(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.adapter = f()}})(function(){var define,module,exports;return (function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    
    'use strict';
    
    var _adapter_factory = require('./adapter_factory.js');
    
    var adapter = (0, _adapter_factory.adapterFactory)({ window: window });
    module.exports = adapter; // this is the difference from adapter_core.
    
    },{"./adapter_factory.js":2}],2:[function(require,module,exports){
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.adapterFactory = adapterFactory;
    
    var _utils = require('./utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    var _chrome_shim = require('./chrome/chrome_shim');
    
    var chromeShim = _interopRequireWildcard(_chrome_shim);
    
    var _edge_shim = require('./edge/edge_shim');
    
    var edgeShim = _interopRequireWildcard(_edge_shim);
    
    var _firefox_shim = require('./firefox/firefox_shim');
    
    var firefoxShim = _interopRequireWildcard(_firefox_shim);
    
    var _safari_shim = require('./safari/safari_shim');
    
    var safariShim = _interopRequireWildcard(_safari_shim);
    
    var _common_shim = require('./common_shim');
    
    var commonShim = _interopRequireWildcard(_common_shim);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    // Shimming starts here.
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    function adapterFactory() {
      var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
          window = _ref.window;
    
      var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
        shimChrome: true,
        shimFirefox: true,
        shimEdge: true,
        shimSafari: true
      };
    
      // Utils.
      var logging = utils.log;
      var browserDetails = utils.detectBrowser(window);
    
      var adapter = {
        browserDetails: browserDetails,
        commonShim: commonShim,
        extractVersion: utils.extractVersion,
        disableLog: utils.disableLog,
        disableWarnings: utils.disableWarnings
      };
    
      // Shim browser if found.
      switch (browserDetails.browser) {
        case 'chrome':
          if (!chromeShim || !chromeShim.shimPeerConnection || !options.shimChrome) {
            logging('Chrome shim is not included in this adapter release.');
            return adapter;
          }
          if (browserDetails.version === null) {
            logging('Chrome shim can not determine version, not shimming.');
            return adapter;
          }
          logging('adapter.js shimming chrome.');
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = chromeShim;
    
          chromeShim.shimGetUserMedia(window);
          chromeShim.shimMediaStream(window);
          chromeShim.shimPeerConnection(window);
          chromeShim.shimOnTrack(window);
          chromeShim.shimAddTrackRemoveTrack(window);
          chromeShim.shimGetSendersWithDtmf(window);
          chromeShim.shimGetStats(window);
          chromeShim.shimSenderReceiverGetStats(window);
          chromeShim.fixNegotiationNeeded(window);
    
          commonShim.shimRTCIceCandidate(window);
          commonShim.shimConnectionState(window);
          commonShim.shimMaxMessageSize(window);
          commonShim.shimSendThrowTypeError(window);
          commonShim.removeAllowExtmapMixed(window);
          break;
        case 'firefox':
          if (!firefoxShim || !firefoxShim.shimPeerConnection || !options.shimFirefox) {
            logging('Firefox shim is not included in this adapter release.');
            return adapter;
          }
          logging('adapter.js shimming firefox.');
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = firefoxShim;
    
          firefoxShim.shimGetUserMedia(window);
          firefoxShim.shimPeerConnection(window);
          firefoxShim.shimOnTrack(window);
          firefoxShim.shimRemoveStream(window);
          firefoxShim.shimSenderGetStats(window);
          firefoxShim.shimReceiverGetStats(window);
          firefoxShim.shimRTCDataChannel(window);
          firefoxShim.shimAddTransceiver(window);
          firefoxShim.shimGetParameters(window);
          firefoxShim.shimCreateOffer(window);
          firefoxShim.shimCreateAnswer(window);
    
          commonShim.shimRTCIceCandidate(window);
          commonShim.shimConnectionState(window);
          commonShim.shimMaxMessageSize(window);
          commonShim.shimSendThrowTypeError(window);
          break;
        case 'edge':
          if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
            logging('MS edge shim is not included in this adapter release.');
            return adapter;
          }
          logging('adapter.js shimming edge.');
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = edgeShim;
    
          edgeShim.shimGetUserMedia(window);
          edgeShim.shimGetDisplayMedia(window);
          edgeShim.shimPeerConnection(window);
          edgeShim.shimReplaceTrack(window);
    
          // the edge shim implements the full RTCIceCandidate object.
    
          commonShim.shimMaxMessageSize(window);
          commonShim.shimSendThrowTypeError(window);
          break;
        case 'safari':
          if (!safariShim || !options.shimSafari) {
            logging('Safari shim is not included in this adapter release.');
            return adapter;
          }
          logging('adapter.js shimming safari.');
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = safariShim;
    
          safariShim.shimRTCIceServerUrls(window);
          safariShim.shimCreateOfferLegacy(window);
          safariShim.shimCallbacksAPI(window);
          safariShim.shimLocalStreamsAPI(window);
          safariShim.shimRemoteStreamsAPI(window);
          safariShim.shimTrackEventTransceiver(window);
          safariShim.shimGetUserMedia(window);
          safariShim.shimAudioContext(window);
    
          commonShim.shimRTCIceCandidate(window);
          commonShim.shimMaxMessageSize(window);
          commonShim.shimSendThrowTypeError(window);
          commonShim.removeAllowExtmapMixed(window);
          break;
        default:
          logging('Unsupported browser!');
          break;
      }
    
      return adapter;
    }
    
    // Browser shims.
    
    },{"./chrome/chrome_shim":3,"./common_shim":6,"./edge/edge_shim":7,"./firefox/firefox_shim":11,"./safari/safari_shim":14,"./utils":15}],3:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    var _getusermedia = require('./getusermedia');
    
    Object.defineProperty(exports, 'shimGetUserMedia', {
      enumerable: true,
      get: function get() {
        return _getusermedia.shimGetUserMedia;
      }
    });
    
    var _getdisplaymedia = require('./getdisplaymedia');
    
    Object.defineProperty(exports, 'shimGetDisplayMedia', {
      enumerable: true,
      get: function get() {
        return _getdisplaymedia.shimGetDisplayMedia;
      }
    });
    exports.shimMediaStream = shimMediaStream;
    exports.shimOnTrack = shimOnTrack;
    exports.shimGetSendersWithDtmf = shimGetSendersWithDtmf;
    exports.shimGetStats = shimGetStats;
    exports.shimSenderReceiverGetStats = shimSenderReceiverGetStats;
    exports.shimAddTrackRemoveTrackWithNative = shimAddTrackRemoveTrackWithNative;
    exports.shimAddTrackRemoveTrack = shimAddTrackRemoveTrack;
    exports.shimPeerConnection = shimPeerConnection;
    exports.fixNegotiationNeeded = fixNegotiationNeeded;
    
    var _utils = require('../utils.js');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
    
    function shimMediaStream(window) {
      window.MediaStream = window.MediaStream || window.webkitMediaStream;
    }
    
    function shimOnTrack(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('ontrack' in window.RTCPeerConnection.prototype)) {
        Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
          get: function get() {
            return this._ontrack;
          },
          set: function set(f) {
            if (this._ontrack) {
              this.removeEventListener('track', this._ontrack);
            }
            this.addEventListener('track', this._ontrack = f);
          },
    
          enumerable: true,
          configurable: true
        });
        var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
        window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
          var _this = this;
    
          if (!this._ontrackpoly) {
            this._ontrackpoly = function (e) {
              // onaddstream does not fire when a track is added to an existing
              // stream. But stream.onaddtrack is implemented so we use that.
              e.stream.addEventListener('addtrack', function (te) {
                var receiver = void 0;
                if (window.RTCPeerConnection.prototype.getReceivers) {
                  receiver = _this.getReceivers().find(function (r) {
                    return r.track && r.track.id === te.track.id;
                  });
                } else {
                  receiver = { track: te.track };
                }
    
                var event = new Event('track');
                event.track = te.track;
                event.receiver = receiver;
                event.transceiver = { receiver: receiver };
                event.streams = [e.stream];
                _this.dispatchEvent(event);
              });
              e.stream.getTracks().forEach(function (track) {
                var receiver = void 0;
                if (window.RTCPeerConnection.prototype.getReceivers) {
                  receiver = _this.getReceivers().find(function (r) {
                    return r.track && r.track.id === track.id;
                  });
                } else {
                  receiver = { track: track };
                }
                var event = new Event('track');
                event.track = track;
                event.receiver = receiver;
                event.transceiver = { receiver: receiver };
                event.streams = [e.stream];
                _this.dispatchEvent(event);
              });
            };
            this.addEventListener('addstream', this._ontrackpoly);
          }
          return origSetRemoteDescription.apply(this, arguments);
        };
      } else {
        // even if RTCRtpTransceiver is in window, it is only used and
        // emitted in unified-plan. Unfortunately this means we need
        // to unconditionally wrap the event.
        utils.wrapPeerConnectionEvent(window, 'track', function (e) {
          if (!e.transceiver) {
            Object.defineProperty(e, 'transceiver', { value: { receiver: e.receiver } });
          }
          return e;
        });
      }
    }
    
    function shimGetSendersWithDtmf(window) {
      // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('getSenders' in window.RTCPeerConnection.prototype) && 'createDTMFSender' in window.RTCPeerConnection.prototype) {
        var shimSenderWithDtmf = function shimSenderWithDtmf(pc, track) {
          return {
            track: track,
            get dtmf() {
              if (this._dtmf === undefined) {
                if (track.kind === 'audio') {
                  this._dtmf = pc.createDTMFSender(track);
                } else {
                  this._dtmf = null;
                }
              }
              return this._dtmf;
            },
            _pc: pc
          };
        };
    
        // augment addTrack when getSenders is not available.
        if (!window.RTCPeerConnection.prototype.getSenders) {
          window.RTCPeerConnection.prototype.getSenders = function getSenders() {
            this._senders = this._senders || [];
            return this._senders.slice(); // return a copy of the internal state.
          };
          var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
          window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
            var sender = origAddTrack.apply(this, arguments);
            if (!sender) {
              sender = shimSenderWithDtmf(this, track);
              this._senders.push(sender);
            }
            return sender;
          };
    
          var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
          window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
            origRemoveTrack.apply(this, arguments);
            var idx = this._senders.indexOf(sender);
            if (idx !== -1) {
              this._senders.splice(idx, 1);
            }
          };
        }
        var origAddStream = window.RTCPeerConnection.prototype.addStream;
        window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
          var _this2 = this;
    
          this._senders = this._senders || [];
          origAddStream.apply(this, [stream]);
          stream.getTracks().forEach(function (track) {
            _this2._senders.push(shimSenderWithDtmf(_this2, track));
          });
        };
    
        var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
        window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
          var _this3 = this;
    
          this._senders = this._senders || [];
          origRemoveStream.apply(this, [stream]);
    
          stream.getTracks().forEach(function (track) {
            var sender = _this3._senders.find(function (s) {
              return s.track === track;
            });
            if (sender) {
              // remove sender
              _this3._senders.splice(_this3._senders.indexOf(sender), 1);
            }
          });
        };
      } else if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && 'getSenders' in window.RTCPeerConnection.prototype && 'createDTMFSender' in window.RTCPeerConnection.prototype && window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
        var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
        window.RTCPeerConnection.prototype.getSenders = function getSenders() {
          var _this4 = this;
    
          var senders = origGetSenders.apply(this, []);
          senders.forEach(function (sender) {
            return sender._pc = _this4;
          });
          return senders;
        };
    
        Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
          get: function get() {
            if (this._dtmf === undefined) {
              if (this.track.kind === 'audio') {
                this._dtmf = this._pc.createDTMFSender(this.track);
              } else {
                this._dtmf = null;
              }
            }
            return this._dtmf;
          }
        });
      }
    }
    
    function shimGetStats(window) {
      if (!window.RTCPeerConnection) {
        return;
      }
    
      var origGetStats = window.RTCPeerConnection.prototype.getStats;
      window.RTCPeerConnection.prototype.getStats = function getStats() {
        var _this5 = this;
    
        var _arguments = Array.prototype.slice.call(arguments),
            selector = _arguments[0],
            onSucc = _arguments[1],
            onErr = _arguments[2];
    
        // If selector is a function then we are in the old style stats so just
        // pass back the original getStats format to avoid breaking old users.
    
    
        if (arguments.length > 0 && typeof selector === 'function') {
          return origGetStats.apply(this, arguments);
        }
    
        // When spec-style getStats is supported, return those when called with
        // either no arguments or the selector argument is null.
        if (origGetStats.length === 0 && (arguments.length === 0 || typeof selector !== 'function')) {
          return origGetStats.apply(this, []);
        }
    
        var fixChromeStats_ = function fixChromeStats_(response) {
          var standardReport = {};
          var reports = response.result();
          reports.forEach(function (report) {
            var standardStats = {
              id: report.id,
              timestamp: report.timestamp,
              type: {
                localcandidate: 'local-candidate',
                remotecandidate: 'remote-candidate'
              }[report.type] || report.type
            };
            report.names().forEach(function (name) {
              standardStats[name] = report.stat(name);
            });
            standardReport[standardStats.id] = standardStats;
          });
    
          return standardReport;
        };
    
        // shim getStats with maplike support
        var makeMapStats = function makeMapStats(stats) {
          return new Map(Object.keys(stats).map(function (key) {
            return [key, stats[key]];
          }));
        };
    
        if (arguments.length >= 2) {
          var successCallbackWrapper_ = function successCallbackWrapper_(response) {
            onSucc(makeMapStats(fixChromeStats_(response)));
          };
    
          return origGetStats.apply(this, [successCallbackWrapper_, selector]);
        }
    
        // promise-support
        return new Promise(function (resolve, reject) {
          origGetStats.apply(_this5, [function (response) {
            resolve(makeMapStats(fixChromeStats_(response)));
          }, reject]);
        }).then(onSucc, onErr);
      };
    }
    
    function shimSenderReceiverGetStats(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender && window.RTCRtpReceiver)) {
        return;
      }
    
      // shim sender stats.
      if (!('getStats' in window.RTCRtpSender.prototype)) {
        var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
        if (origGetSenders) {
          window.RTCPeerConnection.prototype.getSenders = function getSenders() {
            var _this6 = this;
    
            var senders = origGetSenders.apply(this, []);
            senders.forEach(function (sender) {
              return sender._pc = _this6;
            });
            return senders;
          };
        }
    
        var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
        if (origAddTrack) {
          window.RTCPeerConnection.prototype.addTrack = function addTrack() {
            var sender = origAddTrack.apply(this, arguments);
            sender._pc = this;
            return sender;
          };
        }
        window.RTCRtpSender.prototype.getStats = function getStats() {
          var sender = this;
          return this._pc.getStats().then(function (result) {
            return (
              /* Note: this will include stats of all senders that
               *   send a track with the same id as sender.track as
               *   it is not possible to identify the RTCRtpSender.
               */
              utils.filterStats(result, sender.track, true)
            );
          });
        };
      }
    
      // shim receiver stats.
      if (!('getStats' in window.RTCRtpReceiver.prototype)) {
        var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
        if (origGetReceivers) {
          window.RTCPeerConnection.prototype.getReceivers = function getReceivers() {
            var _this7 = this;
    
            var receivers = origGetReceivers.apply(this, []);
            receivers.forEach(function (receiver) {
              return receiver._pc = _this7;
            });
            return receivers;
          };
        }
        utils.wrapPeerConnectionEvent(window, 'track', function (e) {
          e.receiver._pc = e.srcElement;
          return e;
        });
        window.RTCRtpReceiver.prototype.getStats = function getStats() {
          var receiver = this;
          return this._pc.getStats().then(function (result) {
            return utils.filterStats(result, receiver.track, false);
          });
        };
      }
    
      if (!('getStats' in window.RTCRtpSender.prototype && 'getStats' in window.RTCRtpReceiver.prototype)) {
        return;
      }
    
      // shim RTCPeerConnection.getStats(track).
      var origGetStats = window.RTCPeerConnection.prototype.getStats;
      window.RTCPeerConnection.prototype.getStats = function getStats() {
        if (arguments.length > 0 && arguments[0] instanceof window.MediaStreamTrack) {
          var track = arguments[0];
          var sender = void 0;
          var receiver = void 0;
          var err = void 0;
          this.getSenders().forEach(function (s) {
            if (s.track === track) {
              if (sender) {
                err = true;
              } else {
                sender = s;
              }
            }
          });
          this.getReceivers().forEach(function (r) {
            if (r.track === track) {
              if (receiver) {
                err = true;
              } else {
                receiver = r;
              }
            }
            return r.track === track;
          });
          if (err || sender && receiver) {
            return Promise.reject(new DOMException('There are more than one sender or receiver for the track.', 'InvalidAccessError'));
          } else if (sender) {
            return sender.getStats();
          } else if (receiver) {
            return receiver.getStats();
          }
          return Promise.reject(new DOMException('There is no sender or receiver for the track.', 'InvalidAccessError'));
        }
        return origGetStats.apply(this, arguments);
      };
    }
    
    function shimAddTrackRemoveTrackWithNative(window) {
      // shim addTrack/removeTrack with native variants in order to make
      // the interactions with legacy getLocalStreams behave as in other browsers.
      // Keeps a mapping stream.id => [stream, rtpsenders...]
      window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
        var _this8 = this;
    
        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
        return Object.keys(this._shimmedLocalStreams).map(function (streamId) {
          return _this8._shimmedLocalStreams[streamId][0];
        });
      };
    
      var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
      window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
        if (!stream) {
          return origAddTrack.apply(this, arguments);
        }
        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
    
        var sender = origAddTrack.apply(this, arguments);
        if (!this._shimmedLocalStreams[stream.id]) {
          this._shimmedLocalStreams[stream.id] = [stream, sender];
        } else if (this._shimmedLocalStreams[stream.id].indexOf(sender) === -1) {
          this._shimmedLocalStreams[stream.id].push(sender);
        }
        return sender;
      };
    
      var origAddStream = window.RTCPeerConnection.prototype.addStream;
      window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
        var _this9 = this;
    
        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
    
        stream.getTracks().forEach(function (track) {
          var alreadyExists = _this9.getSenders().find(function (s) {
            return s.track === track;
          });
          if (alreadyExists) {
            throw new DOMException('Track already exists.', 'InvalidAccessError');
          }
        });
        var existingSenders = this.getSenders();
        origAddStream.apply(this, arguments);
        var newSenders = this.getSenders().filter(function (newSender) {
          return existingSenders.indexOf(newSender) === -1;
        });
        this._shimmedLocalStreams[stream.id] = [stream].concat(newSenders);
      };
    
      var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
      window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
        delete this._shimmedLocalStreams[stream.id];
        return origRemoveStream.apply(this, arguments);
      };
    
      var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
      window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
        var _this10 = this;
    
        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
        if (sender) {
          Object.keys(this._shimmedLocalStreams).forEach(function (streamId) {
            var idx = _this10._shimmedLocalStreams[streamId].indexOf(sender);
            if (idx !== -1) {
              _this10._shimmedLocalStreams[streamId].splice(idx, 1);
            }
            if (_this10._shimmedLocalStreams[streamId].length === 1) {
              delete _this10._shimmedLocalStreams[streamId];
            }
          });
        }
        return origRemoveTrack.apply(this, arguments);
      };
    }
    
    function shimAddTrackRemoveTrack(window) {
      if (!window.RTCPeerConnection) {
        return;
      }
      var browserDetails = utils.detectBrowser(window);
      // shim addTrack and removeTrack.
      if (window.RTCPeerConnection.prototype.addTrack && browserDetails.version >= 65) {
        return shimAddTrackRemoveTrackWithNative(window);
      }
    
      // also shim pc.getLocalStreams when addTrack is shimmed
      // to return the original streams.
      var origGetLocalStreams = window.RTCPeerConnection.prototype.getLocalStreams;
      window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
        var _this11 = this;
    
        var nativeStreams = origGetLocalStreams.apply(this);
        this._reverseStreams = this._reverseStreams || {};
        return nativeStreams.map(function (stream) {
          return _this11._reverseStreams[stream.id];
        });
      };
    
      var origAddStream = window.RTCPeerConnection.prototype.addStream;
      window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
        var _this12 = this;
    
        this._streams = this._streams || {};
        this._reverseStreams = this._reverseStreams || {};
    
        stream.getTracks().forEach(function (track) {
          var alreadyExists = _this12.getSenders().find(function (s) {
            return s.track === track;
          });
          if (alreadyExists) {
            throw new DOMException('Track already exists.', 'InvalidAccessError');
          }
        });
        // Add identity mapping for consistency with addTrack.
        // Unless this is being used with a stream from addTrack.
        if (!this._reverseStreams[stream.id]) {
          var newStream = new window.MediaStream(stream.getTracks());
          this._streams[stream.id] = newStream;
          this._reverseStreams[newStream.id] = stream;
          stream = newStream;
        }
        origAddStream.apply(this, [stream]);
      };
    
      var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
      window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
        this._streams = this._streams || {};
        this._reverseStreams = this._reverseStreams || {};
    
        origRemoveStream.apply(this, [this._streams[stream.id] || stream]);
        delete this._reverseStreams[this._streams[stream.id] ? this._streams[stream.id].id : stream.id];
        delete this._streams[stream.id];
      };
    
      window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
        var _this13 = this;
    
        if (this.signalingState === 'closed') {
          throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError');
        }
        var streams = [].slice.call(arguments, 1);
        if (streams.length !== 1 || !streams[0].getTracks().find(function (t) {
          return t === track;
        })) {
          // this is not fully correct but all we can manage without
          // [[associated MediaStreams]] internal slot.
          throw new DOMException('The adapter.js addTrack polyfill only supports a single ' + ' stream which is associated with the specified track.', 'NotSupportedError');
        }
    
        var alreadyExists = this.getSenders().find(function (s) {
          return s.track === track;
        });
        if (alreadyExists) {
          throw new DOMException('Track already exists.', 'InvalidAccessError');
        }
    
        this._streams = this._streams || {};
        this._reverseStreams = this._reverseStreams || {};
        var oldStream = this._streams[stream.id];
        if (oldStream) {
          // this is using odd Chrome behaviour, use with caution:
          // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
          // Note: we rely on the high-level addTrack/dtmf shim to
          // create the sender with a dtmf sender.
          oldStream.addTrack(track);
    
          // Trigger ONN async.
          Promise.resolve().then(function () {
            _this13.dispatchEvent(new Event('negotiationneeded'));
          });
        } else {
          var newStream = new window.MediaStream([track]);
          this._streams[stream.id] = newStream;
          this._reverseStreams[newStream.id] = stream;
          this.addStream(newStream);
        }
        return this.getSenders().find(function (s) {
          return s.track === track;
        });
      };
    
      // replace the internal stream id with the external one and
      // vice versa.
      function replaceInternalStreamId(pc, description) {
        var sdp = description.sdp;
        Object.keys(pc._reverseStreams || []).forEach(function (internalId) {
          var externalStream = pc._reverseStreams[internalId];
          var internalStream = pc._streams[externalStream.id];
          sdp = sdp.replace(new RegExp(internalStream.id, 'g'), externalStream.id);
        });
        return new RTCSessionDescription({
          type: description.type,
          sdp: sdp
        });
      }
      function replaceExternalStreamId(pc, description) {
        var sdp = description.sdp;
        Object.keys(pc._reverseStreams || []).forEach(function (internalId) {
          var externalStream = pc._reverseStreams[internalId];
          var internalStream = pc._streams[externalStream.id];
          sdp = sdp.replace(new RegExp(externalStream.id, 'g'), internalStream.id);
        });
        return new RTCSessionDescription({
          type: description.type,
          sdp: sdp
        });
      }
      ['createOffer', 'createAnswer'].forEach(function (method) {
        var nativeMethod = window.RTCPeerConnection.prototype[method];
        var methodObj = _defineProperty({}, method, function () {
          var _this14 = this;
    
          var args = arguments;
          var isLegacyCall = arguments.length && typeof arguments[0] === 'function';
          if (isLegacyCall) {
            return nativeMethod.apply(this, [function (description) {
              var desc = replaceInternalStreamId(_this14, description);
              args[0].apply(null, [desc]);
            }, function (err) {
              if (args[1]) {
                args[1].apply(null, err);
              }
            }, arguments[2]]);
          }
          return nativeMethod.apply(this, arguments).then(function (description) {
            return replaceInternalStreamId(_this14, description);
          });
        });
        window.RTCPeerConnection.prototype[method] = methodObj[method];
      });
    
      var origSetLocalDescription = window.RTCPeerConnection.prototype.setLocalDescription;
      window.RTCPeerConnection.prototype.setLocalDescription = function setLocalDescription() {
        if (!arguments.length || !arguments[0].type) {
          return origSetLocalDescription.apply(this, arguments);
        }
        arguments[0] = replaceExternalStreamId(this, arguments[0]);
        return origSetLocalDescription.apply(this, arguments);
      };
    
      // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier
    
      var origLocalDescription = Object.getOwnPropertyDescriptor(window.RTCPeerConnection.prototype, 'localDescription');
      Object.defineProperty(window.RTCPeerConnection.prototype, 'localDescription', {
        get: function get() {
          var description = origLocalDescription.get.apply(this);
          if (description.type === '') {
            return description;
          }
          return replaceInternalStreamId(this, description);
        }
      });
    
      window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
        var _this15 = this;
    
        if (this.signalingState === 'closed') {
          throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError');
        }
        // We can not yet check for sender instanceof RTCRtpSender
        // since we shim RTPSender. So we check if sender._pc is set.
        if (!sender._pc) {
          throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' + 'does not implement interface RTCRtpSender.', 'TypeError');
        }
        var isLocal = sender._pc === this;
        if (!isLocal) {
          throw new DOMException('Sender was not created by this connection.', 'InvalidAccessError');
        }
    
        // Search for the native stream the senders track belongs to.
        this._streams = this._streams || {};
        var stream = void 0;
        Object.keys(this._streams).forEach(function (streamid) {
          var hasTrack = _this15._streams[streamid].getTracks().find(function (track) {
            return sender.track === track;
          });
          if (hasTrack) {
            stream = _this15._streams[streamid];
          }
        });
    
        if (stream) {
          if (stream.getTracks().length === 1) {
            // if this is the last track of the stream, remove the stream. This
            // takes care of any shimmed _senders.
            this.removeStream(this._reverseStreams[stream.id]);
          } else {
            // relying on the same odd chrome behaviour as above.
            stream.removeTrack(sender.track);
          }
          this.dispatchEvent(new Event('negotiationneeded'));
        }
      };
    }
    
    function shimPeerConnection(window) {
      var browserDetails = utils.detectBrowser(window);
    
      if (!window.RTCPeerConnection && window.webkitRTCPeerConnection) {
        // very basic support for old versions.
        window.RTCPeerConnection = window.webkitRTCPeerConnection;
      }
      if (!window.RTCPeerConnection) {
        return;
      }
    
      var addIceCandidateNullSupported = window.RTCPeerConnection.prototype.addIceCandidate.length === 0;
    
      // shim implicit creation of RTCSessionDescription/RTCIceCandidate
      if (browserDetails.version < 53) {
        ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'].forEach(function (method) {
          var nativeMethod = window.RTCPeerConnection.prototype[method];
          var methodObj = _defineProperty({}, method, function () {
            arguments[0] = new (method === 'addIceCandidate' ? window.RTCIceCandidate : window.RTCSessionDescription)(arguments[0]);
            return nativeMethod.apply(this, arguments);
          });
          window.RTCPeerConnection.prototype[method] = methodObj[method];
        });
      }
    
      // support for addIceCandidate(null or undefined)
      var nativeAddIceCandidate = window.RTCPeerConnection.prototype.addIceCandidate;
      window.RTCPeerConnection.prototype.addIceCandidate = function addIceCandidate() {
        if (!addIceCandidateNullSupported && !arguments[0]) {
          if (arguments[1]) {
            arguments[1].apply(null);
          }
          return Promise.resolve();
        }
        // Firefox 68+ emits and processes {candidate: "", ...}, ignore
        // in older versions. Native support planned for Chrome M77.
        if (browserDetails.version < 78 && arguments[0] && arguments[0].candidate === '') {
          return Promise.resolve();
        }
        return nativeAddIceCandidate.apply(this, arguments);
      };
    }
    
    // Attempt to fix ONN in plan-b mode.
    function fixNegotiationNeeded(window) {
      var browserDetails = utils.detectBrowser(window);
      utils.wrapPeerConnectionEvent(window, 'negotiationneeded', function (e) {
        var pc = e.target;
        if (browserDetails.version < 72 || pc.getConfiguration && pc.getConfiguration().sdpSemantics === 'plan-b') {
          if (pc.signalingState !== 'stable') {
            return;
          }
        }
        return e;
      });
    }
    
    },{"../utils.js":15,"./getdisplaymedia":4,"./getusermedia":5}],4:[function(require,module,exports){
    /*
     *  Copyright (c) 2018 The adapter.js 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.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetDisplayMedia = shimGetDisplayMedia;
    function shimGetDisplayMedia(window, getSourceId) {
      if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
        return;
      }
      if (!window.navigator.mediaDevices) {
        return;
      }
      // getSourceId is a function that returns a promise resolving with
      // the sourceId of the screen/window/tab to be shared.
      if (typeof getSourceId !== 'function') {
        console.error('shimGetDisplayMedia: getSourceId argument is not ' + 'a function');
        return;
      }
      window.navigator.mediaDevices.getDisplayMedia = function getDisplayMedia(constraints) {
        return getSourceId(constraints).then(function (sourceId) {
          var widthSpecified = constraints.video && constraints.video.width;
          var heightSpecified = constraints.video && constraints.video.height;
          var frameRateSpecified = constraints.video && constraints.video.frameRate;
          constraints.video = {
            mandatory: {
              chromeMediaSource: 'desktop',
              chromeMediaSourceId: sourceId,
              maxFrameRate: frameRateSpecified || 3
            }
          };
          if (widthSpecified) {
            constraints.video.mandatory.maxWidth = widthSpecified;
          }
          if (heightSpecified) {
            constraints.video.mandatory.maxHeight = heightSpecified;
          }
          return window.navigator.mediaDevices.getUserMedia(constraints);
        });
      };
    }
    
    },{}],5:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    exports.shimGetUserMedia = shimGetUserMedia;
    
    var _utils = require('../utils.js');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    var logging = utils.log;
    
    function shimGetUserMedia(window) {
      var navigator = window && window.navigator;
    
      if (!navigator.mediaDevices) {
        return;
      }
    
      var browserDetails = utils.detectBrowser(window);
    
      var constraintsToChrome_ = function constraintsToChrome_(c) {
        if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) !== 'object' || c.mandatory || c.optional) {
          return c;
        }
        var cc = {};
        Object.keys(c).forEach(function (key) {
          if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
            return;
          }
          var r = _typeof(c[key]) === 'object' ? c[key] : { ideal: c[key] };
          if (r.exact !== undefined && typeof r.exact === 'number') {
            r.min = r.max = r.exact;
          }
          var oldname_ = function oldname_(prefix, name) {
            if (prefix) {
              return prefix + name.charAt(0).toUpperCase() + name.slice(1);
            }
            return name === 'deviceId' ? 'sourceId' : name;
          };
          if (r.ideal !== undefined) {
            cc.optional = cc.optional || [];
            var oc = {};
            if (typeof r.ideal === 'number') {
              oc[oldname_('min', key)] = r.ideal;
              cc.optional.push(oc);
              oc = {};
              oc[oldname_('max', key)] = r.ideal;
              cc.optional.push(oc);
            } else {
              oc[oldname_('', key)] = r.ideal;
              cc.optional.push(oc);
            }
          }
          if (r.exact !== undefined && typeof r.exact !== 'number') {
            cc.mandatory = cc.mandatory || {};
            cc.mandatory[oldname_('', key)] = r.exact;
          } else {
            ['min', 'max'].forEach(function (mix) {
              if (r[mix] !== undefined) {
                cc.mandatory = cc.mandatory || {};
                cc.mandatory[oldname_(mix, key)] = r[mix];
              }
            });
          }
        });
        if (c.advanced) {
          cc.optional = (cc.optional || []).concat(c.advanced);
        }
        return cc;
      };
    
      var shimConstraints_ = function shimConstraints_(constraints, func) {
        if (browserDetails.version >= 61) {
          return func(constraints);
        }
        constraints = JSON.parse(JSON.stringify(constraints));
        if (constraints && _typeof(constraints.audio) === 'object') {
          var remap = function remap(obj, a, b) {
            if (a in obj && !(b in obj)) {
              obj[b] = obj[a];
              delete obj[a];
            }
          };
          constraints = JSON.parse(JSON.stringify(constraints));
          remap(constraints.audio, 'autoGainControl', 'googAutoGainControl');
          remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression');
          constraints.audio = constraintsToChrome_(constraints.audio);
        }
        if (constraints && _typeof(constraints.video) === 'object') {
          // Shim facingMode for mobile & surface pro.
          var face = constraints.video.facingMode;
          face = face && ((typeof face === 'undefined' ? 'undefined' : _typeof(face)) === 'object' ? face : { ideal: face });
          var getSupportedFacingModeLies = browserDetails.version < 66;
    
          if (face && (face.exact === 'user' || face.exact === 'environment' || face.ideal === 'user' || face.ideal === 'environment') && !(navigator.mediaDevices.getSupportedConstraints && navigator.mediaDevices.getSupportedConstraints().facingMode && !getSupportedFacingModeLies)) {
            delete constraints.video.facingMode;
            var matches = void 0;
            if (face.exact === 'environment' || face.ideal === 'environment') {
              matches = ['back', 'rear'];
            } else if (face.exact === 'user' || face.ideal === 'user') {
              matches = ['front'];
            }
            if (matches) {
              // Look for matches in label, or use last cam for back (typical).
              return navigator.mediaDevices.enumerateDevices().then(function (devices) {
                devices = devices.filter(function (d) {
                  return d.kind === 'videoinput';
                });
                var dev = devices.find(function (d) {
                  return matches.some(function (match) {
                    return d.label.toLowerCase().includes(match);
                  });
                });
                if (!dev && devices.length && matches.includes('back')) {
                  dev = devices[devices.length - 1]; // more likely the back cam
                }
                if (dev) {
                  constraints.video.deviceId = face.exact ? { exact: dev.deviceId } : { ideal: dev.deviceId };
                }
                constraints.video = constraintsToChrome_(constraints.video);
                logging('chrome: ' + JSON.stringify(constraints));
                return func(constraints);
              });
            }
          }
          constraints.video = constraintsToChrome_(constraints.video);
        }
        logging('chrome: ' + JSON.stringify(constraints));
        return func(constraints);
      };
    
      var shimError_ = function shimError_(e) {
        if (browserDetails.version >= 64) {
          return e;
        }
        return {
          name: {
            PermissionDeniedError: 'NotAllowedError',
            PermissionDismissedError: 'NotAllowedError',
            InvalidStateError: 'NotAllowedError',
            DevicesNotFoundError: 'NotFoundError',
            ConstraintNotSatisfiedError: 'OverconstrainedError',
            TrackStartError: 'NotReadableError',
            MediaDeviceFailedDueToShutdown: 'NotAllowedError',
            MediaDeviceKillSwitchOn: 'NotAllowedError',
            TabCaptureError: 'AbortError',
            ScreenCaptureError: 'AbortError',
            DeviceCaptureError: 'AbortError'
          }[e.name] || e.name,
          message: e.message,
          constraint: e.constraint || e.constraintName,
          toString: function toString() {
            return this.name + (this.message && ': ') + this.message;
          }
        };
      };
    
      var getUserMedia_ = function getUserMedia_(constraints, onSuccess, onError) {
        shimConstraints_(constraints, function (c) {
          navigator.webkitGetUserMedia(c, onSuccess, function (e) {
            if (onError) {
              onError(shimError_(e));
            }
          });
        });
      };
      navigator.getUserMedia = getUserMedia_.bind(navigator);
    
      // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
      // function which returns a Promise, it does not accept spec-style
      // constraints.
      if (navigator.mediaDevices.getUserMedia) {
        var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
        navigator.mediaDevices.getUserMedia = function (cs) {
          return shimConstraints_(cs, function (c) {
            return origGetUserMedia(c).then(function (stream) {
              if (c.audio && !stream.getAudioTracks().length || c.video && !stream.getVideoTracks().length) {
                stream.getTracks().forEach(function (track) {
                  track.stop();
                });
                throw new DOMException('', 'NotFoundError');
              }
              return stream;
            }, function (e) {
              return Promise.reject(shimError_(e));
            });
          });
        };
      }
    }
    
    },{"../utils.js":15}],6:[function(require,module,exports){
    /*
     *  Copyright (c) 2017 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.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    exports.shimRTCIceCandidate = shimRTCIceCandidate;
    exports.shimMaxMessageSize = shimMaxMessageSize;
    exports.shimSendThrowTypeError = shimSendThrowTypeError;
    exports.shimConnectionState = shimConnectionState;
    exports.removeAllowExtmapMixed = removeAllowExtmapMixed;
    
    var _sdp = require('sdp');
    
    var _sdp2 = _interopRequireDefault(_sdp);
    
    var _utils = require('./utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
    
    function shimRTCIceCandidate(window) {
      // foundation is arbitrarily chosen as an indicator for full support for
      // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
      if (!window.RTCIceCandidate || window.RTCIceCandidate && 'foundation' in window.RTCIceCandidate.prototype) {
        return;
      }
    
      var NativeRTCIceCandidate = window.RTCIceCandidate;
      window.RTCIceCandidate = function RTCIceCandidate(args) {
        // Remove the a= which shouldn't be part of the candidate string.
        if ((typeof args === 'undefined' ? 'undefined' : _typeof(args)) === 'object' && args.candidate && args.candidate.indexOf('a=') === 0) {
          args = JSON.parse(JSON.stringify(args));
          args.candidate = args.candidate.substr(2);
        }
    
        if (args.candidate && args.candidate.length) {
          // Augment the native candidate with the parsed fields.
          var nativeCandidate = new NativeRTCIceCandidate(args);
          var parsedCandidate = _sdp2.default.parseCandidate(args.candidate);
          var augmentedCandidate = Object.assign(nativeCandidate, parsedCandidate);
    
          // Add a serializer that does not serialize the extra attributes.
          augmentedCandidate.toJSON = function toJSON() {
            return {
              candidate: augmentedCandidate.candidate,
              sdpMid: augmentedCandidate.sdpMid,
              sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
              usernameFragment: augmentedCandidate.usernameFragment
            };
          };
          return augmentedCandidate;
        }
        return new NativeRTCIceCandidate(args);
      };
      window.RTCIceCandidate.prototype = NativeRTCIceCandidate.prototype;
    
      // Hook up the augmented candidate in onicecandidate and
      // addEventListener('icecandidate', ...)
      utils.wrapPeerConnectionEvent(window, 'icecandidate', function (e) {
        if (e.candidate) {
          Object.defineProperty(e, 'candidate', {
            value: new window.RTCIceCandidate(e.candidate),
            writable: 'false'
          });
        }
        return e;
      });
    }
    
    function shimMaxMessageSize(window) {
      if (!window.RTCPeerConnection) {
        return;
      }
      var browserDetails = utils.detectBrowser(window);
    
      if (!('sctp' in window.RTCPeerConnection.prototype)) {
        Object.defineProperty(window.RTCPeerConnection.prototype, 'sctp', {
          get: function get() {
            return typeof this._sctp === 'undefined' ? null : this._sctp;
          }
        });
      }
    
      var sctpInDescription = function sctpInDescription(description) {
        if (!description || !description.sdp) {
          return false;
        }
        var sections = _sdp2.default.splitSections(description.sdp);
        sections.shift();
        return sections.some(function (mediaSection) {
          var mLine = _sdp2.default.parseMLine(mediaSection);
          return mLine && mLine.kind === 'application' && mLine.protocol.indexOf('SCTP') !== -1;
        });
      };
    
      var getRemoteFirefoxVersion = function getRemoteFirefoxVersion(description) {
        // TODO: Is there a better solution for detecting Firefox?
        var match = description.sdp.match(/mozilla...THIS_IS_SDPARTA-(\d+)/);
        if (match === null || match.length < 2) {
          return -1;
        }
        var version = parseInt(match[1], 10);
        // Test for NaN (yes, this is ugly)
        return version !== version ? -1 : version;
      };
    
      var getCanSendMaxMessageSize = function getCanSendMaxMessageSize(remoteIsFirefox) {
        // Every implementation we know can send at least 64 KiB.
        // Note: Although Chrome is technically able to send up to 256 KiB, the
        //       data does not reach the other peer reliably.
        //       See: https://bugs.chromium.org/p/webrtc/issues/detail?id=8419
        var canSendMaxMessageSize = 65536;
        if (browserDetails.browser === 'firefox') {
          if (browserDetails.version < 57) {
            if (remoteIsFirefox === -1) {
              // FF < 57 will send in 16 KiB chunks using the deprecated PPID
              // fragmentation.
              canSendMaxMessageSize = 16384;
            } else {
              // However, other FF (and RAWRTC) can reassemble PPID-fragmented
              // messages. Thus, supporting ~2 GiB when sending.
              canSendMaxMessageSize = 2147483637;
            }
          } else if (browserDetails.version < 60) {
            // Currently, all FF >= 57 will reset the remote maximum message size
            // to the default value when a data channel is created at a later
            // stage. :(
            // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
            canSendMaxMessageSize = browserDetails.version === 57 ? 65535 : 65536;
          } else {
            // FF >= 60 supports sending ~2 GiB
            canSendMaxMessageSize = 2147483637;
          }
        }
        return canSendMaxMessageSize;
      };
    
      var getMaxMessageSize = function getMaxMessageSize(description, remoteIsFirefox) {
        // Note: 65536 bytes is the default value from the SDP spec. Also,
        //       every implementation we know supports receiving 65536 bytes.
        var maxMessageSize = 65536;
    
        // FF 57 has a slightly incorrect default remote max message size, so
        // we need to adjust it here to avoid a failure when sending.
        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1425697
        if (browserDetails.browser === 'firefox' && browserDetails.version === 57) {
          maxMessageSize = 65535;
        }
    
        var match = _sdp2.default.matchPrefix(description.sdp, 'a=max-message-size:');
        if (match.length > 0) {
          maxMessageSize = parseInt(match[0].substr(19), 10);
        } else if (browserDetails.browser === 'firefox' && remoteIsFirefox !== -1) {
          // If the maximum message size is not present in the remote SDP and
          // both local and remote are Firefox, the remote peer can receive
          // ~2 GiB.
          maxMessageSize = 2147483637;
        }
        return maxMessageSize;
      };
    
      var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
      window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
        this._sctp = null;
        // Chrome decided to not expose .sctp in plan-b mode.
        // As usual, adapter.js has to do an 'ugly worakaround'
        // to cover up the mess.
        if (browserDetails.browser === 'chrome' && browserDetails.version >= 76) {
          var _getConfiguration = this.getConfiguration(),
              sdpSemantics = _getConfiguration.sdpSemantics;
    
          if (sdpSemantics === 'plan-b') {
            Object.defineProperty(this, 'sctp', {
              get: function get() {
                return typeof this._sctp === 'undefined' ? null : this._sctp;
              },
    
              enumerable: true,
              configurable: true
            });
          }
        }
    
        if (sctpInDescription(arguments[0])) {
          // Check if the remote is FF.
          var isFirefox = getRemoteFirefoxVersion(arguments[0]);
    
          // Get the maximum message size the local peer is capable of sending
          var canSendMMS = getCanSendMaxMessageSize(isFirefox);
    
          // Get the maximum message size of the remote peer.
          var remoteMMS = getMaxMessageSize(arguments[0], isFirefox);
    
          // Determine final maximum message size
          var maxMessageSize = void 0;
          if (canSendMMS === 0 && remoteMMS === 0) {
            maxMessageSize = Number.POSITIVE_INFINITY;
          } else if (canSendMMS === 0 || remoteMMS === 0) {
            maxMessageSize = Math.max(canSendMMS, remoteMMS);
          } else {
            maxMessageSize = Math.min(canSendMMS, remoteMMS);
          }
    
          // Create a dummy RTCSctpTransport object and the 'maxMessageSize'
          // attribute.
          var sctp = {};
          Object.defineProperty(sctp, 'maxMessageSize', {
            get: function get() {
              return maxMessageSize;
            }
          });
          this._sctp = sctp;
        }
    
        return origSetRemoteDescription.apply(this, arguments);
      };
    }
    
    function shimSendThrowTypeError(window) {
      if (!(window.RTCPeerConnection && 'createDataChannel' in window.RTCPeerConnection.prototype)) {
        return;
      }
    
      // Note: Although Firefox >= 57 has a native implementation, the maximum
      //       message size can be reset for all data channels at a later stage.
      //       See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
    
      function wrapDcSend(dc, pc) {
        var origDataChannelSend = dc.send;
        dc.send = function send() {
          var data = arguments[0];
          var length = data.length || data.size || data.byteLength;
          if (dc.readyState === 'open' && pc.sctp && length > pc.sctp.maxMessageSize) {
            throw new TypeError('Message too large (can send a maximum of ' + pc.sctp.maxMessageSize + ' bytes)');
          }
          return origDataChannelSend.apply(dc, arguments);
        };
      }
      var origCreateDataChannel = window.RTCPeerConnection.prototype.createDataChannel;
      window.RTCPeerConnection.prototype.createDataChannel = function createDataChannel() {
        var dataChannel = origCreateDataChannel.apply(this, arguments);
        wrapDcSend(dataChannel, this);
        return dataChannel;
      };
      utils.wrapPeerConnectionEvent(window, 'datachannel', function (e) {
        wrapDcSend(e.channel, e.target);
        return e;
      });
    }
    
    /* shims RTCConnectionState by pretending it is the same as iceConnectionState.
     * See https://bugs.chromium.org/p/webrtc/issues/detail?id=6145#c12
     * for why this is a valid hack in Chrome. In Firefox it is slightly incorrect
     * since DTLS failures would be hidden. See
     * https://bugzilla.mozilla.org/show_bug.cgi?id=1265827
     * for the Firefox tracking bug.
     */
    function shimConnectionState(window) {
      if (!window.RTCPeerConnection || 'connectionState' in window.RTCPeerConnection.prototype) {
        return;
      }
      var proto = window.RTCPeerConnection.prototype;
      Object.defineProperty(proto, 'connectionState', {
        get: function get() {
          return {
            completed: 'connected',
            checking: 'connecting'
          }[this.iceConnectionState] || this.iceConnectionState;
        },
    
        enumerable: true,
        configurable: true
      });
      Object.defineProperty(proto, 'onconnectionstatechange', {
        get: function get() {
          return this._onconnectionstatechange || null;
        },
        set: function set(cb) {
          if (this._onconnectionstatechange) {
            this.removeEventListener('connectionstatechange', this._onconnectionstatechange);
            delete this._onconnectionstatechange;
          }
          if (cb) {
            this.addEventListener('connectionstatechange', this._onconnectionstatechange = cb);
          }
        },
    
        enumerable: true,
        configurable: true
      });
    
      ['setLocalDescription', 'setRemoteDescription'].forEach(function (method) {
        var origMethod = proto[method];
        proto[method] = function () {
          if (!this._connectionstatechangepoly) {
            this._connectionstatechangepoly = function (e) {
              var pc = e.target;
              if (pc._lastConnectionState !== pc.connectionState) {
                pc._lastConnectionState = pc.connectionState;
                var newEvent = new Event('connectionstatechange', e);
                pc.dispatchEvent(newEvent);
              }
              return e;
            };
            this.addEventListener('iceconnectionstatechange', this._connectionstatechangepoly);
          }
          return origMethod.apply(this, arguments);
        };
      });
    }
    
    function removeAllowExtmapMixed(window) {
      /* remove a=extmap-allow-mixed for webrtc.org < M71 */
      if (!window.RTCPeerConnection) {
        return;
      }
      var browserDetails = utils.detectBrowser(window);
      if (browserDetails.browser === 'chrome' && browserDetails.version >= 71) {
        return;
      }
      if (browserDetails.browser === 'safari' && browserDetails.version >= 605) {
        return;
      }
      var nativeSRD = window.RTCPeerConnection.prototype.setRemoteDescription;
      window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription(desc) {
        if (desc && desc.sdp && desc.sdp.indexOf('\na=extmap-allow-mixed') !== -1) {
          desc.sdp = desc.sdp.split('\n').filter(function (line) {
            return line.trim() !== 'a=extmap-allow-mixed';
          }).join('\n');
        }
        return nativeSRD.apply(this, arguments);
      };
    }
    
    },{"./utils":15,"sdp":17}],7:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;
    
    var _getusermedia = require('./getusermedia');
    
    Object.defineProperty(exports, 'shimGetUserMedia', {
      enumerable: true,
      get: function get() {
        return _getusermedia.shimGetUserMedia;
      }
    });
    
    var _getdisplaymedia = require('./getdisplaymedia');
    
    Object.defineProperty(exports, 'shimGetDisplayMedia', {
      enumerable: true,
      get: function get() {
        return _getdisplaymedia.shimGetDisplayMedia;
      }
    });
    exports.shimPeerConnection = shimPeerConnection;
    exports.shimReplaceTrack = shimReplaceTrack;
    
    var _utils = require('../utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    var _filtericeservers = require('./filtericeservers');
    
    var _rtcpeerconnectionShim = require('rtcpeerconnection-shim');
    
    var _rtcpeerconnectionShim2 = _interopRequireDefault(_rtcpeerconnectionShim);
    
    function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    function shimPeerConnection(window) {
      var browserDetails = utils.detectBrowser(window);
    
      if (window.RTCIceGatherer) {
        if (!window.RTCIceCandidate) {
          window.RTCIceCandidate = function RTCIceCandidate(args) {
            return args;
          };
        }
        if (!window.RTCSessionDescription) {
          window.RTCSessionDescription = function RTCSessionDescription(args) {
            return args;
          };
        }
        // this adds an additional event listener to MediaStrackTrack that signals
        // when a tracks enabled property was changed. Workaround for a bug in
        // addStream, see below. No longer required in 15025+
        if (browserDetails.version < 15025) {
          var origMSTEnabled = Object.getOwnPropertyDescriptor(window.MediaStreamTrack.prototype, 'enabled');
          Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
            set: function set(value) {
              origMSTEnabled.set.call(this, value);
              var ev = new Event('enabled');
              ev.enabled = value;
              this.dispatchEvent(ev);
            }
          });
        }
      }
    
      // ORTC defines the DTMF sender a bit different.
      // https://github.com/w3c/ortc/issues/714
      if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
        Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
          get: function get() {
            if (this._dtmf === undefined) {
              if (this.track.kind === 'audio') {
                this._dtmf = new window.RTCDtmfSender(this);
              } else if (this.track.kind === 'video') {
                this._dtmf = null;
              }
            }
            return this._dtmf;
          }
        });
      }
      // Edge currently only implements the RTCDtmfSender, not the
      // RTCDTMFSender alias. See http://draft.ortc.org/#rtcdtmfsender2*
      if (window.RTCDtmfSender && !window.RTCDTMFSender) {
        window.RTCDTMFSender = window.RTCDtmfSender;
      }
    
      var RTCPeerConnectionShim = (0, _rtcpeerconnectionShim2.default)(window, browserDetails.version);
      window.RTCPeerConnection = function RTCPeerConnection(config) {
        if (config && config.iceServers) {
          config.iceServers = (0, _filtericeservers.filterIceServers)(config.iceServers, browserDetails.version);
          utils.log('ICE servers after filtering:', config.iceServers);
        }
        return new RTCPeerConnectionShim(config);
      };
      window.RTCPeerConnection.prototype = RTCPeerConnectionShim.prototype;
    }
    
    function shimReplaceTrack(window) {
      // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
      if (window.RTCRtpSender && !('replaceTrack' in window.RTCRtpSender.prototype)) {
        window.RTCRtpSender.prototype.replaceTrack = window.RTCRtpSender.prototype.setTrack;
      }
    }
    
    },{"../utils":15,"./filtericeservers":8,"./getdisplaymedia":9,"./getusermedia":10,"rtcpeerconnection-shim":16}],8:[function(require,module,exports){
    /*
     *  Copyright (c) 2018 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.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.filterIceServers = filterIceServers;
    
    var _utils = require('../utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    // Edge does not like
    // 1) stun: filtered after 14393 unless ?transport=udp is present
    // 2) turn: that does not have all of turn:host:port?transport=udp
    // 3) turn: with ipv6 addresses
    // 4) turn: occurring muliple times
    function filterIceServers(iceServers, edgeVersion) {
      var hasTurn = false;
      iceServers = JSON.parse(JSON.stringify(iceServers));
      return iceServers.filter(function (server) {
        if (server && (server.urls || server.url)) {
          var urls = server.urls || server.url;
          if (server.url && !server.urls) {
            utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
          }
          var isString = typeof urls === 'string';
          if (isString) {
            urls = [urls];
          }
          urls = urls.filter(function (url) {
            // filter STUN unconditionally.
            if (url.indexOf('stun:') === 0) {
              return false;
            }
    
            var validTurn = url.startsWith('turn') && !url.startsWith('turn:[') && url.includes('transport=udp');
            if (validTurn && !hasTurn) {
              hasTurn = true;
              return true;
            }
            return validTurn && !hasTurn;
          });
    
          delete server.url;
          server.urls = isString ? urls[0] : urls;
          return !!urls.length;
        }
      });
    }
    
    },{"../utils":15}],9:[function(require,module,exports){
    /*
     *  Copyright (c) 2018 The adapter.js 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.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetDisplayMedia = shimGetDisplayMedia;
    function shimGetDisplayMedia(window) {
      if (!('getDisplayMedia' in window.navigator)) {
        return;
      }
      if (!window.navigator.mediaDevices) {
        return;
      }
      if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
        return;
      }
      window.navigator.mediaDevices.getDisplayMedia = window.navigator.getDisplayMedia.bind(window.navigator);
    }
    
    },{}],10:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetUserMedia = shimGetUserMedia;
    function shimGetUserMedia(window) {
      var navigator = window && window.navigator;
    
      var shimError_ = function shimError_(e) {
        return {
          name: { PermissionDeniedError: 'NotAllowedError' }[e.name] || e.name,
          message: e.message,
          constraint: e.constraint,
          toString: function toString() {
            return this.name;
          }
        };
      };
    
      // getUserMedia error shim.
      var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
      navigator.mediaDevices.getUserMedia = function (c) {
        return origGetUserMedia(c).catch(function (e) {
          return Promise.reject(shimError_(e));
        });
      };
    }
    
    },{}],11:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    var _getusermedia = require('./getusermedia');
    
    Object.defineProperty(exports, 'shimGetUserMedia', {
      enumerable: true,
      get: function get() {
        return _getusermedia.shimGetUserMedia;
      }
    });
    
    var _getdisplaymedia = require('./getdisplaymedia');
    
    Object.defineProperty(exports, 'shimGetDisplayMedia', {
      enumerable: true,
      get: function get() {
        return _getdisplaymedia.shimGetDisplayMedia;
      }
    });
    exports.shimOnTrack = shimOnTrack;
    exports.shimPeerConnection = shimPeerConnection;
    exports.shimSenderGetStats = shimSenderGetStats;
    exports.shimReceiverGetStats = shimReceiverGetStats;
    exports.shimRemoveStream = shimRemoveStream;
    exports.shimRTCDataChannel = shimRTCDataChannel;
    exports.shimAddTransceiver = shimAddTransceiver;
    exports.shimGetParameters = shimGetParameters;
    exports.shimCreateOffer = shimCreateOffer;
    exports.shimCreateAnswer = shimCreateAnswer;
    
    var _utils = require('../utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
    
    function shimOnTrack(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
        Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
          get: function get() {
            return { receiver: this.receiver };
          }
        });
      }
    }
    
    function shimPeerConnection(window) {
      var browserDetails = utils.detectBrowser(window);
    
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !(window.RTCPeerConnection || window.mozRTCPeerConnection)) {
        return; // probably media.peerconnection.enabled=false in about:config
      }
      if (!window.RTCPeerConnection && window.mozRTCPeerConnection) {
        // very basic support for old versions.
        window.RTCPeerConnection = window.mozRTCPeerConnection;
      }
    
      if (browserDetails.version < 53) {
        // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
        ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'].forEach(function (method) {
          var nativeMethod = window.RTCPeerConnection.prototype[method];
          var methodObj = _defineProperty({}, method, function () {
            arguments[0] = new (method === 'addIceCandidate' ? window.RTCIceCandidate : window.RTCSessionDescription)(arguments[0]);
            return nativeMethod.apply(this, arguments);
          });
          window.RTCPeerConnection.prototype[method] = methodObj[method];
        });
      }
    
      // support for addIceCandidate(null or undefined)
      // as well as ignoring {sdpMid, candidate: ""}
      if (browserDetails.version < 68) {
        var nativeAddIceCandidate = window.RTCPeerConnection.prototype.addIceCandidate;
        window.RTCPeerConnection.prototype.addIceCandidate = function addIceCandidate() {
          if (!arguments[0]) {
            if (arguments[1]) {
              arguments[1].apply(null);
            }
            return Promise.resolve();
          }
          // Firefox 68+ emits and processes {candidate: "", ...}, ignore
          // in older versions.
          if (arguments[0] && arguments[0].candidate === '') {
            return Promise.resolve();
          }
          return nativeAddIceCandidate.apply(this, arguments);
        };
      }
    
      var modernStatsTypes = {
        inboundrtp: 'inbound-rtp',
        outboundrtp: 'outbound-rtp',
        candidatepair: 'candidate-pair',
        localcandidate: 'local-candidate',
        remotecandidate: 'remote-candidate'
      };
    
      var nativeGetStats = window.RTCPeerConnection.prototype.getStats;
      window.RTCPeerConnection.prototype.getStats = function getStats() {
        var _arguments = Array.prototype.slice.call(arguments),
            selector = _arguments[0],
            onSucc = _arguments[1],
            onErr = _arguments[2];
    
        return nativeGetStats.apply(this, [selector || null]).then(function (stats) {
          if (browserDetails.version < 53 && !onSucc) {
            // Shim only promise getStats with spec-hyphens in type names
            // Leave callback version alone; misc old uses of forEach before Map
            try {
              stats.forEach(function (stat) {
                stat.type = modernStatsTypes[stat.type] || stat.type;
              });
            } catch (e) {
              if (e.name !== 'TypeError') {
                throw e;
              }
              // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
              stats.forEach(function (stat, i) {
                stats.set(i, Object.assign({}, stat, {
                  type: modernStatsTypes[stat.type] || stat.type
                }));
              });
            }
          }
          return stats;
        }).then(onSucc, onErr);
      };
    }
    
    function shimSenderGetStats(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
        return;
      }
      if (window.RTCRtpSender && 'getStats' in window.RTCRtpSender.prototype) {
        return;
      }
      var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
      if (origGetSenders) {
        window.RTCPeerConnection.prototype.getSenders = function getSenders() {
          var _this = this;
    
          var senders = origGetSenders.apply(this, []);
          senders.forEach(function (sender) {
            return sender._pc = _this;
          });
          return senders;
        };
      }
    
      var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
      if (origAddTrack) {
        window.RTCPeerConnection.prototype.addTrack = function addTrack() {
          var sender = origAddTrack.apply(this, arguments);
          sender._pc = this;
          return sender;
        };
      }
      window.RTCRtpSender.prototype.getStats = function getStats() {
        return this.track ? this._pc.getStats(this.track) : Promise.resolve(new Map());
      };
    }
    
    function shimReceiverGetStats(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
        return;
      }
      if (window.RTCRtpSender && 'getStats' in window.RTCRtpReceiver.prototype) {
        return;
      }
      var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
      if (origGetReceivers) {
        window.RTCPeerConnection.prototype.getReceivers = function getReceivers() {
          var _this2 = this;
    
          var receivers = origGetReceivers.apply(this, []);
          receivers.forEach(function (receiver) {
            return receiver._pc = _this2;
          });
          return receivers;
        };
      }
      utils.wrapPeerConnectionEvent(window, 'track', function (e) {
        e.receiver._pc = e.srcElement;
        return e;
      });
      window.RTCRtpReceiver.prototype.getStats = function getStats() {
        return this._pc.getStats(this.track);
      };
    }
    
    function shimRemoveStream(window) {
      if (!window.RTCPeerConnection || 'removeStream' in window.RTCPeerConnection.prototype) {
        return;
      }
      window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
        var _this3 = this;
    
        utils.deprecated('removeStream', 'removeTrack');
        this.getSenders().forEach(function (sender) {
          if (sender.track && stream.getTracks().includes(sender.track)) {
            _this3.removeTrack(sender);
          }
        });
      };
    }
    
    function shimRTCDataChannel(window) {
      // rename DataChannel to RTCDataChannel (native fix in FF60):
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1173851
      if (window.DataChannel && !window.RTCDataChannel) {
        window.RTCDataChannel = window.DataChannel;
      }
    }
    
    function shimAddTransceiver(window) {
      // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
      // Firefox ignores the init sendEncodings options passed to addTransceiver
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
        return;
      }
      var origAddTransceiver = window.RTCPeerConnection.prototype.addTransceiver;
      if (origAddTransceiver) {
        window.RTCPeerConnection.prototype.addTransceiver = function addTransceiver() {
          this.setParametersPromises = [];
          var initParameters = arguments[1];
          var shouldPerformCheck = initParameters && 'sendEncodings' in initParameters;
          if (shouldPerformCheck) {
            // If sendEncodings params are provided, validate grammar
            initParameters.sendEncodings.forEach(function (encodingParam) {
              if ('rid' in encodingParam) {
                var ridRegex = /^[a-z0-9]{0,16}$/i;
                if (!ridRegex.test(encodingParam.rid)) {
                  throw new TypeError('Invalid RID value provided.');
                }
              }
              if ('scaleResolutionDownBy' in encodingParam) {
                if (!(parseFloat(encodingParam.scaleResolutionDownBy) >= 1.0)) {
                  throw new RangeError('scale_resolution_down_by must be >= 1.0');
                }
              }
              if ('maxFramerate' in encodingParam) {
                if (!(parseFloat(encodingParam.maxFramerate) >= 0)) {
                  throw new RangeError('max_framerate must be >= 0.0');
                }
              }
            });
          }
          var transceiver = origAddTransceiver.apply(this, arguments);
          if (shouldPerformCheck) {
            // Check if the init options were applied. If not we do this in an
            // asynchronous way and save the promise reference in a global object.
            // This is an ugly hack, but at the same time is way more robust than
            // checking the sender parameters before and after the createOffer
            // Also note that after the createoffer we are not 100% sure that
            // the params were asynchronously applied so we might miss the
            // opportunity to recreate offer.
            var sender = transceiver.sender;
    
            var params = sender.getParameters();
            if (!('encodings' in params)) {
              params.encodings = initParameters.sendEncodings;
              sender.sendEncodings = initParameters.sendEncodings;
              this.setParametersPromises.push(sender.setParameters(params).then(function () {
                delete sender.sendEncodings;
              }).catch(function () {
                delete sender.sendEncodings;
              }));
            }
          }
          return transceiver;
        };
      }
    }
    
    function shimGetParameters(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCRtpSender)) {
        return;
      }
      var origGetParameters = window.RTCRtpSender.prototype.getParameters;
      if (origGetParameters) {
        window.RTCRtpSender.prototype.getParameters = function getParameters() {
          var params = origGetParameters.apply(this, arguments);
          if (!('sendEncodings' in this)) {
            return params;
          }
          return Object.assign({}, { encodings: this.sendEncodings }, params);
        };
      }
    }
    
    function shimCreateOffer(window) {
      // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
      // Firefox ignores the init sendEncodings options passed to addTransceiver
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
        return;
      }
      var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
      window.RTCPeerConnection.prototype.createOffer = function createOffer() {
        var _this4 = this,
            _arguments2 = arguments;
    
        if (this.setParametersPromises && this.setParametersPromises.length) {
          return Promise.all(this.setParametersPromises).then(function () {
            return origCreateOffer.apply(_this4, _arguments2);
          }).finally(function () {
            _this4.setParametersPromises = [];
          });
        }
        return origCreateOffer.apply(this, arguments);
      };
    }
    
    function shimCreateAnswer(window) {
      // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
      // Firefox ignores the init sendEncodings options passed to addTransceiver
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
        return;
      }
      var origCreateAnswer = window.RTCPeerConnection.prototype.createAnswer;
      window.RTCPeerConnection.prototype.createAnswer = function createAnswer() {
        var _this5 = this,
            _arguments3 = arguments;
    
        if (this.setParametersPromises && this.setParametersPromises.length) {
          return Promise.all(this.setParametersPromises).then(function () {
            return origCreateAnswer.apply(_this5, _arguments3);
          }).finally(function () {
            _this5.setParametersPromises = [];
          });
        }
        return origCreateAnswer.apply(this, arguments);
      };
    }
    
    },{"../utils":15,"./getdisplaymedia":12,"./getusermedia":13}],12:[function(require,module,exports){
    /*
     *  Copyright (c) 2018 The adapter.js 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.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    exports.shimGetDisplayMedia = shimGetDisplayMedia;
    function shimGetDisplayMedia(window, preferredMediaSource) {
      if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
        return;
      }
      if (!window.navigator.mediaDevices) {
        return;
      }
      window.navigator.mediaDevices.getDisplayMedia = function getDisplayMedia(constraints) {
        if (!(constraints && constraints.video)) {
          var err = new DOMException('getDisplayMedia without video ' + 'constraints is undefined');
          err.name = 'NotFoundError';
          // from https://heycam.github.io/webidl/#idl-DOMException-error-names
          err.code = 8;
          return Promise.reject(err);
        }
        if (constraints.video === true) {
          constraints.video = { mediaSource: preferredMediaSource };
        } else {
          constraints.video.mediaSource = preferredMediaSource;
        }
        return window.navigator.mediaDevices.getUserMedia(constraints);
      };
    }
    
    },{}],13:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    exports.shimGetUserMedia = shimGetUserMedia;
    
    var _utils = require('../utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    function shimGetUserMedia(window) {
      var browserDetails = utils.detectBrowser(window);
      var navigator = window && window.navigator;
      var MediaStreamTrack = window && window.MediaStreamTrack;
    
      navigator.getUserMedia = function (constraints, onSuccess, onError) {
        // Replace Firefox 44+'s deprecation warning with unprefixed version.
        utils.deprecated('navigator.getUserMedia', 'navigator.mediaDevices.getUserMedia');
        navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
      };
    
      if (!(browserDetails.version > 55 && 'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
        var remap = function remap(obj, a, b) {
          if (a in obj && !(b in obj)) {
            obj[b] = obj[a];
            delete obj[a];
          }
        };
    
        var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
        navigator.mediaDevices.getUserMedia = function (c) {
          if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object' && _typeof(c.audio) === 'object') {
            c = JSON.parse(JSON.stringify(c));
            remap(c.audio, 'autoGainControl', 'mozAutoGainControl');
            remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression');
          }
          return nativeGetUserMedia(c);
        };
    
        if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
          var nativeGetSettings = MediaStreamTrack.prototype.getSettings;
          MediaStreamTrack.prototype.getSettings = function () {
            var obj = nativeGetSettings.apply(this, arguments);
            remap(obj, 'mozAutoGainControl', 'autoGainControl');
            remap(obj, 'mozNoiseSuppression', 'noiseSuppression');
            return obj;
          };
        }
    
        if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
          var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints;
          MediaStreamTrack.prototype.applyConstraints = function (c) {
            if (this.kind === 'audio' && (typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object') {
              c = JSON.parse(JSON.stringify(c));
              remap(c, 'autoGainControl', 'mozAutoGainControl');
              remap(c, 'noiseSuppression', 'mozNoiseSuppression');
            }
            return nativeApplyConstraints.apply(this, [c]);
          };
        }
      }
    }
    
    },{"../utils":15}],14:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    exports.shimLocalStreamsAPI = shimLocalStreamsAPI;
    exports.shimRemoteStreamsAPI = shimRemoteStreamsAPI;
    exports.shimCallbacksAPI = shimCallbacksAPI;
    exports.shimGetUserMedia = shimGetUserMedia;
    exports.shimConstraints = shimConstraints;
    exports.shimRTCIceServerUrls = shimRTCIceServerUrls;
    exports.shimTrackEventTransceiver = shimTrackEventTransceiver;
    exports.shimCreateOfferLegacy = shimCreateOfferLegacy;
    exports.shimAudioContext = shimAudioContext;
    
    var _utils = require('../utils');
    
    var utils = _interopRequireWildcard(_utils);
    
    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
    
    function shimLocalStreamsAPI(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
        return;
      }
      if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
        window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
          if (!this._localStreams) {
            this._localStreams = [];
          }
          return this._localStreams;
        };
      }
      if (!('addStream' in window.RTCPeerConnection.prototype)) {
        var _addTrack = window.RTCPeerConnection.prototype.addTrack;
        window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
          var _this = this;
    
          if (!this._localStreams) {
            this._localStreams = [];
          }
          if (!this._localStreams.includes(stream)) {
            this._localStreams.push(stream);
          }
          // Try to emulate Chrome's behaviour of adding in audio-video order.
          // Safari orders by track id.
          stream.getAudioTracks().forEach(function (track) {
            return _addTrack.call(_this, track, stream);
          });
          stream.getVideoTracks().forEach(function (track) {
            return _addTrack.call(_this, track, stream);
          });
        };
    
        window.RTCPeerConnection.prototype.addTrack = function addTrack(track) {
          var _this2 = this;
    
          for (var _len = arguments.length, streams = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
            streams[_key - 1] = arguments[_key];
          }
    
          if (streams) {
            streams.forEach(function (stream) {
              if (!_this2._localStreams) {
                _this2._localStreams = [stream];
              } else if (!_this2._localStreams.includes(stream)) {
                _this2._localStreams.push(stream);
              }
            });
          }
          return _addTrack.apply(this, arguments);
        };
      }
      if (!('removeStream' in window.RTCPeerConnection.prototype)) {
        window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
          var _this3 = this;
    
          if (!this._localStreams) {
            this._localStreams = [];
          }
          var index = this._localStreams.indexOf(stream);
          if (index === -1) {
            return;
          }
          this._localStreams.splice(index, 1);
          var tracks = stream.getTracks();
          this.getSenders().forEach(function (sender) {
            if (tracks.includes(sender.track)) {
              _this3.removeTrack(sender);
            }
          });
        };
      }
    }
    
    function shimRemoteStreamsAPI(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
        return;
      }
      if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
        window.RTCPeerConnection.prototype.getRemoteStreams = function getRemoteStreams() {
          return this._remoteStreams ? this._remoteStreams : [];
        };
      }
      if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
        Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
          get: function get() {
            return this._onaddstream;
          },
          set: function set(f) {
            var _this4 = this;
    
            if (this._onaddstream) {
              this.removeEventListener('addstream', this._onaddstream);
              this.removeEventListener('track', this._onaddstreampoly);
            }
            this.addEventListener('addstream', this._onaddstream = f);
            this.addEventListener('track', this._onaddstreampoly = function (e) {
              e.streams.forEach(function (stream) {
                if (!_this4._remoteStreams) {
                  _this4._remoteStreams = [];
                }
                if (_this4._remoteStreams.includes(stream)) {
                  return;
                }
                _this4._remoteStreams.push(stream);
                var event = new Event('addstream');
                event.stream = stream;
                _this4.dispatchEvent(event);
              });
            });
          }
        });
        var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
        window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
          var pc = this;
          if (!this._onaddstreampoly) {
            this.addEventListener('track', this._onaddstreampoly = function (e) {
              e.streams.forEach(function (stream) {
                if (!pc._remoteStreams) {
                  pc._remoteStreams = [];
                }
                if (pc._remoteStreams.indexOf(stream) >= 0) {
                  return;
                }
                pc._remoteStreams.push(stream);
                var event = new Event('addstream');
                event.stream = stream;
                pc.dispatchEvent(event);
              });
            });
          }
          return origSetRemoteDescription.apply(pc, arguments);
        };
      }
    }
    
    function shimCallbacksAPI(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
        return;
      }
      var prototype = window.RTCPeerConnection.prototype;
      var origCreateOffer = prototype.createOffer;
      var origCreateAnswer = prototype.createAnswer;
      var setLocalDescription = prototype.setLocalDescription;
      var setRemoteDescription = prototype.setRemoteDescription;
      var addIceCandidate = prototype.addIceCandidate;
    
      prototype.createOffer = function createOffer(successCallback, failureCallback) {
        var options = arguments.length >= 2 ? arguments[2] : arguments[0];
        var promise = origCreateOffer.apply(this, [options]);
        if (!failureCallback) {
          return promise;
        }
        promise.then(successCallback, failureCallback);
        return Promise.resolve();
      };
    
      prototype.createAnswer = function createAnswer(successCallback, failureCallback) {
        var options = arguments.length >= 2 ? arguments[2] : arguments[0];
        var promise = origCreateAnswer.apply(this, [options]);
        if (!failureCallback) {
          return promise;
        }
        promise.then(successCallback, failureCallback);
        return Promise.resolve();
      };
    
      var withCallback = function withCallback(description, successCallback, failureCallback) {
        var promise = setLocalDescription.apply(this, [description]);
        if (!failureCallback) {
          return promise;
        }
        promise.then(successCallback, failureCallback);
        return Promise.resolve();
      };
      prototype.setLocalDescription = withCallback;
    
      withCallback = function withCallback(description, successCallback, failureCallback) {
        var promise = setRemoteDescription.apply(this, [description]);
        if (!failureCallback) {
          return promise;
        }
        promise.then(successCallback, failureCallback);
        return Promise.resolve();
      };
      prototype.setRemoteDescription = withCallback;
    
      withCallback = function withCallback(candidate, successCallback, failureCallback) {
        var promise = addIceCandidate.apply(this, [candidate]);
        if (!failureCallback) {
          return promise;
        }
        promise.then(successCallback, failureCallback);
        return Promise.resolve();
      };
      prototype.addIceCandidate = withCallback;
    }
    
    function shimGetUserMedia(window) {
      var navigator = window && window.navigator;
    
      if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        // shim not needed in Safari 12.1
        var mediaDevices = navigator.mediaDevices;
        var _getUserMedia = mediaDevices.getUserMedia.bind(mediaDevices);
        navigator.mediaDevices.getUserMedia = function (constraints) {
          return _getUserMedia(shimConstraints(constraints));
        };
      }
    
      if (!navigator.getUserMedia && navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        navigator.getUserMedia = function getUserMedia(constraints, cb, errcb) {
          navigator.mediaDevices.getUserMedia(constraints).then(cb, errcb);
        }.bind(navigator);
      }
    }
    
    function shimConstraints(constraints) {
      if (constraints && constraints.video !== undefined) {
        return Object.assign({}, constraints, { video: utils.compactObject(constraints.video) });
      }
    
      return constraints;
    }
    
    function shimRTCIceServerUrls(window) {
      if (!window.RTCPeerConnection) {
        return;
      }
      // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
      var OrigPeerConnection = window.RTCPeerConnection;
      window.RTCPeerConnection = function RTCPeerConnection(pcConfig, pcConstraints) {
        if (pcConfig && pcConfig.iceServers) {
          var newIceServers = [];
          for (var i = 0; i < pcConfig.iceServers.length; i++) {
            var server = pcConfig.iceServers[i];
            if (!server.hasOwnProperty('urls') && server.hasOwnProperty('url')) {
              utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
              server = JSON.parse(JSON.stringify(server));
              server.urls = server.url;
              delete server.url;
              newIceServers.push(server);
            } else {
              newIceServers.push(pcConfig.iceServers[i]);
            }
          }
          pcConfig.iceServers = newIceServers;
        }
        return new OrigPeerConnection(pcConfig, pcConstraints);
      };
      window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
      // wrap static methods. Currently just generateCertificate.
      if ('generateCertificate' in OrigPeerConnection) {
        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
          get: function get() {
            return OrigPeerConnection.generateCertificate;
          }
        });
      }
    }
    
    function shimTrackEventTransceiver(window) {
      // Add event.transceiver member over deprecated event.receiver
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
        Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
          get: function get() {
            return { receiver: this.receiver };
          }
        });
      }
    }
    
    function shimCreateOfferLegacy(window) {
      var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
      window.RTCPeerConnection.prototype.createOffer = function createOffer(offerOptions) {
        if (offerOptions) {
          if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
            // support bit values
            offerOptions.offerToReceiveAudio = !!offerOptions.offerToReceiveAudio;
          }
          var audioTransceiver = this.getTransceivers().find(function (transceiver) {
            return transceiver.receiver.track.kind === 'audio';
          });
          if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
            if (audioTransceiver.direction === 'sendrecv') {
              if (audioTransceiver.setDirection) {
                audioTransceiver.setDirection('sendonly');
              } else {
                audioTransceiver.direction = 'sendonly';
              }
            } else if (audioTransceiver.direction === 'recvonly') {
              if (audioTransceiver.setDirection) {
                audioTransceiver.setDirection('inactive');
              } else {
                audioTransceiver.direction = 'inactive';
              }
            }
          } else if (offerOptions.offerToReceiveAudio === true && !audioTransceiver) {
            this.addTransceiver('audio');
          }
    
          if (typeof offerOptions.offerToReceiveVideo !== 'undefined') {
            // support bit values
            offerOptions.offerToReceiveVideo = !!offerOptions.offerToReceiveVideo;
          }
          var videoTransceiver = this.getTransceivers().find(function (transceiver) {
            return transceiver.receiver.track.kind === 'video';
          });
          if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
            if (videoTransceiver.direction === 'sendrecv') {
              if (videoTransceiver.setDirection) {
                videoTransceiver.setDirection('sendonly');
              } else {
                videoTransceiver.direction = 'sendonly';
              }
            } else if (videoTransceiver.direction === 'recvonly') {
              if (videoTransceiver.setDirection) {
                videoTransceiver.setDirection('inactive');
              } else {
                videoTransceiver.direction = 'inactive';
              }
            }
          } else if (offerOptions.offerToReceiveVideo === true && !videoTransceiver) {
            this.addTransceiver('video');
          }
        }
        return origCreateOffer.apply(this, arguments);
      };
    }
    
    function shimAudioContext(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || window.AudioContext) {
        return;
      }
      window.AudioContext = window.webkitAudioContext;
    }
    
    },{"../utils":15}],15:[function(require,module,exports){
    /*
     *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
     *
     *  Use of this source code is governed by a BSD-style license
     *  that can be found in the LICENSE file in the root of the source
     *  tree.
     */
    /* eslint-env node */
    'use strict';
    
    Object.defineProperty(exports, "__esModule", {
      value: true
    });
    
    var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
    
    exports.extractVersion = extractVersion;
    exports.wrapPeerConnectionEvent = wrapPeerConnectionEvent;
    exports.disableLog = disableLog;
    exports.disableWarnings = disableWarnings;
    exports.log = log;
    exports.deprecated = deprecated;
    exports.detectBrowser = detectBrowser;
    exports.compactObject = compactObject;
    exports.walkStats = walkStats;
    exports.filterStats = filterStats;
    
    function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
    
    var logDisabled_ = true;
    var deprecationWarnings_ = true;
    
    /**
     * Extract browser version out of the provided user agent string.
     *
     * @param {!string} uastring userAgent string.
     * @param {!string} expr Regular expression used as match criteria.
     * @param {!number} pos position in the version string to be returned.
     * @return {!number} browser version.
     */
    function extractVersion(uastring, expr, pos) {
      var match = uastring.match(expr);
      return match && match.length >= pos && parseInt(match[pos], 10);
    }
    
    // Wraps the peerconnection event eventNameToWrap in a function
    // which returns the modified event object (or false to prevent
    // the event).
    function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
      if (!window.RTCPeerConnection) {
        return;
      }
      var proto = window.RTCPeerConnection.prototype;
      var nativeAddEventListener = proto.addEventListener;
      proto.addEventListener = function (nativeEventName, cb) {
        if (nativeEventName !== eventNameToWrap) {
          return nativeAddEventListener.apply(this, arguments);
        }
        var wrappedCallback = function wrappedCallback(e) {
          var modifiedEvent = wrapper(e);
          if (modifiedEvent) {
            if (cb.handleEvent) {
              cb.handleEvent(modifiedEvent);
            } else {
              cb(modifiedEvent);
            }
          }
        };
        this._eventMap = this._eventMap || {};
        if (!this._eventMap[eventNameToWrap]) {
          this._eventMap[eventNameToWrap] = new Map();
        }
        this._eventMap[eventNameToWrap].set(cb, wrappedCallback);
        return nativeAddEventListener.apply(this, [nativeEventName, wrappedCallback]);
      };
    
      var nativeRemoveEventListener = proto.removeEventListener;
      proto.removeEventListener = function (nativeEventName, cb) {
        if (nativeEventName !== eventNameToWrap || !this._eventMap || !this._eventMap[eventNameToWrap]) {
          return nativeRemoveEventListener.apply(this, arguments);
        }
        if (!this._eventMap[eventNameToWrap].has(cb)) {
          return nativeRemoveEventListener.apply(this, arguments);
        }
        var unwrappedCb = this._eventMap[eventNameToWrap].get(cb);
        this._eventMap[eventNameToWrap].delete(cb);
        if (this._eventMap[eventNameToWrap].size === 0) {
          delete this._eventMap[eventNameToWrap];
        }
        if (Object.keys(this._eventMap).length === 0) {
          delete this._eventMap;
        }
        return nativeRemoveEventListener.apply(this, [nativeEventName, unwrappedCb]);
      };
    
      Object.defineProperty(proto, 'on' + eventNameToWrap, {
        get: function get() {
          return this['_on' + eventNameToWrap];
        },
        set: function set(cb) {
          if (this['_on' + eventNameToWrap]) {
            this.removeEventListener(eventNameToWrap, this['_on' + eventNameToWrap]);
            delete this['_on' + eventNameToWrap];
          }
          if (cb) {
            this.addEventListener(eventNameToWrap, this['_on' + eventNameToWrap] = cb);
          }
        },
    
        enumerable: true,
        configurable: true
      });
    }
    
    function disableLog(bool) {
      if (typeof bool !== 'boolean') {
        return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.');
      }
      logDisabled_ = bool;
      return bool ? 'adapter.js logging disabled' : 'adapter.js logging enabled';
    }
    
    /**
     * Disable or enable deprecation warnings
     * @param {!boolean} bool set to true to disable warnings.
     */
    function disableWarnings(bool) {
      if (typeof bool !== 'boolean') {
        return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.');
      }
      deprecationWarnings_ = !bool;
      return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
    }
    
    function log() {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object') {
        if (logDisabled_) {
          return;
        }
        if (typeof console !== 'undefined' && typeof console.log === 'function') {
          console.log.apply(console, arguments);
        }
      }
    }
    
    /**
     * Shows a deprecation warning suggesting the modern and spec-compatible API.
     */
    function deprecated(oldMethod, newMethod) {
      if (!deprecationWarnings_) {
        return;
      }
      console.warn(oldMethod + ' is deprecated, please use ' + newMethod + ' instead.');
    }
    
    /**
     * Browser detector.
     *
     * @return {object} result containing browser and version
     *     properties.
     */
    function detectBrowser(window) {
      var navigator = window.navigator;
    
      // Returned result object.
    
      var result = { browser: null, version: null };
    
      // Fail early if it's not a browser
      if (typeof window === 'undefined' || !window.navigator) {
        result.browser = 'Not a browser.';
        return result;
      }
    
      if (navigator.mozGetUserMedia) {
        // Firefox.
        result.browser = 'firefox';
        result.version = extractVersion(navigator.userAgent, /Firefox\/(\d+)\./, 1);
      } else if (navigator.webkitGetUserMedia || window.isSecureContext === false && window.webkitRTCPeerConnection && !window.RTCIceGatherer) {
        // Chrome, Chromium, Webview, Opera.
        // Version matches Chrome/WebRTC version.
        // Chrome 74 removed webkitGetUserMedia on http as well so we need the
        // more complicated fallback to webkitRTCPeerConnection.
        result.browser = 'chrome';
        result.version = extractVersion(navigator.userAgent, /Chrom(e|ium)\/(\d+)\./, 2);
      } else if (navigator.mediaDevices && navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) {
        // Edge.
        result.browser = 'edge';
        result.version = extractVersion(navigator.userAgent, /Edge\/(\d+).(\d+)$/, 2);
      } else if (window.RTCPeerConnection && navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
        // Safari.
        result.browser = 'safari';
        result.version = extractVersion(navigator.userAgent, /AppleWebKit\/(\d+)\./, 1);
        result.supportsUnifiedPlan = window.RTCRtpTransceiver && 'currentDirection' in window.RTCRtpTransceiver.prototype;
      } else {
        // Default fallthrough: not supported.
        result.browser = 'Not a supported browser.';
        return result;
      }
    
      return result;
    }
    
    /**
     * Checks if something is an object.
     *
     * @param {*} val The something you want to check.
     * @return true if val is an object, false otherwise.
     */
    function isObject(val) {
      return Object.prototype.toString.call(val) === '[object Object]';
    }
    
    /**
     * Remove all empty objects and undefined values
     * from a nested object -- an enhanced and vanilla version
     * of Lodash's `compact`.
     */
    function compactObject(data) {
      if (!isObject(data)) {
        return data;
      }
    
      return Object.keys(data).reduce(function (accumulator, key) {
        var isObj = isObject(data[key]);
        var value = isObj ? compactObject(data[key]) : data[key];
        var isEmptyObject = isObj && !Object.keys(value).length;
        if (value === undefined || isEmptyObject) {
          return accumulator;
        }
        return Object.assign(accumulator, _defineProperty({}, key, value));
      }, {});
    }
    
    /* iterates the stats graph recursively. */
    function walkStats(stats, base, resultSet) {
      if (!base || resultSet.has(base.id)) {
        return;
      }
      resultSet.set(base.id, base);
      Object.keys(base).forEach(function (name) {
        if (name.endsWith('Id')) {
          walkStats(stats, stats.get(base[name]), resultSet);
        } else if (name.endsWith('Ids')) {
          base[name].forEach(function (id) {
            walkStats(stats, stats.get(id), resultSet);
          });
        }
      });
    }
    
    /* filter getStats for a sender/receiver track. */
    function filterStats(result, track, outbound) {
      var streamStatsType = outbound ? 'outbound-rtp' : 'inbound-rtp';
      var filteredResult = new Map();
      if (track === null) {
        return filteredResult;
      }
      var trackStats = [];
      result.forEach(function (value) {
        if (value.type === 'track' && value.trackIdentifier === track.id) {
          trackStats.push(value);
        }
      });
      trackStats.forEach(function (trackStat) {
        result.forEach(function (stats) {
          if (stats.type === streamStatsType && stats.trackId === trackStat.id) {
            walkStats(result, stats, filteredResult);
          }
        });
      });
      return filteredResult;
    }
    
    },{}],16:[function(require,module,exports){
    /*
     *  Copyright (c) 2017 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.
     */
     /* eslint-env node */
    'use strict';
    
    var SDPUtils = require('sdp');
    
    function fixStatsType(stat) {
      return {
        inboundrtp: 'inbound-rtp',
        outboundrtp: 'outbound-rtp',
        candidatepair: 'candidate-pair',
        localcandidate: 'local-candidate',
        remotecandidate: 'remote-candidate'
      }[stat.type] || stat.type;
    }
    
    function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
      var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
    
      // Map ICE parameters (ufrag, pwd) to SDP.
      sdp += SDPUtils.writeIceParameters(
          transceiver.iceGatherer.getLocalParameters());
    
      // Map DTLS parameters to SDP.
      sdp += SDPUtils.writeDtlsParameters(
          transceiver.dtlsTransport.getLocalParameters(),
          type === 'offer' ? 'actpass' : dtlsRole || 'active');
    
      sdp += 'a=mid:' + transceiver.mid + '\r\n';
    
      if (transceiver.rtpSender && transceiver.rtpReceiver) {
        sdp += 'a=sendrecv\r\n';
      } else if (transceiver.rtpSender) {
        sdp += 'a=sendonly\r\n';
      } else if (transceiver.rtpReceiver) {
        sdp += 'a=recvonly\r\n';
      } else {
        sdp += 'a=inactive\r\n';
      }
    
      if (transceiver.rtpSender) {
        var trackId = transceiver.rtpSender._initialTrackId ||
            transceiver.rtpSender.track.id;
        transceiver.rtpSender._initialTrackId = trackId;
        // spec.
        var msid = 'msid:' + (stream ? stream.id : '-') + ' ' +
            trackId + '\r\n';
        sdp += 'a=' + msid;
        // for Chrome. Legacy should no longer be required.
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
            ' ' + msid;
    
        // RTX
        if (transceiver.sendEncodingParameters[0].rtx) {
          sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
              ' ' + msid;
          sdp += 'a=ssrc-group:FID ' +
              transceiver.sendEncodingParameters[0].ssrc + ' ' +
              transceiver.sendEncodingParameters[0].rtx.ssrc +
              '\r\n';
        }
      }
      // FIXME: this should be written by writeRtpDescription.
      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
          ' cname:' + SDPUtils.localCName + '\r\n';
      if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
            ' cname:' + SDPUtils.localCName + '\r\n';
      }
      return sdp;
    }
    
    // Edge does not like
    // 1) stun: filtered after 14393 unless ?transport=udp is present
    // 2) turn: that does not have all of turn:host:port?transport=udp
    // 3) turn: with ipv6 addresses
    // 4) turn: occurring muliple times
    function filterIceServers(iceServers, edgeVersion) {
      var hasTurn = false;
      iceServers = JSON.parse(JSON.stringify(iceServers));
      return iceServers.filter(function(server) {
        if (server && (server.urls || server.url)) {
          var urls = server.urls || server.url;
          if (server.url && !server.urls) {
            console.warn('RTCIceServer.url is deprecated! Use urls instead.');
          }
          var isString = typeof urls === 'string';
          if (isString) {
            urls = [urls];
          }
          urls = urls.filter(function(url) {
            var validTurn = url.indexOf('turn:') === 0 &&
                url.indexOf('transport=udp') !== -1 &&
                url.indexOf('turn:[') === -1 &&
                !hasTurn;
    
            if (validTurn) {
              hasTurn = true;
              return true;
            }
            return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
                url.indexOf('?transport=udp') === -1;
          });
    
          delete server.url;
          server.urls = isString ? urls[0] : urls;
          return !!urls.length;
        }
      });
    }
    
    // Determines the intersection of local and remote capabilities.
    function getCommonCapabilities(localCapabilities, remoteCapabilities) {
      var commonCapabilities = {
        codecs: [],
        headerExtensions: [],
        fecMechanisms: []
      };
    
      var findCodecByPayloadType = function(pt, codecs) {
        pt = parseInt(pt, 10);
        for (var i = 0; i < codecs.length; i++) {
          if (codecs[i].payloadType === pt ||
              codecs[i].preferredPayloadType === pt) {
            return codecs[i];
          }
        }
      };
    
      var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
        var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs);
        var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs);
        return lCodec && rCodec &&
            lCodec.name.toLowerCase() === rCodec.name.toLowerCase();
      };
    
      localCapabilities.codecs.forEach(function(lCodec) {
        for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
          var rCodec = remoteCapabilities.codecs[i];
          if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
              lCodec.clockRate === rCodec.clockRate) {
            if (lCodec.name.toLowerCase() === 'rtx' &&
                lCodec.parameters && rCodec.parameters.apt) {
              // for RTX we need to find the local rtx that has a apt
              // which points to the same local codec as the remote one.
              if (!rtxCapabilityMatches(lCodec, rCodec,
                  localCapabilities.codecs, remoteCapabilities.codecs)) {
                continue;
              }
            }
            rCodec = JSON.parse(JSON.stringify(rCodec)); // deepcopy
            // number of channels is the highest common number of channels
            rCodec.numChannels = Math.min(lCodec.numChannels,
                rCodec.numChannels);
            // push rCodec so we reply with offerer payload type
            commonCapabilities.codecs.push(rCodec);
    
            // determine common feedback mechanisms
            rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
              for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
                if (lCodec.rtcpFeedback[j].type === fb.type &&
                    lCodec.rtcpFeedback[j].parameter === fb.parameter) {
                  return true;
                }
              }
              return false;
            });
            // FIXME: also need to determine .parameters
            //  see https://github.com/openpeer/ortc/issues/569
            break;
          }
        }
      });
    
      localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
        for (var i = 0; i < remoteCapabilities.headerExtensions.length;
             i++) {
          var rHeaderExtension = remoteCapabilities.headerExtensions[i];
          if (lHeaderExtension.uri === rHeaderExtension.uri) {
            commonCapabilities.headerExtensions.push(rHeaderExtension);
            break;
          }
        }
      });
    
      // FIXME: fecMechanisms
      return commonCapabilities;
    }
    
    // is action=setLocalDescription with type allowed in signalingState
    function isActionAllowedInSignalingState(action, type, signalingState) {
      return {
        offer: {
          setLocalDescription: ['stable', 'have-local-offer'],
          setRemoteDescription: ['stable', 'have-remote-offer']
        },
        answer: {
          setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
          setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
        }
      }[type][action].indexOf(signalingState) !== -1;
    }
    
    function maybeAddCandidate(iceTransport, candidate) {
      // Edge's internal representation adds some fields therefore
      // not all fieldѕ are taken into account.
      var alreadyAdded = iceTransport.getRemoteCandidates()
          .find(function(remoteCandidate) {
            return candidate.foundation === remoteCandidate.foundation &&
                candidate.ip === remoteCandidate.ip &&
                candidate.port === remoteCandidate.port &&
                candidate.priority === remoteCandidate.priority &&
                candidate.protocol === remoteCandidate.protocol &&
                candidate.type === remoteCandidate.type;
          });
      if (!alreadyAdded) {
        iceTransport.addRemoteCandidate(candidate);
      }
      return !alreadyAdded;
    }
    
    
    function makeError(name, description) {
      var e = new Error(description);
      e.name = name;
      // legacy error codes from https://heycam.github.io/webidl/#idl-DOMException-error-names
      e.code = {
        NotSupportedError: 9,
        InvalidStateError: 11,
        InvalidAccessError: 15,
        TypeError: undefined,
        OperationError: undefined
      }[name];
      return e;
    }
    
    module.exports = function(window, edgeVersion) {
      // https://w3c.github.io/mediacapture-main/#mediastream
      // Helper function to add the track to the stream and
      // dispatch the event ourselves.
      function addTrackToStreamAndFireEvent(track, stream) {
        stream.addTrack(track);
        stream.dispatchEvent(new window.MediaStreamTrackEvent('addtrack',
            {track: track}));
      }
    
      function removeTrackFromStreamAndFireEvent(track, stream) {
        stream.removeTrack(track);
        stream.dispatchEvent(new window.MediaStreamTrackEvent('removetrack',
            {track: track}));
      }
    
      function fireAddTrack(pc, track, receiver, streams) {
        var trackEvent = new Event('track');
        trackEvent.track = track;
        trackEvent.receiver = receiver;
        trackEvent.transceiver = {receiver: receiver};
        trackEvent.streams = streams;
        window.setTimeout(function() {
          pc._dispatchEvent('track', trackEvent);
        });
      }
    
      var RTCPeerConnection = function(config) {
        var pc = this;
    
        var _eventTarget = document.createDocumentFragment();
        ['addEventListener', 'removeEventListener', 'dispatchEvent']
            .forEach(function(method) {
              pc[method] = _eventTarget[method].bind(_eventTarget);
            });
    
        this.canTrickleIceCandidates = null;
    
        this.needNegotiation = false;
    
        this.localStreams = [];
        this.remoteStreams = [];
    
        this._localDescription = null;
        this._remoteDescription = null;
    
        this.signalingState = 'stable';
        this.iceConnectionState = 'new';
        this.connectionState = 'new';
        this.iceGatheringState = 'new';
    
        config = JSON.parse(JSON.stringify(config || {}));
    
        this.usingBundle = config.bundlePolicy === 'max-bundle';
        if (config.rtcpMuxPolicy === 'negotiate') {
          throw(makeError('NotSupportedError',
              'rtcpMuxPolicy \'negotiate\' is not supported'));
        } else if (!config.rtcpMuxPolicy) {
          config.rtcpMuxPolicy = 'require';
        }
    
        switch (config.iceTransportPolicy) {
          case 'all':
          case 'relay':
            break;
          default:
            config.iceTransportPolicy = 'all';
            break;
        }
    
        switch (config.bundlePolicy) {
          case 'balanced':
          case 'max-compat':
          case 'max-bundle':
            break;
          default:
            config.bundlePolicy = 'balanced';
            break;
        }
    
        config.iceServers = filterIceServers(config.iceServers || [], edgeVersion);
    
        this._iceGatherers = [];
        if (config.iceCandidatePoolSize) {
          for (var i = config.iceCandidatePoolSize; i > 0; i--) {
            this._iceGatherers.push(new window.RTCIceGatherer({
              iceServers: config.iceServers,
              gatherPolicy: config.iceTransportPolicy
            }));
          }
        } else {
          config.iceCandidatePoolSize = 0;
        }
    
        this._config = config;
    
        // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
        // everything that is needed to describe a SDP m-line.
        this.transceivers = [];
    
        this._sdpSessionId = SDPUtils.generateSessionId();
        this._sdpSessionVersion = 0;
    
        this._dtlsRole = undefined; // role for a=setup to use in answers.
    
        this._isClosed = false;
      };
    
      Object.defineProperty(RTCPeerConnection.prototype, 'localDescription', {
        configurable: true,
        get: function() {
          return this._localDescription;
        }
      });
      Object.defineProperty(RTCPeerConnection.prototype, 'remoteDescription', {
        configurable: true,
        get: function() {
          return this._remoteDescription;
        }
      });
    
      // set up event handlers on prototype
      RTCPeerConnection.prototype.onicecandidate = null;
      RTCPeerConnection.prototype.onaddstream = null;
      RTCPeerConnection.prototype.ontrack = null;
      RTCPeerConnection.prototype.onremovestream = null;
      RTCPeerConnection.prototype.onsignalingstatechange = null;
      RTCPeerConnection.prototype.oniceconnectionstatechange = null;
      RTCPeerConnection.prototype.onconnectionstatechange = null;
      RTCPeerConnection.prototype.onicegatheringstatechange = null;
      RTCPeerConnection.prototype.onnegotiationneeded = null;
      RTCPeerConnection.prototype.ondatachannel = null;
    
      RTCPeerConnection.prototype._dispatchEvent = function(name, event) {
        if (this._isClosed) {
          return;
        }
        this.dispatchEvent(event);
        if (typeof this['on' + name] === 'function') {
          this['on' + name](event);
        }
      };
    
      RTCPeerConnection.prototype._emitGatheringStateChange = function() {
        var event = new Event('icegatheringstatechange');
        this._dispatchEvent('icegatheringstatechange', event);
      };
    
      RTCPeerConnection.prototype.getConfiguration = function() {
        return this._config;
      };
    
      RTCPeerConnection.prototype.getLocalStreams = function() {
        return this.localStreams;
      };
    
      RTCPeerConnection.prototype.getRemoteStreams = function() {
        return this.remoteStreams;
      };
    
      // internal helper to create a transceiver object.
      // (which is not yet the same as the WebRTC 1.0 transceiver)
      RTCPeerConnection.prototype._createTransceiver = function(kind, doNotAdd) {
        var hasBundleTransport = this.transceivers.length > 0;
        var transceiver = {
          track: null,
          iceGatherer: null,
          iceTransport: null,
          dtlsTransport: null,
          localCapabilities: null,
          remoteCapabilities: null,
          rtpSender: null,
          rtpReceiver: null,
          kind: kind,
          mid: null,
          sendEncodingParameters: null,
          recvEncodingParameters: null,
          stream: null,
          associatedRemoteMediaStreams: [],
          wantReceive: true
        };
        if (this.usingBundle && hasBundleTransport) {
          transceiver.iceTransport = this.transceivers[0].iceTransport;
          transceiver.dtlsTransport = this.transceivers[0].dtlsTransport;
        } else {
          var transports = this._createIceAndDtlsTransports();
          transceiver.iceTransport = transports.iceTransport;
          transceiver.dtlsTransport = transports.dtlsTransport;
        }
        if (!doNotAdd) {
          this.transceivers.push(transceiver);
        }
        return transceiver;
      };
    
      RTCPeerConnection.prototype.addTrack = function(track, stream) {
        if (this._isClosed) {
          throw makeError('InvalidStateError',
              'Attempted to call addTrack on a closed peerconnection.');
        }
    
        var alreadyExists = this.transceivers.find(function(s) {
          return s.track === track;
        });
    
        if (alreadyExists) {
          throw makeError('InvalidAccessError', 'Track already exists.');
        }
    
        var transceiver;
        for (var i = 0; i < this.transceivers.length; i++) {
          if (!this.transceivers[i].track &&
              this.transceivers[i].kind === track.kind) {
            transceiver = this.transceivers[i];
          }
        }
        if (!transceiver) {
          transceiver = this._createTransceiver(track.kind);
        }
    
        this._maybeFireNegotiationNeeded();
    
        if (this.localStreams.indexOf(stream) === -1) {
          this.localStreams.push(stream);
        }
    
        transceiver.track = track;
        transceiver.stream = stream;
        transceiver.rtpSender = new window.RTCRtpSender(track,
            transceiver.dtlsTransport);
        return transceiver.rtpSender;
      };
    
      RTCPeerConnection.prototype.addStream = function(stream) {
        var pc = this;
        if (edgeVersion >= 15025) {
          stream.getTracks().forEach(function(track) {
            pc.addTrack(track, stream);
          });
        } else {
          // Clone is necessary for local demos mostly, attaching directly
          // to two different senders does not work (build 10547).
          // Fixed in 15025 (or earlier)
          var clonedStream = stream.clone();
          stream.getTracks().forEach(function(track, idx) {
            var clonedTrack = clonedStream.getTracks()[idx];
            track.addEventListener('enabled', function(event) {
              clonedTrack.enabled = event.enabled;
            });
          });
          clonedStream.getTracks().forEach(function(track) {
            pc.addTrack(track, clonedStream);
          });
        }
      };
    
      RTCPeerConnection.prototype.removeTrack = function(sender) {
        if (this._isClosed) {
          throw makeError('InvalidStateError',
              'Attempted to call removeTrack on a closed peerconnection.');
        }
    
        if (!(sender instanceof window.RTCRtpSender)) {
          throw new TypeError('Argument 1 of RTCPeerConnection.removeTrack ' +
              'does not implement interface RTCRtpSender.');
        }
    
        var transceiver = this.transceivers.find(function(t) {
          return t.rtpSender === sender;
        });
    
        if (!transceiver) {
          throw makeError('InvalidAccessError',
              'Sender was not created by this connection.');
        }
        var stream = transceiver.stream;
    
        transceiver.rtpSender.stop();
        transceiver.rtpSender = null;
        transceiver.track = null;
        transceiver.stream = null;
    
        // remove the stream from the set of local streams
        var localStreams = this.transceivers.map(function(t) {
          return t.stream;
        });
        if (localStreams.indexOf(stream) === -1 &&
            this.localStreams.indexOf(stream) > -1) {
          this.localStreams.splice(this.localStreams.indexOf(stream), 1);
        }
    
        this._maybeFireNegotiationNeeded();
      };
    
      RTCPeerConnection.prototype.removeStream = function(stream) {
        var pc = this;
        stream.getTracks().forEach(function(track) {
          var sender = pc.getSenders().find(function(s) {
            return s.track === track;
          });
          if (sender) {
            pc.removeTrack(sender);
          }
        });
      };
    
      RTCPeerConnection.prototype.getSenders = function() {
        return this.transceivers.filter(function(transceiver) {
          return !!transceiver.rtpSender;
        })
        .map(function(transceiver) {
          return transceiver.rtpSender;
        });
      };
    
      RTCPeerConnection.prototype.getReceivers = function() {
        return this.transceivers.filter(function(transceiver) {
          return !!transceiver.rtpReceiver;
        })
        .map(function(transceiver) {
          return transceiver.rtpReceiver;
        });
      };
    
    
      RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
          usingBundle) {
        var pc = this;
        if (usingBundle && sdpMLineIndex > 0) {
          return this.transceivers[0].iceGatherer;
        } else if (this._iceGatherers.length) {
          return this._iceGatherers.shift();
        }
        var iceGatherer = new window.RTCIceGatherer({
          iceServers: this._config.iceServers,
          gatherPolicy: this._config.iceTransportPolicy
        });
        Object.defineProperty(iceGatherer, 'state',
            {value: 'new', writable: true}
        );
    
        this.transceivers[sdpMLineIndex].bufferedCandidateEvents = [];
        this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
          var end = !event.candidate || Object.keys(event.candidate).length === 0;
          // polyfill since RTCIceGatherer.state is not implemented in
          // Edge 10547 yet.
          iceGatherer.state = end ? 'completed' : 'gathering';
          if (pc.transceivers[sdpMLineIndex].bufferedCandidateEvents !== null) {
            pc.transceivers[sdpMLineIndex].bufferedCandidateEvents.push(event);
          }
        };
        iceGatherer.addEventListener('localcandidate',
          this.transceivers[sdpMLineIndex].bufferCandidates);
        return iceGatherer;
      };
    
      // start gathering from an RTCIceGatherer.
      RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
        var pc = this;
        var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
        if (iceGatherer.onlocalcandidate) {
          return;
        }
        var bufferedCandidateEvents =
          this.transceivers[sdpMLineIndex].bufferedCandidateEvents;
        this.transceivers[sdpMLineIndex].bufferedCandidateEvents = null;
        iceGatherer.removeEventListener('localcandidate',
          this.transceivers[sdpMLineIndex].bufferCandidates);
        iceGatherer.onlocalcandidate = function(evt) {
          if (pc.usingBundle && sdpMLineIndex > 0) {
            // if we know that we use bundle we can drop candidates with
            // ѕdpMLineIndex > 0. If we don't do this then our state gets
            // confused since we dispose the extra ice gatherer.
            return;
          }
          var event = new Event('icecandidate');
          event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};
    
          var cand = evt.candidate;
          // Edge emits an empty object for RTCIceCandidateComplete‥
          var end = !cand || Object.keys(cand).length === 0;
          if (end) {
            // polyfill since RTCIceGatherer.state is not implemented in
            // Edge 10547 yet.
            if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
              iceGatherer.state = 'completed';
            }
          } else {
            if (iceGatherer.state === 'new') {
              iceGatherer.state = 'gathering';
            }
            // RTCIceCandidate doesn't have a component, needs to be added
            cand.component = 1;
            // also the usernameFragment. TODO: update SDP to take both variants.
            cand.ufrag = iceGatherer.getLocalParameters().usernameFragment;
    
            var serializedCandidate = SDPUtils.writeCandidate(cand);
            event.candidate = Object.assign(event.candidate,
                SDPUtils.parseCandidate(serializedCandidate));
    
            event.candidate.candidate = serializedCandidate;
            event.candidate.toJSON = function() {
              return {
                candidate: event.candidate.candidate,
                sdpMid: event.candidate.sdpMid,
                sdpMLineIndex: event.candidate.sdpMLineIndex,
                usernameFragment: event.candidate.usernameFragment
              };
            };
          }
    
          // update local description.
          var sections = SDPUtils.getMediaSections(pc._localDescription.sdp);
          if (!end) {
            sections[event.candidate.sdpMLineIndex] +=
                'a=' + event.candidate.candidate + '\r\n';
          } else {
            sections[event.candidate.sdpMLineIndex] +=
                'a=end-of-candidates\r\n';
          }
          pc._localDescription.sdp =
              SDPUtils.getDescription(pc._localDescription.sdp) +
              sections.join('');
          var complete = pc.transceivers.every(function(transceiver) {
            return transceiver.iceGatherer &&
                transceiver.iceGatherer.state === 'completed';
          });
    
          if (pc.iceGatheringState !== 'gathering') {
            pc.iceGatheringState = 'gathering';
            pc._emitGatheringStateChange();
          }
    
          // Emit candidate. Also emit null candidate when all gatherers are
          // complete.
          if (!end) {
            pc._dispatchEvent('icecandidate', event);
          }
          if (complete) {
            pc._dispatchEvent('icecandidate', new Event('icecandidate'));
            pc.iceGatheringState = 'complete';
            pc._emitGatheringStateChange();
          }
        };
    
        // emit already gathered candidates.
        window.setTimeout(function() {
          bufferedCandidateEvents.forEach(function(e) {
            iceGatherer.onlocalcandidate(e);
          });
        }, 0);
      };
    
      // Create ICE transport and DTLS transport.
      RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
        var pc = this;
        var iceTransport = new window.RTCIceTransport(null);
        iceTransport.onicestatechange = function() {
          pc._updateIceConnectionState();
          pc._updateConnectionState();
        };
    
        var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
        dtlsTransport.ondtlsstatechange = function() {
          pc._updateConnectionState();
        };
        dtlsTransport.onerror = function() {
          // onerror does not set state to failed by itself.
          Object.defineProperty(dtlsTransport, 'state',
              {value: 'failed', writable: true});
          pc._updateConnectionState();
        };
    
        return {
          iceTransport: iceTransport,
          dtlsTransport: dtlsTransport
        };
      };
    
      // Destroy ICE gatherer, ICE transport and DTLS transport.
      // Without triggering the callbacks.
      RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
          sdpMLineIndex) {
        var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
        if (iceGatherer) {
          delete iceGatherer.onlocalcandidate;
          delete this.transceivers[sdpMLineIndex].iceGatherer;
        }
        var iceTransport = this.transceivers[sdpMLineIndex].iceTransport;
        if (iceTransport) {
          delete iceTransport.onicestatechange;
          delete this.transceivers[sdpMLineIndex].iceTransport;
        }
        var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport;
        if (dtlsTransport) {
          delete dtlsTransport.ondtlsstatechange;
          delete dtlsTransport.onerror;
          delete this.transceivers[sdpMLineIndex].dtlsTransport;
        }
      };
    
      // Start the RTP Sender and Receiver for a transceiver.
      RTCPeerConnection.prototype._transceive = function(transceiver,
          send, recv) {
        var params = getCommonCapabilities(transceiver.localCapabilities,
            transceiver.remoteCapabilities);
        if (send && transceiver.rtpSender) {
          params.encodings = transceiver.sendEncodingParameters;
          params.rtcp = {
            cname: SDPUtils.localCName,
            compound: transceiver.rtcpParameters.compound
          };
          if (transceiver.recvEncodingParameters.length) {
            params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
          }
          transceiver.rtpSender.send(params);
        }
        if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
          // remove RTX field in Edge 14942
          if (transceiver.kind === 'video'
              && transceiver.recvEncodingParameters
              && edgeVersion < 15019) {
            transceiver.recvEncodingParameters.forEach(function(p) {
              delete p.rtx;
            });
          }
          if (transceiver.recvEncodingParameters.length) {
            params.encodings = transceiver.recvEncodingParameters;
          } else {
            params.encodings = [{}];
          }
          params.rtcp = {
            compound: transceiver.rtcpParameters.compound
          };
          if (transceiver.rtcpParameters.cname) {
            params.rtcp.cname = transceiver.rtcpParameters.cname;
          }
          if (transceiver.sendEncodingParameters.length) {
            params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
          }
          transceiver.rtpReceiver.receive(params);
        }
      };
    
      RTCPeerConnection.prototype.setLocalDescription = function(description) {
        var pc = this;
    
        // Note: pranswer is not supported.
        if (['offer', 'answer'].indexOf(description.type) === -1) {
          return Promise.reject(makeError('TypeError',
              'Unsupported type "' + description.type + '"'));
        }
    
        if (!isActionAllowedInSignalingState('setLocalDescription',
            description.type, pc.signalingState) || pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
              'Can not set local ' + description.type +
              ' in state ' + pc.signalingState));
        }
    
        var sections;
        var sessionpart;
        if (description.type === 'offer') {
          // VERY limited support for SDP munging. Limited to:
          // * changing the order of codecs
          sections = SDPUtils.splitSections(description.sdp);
          sessionpart = sections.shift();
          sections.forEach(function(mediaSection, sdpMLineIndex) {
            var caps = SDPUtils.parseRtpParameters(mediaSection);
            pc.transceivers[sdpMLineIndex].localCapabilities = caps;
          });
    
          pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
            pc._gather(transceiver.mid, sdpMLineIndex);
          });
        } else if (description.type === 'answer') {
          sections = SDPUtils.splitSections(pc._remoteDescription.sdp);
          sessionpart = sections.shift();
          var isIceLite = SDPUtils.matchPrefix(sessionpart,
              'a=ice-lite').length > 0;
          sections.forEach(function(mediaSection, sdpMLineIndex) {
            var transceiver = pc.transceivers[sdpMLineIndex];
            var iceGatherer = transceiver.iceGatherer;
            var iceTransport = transceiver.iceTransport;
            var dtlsTransport = transceiver.dtlsTransport;
            var localCapabilities = transceiver.localCapabilities;
            var remoteCapabilities = transceiver.remoteCapabilities;
    
            // treat bundle-only as not-rejected.
            var rejected = SDPUtils.isRejected(mediaSection) &&
                SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;
    
            if (!rejected && !transceiver.rejected) {
              var remoteIceParameters = SDPUtils.getIceParameters(
                  mediaSection, sessionpart);
              var remoteDtlsParameters = SDPUtils.getDtlsParameters(
                  mediaSection, sessionpart);
              if (isIceLite) {
                remoteDtlsParameters.role = 'server';
              }
    
              if (!pc.usingBundle || sdpMLineIndex === 0) {
                pc._gather(transceiver.mid, sdpMLineIndex);
                if (iceTransport.state === 'new') {
                  iceTransport.start(iceGatherer, remoteIceParameters,
                      isIceLite ? 'controlling' : 'controlled');
                }
                if (dtlsTransport.state === 'new') {
                  dtlsTransport.start(remoteDtlsParameters);
                }
              }
    
              // Calculate intersection of capabilities.
              var params = getCommonCapabilities(localCapabilities,
                  remoteCapabilities);
    
              // Start the RTCRtpSender. The RTCRtpReceiver for this
              // transceiver has already been started in setRemoteDescription.
              pc._transceive(transceiver,
                  params.codecs.length > 0,
                  false);
            }
          });
        }
    
        pc._localDescription = {
          type: description.type,
          sdp: description.sdp
        };
        if (description.type === 'offer') {
          pc._updateSignalingState('have-local-offer');
        } else {
          pc._updateSignalingState('stable');
        }
    
        return Promise.resolve();
      };
    
      RTCPeerConnection.prototype.setRemoteDescription = function(description) {
        var pc = this;
    
        // Note: pranswer is not supported.
        if (['offer', 'answer'].indexOf(description.type) === -1) {
          return Promise.reject(makeError('TypeError',
              'Unsupported type "' + description.type + '"'));
        }
    
        if (!isActionAllowedInSignalingState('setRemoteDescription',
            description.type, pc.signalingState) || pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
              'Can not set remote ' + description.type +
              ' in state ' + pc.signalingState));
        }
    
        var streams = {};
        pc.remoteStreams.forEach(function(stream) {
          streams[stream.id] = stream;
        });
        var receiverList = [];
        var sections = SDPUtils.splitSections(description.sdp);
        var sessionpart = sections.shift();
        var isIceLite = SDPUtils.matchPrefix(sessionpart,
            'a=ice-lite').length > 0;
        var usingBundle = SDPUtils.matchPrefix(sessionpart,
            'a=group:BUNDLE ').length > 0;
        pc.usingBundle = usingBundle;
        var iceOptions = SDPUtils.matchPrefix(sessionpart,
            'a=ice-options:')[0];
        if (iceOptions) {
          pc.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
              .indexOf('trickle') >= 0;
        } else {
          pc.canTrickleIceCandidates = false;
        }
    
        sections.forEach(function(mediaSection, sdpMLineIndex) {
          var lines = SDPUtils.splitLines(mediaSection);
          var kind = SDPUtils.getKind(mediaSection);
          // treat bundle-only as not-rejected.
          var rejected = SDPUtils.isRejected(mediaSection) &&
              SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;
          var protocol = lines[0].substr(2).split(' ')[2];
    
          var direction = SDPUtils.getDirection(mediaSection, sessionpart);
          var remoteMsid = SDPUtils.parseMsid(mediaSection);
    
          var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier();
    
          // Reject datachannels which are not implemented yet.
          if (rejected || (kind === 'application' && (protocol === 'DTLS/SCTP' ||
              protocol === 'UDP/DTLS/SCTP'))) {
            // TODO: this is dangerous in the case where a non-rejected m-line
            //     becomes rejected.
            pc.transceivers[sdpMLineIndex] = {
              mid: mid,
              kind: kind,
              protocol: protocol,
              rejected: true
            };
            return;
          }
    
          if (!rejected && pc.transceivers[sdpMLineIndex] &&
              pc.transceivers[sdpMLineIndex].rejected) {
            // recycle a rejected transceiver.
            pc.transceivers[sdpMLineIndex] = pc._createTransceiver(kind, true);
          }
    
          var transceiver;
          var iceGatherer;
          var iceTransport;
          var dtlsTransport;
          var rtpReceiver;
          var sendEncodingParameters;
          var recvEncodingParameters;
          var localCapabilities;
    
          var track;
          // FIXME: ensure the mediaSection has rtcp-mux set.
          var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
          var remoteIceParameters;
          var remoteDtlsParameters;
          if (!rejected) {
            remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
                sessionpart);
            remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
                sessionpart);
            remoteDtlsParameters.role = 'client';
          }
          recvEncodingParameters =
              SDPUtils.parseRtpEncodingParameters(mediaSection);
    
          var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection);
    
          var isComplete = SDPUtils.matchPrefix(mediaSection,
              'a=end-of-candidates', sessionpart).length > 0;
          var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
              .map(function(cand) {
                return SDPUtils.parseCandidate(cand);
              })
              .filter(function(cand) {
                return cand.component === 1;
              });
    
          // Check if we can use BUNDLE and dispose transports.
          if ((description.type === 'offer' || description.type === 'answer') &&
              !rejected && usingBundle && sdpMLineIndex > 0 &&
              pc.transceivers[sdpMLineIndex]) {
            pc._disposeIceAndDtlsTransports(sdpMLineIndex);
            pc.transceivers[sdpMLineIndex].iceGatherer =
                pc.transceivers[0].iceGatherer;
            pc.transceivers[sdpMLineIndex].iceTransport =
                pc.transceivers[0].iceTransport;
            pc.transceivers[sdpMLineIndex].dtlsTransport =
                pc.transceivers[0].dtlsTransport;
            if (pc.transceivers[sdpMLineIndex].rtpSender) {
              pc.transceivers[sdpMLineIndex].rtpSender.setTransport(
                  pc.transceivers[0].dtlsTransport);
            }
            if (pc.transceivers[sdpMLineIndex].rtpReceiver) {
              pc.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
                  pc.transceivers[0].dtlsTransport);
            }
          }
          if (description.type === 'offer' && !rejected) {
            transceiver = pc.transceivers[sdpMLineIndex] ||
                pc._createTransceiver(kind);
            transceiver.mid = mid;
    
            if (!transceiver.iceGatherer) {
              transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                  usingBundle);
            }
    
            if (cands.length && transceiver.iceTransport.state === 'new') {
              if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
                transceiver.iceTransport.setRemoteCandidates(cands);
              } else {
                cands.forEach(function(candidate) {
                  maybeAddCandidate(transceiver.iceTransport, candidate);
                });
              }
            }
    
            localCapabilities = window.RTCRtpReceiver.getCapabilities(kind);
    
            // filter RTX until additional stuff needed for RTX is implemented
            // in adapter.js
            if (edgeVersion < 15019) {
              localCapabilities.codecs = localCapabilities.codecs.filter(
                  function(codec) {
                    return codec.name !== 'rtx';
                  });
            }
    
            sendEncodingParameters = transceiver.sendEncodingParameters || [{
              ssrc: (2 * sdpMLineIndex + 2) * 1001
            }];
    
            // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
            var isNewTrack = false;
            if (direction === 'sendrecv' || direction === 'sendonly') {
              isNewTrack = !transceiver.rtpReceiver;
              rtpReceiver = transceiver.rtpReceiver ||
                  new window.RTCRtpReceiver(transceiver.dtlsTransport, kind);
    
              if (isNewTrack) {
                var stream;
                track = rtpReceiver.track;
                // FIXME: does not work with Plan B.
                if (remoteMsid && remoteMsid.stream === '-') {
                  // no-op. a stream id of '-' means: no associated stream.
                } else if (remoteMsid) {
                  if (!streams[remoteMsid.stream]) {
                    streams[remoteMsid.stream] = new window.MediaStream();
                    Object.defineProperty(streams[remoteMsid.stream], 'id', {
                      get: function() {
                        return remoteMsid.stream;
                      }
                    });
                  }
                  Object.defineProperty(track, 'id', {
                    get: function() {
                      return remoteMsid.track;
                    }
                  });
                  stream = streams[remoteMsid.stream];
                } else {
                  if (!streams.default) {
                    streams.default = new window.MediaStream();
                  }
                  stream = streams.default;
                }
                if (stream) {
                  addTrackToStreamAndFireEvent(track, stream);
                  transceiver.associatedRemoteMediaStreams.push(stream);
                }
                receiverList.push([track, rtpReceiver, stream]);
              }
            } else if (transceiver.rtpReceiver && transceiver.rtpReceiver.track) {
              transceiver.associatedRemoteMediaStreams.forEach(function(s) {
                var nativeTrack = s.getTracks().find(function(t) {
                  return t.id === transceiver.rtpReceiver.track.id;
                });
                if (nativeTrack) {
                  removeTrackFromStreamAndFireEvent(nativeTrack, s);
                }
              });
              transceiver.associatedRemoteMediaStreams = [];
            }
    
            transceiver.localCapabilities = localCapabilities;
            transceiver.remoteCapabilities = remoteCapabilities;
            transceiver.rtpReceiver = rtpReceiver;
            transceiver.rtcpParameters = rtcpParameters;
            transceiver.sendEncodingParameters = sendEncodingParameters;
            transceiver.recvEncodingParameters = recvEncodingParameters;
    
            // Start the RTCRtpReceiver now. The RTPSender is started in
            // setLocalDescription.
            pc._transceive(pc.transceivers[sdpMLineIndex],
                false,
                isNewTrack);
          } else if (description.type === 'answer' && !rejected) {
            transceiver = pc.transceivers[sdpMLineIndex];
            iceGatherer = transceiver.iceGatherer;
            iceTransport = transceiver.iceTransport;
            dtlsTransport = transceiver.dtlsTransport;
            rtpReceiver = transceiver.rtpReceiver;
            sendEncodingParameters = transceiver.sendEncodingParameters;
            localCapabilities = transceiver.localCapabilities;
    
            pc.transceivers[sdpMLineIndex].recvEncodingParameters =
                recvEncodingParameters;
            pc.transceivers[sdpMLineIndex].remoteCapabilities =
                remoteCapabilities;
            pc.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters;
    
            if (cands.length && iceTransport.state === 'new') {
              if ((isIceLite || isComplete) &&
                  (!usingBundle || sdpMLineIndex === 0)) {
                iceTransport.setRemoteCandidates(cands);
              } else {
                cands.forEach(function(candidate) {
                  maybeAddCandidate(transceiver.iceTransport, candidate);
                });
              }
            }
    
            if (!usingBundle || sdpMLineIndex === 0) {
              if (iceTransport.state === 'new') {
                iceTransport.start(iceGatherer, remoteIceParameters,
                    'controlling');
              }
              if (dtlsTransport.state === 'new') {
                dtlsTransport.start(remoteDtlsParameters);
              }
            }
    
            // If the offer contained RTX but the answer did not,
            // remove RTX from sendEncodingParameters.
            var commonCapabilities = getCommonCapabilities(
              transceiver.localCapabilities,
              transceiver.remoteCapabilities);
    
            var hasRtx = commonCapabilities.codecs.filter(function(c) {
              return c.name.toLowerCase() === 'rtx';
            }).length;
            if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
              delete transceiver.sendEncodingParameters[0].rtx;
            }
    
            pc._transceive(transceiver,
                direction === 'sendrecv' || direction === 'recvonly',
                direction === 'sendrecv' || direction === 'sendonly');
    
            // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
            if (rtpReceiver &&
                (direction === 'sendrecv' || direction === 'sendonly')) {
              track = rtpReceiver.track;
              if (remoteMsid) {
                if (!streams[remoteMsid.stream]) {
                  streams[remoteMsid.stream] = new window.MediaStream();
                }
                addTrackToStreamAndFireEvent(track, streams[remoteMsid.stream]);
                receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]]);
              } else {
                if (!streams.default) {
                  streams.default = new window.MediaStream();
                }
                addTrackToStreamAndFireEvent(track, streams.default);
                receiverList.push([track, rtpReceiver, streams.default]);
              }
            } else {
              // FIXME: actually the receiver should be created later.
              delete transceiver.rtpReceiver;
            }
          }
        });
    
        if (pc._dtlsRole === undefined) {
          pc._dtlsRole = description.type === 'offer' ? 'active' : 'passive';
        }
    
        pc._remoteDescription = {
          type: description.type,
          sdp: description.sdp
        };
        if (description.type === 'offer') {
          pc._updateSignalingState('have-remote-offer');
        } else {
          pc._updateSignalingState('stable');
        }
        Object.keys(streams).forEach(function(sid) {
          var stream = streams[sid];
          if (stream.getTracks().length) {
            if (pc.remoteStreams.indexOf(stream) === -1) {
              pc.remoteStreams.push(stream);
              var event = new Event('addstream');
              event.stream = stream;
              window.setTimeout(function() {
                pc._dispatchEvent('addstream', event);
              });
            }
    
            receiverList.forEach(function(item) {
              var track = item[0];
              var receiver = item[1];
              if (stream.id !== item[2].id) {
                return;
              }
              fireAddTrack(pc, track, receiver, [stream]);
            });
          }
        });
        receiverList.forEach(function(item) {
          if (item[2]) {
            return;
          }
          fireAddTrack(pc, item[0], item[1], []);
        });
    
        // check whether addIceCandidate({}) was called within four seconds after
        // setRemoteDescription.
        window.setTimeout(function() {
          if (!(pc && pc.transceivers)) {
            return;
          }
          pc.transceivers.forEach(function(transceiver) {
            if (transceiver.iceTransport &&
                transceiver.iceTransport.state === 'new' &&
                transceiver.iceTransport.getRemoteCandidates().length > 0) {
              console.warn('Timeout for addRemoteCandidate. Consider sending ' +
                  'an end-of-candidates notification');
              transceiver.iceTransport.addRemoteCandidate({});
            }
          });
        }, 4000);
    
        return Promise.resolve();
      };
    
      RTCPeerConnection.prototype.close = function() {
        this.transceivers.forEach(function(transceiver) {
          /* not yet
          if (transceiver.iceGatherer) {
            transceiver.iceGatherer.close();
          }
          */
          if (transceiver.iceTransport) {
            transceiver.iceTransport.stop();
          }
          if (transceiver.dtlsTransport) {
            transceiver.dtlsTransport.stop();
          }
          if (transceiver.rtpSender) {
            transceiver.rtpSender.stop();
          }
          if (transceiver.rtpReceiver) {
            transceiver.rtpReceiver.stop();
          }
        });
        // FIXME: clean up tracks, local streams, remote streams, etc
        this._isClosed = true;
        this._updateSignalingState('closed');
      };
    
      // Update the signaling state.
      RTCPeerConnection.prototype._updateSignalingState = function(newState) {
        this.signalingState = newState;
        var event = new Event('signalingstatechange');
        this._dispatchEvent('signalingstatechange', event);
      };
    
      // Determine whether to fire the negotiationneeded event.
      RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
        var pc = this;
        if (this.signalingState !== 'stable' || this.needNegotiation === true) {
          return;
        }
        this.needNegotiation = true;
        window.setTimeout(function() {
          if (pc.needNegotiation) {
            pc.needNegotiation = false;
            var event = new Event('negotiationneeded');
            pc._dispatchEvent('negotiationneeded', event);
          }
        }, 0);
      };
    
      // Update the ice connection state.
      RTCPeerConnection.prototype._updateIceConnectionState = function() {
        var newState;
        var states = {
          'new': 0,
          closed: 0,
          checking: 0,
          connected: 0,
          completed: 0,
          disconnected: 0,
          failed: 0
        };
        this.transceivers.forEach(function(transceiver) {
          if (transceiver.iceTransport && !transceiver.rejected) {
            states[transceiver.iceTransport.state]++;
          }
        });
    
        newState = 'new';
        if (states.failed > 0) {
          newState = 'failed';
        } else if (states.checking > 0) {
          newState = 'checking';
        } else if (states.disconnected > 0) {
          newState = 'disconnected';
        } else if (states.new > 0) {
          newState = 'new';
        } else if (states.connected > 0) {
          newState = 'connected';
        } else if (states.completed > 0) {
          newState = 'completed';
        }
    
        if (newState !== this.iceConnectionState) {
          this.iceConnectionState = newState;
          var event = new Event('iceconnectionstatechange');
          this._dispatchEvent('iceconnectionstatechange', event);
        }
      };
    
      // Update the connection state.
      RTCPeerConnection.prototype._updateConnectionState = function() {
        var newState;
        var states = {
          'new': 0,
          closed: 0,
          connecting: 0,
          connected: 0,
          completed: 0,
          disconnected: 0,
          failed: 0
        };
        this.transceivers.forEach(function(transceiver) {
          if (transceiver.iceTransport && transceiver.dtlsTransport &&
              !transceiver.rejected) {
            states[transceiver.iceTransport.state]++;
            states[transceiver.dtlsTransport.state]++;
          }
        });
        // ICETransport.completed and connected are the same for this purpose.
        states.connected += states.completed;
    
        newState = 'new';
        if (states.failed > 0) {
          newState = 'failed';
        } else if (states.connecting > 0) {
          newState = 'connecting';
        } else if (states.disconnected > 0) {
          newState = 'disconnected';
        } else if (states.new > 0) {
          newState = 'new';
        } else if (states.connected > 0) {
          newState = 'connected';
        }
    
        if (newState !== this.connectionState) {
          this.connectionState = newState;
          var event = new Event('connectionstatechange');
          this._dispatchEvent('connectionstatechange', event);
        }
      };
    
      RTCPeerConnection.prototype.createOffer = function() {
        var pc = this;
    
        if (pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
              'Can not call createOffer after close'));
        }
    
        var numAudioTracks = pc.transceivers.filter(function(t) {
          return t.kind === 'audio';
        }).length;
        var numVideoTracks = pc.transceivers.filter(function(t) {
          return t.kind === 'video';
        }).length;
    
        // Determine number of audio and video tracks we need to send/recv.
        var offerOptions = arguments[0];
        if (offerOptions) {
          // Reject Chrome legacy constraints.
          if (offerOptions.mandatory || offerOptions.optional) {
            throw new TypeError(
                'Legacy mandatory/optional constraints not supported.');
          }
          if (offerOptions.offerToReceiveAudio !== undefined) {
            if (offerOptions.offerToReceiveAudio === true) {
              numAudioTracks = 1;
            } else if (offerOptions.offerToReceiveAudio === false) {
              numAudioTracks = 0;
            } else {
              numAudioTracks = offerOptions.offerToReceiveAudio;
            }
          }
          if (offerOptions.offerToReceiveVideo !== undefined) {
            if (offerOptions.offerToReceiveVideo === true) {
              numVideoTracks = 1;
            } else if (offerOptions.offerToReceiveVideo === false) {
              numVideoTracks = 0;
            } else {
              numVideoTracks = offerOptions.offerToReceiveVideo;
            }
          }
        }
    
        pc.transceivers.forEach(function(transceiver) {
          if (transceiver.kind === 'audio') {
            numAudioTracks--;
            if (numAudioTracks < 0) {
              transceiver.wantReceive = false;
            }
          } else if (transceiver.kind === 'video') {
            numVideoTracks--;
            if (numVideoTracks < 0) {
              transceiver.wantReceive = false;
            }
          }
        });
    
        // Create M-lines for recvonly streams.
        while (numAudioTracks > 0 || numVideoTracks > 0) {
          if (numAudioTracks > 0) {
            pc._createTransceiver('audio');
            numAudioTracks--;
          }
          if (numVideoTracks > 0) {
            pc._createTransceiver('video');
            numVideoTracks--;
          }
        }
    
        var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
            pc._sdpSessionVersion++);
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          // For each track, create an ice gatherer, ice transport,
          // dtls transport, potentially rtpsender and rtpreceiver.
          var track = transceiver.track;
          var kind = transceiver.kind;
          var mid = transceiver.mid || SDPUtils.generateIdentifier();
          transceiver.mid = mid;
    
          if (!transceiver.iceGatherer) {
            transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                pc.usingBundle);
          }
    
          var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
          // filter RTX until additional stuff needed for RTX is implemented
          // in adapter.js
          if (edgeVersion < 15019) {
            localCapabilities.codecs = localCapabilities.codecs.filter(
                function(codec) {
                  return codec.name !== 'rtx';
                });
          }
          localCapabilities.codecs.forEach(function(codec) {
            // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
            // by adding level-asymmetry-allowed=1
            if (codec.name === 'H264' &&
                codec.parameters['level-asymmetry-allowed'] === undefined) {
              codec.parameters['level-asymmetry-allowed'] = '1';
            }
    
            // for subsequent offers, we might have to re-use the payload
            // type of the last offer.
            if (transceiver.remoteCapabilities &&
                transceiver.remoteCapabilities.codecs) {
              transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
                if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                    codec.clockRate === remoteCodec.clockRate) {
                  codec.preferredPayloadType = remoteCodec.payloadType;
                }
              });
            }
          });
          localCapabilities.headerExtensions.forEach(function(hdrExt) {
            var remoteExtensions = transceiver.remoteCapabilities &&
                transceiver.remoteCapabilities.headerExtensions || [];
            remoteExtensions.forEach(function(rHdrExt) {
              if (hdrExt.uri === rHdrExt.uri) {
                hdrExt.id = rHdrExt.id;
              }
            });
          });
    
          // generate an ssrc now, to be used later in rtpSender.send
          var sendEncodingParameters = transceiver.sendEncodingParameters || [{
            ssrc: (2 * sdpMLineIndex + 1) * 1001
          }];
          if (track) {
            // add RTX
            if (edgeVersion >= 15019 && kind === 'video' &&
                !sendEncodingParameters[0].rtx) {
              sendEncodingParameters[0].rtx = {
                ssrc: sendEncodingParameters[0].ssrc + 1
              };
            }
          }
    
          if (transceiver.wantReceive) {
            transceiver.rtpReceiver = new window.RTCRtpReceiver(
                transceiver.dtlsTransport, kind);
          }
    
          transceiver.localCapabilities = localCapabilities;
          transceiver.sendEncodingParameters = sendEncodingParameters;
        });
    
        // always offer BUNDLE and dispose on return if not supported.
        if (pc._config.bundlePolicy !== 'max-compat') {
          sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
            return t.mid;
          }).join(' ') + '\r\n';
        }
        sdp += 'a=ice-options:trickle\r\n';
    
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
              'offer', transceiver.stream, pc._dtlsRole);
          sdp += 'a=rtcp-rsize\r\n';
    
          if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
              (sdpMLineIndex === 0 || !pc.usingBundle)) {
            transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
              cand.component = 1;
              sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
            });
    
            if (transceiver.iceGatherer.state === 'completed') {
              sdp += 'a=end-of-candidates\r\n';
            }
          }
        });
    
        var desc = new window.RTCSessionDescription({
          type: 'offer',
          sdp: sdp
        });
        return Promise.resolve(desc);
      };
    
      RTCPeerConnection.prototype.createAnswer = function() {
        var pc = this;
    
        if (pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
              'Can not call createAnswer after close'));
        }
    
        if (!(pc.signalingState === 'have-remote-offer' ||
            pc.signalingState === 'have-local-pranswer')) {
          return Promise.reject(makeError('InvalidStateError',
              'Can not call createAnswer in signalingState ' + pc.signalingState));
        }
    
        var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
            pc._sdpSessionVersion++);
        if (pc.usingBundle) {
          sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
            return t.mid;
          }).join(' ') + '\r\n';
        }
        sdp += 'a=ice-options:trickle\r\n';
    
        var mediaSectionsInOffer = SDPUtils.getMediaSections(
            pc._remoteDescription.sdp).length;
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
            return;
          }
          if (transceiver.rejected) {
            if (transceiver.kind === 'application') {
              if (transceiver.protocol === 'DTLS/SCTP') { // legacy fmt
                sdp += 'm=application 0 DTLS/SCTP 5000\r\n';
              } else {
                sdp += 'm=application 0 ' + transceiver.protocol +
                    ' webrtc-datachannel\r\n';
              }
            } else if (transceiver.kind === 'audio') {
              sdp += 'm=audio 0 UDP/TLS/RTP/SAVPF 0\r\n' +
                  'a=rtpmap:0 PCMU/8000\r\n';
            } else if (transceiver.kind === 'video') {
              sdp += 'm=video 0 UDP/TLS/RTP/SAVPF 120\r\n' +
                  'a=rtpmap:120 VP8/90000\r\n';
            }
            sdp += 'c=IN IP4 0.0.0.0\r\n' +
                'a=inactive\r\n' +
                'a=mid:' + transceiver.mid + '\r\n';
            return;
          }
    
          // FIXME: look at direction.
          if (transceiver.stream) {
            var localTrack;
            if (transceiver.kind === 'audio') {
              localTrack = transceiver.stream.getAudioTracks()[0];
            } else if (transceiver.kind === 'video') {
              localTrack = transceiver.stream.getVideoTracks()[0];
            }
            if (localTrack) {
              // add RTX
              if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
                  !transceiver.sendEncodingParameters[0].rtx) {
                transceiver.sendEncodingParameters[0].rtx = {
                  ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
                };
              }
            }
          }
    
          // Calculate intersection of capabilities.
          var commonCapabilities = getCommonCapabilities(
              transceiver.localCapabilities,
              transceiver.remoteCapabilities);
    
          var hasRtx = commonCapabilities.codecs.filter(function(c) {
            return c.name.toLowerCase() === 'rtx';
          }).length;
          if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
            delete transceiver.sendEncodingParameters[0].rtx;
          }
    
          sdp += writeMediaSection(transceiver, commonCapabilities,
              'answer', transceiver.stream, pc._dtlsRole);
          if (transceiver.rtcpParameters &&
              transceiver.rtcpParameters.reducedSize) {
            sdp += 'a=rtcp-rsize\r\n';
          }
        });
    
        var desc = new window.RTCSessionDescription({
          type: 'answer',
          sdp: sdp
        });
        return Promise.resolve(desc);
      };
    
      RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
        var pc = this;
        var sections;
        if (candidate && !(candidate.sdpMLineIndex !== undefined ||
            candidate.sdpMid)) {
          return Promise.reject(new TypeError('sdpMLineIndex or sdpMid required'));
        }
    
        // TODO: needs to go into ops queue.
        return new Promise(function(resolve, reject) {
          if (!pc._remoteDescription) {
            return reject(makeError('InvalidStateError',
                'Can not add ICE candidate without a remote description'));
          } else if (!candidate || candidate.candidate === '') {
            for (var j = 0; j < pc.transceivers.length; j++) {
              if (pc.transceivers[j].rejected) {
                continue;
              }
              pc.transceivers[j].iceTransport.addRemoteCandidate({});
              sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp);
              sections[j] += 'a=end-of-candidates\r\n';
              pc._remoteDescription.sdp =
                  SDPUtils.getDescription(pc._remoteDescription.sdp) +
                  sections.join('');
              if (pc.usingBundle) {
                break;
              }
            }
          } else {
            var sdpMLineIndex = candidate.sdpMLineIndex;
            if (candidate.sdpMid) {
              for (var i = 0; i < pc.transceivers.length; i++) {
                if (pc.transceivers[i].mid === candidate.sdpMid) {
                  sdpMLineIndex = i;
                  break;
                }
              }
            }
            var transceiver = pc.transceivers[sdpMLineIndex];
            if (transceiver) {
              if (transceiver.rejected) {
                return resolve();
              }
              var cand = Object.keys(candidate.candidate).length > 0 ?
                  SDPUtils.parseCandidate(candidate.candidate) : {};
              // Ignore Chrome's invalid candidates since Edge does not like them.
              if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
                return resolve();
              }
              // Ignore RTCP candidates, we assume RTCP-MUX.
              if (cand.component && cand.component !== 1) {
                return resolve();
              }
              // when using bundle, avoid adding candidates to the wrong
              // ice transport. And avoid adding candidates added in the SDP.
              if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
                  transceiver.iceTransport !== pc.transceivers[0].iceTransport)) {
                if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
                  return reject(makeError('OperationError',
                      'Can not add ICE candidate'));
                }
              }
    
              // update the remoteDescription.
              var candidateString = candidate.candidate.trim();
              if (candidateString.indexOf('a=') === 0) {
                candidateString = candidateString.substr(2);
              }
              sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp);
              sections[sdpMLineIndex] += 'a=' +
                  (cand.type ? candidateString : 'end-of-candidates')
                  + '\r\n';
              pc._remoteDescription.sdp =
                  SDPUtils.getDescription(pc._remoteDescription.sdp) +
                  sections.join('');
            } else {
              return reject(makeError('OperationError',
                  'Can not add ICE candidate'));
            }
          }
          resolve();
        });
      };
    
      RTCPeerConnection.prototype.getStats = function(selector) {
        if (selector && selector instanceof window.MediaStreamTrack) {
          var senderOrReceiver = null;
          this.transceivers.forEach(function(transceiver) {
            if (transceiver.rtpSender &&
                transceiver.rtpSender.track === selector) {
              senderOrReceiver = transceiver.rtpSender;
            } else if (transceiver.rtpReceiver &&
                transceiver.rtpReceiver.track === selector) {
              senderOrReceiver = transceiver.rtpReceiver;
            }
          });
          if (!senderOrReceiver) {
            throw makeError('InvalidAccessError', 'Invalid selector.');
          }
          return senderOrReceiver.getStats();
        }
    
        var promises = [];
        this.transceivers.forEach(function(transceiver) {
          ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
              'dtlsTransport'].forEach(function(method) {
                if (transceiver[method]) {
                  promises.push(transceiver[method].getStats());
                }
              });
        });
        return Promise.all(promises).then(function(allStats) {
          var results = new Map();
          allStats.forEach(function(stats) {
            stats.forEach(function(stat) {
              results.set(stat.id, stat);
            });
          });
          return results;
        });
      };
    
      // fix low-level stat names and return Map instead of object.
      var ortcObjects = ['RTCRtpSender', 'RTCRtpReceiver', 'RTCIceGatherer',
        'RTCIceTransport', 'RTCDtlsTransport'];
      ortcObjects.forEach(function(ortcObjectName) {
        var obj = window[ortcObjectName];
        if (obj && obj.prototype && obj.prototype.getStats) {
          var nativeGetstats = obj.prototype.getStats;
          obj.prototype.getStats = function() {
            return nativeGetstats.apply(this)
            .then(function(nativeStats) {
              var mapStats = new Map();
              Object.keys(nativeStats).forEach(function(id) {
                nativeStats[id].type = fixStatsType(nativeStats[id]);
                mapStats.set(id, nativeStats[id]);
              });
              return mapStats;
            });
          };
        }
      });
    
      // legacy callback shims. Should be moved to adapter.js some days.
      var methods = ['createOffer', 'createAnswer'];
      methods.forEach(function(method) {
        var nativeMethod = RTCPeerConnection.prototype[method];
        RTCPeerConnection.prototype[method] = function() {
          var args = arguments;
          if (typeof args[0] === 'function' ||
              typeof args[1] === 'function') { // legacy
            return nativeMethod.apply(this, [arguments[2]])
            .then(function(description) {
              if (typeof args[0] === 'function') {
                args[0].apply(null, [description]);
              }
            }, function(error) {
              if (typeof args[1] === 'function') {
                args[1].apply(null, [error]);
              }
            });
          }
          return nativeMethod.apply(this, arguments);
        };
      });
    
      methods = ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'];
      methods.forEach(function(method) {
        var nativeMethod = RTCPeerConnection.prototype[method];
        RTCPeerConnection.prototype[method] = function() {
          var args = arguments;
          if (typeof args[1] === 'function' ||
              typeof args[2] === 'function') { // legacy
            return nativeMethod.apply(this, arguments)
            .then(function() {
              if (typeof args[1] === 'function') {
                args[1].apply(null);
              }
            }, function(error) {
              if (typeof args[2] === 'function') {
                args[2].apply(null, [error]);
              }
            });
          }
          return nativeMethod.apply(this, arguments);
        };
      });
    
      // getStats is special. It doesn't have a spec legacy method yet we support
      // getStats(something, cb) without error callbacks.
      ['getStats'].forEach(function(method) {
        var nativeMethod = RTCPeerConnection.prototype[method];
        RTCPeerConnection.prototype[method] = function() {
          var args = arguments;
          if (typeof args[1] === 'function') {
            return nativeMethod.apply(this, arguments)
            .then(function() {
              if (typeof args[1] === 'function') {
                args[1].apply(null);
              }
            });
          }
          return nativeMethod.apply(this, arguments);
        };
      });
    
      return RTCPeerConnection;
    };
    
    },{"sdp":17}],17:[function(require,module,exports){
    /* eslint-env node */
    'use strict';
    
    // SDP helpers.
    var SDPUtils = {};
    
    // Generate an alphanumeric identifier for cname or mids.
    // TODO: use UUIDs instead? https://gist.github.com/jed/982883
    SDPUtils.generateIdentifier = function() {
      return Math.random().toString(36).substr(2, 10);
    };
    
    // The RTCP CNAME used by all peerconnections from the same JS.
    SDPUtils.localCName = SDPUtils.generateIdentifier();
    
    // Splits SDP into lines, dealing with both CRLF and LF.
    SDPUtils.splitLines = function(blob) {
      return blob.trim().split('\n').map(function(line) {
        return line.trim();
      });
    };
    // Splits SDP into sessionpart and mediasections. Ensures CRLF.
    SDPUtils.splitSections = function(blob) {
      var parts = blob.split('\nm=');
      return parts.map(function(part, index) {
        return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
      });
    };
    
    // returns the session description.
    SDPUtils.getDescription = function(blob) {
      var sections = SDPUtils.splitSections(blob);
      return sections && sections[0];
    };
    
    // returns the individual media sections.
    SDPUtils.getMediaSections = function(blob) {
      var sections = SDPUtils.splitSections(blob);
      sections.shift();
      return sections;
    };
    
    // Returns lines that start with a certain prefix.
    SDPUtils.matchPrefix = function(blob, prefix) {
      return SDPUtils.splitLines(blob).filter(function(line) {
        return line.indexOf(prefix) === 0;
      });
    };
    
    // Parses an ICE candidate line. Sample input:
    // candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
    // rport 55996"
    SDPUtils.parseCandidate = function(line) {
      var parts;
      // Parse both variants.
      if (line.indexOf('a=candidate:') === 0) {
        parts = line.substring(12).split(' ');
      } else {
        parts = line.substring(10).split(' ');
      }
    
      var candidate = {
        foundation: parts[0],
        component: parseInt(parts[1], 10),
        protocol: parts[2].toLowerCase(),
        priority: parseInt(parts[3], 10),
        ip: parts[4],
        address: parts[4], // address is an alias for ip.
        port: parseInt(parts[5], 10),
        // skip parts[6] == 'typ'
        type: parts[7]
      };
    
      for (var i = 8; i < parts.length; i += 2) {
        switch (parts[i]) {
          case 'raddr':
            candidate.relatedAddress = parts[i + 1];
            break;
          case 'rport':
            candidate.relatedPort = parseInt(parts[i + 1], 10);
            break;
          case 'tcptype':
            candidate.tcpType = parts[i + 1];
            break;
          case 'ufrag':
            candidate.ufrag = parts[i + 1]; // for backward compability.
            candidate.usernameFragment = parts[i + 1];
            break;
          default: // extension handling, in particular ufrag
            candidate[parts[i]] = parts[i + 1];
            break;
        }
      }
      return candidate;
    };
    
    // Translates a candidate object into SDP candidate attribute.
    SDPUtils.writeCandidate = function(candidate) {
      var sdp = [];
      sdp.push(candidate.foundation);
      sdp.push(candidate.component);
      sdp.push(candidate.protocol.toUpperCase());
      sdp.push(candidate.priority);
      sdp.push(candidate.address || candidate.ip);
      sdp.push(candidate.port);
    
      var type = candidate.type;
      sdp.push('typ');
      sdp.push(type);
      if (type !== 'host' && candidate.relatedAddress &&
          candidate.relatedPort) {
        sdp.push('raddr');
        sdp.push(candidate.relatedAddress);
        sdp.push('rport');
        sdp.push(candidate.relatedPort);
      }
      if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
        sdp.push('tcptype');
        sdp.push(candidate.tcpType);
      }
      if (candidate.usernameFragment || candidate.ufrag) {
        sdp.push('ufrag');
        sdp.push(candidate.usernameFragment || candidate.ufrag);
      }
      return 'candidate:' + sdp.join(' ');
    };
    
    // Parses an ice-options line, returns an array of option tags.
    // a=ice-options:foo bar
    SDPUtils.parseIceOptions = function(line) {
      return line.substr(14).split(' ');
    };
    
    // Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
    // a=rtpmap:111 opus/48000/2
    SDPUtils.parseRtpMap = function(line) {
      var parts = line.substr(9).split(' ');
      var parsed = {
        payloadType: parseInt(parts.shift(), 10) // was: id
      };
    
      parts = parts[0].split('/');
    
      parsed.name = parts[0];
      parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
      parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
      // legacy alias, got renamed back to channels in ORTC.
      parsed.numChannels = parsed.channels;
      return parsed;
    };
    
    // Generate an a=rtpmap line from RTCRtpCodecCapability or
    // RTCRtpCodecParameters.
    SDPUtils.writeRtpMap = function(codec) {
      var pt = codec.payloadType;
      if (codec.preferredPayloadType !== undefined) {
        pt = codec.preferredPayloadType;
      }
      var channels = codec.channels || codec.numChannels || 1;
      return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
          (channels !== 1 ? '/' + channels : '') + '\r\n';
    };
    
    // Parses an a=extmap line (headerextension from RFC 5285). Sample input:
    // a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
    // a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
    SDPUtils.parseExtmap = function(line) {
      var parts = line.substr(9).split(' ');
      return {
        id: parseInt(parts[0], 10),
        direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
        uri: parts[1]
      };
    };
    
    // Generates a=extmap line from RTCRtpHeaderExtensionParameters or
    // RTCRtpHeaderExtension.
    SDPUtils.writeExtmap = function(headerExtension) {
      return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
          (headerExtension.direction && headerExtension.direction !== 'sendrecv'
            ? '/' + headerExtension.direction
            : '') +
          ' ' + headerExtension.uri + '\r\n';
    };
    
    // Parses an ftmp line, returns dictionary. Sample input:
    // a=fmtp:96 vbr=on;cng=on
    // Also deals with vbr=on; cng=on
    SDPUtils.parseFmtp = function(line) {
      var parsed = {};
      var kv;
      var parts = line.substr(line.indexOf(' ') + 1).split(';');
      for (var j = 0; j < parts.length; j++) {
        kv = parts[j].trim().split('=');
        parsed[kv[0].trim()] = kv[1];
      }
      return parsed;
    };
    
    // Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
    SDPUtils.writeFmtp = function(codec) {
      var line = '';
      var pt = codec.payloadType;
      if (codec.preferredPayloadType !== undefined) {
        pt = codec.preferredPayloadType;
      }
      if (codec.parameters && Object.keys(codec.parameters).length) {
        var params = [];
        Object.keys(codec.parameters).forEach(function(param) {
          if (codec.parameters[param]) {
            params.push(param + '=' + codec.parameters[param]);
          } else {
            params.push(param);
          }
        });
        line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
      }
      return line;
    };
    
    // Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
    // a=rtcp-fb:98 nack rpsi
    SDPUtils.parseRtcpFb = function(line) {
      var parts = line.substr(line.indexOf(' ') + 1).split(' ');
      return {
        type: parts.shift(),
        parameter: parts.join(' ')
      };
    };
    // Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
    SDPUtils.writeRtcpFb = function(codec) {
      var lines = '';
      var pt = codec.payloadType;
      if (codec.preferredPayloadType !== undefined) {
        pt = codec.preferredPayloadType;
      }
      if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
        // FIXME: special handling for trr-int?
        codec.rtcpFeedback.forEach(function(fb) {
          lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
          (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
              '\r\n';
        });
      }
      return lines;
    };
    
    // Parses an RFC 5576 ssrc media attribute. Sample input:
    // a=ssrc:3735928559 cname:something
    SDPUtils.parseSsrcMedia = function(line) {
      var sp = line.indexOf(' ');
      var parts = {
        ssrc: parseInt(line.substr(7, sp - 7), 10)
      };
      var colon = line.indexOf(':', sp);
      if (colon > -1) {
        parts.attribute = line.substr(sp + 1, colon - sp - 1);
        parts.value = line.substr(colon + 1);
      } else {
        parts.attribute = line.substr(sp + 1);
      }
      return parts;
    };
    
    SDPUtils.parseSsrcGroup = function(line) {
      var parts = line.substr(13).split(' ');
      return {
        semantics: parts.shift(),
        ssrcs: parts.map(function(ssrc) {
          return parseInt(ssrc, 10);
        })
      };
    };
    
    // Extracts the MID (RFC 5888) from a media section.
    // returns the MID or undefined if no mid line was found.
    SDPUtils.getMid = function(mediaSection) {
      var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
      if (mid) {
        return mid.substr(6);
      }
    };
    
    SDPUtils.parseFingerprint = function(line) {
      var parts = line.substr(14).split(' ');
      return {
        algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
        value: parts[1]
      };
    };
    
    // Extracts DTLS parameters from SDP media section or sessionpart.
    // FIXME: for consistency with other functions this should only
    //   get the fingerprint line as input. See also getIceParameters.
    SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
      var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=fingerprint:');
      // Note: a=setup line is ignored since we use the 'auto' role.
      // Note2: 'algorithm' is not case sensitive except in Edge.
      return {
        role: 'auto',
        fingerprints: lines.map(SDPUtils.parseFingerprint)
      };
    };
    
    // Serializes DTLS parameters to SDP.
    SDPUtils.writeDtlsParameters = function(params, setupType) {
      var sdp = 'a=setup:' + setupType + '\r\n';
      params.fingerprints.forEach(function(fp) {
        sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
      });
      return sdp;
    };
    
    // Parses a=crypto lines into
    //   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#dictionary-rtcsrtpsdesparameters-members
    SDPUtils.parseCryptoLine = function(line) {
      var parts = line.substr(9).split(' ');
      return {
        tag: parseInt(parts[0], 10),
        cryptoSuite: parts[1],
        keyParams: parts[2],
        sessionParams: parts.slice(3),
      };
    };
    
    SDPUtils.writeCryptoLine = function(parameters) {
      return 'a=crypto:' + parameters.tag + ' ' +
        parameters.cryptoSuite + ' ' +
        (typeof parameters.keyParams === 'object'
          ? SDPUtils.writeCryptoKeyParams(parameters.keyParams)
          : parameters.keyParams) +
        (parameters.sessionParams ? ' ' + parameters.sessionParams.join(' ') : '') +
        '\r\n';
    };
    
    // Parses the crypto key parameters into
    //   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#rtcsrtpkeyparam*
    SDPUtils.parseCryptoKeyParams = function(keyParams) {
      if (keyParams.indexOf('inline:') !== 0) {
        return null;
      }
      var parts = keyParams.substr(7).split('|');
      return {
        keyMethod: 'inline',
        keySalt: parts[0],
        lifeTime: parts[1],
        mkiValue: parts[2] ? parts[2].split(':')[0] : undefined,
        mkiLength: parts[2] ? parts[2].split(':')[1] : undefined,
      };
    };
    
    SDPUtils.writeCryptoKeyParams = function(keyParams) {
      return keyParams.keyMethod + ':'
        + keyParams.keySalt +
        (keyParams.lifeTime ? '|' + keyParams.lifeTime : '') +
        (keyParams.mkiValue && keyParams.mkiLength
          ? '|' + keyParams.mkiValue + ':' + keyParams.mkiLength
          : '');
    };
    
    // Extracts all SDES paramters.
    SDPUtils.getCryptoParameters = function(mediaSection, sessionpart) {
      var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=crypto:');
      return lines.map(SDPUtils.parseCryptoLine);
    };
    
    // Parses ICE information from SDP media section or sessionpart.
    // FIXME: for consistency with other functions this should only
    //   get the ice-ufrag and ice-pwd lines as input.
    SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
      var ufrag = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=ice-ufrag:')[0];
      var pwd = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=ice-pwd:')[0];
      if (!(ufrag && pwd)) {
        return null;
      }
      return {
        usernameFragment: ufrag.substr(12),
        password: pwd.substr(10),
      };
    };
    
    // Serializes ICE parameters to SDP.
    SDPUtils.writeIceParameters = function(params) {
      return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
          'a=ice-pwd:' + params.password + '\r\n';
    };
    
    // Parses the SDP media section and returns RTCRtpParameters.
    SDPUtils.parseRtpParameters = function(mediaSection) {
      var description = {
        codecs: [],
        headerExtensions: [],
        fecMechanisms: [],
        rtcp: []
      };
      var lines = SDPUtils.splitLines(mediaSection);
      var mline = lines[0].split(' ');
      for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
        var pt = mline[i];
        var rtpmapline = SDPUtils.matchPrefix(
          mediaSection, 'a=rtpmap:' + pt + ' ')[0];
        if (rtpmapline) {
          var codec = SDPUtils.parseRtpMap(rtpmapline);
          var fmtps = SDPUtils.matchPrefix(
            mediaSection, 'a=fmtp:' + pt + ' ');
          // Only the first a=fmtp:<pt> is considered.
          codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
          codec.rtcpFeedback = SDPUtils.matchPrefix(
            mediaSection, 'a=rtcp-fb:' + pt + ' ')
            .map(SDPUtils.parseRtcpFb);
          description.codecs.push(codec);
          // parse FEC mechanisms from rtpmap lines.
          switch (codec.name.toUpperCase()) {
            case 'RED':
            case 'ULPFEC':
              description.fecMechanisms.push(codec.name.toUpperCase());
              break;
            default: // only RED and ULPFEC are recognized as FEC mechanisms.
              break;
          }
        }
      }
      SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
        description.headerExtensions.push(SDPUtils.parseExtmap(line));
      });
      // FIXME: parse rtcp.
      return description;
    };
    
    // Generates parts of the SDP media section describing the capabilities /
    // parameters.
    SDPUtils.writeRtpDescription = function(kind, caps) {
      var sdp = '';
    
      // Build the mline.
      sdp += 'm=' + kind + ' ';
      sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
      sdp += ' UDP/TLS/RTP/SAVPF ';
      sdp += caps.codecs.map(function(codec) {
        if (codec.preferredPayloadType !== undefined) {
          return codec.preferredPayloadType;
        }
        return codec.payloadType;
      }).join(' ') + '\r\n';
    
      sdp += 'c=IN IP4 0.0.0.0\r\n';
      sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
    
      // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
      caps.codecs.forEach(function(codec) {
        sdp += SDPUtils.writeRtpMap(codec);
        sdp += SDPUtils.writeFmtp(codec);
        sdp += SDPUtils.writeRtcpFb(codec);
      });
      var maxptime = 0;
      caps.codecs.forEach(function(codec) {
        if (codec.maxptime > maxptime) {
          maxptime = codec.maxptime;
        }
      });
      if (maxptime > 0) {
        sdp += 'a=maxptime:' + maxptime + '\r\n';
      }
      sdp += 'a=rtcp-mux\r\n';
    
      if (caps.headerExtensions) {
        caps.headerExtensions.forEach(function(extension) {
          sdp += SDPUtils.writeExtmap(extension);
        });
      }
      // FIXME: write fecMechanisms.
      return sdp;
    };
    
    // Parses the SDP media section and returns an array of
    // RTCRtpEncodingParameters.
    SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
      var encodingParameters = [];
      var description = SDPUtils.parseRtpParameters(mediaSection);
      var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
      var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
    
      // filter a=ssrc:... cname:, ignore PlanB-msid
      var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
        .map(function(line) {
          return SDPUtils.parseSsrcMedia(line);
        })
        .filter(function(parts) {
          return parts.attribute === 'cname';
        });
      var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
      var secondarySsrc;
    
      var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
        .map(function(line) {
          var parts = line.substr(17).split(' ');
          return parts.map(function(part) {
            return parseInt(part, 10);
          });
        });
      if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
        secondarySsrc = flows[0][1];
      }
    
      description.codecs.forEach(function(codec) {
        if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
          var encParam = {
            ssrc: primarySsrc,
            codecPayloadType: parseInt(codec.parameters.apt, 10)
          };
          if (primarySsrc && secondarySsrc) {
            encParam.rtx = {ssrc: secondarySsrc};
          }
          encodingParameters.push(encParam);
          if (hasRed) {
            encParam = JSON.parse(JSON.stringify(encParam));
            encParam.fec = {
              ssrc: primarySsrc,
              mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
            };
            encodingParameters.push(encParam);
          }
        }
      });
      if (encodingParameters.length === 0 && primarySsrc) {
        encodingParameters.push({
          ssrc: primarySsrc
        });
      }
    
      // we support both b=AS and b=TIAS but interpret AS as TIAS.
      var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
      if (bandwidth.length) {
        if (bandwidth[0].indexOf('b=TIAS:') === 0) {
          bandwidth = parseInt(bandwidth[0].substr(7), 10);
        } else if (bandwidth[0].indexOf('b=AS:') === 0) {
          // use formula from JSEP to convert b=AS to TIAS value.
          bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95
              - (50 * 40 * 8);
        } else {
          bandwidth = undefined;
        }
        encodingParameters.forEach(function(params) {
          params.maxBitrate = bandwidth;
        });
      }
      return encodingParameters;
    };
    
    // parses http://draft.ortc.org/#rtcrtcpparameters*
    SDPUtils.parseRtcpParameters = function(mediaSection) {
      var rtcpParameters = {};
    
      // Gets the first SSRC. Note tha with RTX there might be multiple
      // SSRCs.
      var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
        .map(function(line) {
          return SDPUtils.parseSsrcMedia(line);
        })
        .filter(function(obj) {
          return obj.attribute === 'cname';
        })[0];
      if (remoteSsrc) {
        rtcpParameters.cname = remoteSsrc.value;
        rtcpParameters.ssrc = remoteSsrc.ssrc;
      }
    
      // Edge uses the compound attribute instead of reducedSize
      // compound is !reducedSize
      var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
      rtcpParameters.reducedSize = rsize.length > 0;
      rtcpParameters.compound = rsize.length === 0;
    
      // parses the rtcp-mux attrіbute.
      // Note that Edge does not support unmuxed RTCP.
      var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
      rtcpParameters.mux = mux.length > 0;
    
      return rtcpParameters;
    };
    
    // parses either a=msid: or a=ssrc:... msid lines and returns
    // the id of the MediaStream and MediaStreamTrack.
    SDPUtils.parseMsid = function(mediaSection) {
      var parts;
      var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
      if (spec.length === 1) {
        parts = spec[0].substr(7).split(' ');
        return {stream: parts[0], track: parts[1]};
      }
      var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
        .map(function(line) {
          return SDPUtils.parseSsrcMedia(line);
        })
        .filter(function(msidParts) {
          return msidParts.attribute === 'msid';
        });
      if (planB.length > 0) {
        parts = planB[0].value.split(' ');
        return {stream: parts[0], track: parts[1]};
      }
    };
    
    // SCTP
    // parses draft-ietf-mmusic-sctp-sdp-26 first and falls back
    // to draft-ietf-mmusic-sctp-sdp-05
    SDPUtils.parseSctpDescription = function(mediaSection) {
      var mline = SDPUtils.parseMLine(mediaSection);
      var maxSizeLine = SDPUtils.matchPrefix(mediaSection, 'a=max-message-size:');
      var maxMessageSize;
      if (maxSizeLine.length > 0) {
        maxMessageSize = parseInt(maxSizeLine[0].substr(19), 10);
      }
      if (isNaN(maxMessageSize)) {
        maxMessageSize = 65536;
      }
      var sctpPort = SDPUtils.matchPrefix(mediaSection, 'a=sctp-port:');
      if (sctpPort.length > 0) {
        return {
          port: parseInt(sctpPort[0].substr(12), 10),
          protocol: mline.fmt,
          maxMessageSize: maxMessageSize
        };
      }
      var sctpMapLines = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:');
      if (sctpMapLines.length > 0) {
        var parts = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:')[0]
          .substr(10)
          .split(' ');
        return {
          port: parseInt(parts[0], 10),
          protocol: parts[1],
          maxMessageSize: maxMessageSize
        };
      }
    };
    
    // SCTP
    // outputs the draft-ietf-mmusic-sctp-sdp-26 version that all browsers
    // support by now receiving in this format, unless we originally parsed
    // as the draft-ietf-mmusic-sctp-sdp-05 format (indicated by the m-line
    // protocol of DTLS/SCTP -- without UDP/ or TCP/)
    SDPUtils.writeSctpDescription = function(media, sctp) {
      var output = [];
      if (media.protocol !== 'DTLS/SCTP') {
        output = [
          'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.protocol + '\r\n',
          'c=IN IP4 0.0.0.0\r\n',
          'a=sctp-port:' + sctp.port + '\r\n'
        ];
      } else {
        output = [
          'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.port + '\r\n',
          'c=IN IP4 0.0.0.0\r\n',
          'a=sctpmap:' + sctp.port + ' ' + sctp.protocol + ' 65535\r\n'
        ];
      }
      if (sctp.maxMessageSize !== undefined) {
        output.push('a=max-message-size:' + sctp.maxMessageSize + '\r\n');
      }
      return output.join('');
    };
    
    // Generate a session ID for SDP.
    // https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
    // recommends using a cryptographically random +ve 64-bit value
    // but right now this should be acceptable and within the right range
    SDPUtils.generateSessionId = function() {
      return Math.random().toString().substr(2, 21);
    };
    
    // Write boilder plate for start of SDP
    // sessId argument is optional - if not supplied it will
    // be generated randomly
    // sessVersion is optional and defaults to 2
    // sessUser is optional and defaults to 'thisisadapterortc'
    SDPUtils.writeSessionBoilerplate = function(sessId, sessVer, sessUser) {
      var sessionId;
      var version = sessVer !== undefined ? sessVer : 2;
      if (sessId) {
        sessionId = sessId;
      } else {
        sessionId = SDPUtils.generateSessionId();
      }
      var user = sessUser || 'thisisadapterortc';
      // FIXME: sess-id should be an NTP timestamp.
      return 'v=0\r\n' +
          'o=' + user + ' ' + sessionId + ' ' + version +
            ' IN IP4 127.0.0.1\r\n' +
          's=-\r\n' +
          't=0 0\r\n';
    };
    
    SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
      var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
    
      // Map ICE parameters (ufrag, pwd) to SDP.
      sdp += SDPUtils.writeIceParameters(
        transceiver.iceGatherer.getLocalParameters());
    
      // Map DTLS parameters to SDP.
      sdp += SDPUtils.writeDtlsParameters(
        transceiver.dtlsTransport.getLocalParameters(),
        type === 'offer' ? 'actpass' : 'active');
    
      sdp += 'a=mid:' + transceiver.mid + '\r\n';
    
      if (transceiver.direction) {
        sdp += 'a=' + transceiver.direction + '\r\n';
      } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
        sdp += 'a=sendrecv\r\n';
      } else if (transceiver.rtpSender) {
        sdp += 'a=sendonly\r\n';
      } else if (transceiver.rtpReceiver) {
        sdp += 'a=recvonly\r\n';
      } else {
        sdp += 'a=inactive\r\n';
      }
    
      if (transceiver.rtpSender) {
        // spec.
        var msid = 'msid:' + stream.id + ' ' +
            transceiver.rtpSender.track.id + '\r\n';
        sdp += 'a=' + msid;
    
        // for Chrome.
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
            ' ' + msid;
        if (transceiver.sendEncodingParameters[0].rtx) {
          sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
              ' ' + msid;
          sdp += 'a=ssrc-group:FID ' +
              transceiver.sendEncodingParameters[0].ssrc + ' ' +
              transceiver.sendEncodingParameters[0].rtx.ssrc +
              '\r\n';
        }
      }
      // FIXME: this should be written by writeRtpDescription.
      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
          ' cname:' + SDPUtils.localCName + '\r\n';
      if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
            ' cname:' + SDPUtils.localCName + '\r\n';
      }
      return sdp;
    };
    
    // Gets the direction from the mediaSection or the sessionpart.
    SDPUtils.getDirection = function(mediaSection, sessionpart) {
      // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
      var lines = SDPUtils.splitLines(mediaSection);
      for (var i = 0; i < lines.length; i++) {
        switch (lines[i]) {
          case 'a=sendrecv':
          case 'a=sendonly':
          case 'a=recvonly':
          case 'a=inactive':
            return lines[i].substr(2);
          default:
            // FIXME: What should happen here?
        }
      }
      if (sessionpart) {
        return SDPUtils.getDirection(sessionpart);
      }
      return 'sendrecv';
    };
    
    SDPUtils.getKind = function(mediaSection) {
      var lines = SDPUtils.splitLines(mediaSection);
      var mline = lines[0].split(' ');
      return mline[0].substr(2);
    };
    
    SDPUtils.isRejected = function(mediaSection) {
      return mediaSection.split(' ', 2)[1] === '0';
    };
    
    SDPUtils.parseMLine = function(mediaSection) {
      var lines = SDPUtils.splitLines(mediaSection);
      var parts = lines[0].substr(2).split(' ');
      return {
        kind: parts[0],
        port: parseInt(parts[1], 10),
        protocol: parts[2],
        fmt: parts.slice(3).join(' ')
      };
    };
    
    SDPUtils.parseOLine = function(mediaSection) {
      var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
      var parts = line.substr(2).split(' ');
      return {
        username: parts[0],
        sessionId: parts[1],
        sessionVersion: parseInt(parts[2], 10),
        netType: parts[3],
        addressType: parts[4],
        address: parts[5]
      };
    };
    
    // a very naive interpretation of a valid SDP.
    SDPUtils.isValidSDP = function(blob) {
      if (typeof blob !== 'string' || blob.length === 0) {
        return false;
      }
      var lines = SDPUtils.splitLines(blob);
      for (var i = 0; i < lines.length; i++) {
        if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
          return false;
        }
        // TODO: check the modifier a bit more.
      }
      return true;
    };
    
    // Expose public methods.
    if (typeof module === 'object') {
      module.exports = SDPUtils;
    }
    
    },{}]},{},[1])(1)
    });