fix issue #169.

Author: cloudwebrtc

lib/src/rtc_session.dart

@@ -359,7 +359,7 @@ class RTCSession extends EventManager {
 
     _newRTCSession('local', _request);
     await _sendInitialRequest(
-        mediaConstraints, rtcOfferConstraints, mediaStream);
+        pcConfig, mediaConstraints, rtcOfferConstraints, mediaStream);
   }
 
   void init_incoming(IncomingRequest request,
@@ -475,6 +475,12 @@ class RTCSession extends EventManager {
     bool peerOffersFullAudio = false;
     bool peerOffersFullVideo = false;
 
+    // In future versions, unified-plan will be used by default
+    String sdpSemantics = 'unified-plan';
+    if (pcConfig['sdpSemantics'] != null) {
+      sdpSemantics = pcConfig['sdpSemantics'];
+    }
+
     _rtcAnswerConstraints = rtcAnswerConstraints;
     _rtcOfferConstraints = options['rtcOfferConstraints'] ?? null;
 
@@ -615,8 +621,22 @@ class RTCSession extends EventManager {
 
     // Attach MediaStream to RTCPeerconnection.
     _localMediaStream = stream;
+
     if (stream != null) {
-      _connection.addStream(stream);
+      switch (sdpSemantics) {
+        case 'unified-plan':
+          stream.getTracks().forEach((MediaStreamTrack track) {
+            _connection.addTrack(track, stream);
+          });
+          break;
+        case 'plan-b':
+          _connection.addStream(stream);
+          break;
+        default:
+          logger.error('Unkown sdp semantics $sdpSemantics');
+          throw Exceptions.NotReadyError('Unkown sdp semantics $sdpSemantics');
+          break;
+      }
     }
 
     // Set remote description.
@@ -1565,9 +1585,28 @@ class RTCSession extends EventManager {
       }
     };
 
-    _connection.onAddStream = (MediaStream stream) {
-      emit(EventStream(session: this, originator: 'remote', stream: stream));
-    };
+    // In future versions, unified-plan will be used by default
+    String sdpSemantics = 'unified-plan';
+    if (pcConfig['sdpSemantics'] != null) {
+      sdpSemantics = pcConfig['sdpSemantics'];
+    }
+
+    switch (sdpSemantics) {
+      case 'unified-plan':
+        _connection.onTrack = (RTCTrackEvent event) {
+          if (event.track.kind == 'video' && event.streams.isNotEmpty) {
+            emit(EventStream(
+                session: this, originator: 'remote', stream: event.streams[0]));
+          }
+        };
+        break;
+      case 'plan-b':
+        _connection.onAddStream = (MediaStream stream) {
+          emit(
+              EventStream(session: this, originator: 'remote', stream: stream));
+        };
+        break;
+    }
 
     logger.debug('emit "peerconnection"');
     emit(EventPeerConnection(_connection));
@@ -2121,8 +2160,11 @@ class RTCSession extends EventManager {
   /**
    * Initial Request Sender
    */
-  Future<Null> _sendInitialRequest(Map<String, dynamic> mediaConstraints,
-      Map<String, dynamic> rtcOfferConstraints, MediaStream mediaStream) async {
+  Future<Null> _sendInitialRequest(
+      Map<String, dynamic> pcConfig,
+      Map<String, dynamic> mediaConstraints,
+      Map<String, dynamic> rtcOfferConstraints,
+      MediaStream mediaStream) async {
     EventManager handlers = EventManager();
     handlers.on(EventOnRequestTimeout(), (EventOnRequestTimeout value) {
       onRequestTimeout();
@@ -2139,6 +2181,12 @@ class RTCSession extends EventManager {
 
     RequestSender request_sender = RequestSender(_ua, _request, handlers);
 
+    // In future versions, unified-plan will be used by default
+    String sdpSemantics = 'unified-plan';
+    if (pcConfig['sdpSemantics'] != null) {
+      sdpSemantics = pcConfig['sdpSemantics'];
+    }
+
     // This Promise is resolved within the next iteration, so the app has now
     // a chance to set events such as 'peerconnection' and 'connecting'.
     MediaStream stream;
@@ -2177,7 +2225,20 @@ class RTCSession extends EventManager {
     _localMediaStream = stream;
 
     if (stream != null) {
-      _connection.addStream(stream);
+      switch (sdpSemantics) {
+        case 'unified-plan':
+          stream.getTracks().forEach((MediaStreamTrack track) {
+            _connection.addTrack(track, stream);
+          });
+          break;
+        case 'plan-b':
+          _connection.addStream(stream);
+          break;
+        default:
+          logger.error('Unkown sdp semantics $sdpSemantics');
+          throw Exceptions.NotReadyError('Unkown sdp semantics $sdpSemantics');
+          break;
+      }
     }
 
     // TODO(cloudwebrtc): should this be triggered here?

lib/src/sip_ua_helper.dart

@@ -156,8 +156,8 @@ class SIPUAHelper extends EventManager {
         RTCSession session = event.session;
         if (session.direction == 'incoming') {
           // Set event handlers.
-          session
-              .addAllEventHandlers(buildCallOptions()['eventHandlers'] as EventManager);
+          session.addAllEventHandlers(
+              buildCallOptions()['eventHandlers'] as EventManager);
         }
         _calls[event.id] =
             Call(event.id, session, CallStateEnum.CALL_INITIATION);
@@ -268,7 +268,10 @@ class SIPUAHelper extends EventManager {
 
     Map<String, Object> _defaultOptions = <String, dynamic>{
       'eventHandlers': handlers,
-      'pcConfig': <String, dynamic>{'iceServers': _uaSettings.iceServers},
+      'pcConfig': <String, dynamic>{
+        'sdpSemantics': 'unified-plan',
+        'iceServers': _uaSettings.iceServers
+      },
       'mediaConstraints': <String, dynamic>{
         'audio': true,
         'video': voiceonly