {
                currentlyAvailableMediaDevices = ds.slice(0);
            } else if (compareAvailableMediaDevices(ds)) {
                onMediaDevicesListChanged(ds);
            }

            window.setTimeout(pollForAvailableMediaDevices,
                AVAILABLE_DEVICES_POLL_INTERVAL_TIME);
        });
    }
}

/**
 * Sends analytics event with the passed device list.
 *
 * @param {Array<MediaDeviceInfo>} deviceList - List with info about the
 * available devices.
 * @returns {void}
 */
function sendDeviceListToAnalytics(deviceList) {
    const devicesPropsArray
        = deviceList.map(
            ({ deviceId, groupId, kind, label }) => {
                // Filter the props of the device object.
                return {
                    deviceId,
                    groupId,
                    kind,
                    label
                };
            });

    Statistics.analytics.sendEvent(
        'devices.deviceList', {
            devices: devicesPropsArray
        });
}

/**
 * Event handler for the 'devicechange' event.
 *
 * @param {MediaDeviceInfo[]} devices - list of media devices.
 * @emits RTCEvents.DEVICE_LIST_CHANGED
 */
function onMediaDevicesListChanged(devicesReceived) {
    currentlyAvailableMediaDevices = devicesReceived.slice(0);
    logger.info(
        'list of media devices has changed:',
        currentlyAvailableMediaDevices);

    sendDeviceListToAnalytics(currentlyAvailableMediaDevices);

    const videoInputDevices
        = currentlyAvailableMediaDevices.filter(d => d.kind === 'videoinput');
    const audioInputDevices
        = currentlyAvailableMediaDevices.filter(d => d.kind === 'audioinput');
    const videoInputDevicesWithEmptyLabels
        = videoInputDevices.filter(d => d.label === '');
    const audioInputDevicesWithEmptyLabels
        = audioInputDevices.filter(d => d.label === '');

    if (videoInputDevices.length
            && videoInputDevices.length
                === videoInputDevicesWithEmptyLabels.length) {
        devices.video = false;
    }

    if (audioInputDevices.length
            && audioInputDevices.length
                === audioInputDevicesWithEmptyLabels.length) {
        devices.audio = false;
    }

    eventEmitter.emit(RTCEvents.DEVICE_LIST_CHANGED, devicesReceived);
}

/**
 * Apply function with arguments if function exists.
 * Do nothing if function not provided.
 * @param {function} [fn] function to apply
 * @param {Array} [args=[]] arguments for function
 */
function maybeApply(fn, args) {
    fn && fn(...args);
}

/**
 * Wrap `getUserMedia` in order to convert between callback and Promise based
 * APIs.
 * @param {Function} getUserMedia native function
 * @returns {Function} wrapped function
 */
function wrapGetUserMedia(getUserMedia, usePromises = false) {
    let gUM;

    if (usePromises) {
        gUM = function(constraints, successCallback, errorCallback) {
            return getUserMedia(constraints)
                .then(stream => {
                    maybeApply(successCallback, [ stream ]);

                    return stream;
                })
                .catch(error => {
                    maybeApply(errorCallback, [ error ]);

                    throw error;
                });
        };
    } else {
        gUM = function(constraints, successCallback, errorCallback) {
            getUserMedia(constraints, stream => {
                maybeApply(successCallback, [ stream ]);
            }, error => {
                maybeApply(errorCallback, [ error ]);
            });
        };
    }

    return gUM;
}

/**
 * Use old MediaStreamTrack to get devices list and
 * convert it to enumerateDevices format.
 * @param {Function} callback function to call when received devices list.
 */
function enumerateDevicesThroughMediaStreamTrack(callback) {
    MediaStreamTrack.getSources(
        sources => callback(sources.map(convertMediaStreamTrackSource)));
}

/**
 * Converts MediaStreamTrack Source to enumerateDevices format.
 * @param {Object} source
 */
function convertMediaStreamTrackSource(source) {
    const kind = (source.kind || '').toLowerCase();

    return {
        facing: source.facing || null,
        label: source.label,

        // theoretically deprecated MediaStreamTrack.getSources should
        // not return 'audiooutput' devices but let's handle it in any
        // case
        kind: kind
            ? kind === 'audiooutput' ? kind : `${kind}input`
            : null,
        deviceId: source.id,
        groupId: source.groupId || null
    };
}

/**
 * Handles the newly created Media Streams.
 * @param streams the new Media Streams
 * @param resolution the resolution of the video streams
 * @returns {*[]} object that describes the new streams
 */
function handleLocalStream(streams, resolution) {
    let audioStream, desktopStream, videoStream;
    const res = [];

    // XXX The function obtainAudioAndVideoPermissions has examined the type of
    // the browser, its capabilities, etc. and has taken the decision whether to
    // invoke getUserMedia per device (e.g. Firefox) or once for both audio and
    // video (e.g. Chrome). In order to not duplicate the logic here, examine
    // the specified streams and figure out what we've received based on
    // obtainAudioAndVideoPermissions' decision.
    if (streams) {
        // As mentioned above, certian types of browser (e.g. Chrome) support
        // (with a result which meets our requirements expressed bellow) calling
        // getUserMedia once for both audio and video.
        const audioVideo = streams.audioVideo;

        if (audioVideo) {
            const NativeMediaStream
                 = window.webkitMediaStream || window.MediaStream;
            const audioTracks = audioVideo.getAudioTracks();

            if (audioTracks.length) {
                // eslint-disable-next-line new-cap
                audioStream = new NativeMediaStream();
                for (let i = 0; i < audioTracks.length; i++) {
                    audioStream.addTrack(audioTracks[i]);
                }
            }

            const videoTracks = audioVideo.getVideoTracks();

            if (videoTracks.length) {
                // eslint-disable-next-line new-cap
                videoStream = new NativeMediaStream();
                for (let j = 0; j < videoTracks.length; j++) {
                    videoStream.addTrack(videoTracks[j]);
                }
            }
        } else {
            // On other types of browser (e.g. Firefox) we choose (namely,
            // obtainAudioAndVideoPermissions) to call getUserMedia per device
            // (type).
            audioStream = streams.audio;
            videoStream = streams.video;
        }

        desktopStream = streams.desktop;
    }

    if (desktopStream) {
        const { stream, sourceId, sourceType } = desktopStream;

        res.push({
            stream,
            sourceId,
            sourceType,
            track: stream.getVideoTracks()[0],
            mediaType: MediaType.VIDEO,
            videoType: VideoType.DESKTOP
        });
    }
    if (audioStream) {
        res.push({
            stream: audioStream,
            track: audioStream.getAudioTracks()[0],
            mediaType: MediaType.AUDIO,
            videoType: null
        });
    }
    if (videoStream) {
        res.push({
            stream: videoStream,
            track: videoStream.getVideoTracks()[0],
            mediaType: MediaType.VIDEO,
            videoType: VideoType.CAMERA,
            resolution
        });
    }

    return res;
}

/**
 * Represents a default implementation of setting a <tt>MediaStream</tt> as the
 * source of a video element that tries to be browser-agnostic through feature
 * checking. Note though that it was not completely clear from the predating
 * browser-specific implementations what &quot;videoSrc&quot; was because one
 * implementation of {@link RTCUtils#getVideoSrc} would return
 * <tt>MediaStream</tt> (e.g. Firefox), another a <tt>string</tt> representation
 * of the <tt>URL</tt> of the <tt>MediaStream</tt> (e.g. Chrome) and the return
 * value was only used by {@link RTCUIHelper#getVideoId} which itself did not
 * appear to be used anywhere. Generally, the implementation will try to follow
 * the related standards i.e. work with the <tt>srcObject</tt> and <tt>src</tt>
 * properties of the specified <tt>element</tt> taking into account vender
 * prefixes.
 *
 * @param element the element whose video source/src is to be set to the
 * specified <tt>stream</tt>
 * @param {MediaStream} stream the <tt>MediaStream</tt> to set as the video
 * source/src of <tt>element</tt>
 */
function defaultSetVideoSrc(element, stream) {
    // srcObject
    let srcObjectPropertyName = 'srcObject';

    if (!(srcObjectPropertyName in element)) {
        srcObjectPropertyName = 'mozSrcObject';
        if (!(srcObjectPropertyName in element)) {
            srcObjectPropertyName = null;
        }
    }
    if (srcObjectPropertyName) {
        element[srcObjectPropertyName] = stream;

        return;
    }

    // src
    let src;

    if (stream) {
        src = stream.jitsiObjectURL;

        // Save the created URL for stream so we can reuse it and not keep
        // creating URLs.
        if (!src) {
            stream.jitsiObjectURL
                = src
                    = (URL || webkitURL).createObjectURL(stream);
        }
    }
    element.src = src || '';
}

/**
 *
 */
class RTCUtils extends Listenable {
    /**
     *
     */
    constructor() {
        super(eventEmitter);
    }

    /**
     * Depending on the browser, sets difference instance methods for
     * interacting with user media and adds methods to native webrtc related
     * objects. Also creates an instance variable for peer connection
     * constraints.
     *
     * @param {Object} options
     * @returns {void}
     */
    init(options = {}) {
        if (typeof options.disableAEC === 'boolean') {
            disableAEC = options.disableAEC;
            logger.info(`Disable AEC: ${disableAEC}`);
        }
        if (typeof options.disableNS === 'boolean') {
            disableNS = options.disableNS;
            logger.info(`Disable NS: ${disableNS}`);
        }
        if (typeof options.disableAP === 'boolean') {
            disableAP = options.disableAP;
            logger.info(`Disable AP: ${disableAP}`);
        }
        if (typeof options.disableAGC === 'boolean') {
            disableAGC = options.disableAGC;
            logger.info(`Disable AGC: ${disableAGC}`);
        }
        if (typeof options.disableHPF === 'boolean') {
            disableHPF = options.disableHPF;
            logger.info(`Disable HPF: ${disableHPF}`);
        }

        // Initialize rawEnumerateDevicesWithCallback
        initRawEnumerateDevicesWithCallback();

        return new Promise((resolve, reject) => {
            if (RTCBrowserType.usesNewGumFlow()) {
                this.RTCPeerConnectionType = window.RTCPeerConnection;

                this.getUserMedia
                    = (constraints, successCallback, errorCallback) =>
                        window.navigator.mediaDevices
                            .getUserMedia(constraints)
                            .then(stream => {
                                successCallback && successCallback(stream);

                                return stream;
                            })
                            .catch(err => {
                                errorCallback && errorCallback(err);

                                return Promise.reject(err);
                            });

                this.enumerateDevices = callback =>
                    window.navigator.mediaDevices.enumerateDevices()
                        .then(foundDevices => {
                            callback(foundDevices);

                            return foundDevices;
                        })
                        .catch(err => {
                            logger.error(`Error enumerating devices: ${err}`);

                            callback([]);

                            return [];
                        });

                this.attachMediaStream = (element, stream) => {
                    if (element) {
                        element.srcObject = stream;
                    }

                    return element;
                };
                this.getStreamID = stream => stream.id;
                this.getTrackID = track => track.id;
            } else if (RTCBrowserType.isOpera()
                    || RTCBrowserType.isNWJS()
                    || RTCBrowserType.isElectron()
                    || RTCBrowserType.isReactNative()) {

                this.RTCPeerConnectionType = webkitRTCPeerConnection;
                const getUserMedia
                    = navigator.webkitGetUserMedia.bind(navigator);

                this.getUserMedia = wrapGetUserMedia(getUserMedia);
                this.enumerateDevices = rawEnumerateDevicesWithCallback;

                this.attachMediaStream
                    = wrapAttachMediaStream((element, stream) => {
                        defaultSetVideoSrc(element, stream);

                        return element;
                    });
                this.getStreamID = function(stream) {
                    // A. MediaStreams from FF endpoints have the characters '{'
                    // and '}' that make jQuery choke.
                    // B. The react-native-webrtc implementation that we use on
                    // React Native at the time of this writing returns a number
                    // for the id of MediaStream. Let's just say that a number
                    // contains no special characters.
                    const id = stream.id;

                    // XXX The return statement is affected by automatic
                    // semicolon insertion (ASI). No line terminator is allowed
                    // between the return keyword and the expression.
                    return (
                        typeof id === 'number'
                            ? id
                            : SDPUtil.filterSpecialChars(id));
                };
                this.getTrackID = function(track) {
                    return track.id;
                };

                if (!webkitMediaStream.prototype.getVideoTracks) {
                    webkitMediaStream.prototype.getVideoTracks = function() {
                        return this.videoTracks;
                    };
                }
                if (!webkitMediaStream.prototype.getAudioTracks) {
                    webkitMediaStream.prototype.getAudioTracks = function() {
                        return this.audioTracks;
                    };
                }
            } else if (RTCBrowserType.isEdge()) {
                this.RTCPeerConnectionType = ortcRTCPeerConnection;
                this.getUserMedia
                    = wrapGetUserMedia(
                        navigator.mediaDevices.getUserMedia.bind(
                            navigator.mediaDevices),
                        true);
                this.enumerateDevices = rawEnumerateDevicesWithCallback;
                this.attachMediaStream
                    = wrapAttachMediaStream((element, stream) => {
                        defaultSetVideoSrc(element, stream);

                        return element;
                    });

                // ORTC does not generate remote MediaStreams so those are
                // manually created by the ORTC shim. This means that their
                // id (internally generated) does not match the stream id
                // signaled into the remote SDP. Therefore, the shim adds a
                // custom jitsiRemoteId property with the original stream id.
                this.getStreamID = function(stream) {
                    const id = stream.jitsiRemoteId || stream.id;

                    return SDPUtil.filterSpecialChars(id);
                };

                // Remote MediaStreamTracks generated by ORTC (within a
                // RTCRtpReceiver) have an internally/random id which does not
                // match the track id signaled in the remote SDP. The shim adds
                // a custom jitsi-id property with the original track id.
                this.getTrackID = function(track) {
                    return track.jitsiRemoteId || track.id;
                };
            } else if (RTCBrowserType.isTemasysPluginUsed()) {
                // Detect IE/Safari
                const webRTCReadyCb = () => {
                    this.RTCPeerConnectionType = RTCPeerConnection;
                    this.getUserMedia = window.getUserMedia;
                    this.enumerateDevices
                        = enumerateDevicesThroughMediaStreamTrack;
                    this.attachMediaStream
                        = wrapAttachMediaStream((element, stream) => {
                            if (stream) {
                                if (stream.id === 'dummyAudio'
                                        || stream.id === 'dummyVideo') {
                                    return;
                                }

                                // The container must be visible in order to
                                // play or attach the stream when Temasys plugin
                                // is in use
                                const containerSel = $(element);

                                if (RTCBrowserType.isTemasysPluginUsed()
                                        && !containerSel.is(':visible')) {
                                    containerSel.show();
                                }
                                const video
                                    = stream.getVideoTracks().length > 0;

                                if (video && !$(element).is(':visible')) {
                                    throw new Error(
                                        'video element must be visible to'
                                            + ' attach video stream');
                                }
                            }

                            return attachMediaStream(element, stream);
                        });
                    this.getStreamID
                        = stream => SDPUtil.filterSpecialChars(stream.label);
                    this.getTrackID
                        = track => track.id;

                    onReady(
                        options,
                        this.getUserMediaWithConstraints.bind(this));
                };
                const webRTCReadyPromise
                    = new Promise(r => AdapterJS.webRTCReady(r));

                // Resolve or reject depending on whether the Temasys plugin is
                // installed.
                AdapterJS.WebRTCPlugin.isPluginInstalled(
                    AdapterJS.WebRTCPlugin.pluginInfo.prefix,
                    AdapterJS.WebRTCPlugin.pluginInfo.plugName,
                    AdapterJS.WebRTCPlugin.pluginInfo.type,
                    /* installed */ () => {
                        webRTCReadyPromise.then(() => {
                            webRTCReadyCb();
                            resolve();
                        });
                    },
                    /* not installed */ () => {
                        const error
                            = new Error('Temasys plugin is not installed');

                        error.name = 'WEBRTC_NOT_READY';
                        error.webRTCReadyPromise = webRTCReadyPromise;

                        reject(error);
                    });
            } else {
                rejectWithWebRTCNotSupported(
                    'Browser does not appear to be WebRTC-capable',
                    reject);

                return;
            }

            this._initPCConstraints(options);

            // Call onReady() if Temasys plugin is not used
            if (!RTCBrowserType.isTemasysPluginUsed()) {
                onReady(options, this.getUserMediaWithConstraints.bind(this));
                resolve();
            }
        });
    }

    /**
     * Creates instance objects for peer connection constraints both for p2p
     * and outside of p2p.
     *
     * @params {Object} options - Configuration for setting RTCUtil's instance
     * objects for peer connection constraints.
     * @params {boolean} options.useIPv6 - Set to true if IPv6 should be used.
     * @params {boolean} options.disableSuspendVideo - Whether or not video
     * should become suspended if bandwidth estimation becomes low.
     * @params {Object} options.testing - Additional configuration for work in
     * development.
     * @params {Object} options.testing.forceP2PSuspendVideoRatio - True if
     * video should become suspended if bandwidth estimation becomes low while
     * in peer to peer connection mode.
     */
    _initPCConstraints(options) {
        if (RTCBrowserType.isFirefox()) {
            this.pcConstraints = {};
        } else if (RTCBrowserType.isChrome()
            || RTCBrowserType.isOpera()
            || RTCBrowserType.isNWJS()
            || RTCBrowserType.isElectron()
            || RTCBrowserType.isReactNative()) {
            this.pcConstraints = { optional: [] };

            if (options.useIPv6) {
                // https://code.google.com/p/webrtc/issues/detail?id=2828
                this.pcConstraints.optional.push({ googIPv6: true });
            }

            this.p2pPcConstraints
                = JSON.parse(JSON.stringify(this.pcConstraints));

            // Allows sending of video to be suspended if the bandwidth
            // estimation is too low.
            if (!options.disableSuspendVideo) {
                this.pcConstraints.optional.push(
                    { googSuspendBelowMinBitrate: true });
            }

            // There's no reason not to use this for p2p
            this.p2pPcConstraints.optional.push({
                googSuspendBelowMinBitrate: true
            });
        }

        this.p2pPcConstraints = this.p2pPcConstraints || this.pcConstraints;
    }

    /* eslint-disable max-params */

    /**
    * @param {string[]} um required user media types
    * @param {function} successCallback
    * @param {Function} failureCallback
    * @param {Object} [options] optional parameters
    * @param {string} options.resolution
    * @param {number} options.bandwidth
    * @param {number} options.fps
    * @param {string} options.desktopStream
    * @param {string} options.cameraDeviceId
    * @param {string} options.micDeviceId
    **/
    getUserMediaWithConstraints(
            um,
            successCallback,
            failureCallback,
            options = {}) {
        const constraints = getConstraints(um, options);

        logger.info('Get media constraints', constraints);

        try {
            this.getUserMedia(
                constraints,
                stream => {
                    logger.log('onUserMediaSuccess');
                    setAvailableDevices(um, stream);
                    successCallback(stream);
                },
                error => {
                    setAvailableDevices(um, undefined);
                    logger.warn('Failed to get access to local media. Error ',
                        error, constraints);

                    if (failureCallback) {
                        failureCallback(
                            new JitsiTrackError(error, constraints, um));
                    }
                });
        } catch (e) {
            logger.error('GUM failed: ', e);

            if (failureCallback) {
                failureCallback(new JitsiTrackError(e, constraints, um));
            }
        }
    }

    /**
     * Acquires a media stream via getUserMedia that
     * matches the given constraints
     *
     * @param {array} umDevices which devices to acquire (e.g. audio, video)
     * @param {Object} constraints - Stream specifications to use.
     * @returns {Promise}
     */
    _newGetUserMediaWithConstraints(umDevices, constraints = {}) {
        return new Promise((resolve, reject) => {
            try {
                this.getUserMedia(
                    constraints,
                    stream => {
                        logger.log('onUserMediaSuccess');

                        // TODO(brian): Is this call needed? Why is this
                        // happening at gUM time? Isn't there an event listener
                        // for this?
                        setAvailableDevices(umDevices, stream);

                        resolve(stream);
                    },
                    error => {
                        logger.warn('Failed to get access to local media. '
                            + ` ${error} ${constraints} `);

                        // TODO(brian): Is this call needed? Why is this
                        // happening at gUM time? Isn't there an event listener
                        // for this?
                        setAvailableDevices(umDevices, undefined);
                        reject(new JitsiTrackError(
                            error, constraints, umDevices));
                    });
            } catch (error) {
                logger.error(`GUM failed: ${error}`);
                reject(new JitsiTrackError(error, constraints, umDevices));
            }
        });
    }

    /**
     * Acquire a display stream via the screenObtainer. This requires extra
     * logic compared to use screenObtainer versus normal device capture logic
     * in RTCUtils#_newGetUserMediaWithConstraints.
     *
     * @param {Object} desktopSharingExtensionExternalInstallation
     * @param {string[]} desktopSharingSources
     * @returns {Promise} A promise which will be resolved with an object whic
     * contains the acquired display stream. If desktop sharing is not supported
     * then a rejected promise will be returned.
     */
    _newGetDesktopMedia(
            desktopSharingExtensionExternalInstallation,
            desktopSharingSources) {
        if (!screenObtainer.isSupported() || !RTCBrowserType.supportsVideo()) {
            return Promise.reject(
                new Error('Desktop sharing is not supported!'));
        }

        const desktopSharingOptions = {
            ...desktopSharingExtensionExternalInstallation,
            desktopSharingSources
        };

        return new Promise((resolve, reject) => {
            screenObtainer.obtainStream(
                desktopSharingOptions,
                stream => {
                    resolve(stream);
                },
                error => {
                    reject(error);
                });
        });
    }

    /* eslint-enable max-params */

    /**
     * Creates the local MediaStreams.
     * @param {Object} [options] optional parameters
     * @param {Array} options.devices the devices that will be requested
     * @param {string} options.resolution resolution constraints
     * @param {bool} options.dontCreateJitsiTrack if <tt>true</tt> objects with
     * the following structure {stream: the Media Stream, type: "audio" or
     * "video", videoType: "camera" or "desktop"} will be returned trough the
     * Promise, otherwise JitsiTrack objects will be returned.
     * @param {string} options.cameraDeviceId
     * @param {string} options.micDeviceId
     * @returns {*} Promise object that will receive the new JitsiTracks
     */
    obtainAudioAndVideoPermissions(options = {}) {
        const self = this;

        const dsOptions = {
            ...options.desktopSharingExtensionExternalInstallation,
            desktopSharingSources: options.desktopSharingSources
        };

        return new Promise((resolve, reject) => {
            const successCallback = function(stream) {
                resolve(handleLocalStream(stream, options.resolution));
            };

            options.devices = options.devices || [ 'audio', 'video' ];
            options.resolution = options.resolution || '720';

            if (!screenObtainer.isSupported()
                && options.devices.indexOf('desktop') !== -1) {
                reject(new Error('Desktop sharing is not supported!'));
            }
            if (RTCBrowserType.isFirefox()

                    // XXX The react-native-webrtc implementation that we
                    // utilize on React Native at the time of this writing does
                    // not support the MediaStream constructors defined by
                    // https://www.w3.org/TR/mediacapture-streams/#constructors
                    // and instead has a single constructor which expects (an
                    // NSNumber as) a MediaStream ID.
                    || RTCBrowserType.isReactNative()
                    || RTCBrowserType.isTemasysPluginUsed()) {
                const GUM = function(device, s, e) {
                    this.getUserMediaWithConstraints(device, s, e, options);
                };

                const deviceGUM = {
                    'audio': GUM.bind(self, [ 'audio' ]),
                    'video': GUM.bind(self, [ 'video' ])
                };

                if (screenObtainer.isSupported()) {
                    deviceGUM.desktop = screenObtainer.obtainStream.bind(
                        screenObtainer,
                        dsOptions);
                }

                // With FF/IE we can't split the stream into audio and video
                // because FF doesn't support media stream constructors. So, we
                // need to get the audio stream separately from the video stream
                // using two distinct GUM calls. Not very user friendly :-( but
                // we don't have many other options neither.
                //
                // Note that we pack those 2 streams in a single object and pass
                // it to the successCallback method.
                obtainDevices({
                    devices: options.devices,
                    streams: [],
                    successCallback,
                    errorCallback: reject,
                    deviceGUM
                });
            } else {
                const hasDesktop = options.devices.indexOf('desktop') > -1;

                if (hasDesktop) {
                    options.devices.splice(
                        options.devices.indexOf('desktop'),
                        1);
                }

                if (options.devices.length) {
                    this.getUserMediaWithConstraints(
                        options.devices,
                        stream => {
                            const audioDeviceRequested
                                = options.devices.indexOf('audio') !== -1;
                            const videoDeviceRequested
                                = options.devices.indexOf('video') !== -1;
                            const audioTracksReceived
                                = stream.getAudioTracks().length > 0;
                            const videoTracksReceived
                                = stream.getVideoTracks().length > 0;

                            if ((audioDeviceRequested && !audioTracksReceived)
                                    || (videoDeviceRequested
                                        && !videoTracksReceived)) {
                                self.stopMediaStream(stream);

                                // We are getting here in case if we requested
                                // 'audio' or 'video' devices or both, but
                                // didn't get corresponding MediaStreamTrack in
                                // response stream. We don't know the reason why
                                // this happened, so reject with general error.
                                // eslint-disable-next-line no-shadow
                                const devices = [];

                                if (audioDeviceRequested
                                        && !audioTracksReceived) {
                                    devices.push('audio');
                                }

                                if (videoDeviceRequested
                                        && !videoTracksReceived) {
                                    devices.push('video');
                                }

                                // we are missing one of the media we requested
                                // in order to get the actual error that caused
                                // this missing media we will call one more time
                                // getUserMedia so we can obtain the actual
                                // error (Example usecases are requesting
                                // audio and video and video device is missing
                                // or device is denied to be used and chrome is
                                // set to not ask for permissions)
                                self.getUserMediaWithConstraints(
                                    devices,
                                    () => {
                                        // we already failed to obtain this
                                        // media, so we are not supposed in any
                                        // way to receive success for this call
                                        // any way we will throw an error to be
                                        // sure the promise will finish
                                        reject(new JitsiTrackError(
                                            { name: 'UnknownError' },
                                            getConstraints(
                                                options.devices,
                                                options),
                                            devices)
                                        );
                                    },
                                    error => {
                                        // rejects with real error for not
                                        // obtaining the media
                                        reject(error);
                                    }, options);

                                return;
                            }
                            if (hasDesktop) {
                                screenObtainer.obtainStream(
                                    dsOptions,
                                    desktop => {
                                        successCallback({ audioVideo: stream,
                                            desktop });
                                    }, error => {
                                        self.stopMediaStream(stream);

                                        reject(error);
                                    });
                            } else {
                                successCallback({ audioVideo: stream });
                            }
                        },
                        error => reject(error),
                        options);
                } else if (hasDesktop) {
                    screenObtainer.obtainStream(
                        dsOptions,
                        desktop => successCallback({ desktop }),
                        error => reject(error));
                }
            }
        });
    }

    /**
     * Gets streams from specified device types. This function intentionally
     * ignores errors for upstream to catch and handle instead.
     *
     * @param {Object} options - A hash describing what devices to get and
     * relevant constraints.
     * @param {string[]} options.devices - The types of media to capture. Valid
     * values are "desktop", "audio", and "video".
     * @returns {Promise} The promise, when successful, will return an array of
     * meta data for the requested device type, which includes the stream and
     * track. If an error occurs, it will be deferred to the caller for
     * handling.
     */
    newObtainAudioAndVideoPermissions(options) {
        logger.info('Using the new gUM flow');

        const mediaStreamsMetaData = [];

        // Declare private functions to be used in the promise chain below.
        // These functions are declared in the scope of this function because
        // they are not being used anywhere else, so only this function needs to
        // know about them.

        /**
         * Executes a request for desktop media if specified in options.
         *
         * @returns {Promise}
         */
        const maybeRequestDesktopDevice = function() {
            const umDevices = options.devices || [];
            const isDesktopDeviceRequsted = umDevices.indexOf('desktop') !== -1;

            return isDesktopDeviceRequsted
                ? this._newGetDesktopMedia(
                    options.desktopSharingExtensionExternalInstallation,
                    options.desktopSharingSources)
                : Promise.resolve();
        }.bind(this);

        /**
         * Creates a meta data object about the passed in desktopStream and
         * pushes the meta data to the internal array mediaStreamsMetaData to be
         * returned later.
         *
         * @param {MediaStreamTrack} desktopStream - A track for a desktop
         * capture.
         * @returns {void}
         */
        const maybeCreateAndAddDesktopTrack = function(desktopStream) {
            if (!desktopStream) {
                return;
            }

            const { stream, sourceId, sourceType } = desktopStream;

            mediaStreamsMetaData.push({
                stream,
                sourceId,
                sourceType,
                track: stream.getVideoTracks()[0],
                videoType: VideoType.DESKTOP
            });
        };

        /**
         * Executes a request for audio and/or video, as specified in options.
         * By default both audio and video will be captured if options.devices
         * is not defined.
         *
         * @returns {Promise}
         */
        const maybeRequestCaptureDevices = function() {
            const umDevices = options.devices || [ 'audio', 'video' ];
            const requestedCaptureDevices = umDevices.filter(device =>
                device === 'audio'
                || (device === 'video' && RTCBrowserType.supportsVideo()));

            if (!requestedCaptureDevices.length) {
                return Promise.resolve();
            }

            const constraints = newGetConstraints(
                requestedCaptureDevices, options);

            logger.info('Got media constraints: ', constraints);

            return this._newGetUserMediaWithConstraints(
                requestedCaptureDevices, constraints);
        }.bind(this);

        /**
         * Splits the passed in media stream into separate audio and video
         * streams and creates meta data objects for each and pushes them to the
         * internal array mediaStreamsMetaData to be returned later.
         *
         * @param {MediaStreamTrack} avStream - A track for with audio and/or
         * video track.
         * @returns {void}
         */
        const maybeCreateAndAddAVTracks = function(avStream) {
            if (!avStream) {
                return;
            }

            const audioTracks = avStream.getAudioTracks();

            if (audioTracks.length) {
                const audioStream = new MediaStream(audioTracks);

                mediaStreamsMetaData.push({
                    stream: audioStream,
                    track: audioStream.getAudioTracks()[0]
                });
            }

            const videoTracks = avStream.getVideoTracks();

            if (videoTracks.length) {
                const videoStream = new MediaStream(videoTracks);

                mediaStreamsMetaData.push({
                    stream: videoStream,
                    track: videoStream.getVideoTracks()[0],
                    videoType: VideoType.CAMERA
                });
            }
        };

        return maybeRequestDesktopDevice()
            .then(maybeCreateAndAddDesktopTrack)
            .then(maybeRequestCaptureDevices)
            .then(maybeCreateAndAddAVTracks)
            .then(() => mediaStreamsMetaData);
    }

    /**
     *
     */
    getDeviceAvailability() {
        return devices;
    }

    /**
     *
     */
    isRTCReady() {
        return rtcReady;
    }

    /**
     *
     */
    _isDeviceListAvailable() {
        if (!rtcReady) {
            throw new Error('WebRTC not ready yet');
        }

        return Boolean(
            (navigator.mediaDevices
                && navigator.mediaDevices.enumerateDevices)
            || (typeof MediaStreamTrack !== 'undefined'
                && MediaStreamTrack.getSources));
    }

    /**
     * Returns a promise which can be used to make sure that the WebRTC stack
     * has been initialized.
     *
     * @returns {Promise} which is resolved only if the WebRTC stack is ready.
     * Note that currently we do not detect stack initialization failure and
     * the promise is never rejected(unless unexpected error occurs).
     */
    onRTCReady() {
        if (rtcReady) {
            return Promise.resolve();
        }

        return new Promise(resolve => {
            const listener = () => {
                eventEmitter.removeListener(RTCEvents.RTC_READY, listener);
                resolve();
            };

            eventEmitter.addListener(RTCEvents.RTC_READY, listener);

            // We have no failed event, so... it either resolves or nothing
            // happens.
        });

    }

    /**
     * Checks if its possible to enumerate available cameras/microphones.
     *
     * @returns {Promise<boolean>} a Promise which will be resolved only once
     * the WebRTC stack is ready, either with true if the device listing is
     * available available or with false otherwise.
     */
    isDeviceListAvailable() {
        return this.onRTCReady().then(this._isDeviceListAvailable.bind(this));
    }

    /**
     * Returns true if changing the input (camera / microphone) or output
     * (audio) device is supported and false if not.
     * @params {string} [deviceType] - type of device to change. Default is
     *      undefined or 'input', 'output' - for audio output device change.
     * @returns {boolean} true if available, false otherwise.
     */
    isDeviceChangeAvailable(deviceType) {
        return deviceType === 'output' || deviceType === 'audiooutput'
            ? isAudioOutputDeviceChangeAvailable
            : RTCBrowserType.isChrome()
                || RTCBrowserType.isFirefox()
                || RTCBrowserType.isOpera()
                || RTCBrowserType.isTemasysPluginUsed()
                || RTCBrowserType.isNWJS()
                || RTCBrowserType.isElectron()
                || RTCBrowserType.isEdge();
    }

    /**
     * A method to handle stopping of the stream.
     * One point to handle the differences in various implementations.
     * @param mediaStream MediaStream object to stop.
     */
    stopMediaStream(mediaStream) {
        mediaStream.getTracks().forEach(track => {
            // stop() not supported with IE
            if (!RTCBrowserType.isTemasysPluginUsed() && track.stop) {
                track.stop();
            }
        });

        // leave stop for implementation still using it
        if (mediaStream.stop) {
            mediaStream.stop();
        }

        // The MediaStream implementation of the react-native-webrtc project has
        // an explicit release method that is to be invoked in order to release
        // used resources such as memory.
        if (mediaStream.release) {
            mediaStream.release();
        }

        // if we have done createObjectURL, lets clean it
        const url = mediaStream.jitsiObjectURL;

        if (url) {
            delete mediaStream.jitsiObjectURL;
            (URL || webkitURL).revokeObjectURL(url);
        }
    }

    /**
     * Returns whether the desktop sharing is enabled or not.
     * @returns {boolean}
     */
    isDesktopSharingEnabled() {
        return screenObtainer.isSupported();
    }

    /**
     * Sets current audio output device.
     * @param {string} deviceId - id of 'audiooutput' device from
     *      navigator.mediaDevices.enumerateDevices(), 'default' for default
     *      device
     * @returns {Promise} - resolves when audio output is changed, is rejected
     *      otherwise
     */
    setAudioOutputDevice(deviceId) {
        if (!this.isDeviceChangeAvailable('output')) {
            Promise.reject(
                new Error('Audio output device change is not supported'));
        }

        return featureDetectionAudioEl.setSinkId(deviceId)
            .then(() => {
                audioOutputDeviceId = deviceId;
                audioOutputChanged = true;

                logger.log(`Audio output device set to ${deviceId}`);

                eventEmitter.emit(RTCEvents.AUDIO_OUTPUT_DEVICE_CHANGED,
                    deviceId);
            });
    }

    /**
     * Returns currently used audio output device id, '' stands for default
     * device
     * @returns {string}
     */
    getAudioOutputDevice() {
        return audioOutputDeviceId;
    }

    /**
     * Returns list of available media devices if its obtained, otherwise an
     * empty array is returned/
     * @returns {Array} list of available media devices.
     */
    getCurrentlyAvailableMediaDevices() {
        return currentlyAvailableMediaDevices;
    }

    /**
     * Returns event data for device to be reported to stats.
     * @returns {MediaDeviceInfo} device.
     */
    getEventDataForActiveDevice(device) {
        const deviceList = [];
        const deviceData = {
            'deviceId': device.deviceId,
            'kind': device.kind,
            'label': device.label,
            'groupId': device.groupId
        };

        deviceList.push(deviceData);

        return { deviceList };
    }

    /**
     * Configures the given PeerConnection constraints to either enable or
     * disable (according to the value of the 'enable' parameter) the
     * 'googSuspendBelowMinBitrate' option.
     * @param constraints the constraints on which to operate.
     * @param enable {boolean} whether to enable or disable the suspend video
     * option.
     */
    setSuspendVideo(constraints, enable) {
        if (!constraints.optional) {
            constraints.optional = [];
        }

        // Get rid of all "googSuspendBelowMinBitrate" constraints (we assume
        // that the elements of constraints.optional contain a single property).
        constraints.optional
            = constraints.optional.filter(
                c => !c.hasOwnProperty('googSuspendBelowMinBitrate'));

        if (enable) {
            constraints.optional.push({ googSuspendBelowMinBitrate: 'true' });
        }
    }
}

/**
 * Rejects a Promise because WebRTC is not supported.
 *
 * @param {string} errorMessage - The human-readable message of the Error which
 * is the reason for the rejection.
 * @param {Function} reject - The reject function of the Promise.
 * @returns {void}
 */
function rejectWithWebRTCNotSupported(errorMessage, reject) {
    const error = new Error(errorMessage);

    // WebRTC is not supported either natively or via a known plugin such as
    // Temasys.
    // XXX The Error class already has a property name which is commonly used to
    // detail the represented error in a non-human-readable way (in contrast to
    // the human-readable property message). I explicitly did not want to
    // introduce a new specific property.
    // FIXME None of the existing JitsiXXXErrors seemed to be appropriate
    // recipients of the constant WEBRTC_NOT_SUPPORTED so I explicitly chose to
    // leave it as a magic string at the time of this writing.
    error.name = 'WEBRTC_NOT_SUPPORTED';

    logger.error(errorMessage);
    reject(error);
}

const rtcUtils = new RTCUtils();

/**
 *
 * @param options
 */
function obtainDevices(options) {
    if (!options.devices || options.devices.length === 0) {
        return options.successCallback(options.streams || {});
    }

    const device = options.devices.splice(0, 1);

    options.deviceGUM[device](
        stream => {
            options.streams = options.streams || {};
            options.streams[device] = stream;
            obtainDevices(options);
        },
        error => {
            Object.keys(options.streams).forEach(
                d => rtcUtils.stopMediaStream(options.streams[d]));
            logger.error(
                `failed to obtain ${device} stream - stop`, error);

            options.errorCallback(error);
        });
}

/**
 * In case of IE we continue from 'onReady' callback passed to RTCUtils
 * constructor. It will be invoked by Temasys plugin once it is initialized.
 *
 * @param options
 * @param GUM
 */
function onReady(options, GUM) {
    rtcReady = true;
    eventEmitter.emit(RTCEvents.RTC_READY, true);
    screenObtainer.init(options, GUM);

    if (rtcUtils.isDeviceListAvailable() && rawEnumerateDevicesWithCallback) {
        rawEnumerateDevicesWithCallback(ds => {
            currentlyAvailableMediaDevices = ds.splice(0);

            logger.info('Available devices: ', currentlyAvailableMediaDevices);
            sendDeviceListToAnalytics(currentlyAvailableMediaDevices);

            eventEmitter.emit(RTCEvents.DEVICE_LIST_AVAILABLE,
                currentlyAvailableMediaDevices);

            if (isDeviceChangeEventSupported) {
                navigator.mediaDevices.addEventListener(
                    'devicechange',
                    () => rtcUtils.enumerateDevices(onMediaDevicesListChanged));
            } else {
                pollForAvailableMediaDevices();
            }
        });
    }
}

/**
 * Wraps original attachMediaStream function to set current audio output device
 * if this is supported.
 * @param {Function} origAttachMediaStream
 * @returns {Function}
 */
function wrapAttachMediaStream(origAttachMediaStream) {
    return function(element, stream) {
        // eslint-disable-next-line prefer-rest-params
        const res = origAttachMediaStream.apply(rtcUtils, arguments);

        if (stream
                && rtcUtils.isDeviceChangeAvailable('output')
                && stream.getAudioTracks
                && stream.getAudioTracks().length

                // we skip setting audio output if there was no explicit change
                && audioOutputChanged) {
            element.setSinkId(rtcUtils.getAudioOutputDevice())
                .catch(function(ex) {
                    const err
                        = new JitsiTrackError(ex, null, [ 'audiooutput' ]);

                    GlobalOnErrorHandler.callUnhandledRejectionHandler({
                        promise: this, // eslint-disable-line no-invalid-this
                        reason: err
                    });

                    logger.warn(
                        'Failed to set audio output device for the element.'
                            + ' Default audio output device will be used'
                            + ' instead',
                        element,
                        err);
                });
        }

        return res;
    };
}

export default rtcUtils;