diff --git a/lib/src/extensions.dart b/lib/src/extensions.dart
index 4949cfa..0afc7c8 100644
--- a/lib/src/extensions.dart
+++ b/lib/src/extensions.dart
@@ -40,6 +40,7 @@ extension ProtocolVersionExt on ProtocolVersion {
   String toStringValue() => {
         ProtocolVersion.protocol2: '2',
         ProtocolVersion.protocol3: '3',
+        ProtocolVersion.protocol4: '4',
       }[this]!;
 }
 
diff --git a/lib/src/participant/remote_participant.dart b/lib/src/participant/remote_participant.dart
index 418572d..8ba718e 100644
--- a/lib/src/participant/remote_participant.dart
+++ b/lib/src/participant/remote_participant.dart
@@ -1,4 +1,6 @@
 import 'package:flutter_webrtc/flutter_webrtc.dart' as rtc;
+import 'package:livekit_client/src/track/remote_audio_track.dart';
+import 'package:livekit_client/src/track/remote_video_track.dart';
 import 'package:meta/meta.dart';
 
 import '../constants.dart';
@@ -8,10 +10,8 @@ import '../logger.dart';
 import '../managers/event.dart';
 import '../proto/livekit_models.pb.dart' as lk_models;
 import '../signal_client.dart';
-import '../track/audio_track.dart';
 import '../track/remote_track_publication.dart';
 import '../track/track.dart';
-import '../track/video_track.dart';
 import '../types.dart';
 import 'participant.dart';
 
@@ -91,14 +91,14 @@ class RemoteParticipant extends Participant {
     final Track track;
     if (pub.kind == lk_models.TrackType.AUDIO) {
       // audio track
-      final audioTrack = AudioTrack(pub.name, mediaTrack, stream);
-      await audioTrack.start();
-      track = audioTrack;
+      track = RemoteAudioTrack(pub.name, mediaTrack, stream);
     } else {
       // video track
-      track = VideoTrack(pub.name, mediaTrack, stream);
+      track = RemoteVideoTrack(pub.name, mediaTrack, stream);
     }
 
+    await track.start();
+
     pub.track = track;
     addTrackPublication(pub);
 
diff --git a/lib/src/rtc_engine.dart b/lib/src/rtc_engine.dart
index 29b073c..6cdee1e 100644
--- a/lib/src/rtc_engine.dart
+++ b/lib/src/rtc_engine.dart
@@ -495,6 +495,7 @@ class RTCEngine extends Disposable with EventsEmittable<EngineEvent> {
 
       logger.fine('[$objectId] Received server offer(type: ${event.sd.type}, '
           '${subscriber!.pc.signalingState})');
+      logger.finer('sdp: ${event.sd.sdp}');
 
       await subscriber!.setRemoteDescription(event.sd);
 
diff --git a/lib/src/signal_client.dart b/lib/src/signal_client.dart
index 538d915..44382c8 100644
--- a/lib/src/signal_client.dart
+++ b/lib/src/signal_client.dart
@@ -24,7 +24,7 @@ class SignalClient extends Disposable with EventsEmittable<SignalEvent> {
   LiveKitWebSocket? _ws;
 
   SignalClient({
-    this.protocol = ProtocolVersion.protocol3,
+    this.protocol = ProtocolVersion.protocol4,
   }) {
     events.listen((event) {
       logger.fine('[SignalEvent] $event');
diff --git a/lib/src/track/audio_track.dart b/lib/src/track/audio_track.dart
index 26808ec..2a7ac9d 100644
--- a/lib/src/track/audio_track.dart
+++ b/lib/src/track/audio_track.dart
@@ -8,7 +8,7 @@ import 'package:synchronized/synchronized.dart' as sync;
 import '../logger.dart';
 import '../proto/livekit_models.pb.dart' as lk_models;
 import '../support/native_audio.dart';
-import '_audio_api.dart' if (dart.library.html) '_audio_html.dart' as audio;
+
 import 'local_audio_track.dart';
 import 'track.dart';
 
@@ -22,7 +22,7 @@ enum AudioTrackState {
 typedef ConfigureNativeAudioFunc = Future<NativeAudioConfiguration> Function(
     AudioTrackState state);
 
-class AudioTrack extends Track {
+abstract class AudioTrack extends Track {
   // it's possible to set custom function here to customize audio session configuration
   static ConfigureNativeAudioFunc nativeAudioConfigurationForAudioTrackState =
       defaultNativeAudioConfigurationFunc;
@@ -50,10 +50,6 @@ class AudioTrack extends Track {
   Future<bool> start() async {
     final didStart = await super.start();
     if (didStart) {
-      if (this is! LocalAudioTrack) {
-        audio.startAudio(getCid(), mediaStreamTrack);
-      }
-
       // update counter
       await _trackCounterLock.synchronized(() async {
         if (this is LocalAudioTrack) {
@@ -64,7 +60,6 @@ class AudioTrack extends Track {
         await _onAudioTrackCountDidChange();
       });
     }
-
     return didStart;
   }
 
@@ -72,10 +67,6 @@ class AudioTrack extends Track {
   Future<bool> stop() async {
     final didStop = await super.stop();
     if (didStop) {
-      await mediaStream?.dispose();
-      mediaStream = null;
-      audio.stopAudio(getCid());
-
       // update counter
       await _trackCounterLock.synchronized(() async {
         if (this is LocalAudioTrack) {
@@ -86,7 +77,6 @@ class AudioTrack extends Track {
         await _onAudioTrackCountDidChange();
       });
     }
-
     return didStop;
   }
 
diff --git a/lib/src/track/local_audio_track.dart b/lib/src/track/local_audio_track.dart
index ff8201f..9b0709f 100644
--- a/lib/src/track/local_audio_track.dart
+++ b/lib/src/track/local_audio_track.dart
@@ -7,7 +7,8 @@ import 'audio_track.dart';
 import 'options.dart';
 
 class LocalAudioTrack extends AudioTrack {
-  LocalAudioTrack(
+  // private constructor
+  LocalAudioTrack._(
     String name,
     rtc.MediaStreamTrack track,
     rtc.MediaStream stream,
@@ -29,6 +30,15 @@ class LocalAudioTrack extends AudioTrack {
 
     if (stream.getAudioTracks().isEmpty) throw TrackCreateException();
 
-    return LocalAudioTrack('', stream.getAudioTracks().first, stream);
+    return LocalAudioTrack._('', stream.getAudioTracks().first, stream);
+  }
+
+  @override
+  Future<bool> stop() async {
+    final didStop = await super.stop();
+    if (didStop) {
+      await mediaStreamTrack.stop();
+    }
+    return didStop;
   }
 }
diff --git a/lib/src/track/local_video_track.dart b/lib/src/track/local_video_track.dart
index c7197f6..4ce5280 100644
--- a/lib/src/track/local_video_track.dart
+++ b/lib/src/track/local_video_track.dart
@@ -92,6 +92,15 @@ class LocalVideoTrack extends VideoTrack {
     if (stream.getVideoTracks().isEmpty) throw TrackCreateException();
     return stream;
   }
+
+  @override
+  Future<bool> stop() async {
+    final didStop = await super.stop();
+    if (didStop) {
+      await mediaStreamTrack.stop();
+    }
+    return didStop;
+  }
 }
 
 //
diff --git a/lib/src/track/remote_audio_track.dart b/lib/src/track/remote_audio_track.dart
new file mode 100644
index 0000000..cf15310
--- /dev/null
+++ b/lib/src/track/remote_audio_track.dart
@@ -0,0 +1,34 @@
+import 'package:flutter_webrtc/flutter_webrtc.dart' as rtc;
+import '_audio_api.dart' if (dart.library.html) '_audio_html.dart' as audio;
+import 'audio_track.dart';
+
+class RemoteAudioTrack extends AudioTrack {
+  //
+  RemoteAudioTrack(
+    String name,
+    rtc.MediaStreamTrack track,
+    rtc.MediaStream stream,
+  ) : super(name, track, stream);
+
+  @override
+  Future<bool> start() async {
+    final didStart = await super.start();
+    if (didStart) {
+      // web support
+      audio.startAudio(getCid(), mediaStreamTrack);
+      await enable();
+    }
+    return didStart;
+  }
+
+  @override
+  Future<bool> stop() async {
+    final didStop = await super.stop();
+    if (didStop) {
+      // web support
+      audio.stopAudio(getCid());
+      await disable();
+    }
+    return didStop;
+  }
+}
diff --git a/lib/src/track/remote_video_track.dart b/lib/src/track/remote_video_track.dart
new file mode 100644
index 0000000..e976ef2
--- /dev/null
+++ b/lib/src/track/remote_video_track.dart
@@ -0,0 +1,29 @@
+import 'package:flutter_webrtc/flutter_webrtc.dart' as rtc;
+import 'package:livekit_client/src/track/video_track.dart';
+
+class RemoteVideoTrack extends VideoTrack {
+  //
+  RemoteVideoTrack(
+    String name,
+    rtc.MediaStreamTrack mediaTrack,
+    rtc.MediaStream stream,
+  ) : super(name, mediaTrack, stream);
+
+  @override
+  Future<bool> start() async {
+    final didStart = await super.start();
+    if (didStart) {
+      await enable();
+    }
+    return didStart;
+  }
+
+  @override
+  Future<bool> stop() async {
+    final didStop = await super.stop();
+    if (didStop) {
+      await disable();
+    }
+    return didStop;
+  }
+}
diff --git a/lib/src/track/track.dart b/lib/src/track/track.dart
index 689e16f..f258e89 100644
--- a/lib/src/track/track.dart
+++ b/lib/src/track/track.dart
@@ -76,6 +76,8 @@ abstract class Track extends DisposableChangeNotifier
       return false;
     }
 
+    logger.fine('Track.start()');
+
     _active = true;
     return true;
   }
@@ -88,13 +90,29 @@ abstract class Track extends DisposableChangeNotifier
       return false;
     }
 
-    try {
-      await mediaStreamTrack.stop();
-    } catch (_) {
-      logger.warning('[$objectId] rtc.mediaStreamTrack.stop() did throw ${_}');
-    }
+    logger.fine('Track.stop()');
 
     _active = false;
     return true;
   }
+
+  Future<void> enable() async {
+    logger.fine('Track.enable()');
+    try {
+      mediaStreamTrack.enabled = true;
+    } catch (_) {
+      logger.warning(
+          '[$objectId] set rtc.mediaStreamTrack.enabled did throw ${_}');
+    }
+  }
+
+  Future<void> disable() async {
+    logger.fine('Track.disable()');
+    try {
+      mediaStreamTrack.enabled = false;
+    } catch (_) {
+      logger.warning(
+          '[$objectId] set rtc.mediaStreamTrack.enabled did throw ${_}');
+    }
+  }
 }
diff --git a/lib/src/track/video_track.dart b/lib/src/track/video_track.dart
index 0677b9d..171ed17 100644
--- a/lib/src/track/video_track.dart
+++ b/lib/src/track/video_track.dart
@@ -5,7 +5,7 @@ import '../proto/livekit_models.pb.dart' as lk_models;
 import 'track.dart';
 
 /// A video track will notify when its mediaTrack has changed.
-class VideoTrack extends Track {
+abstract class VideoTrack extends Track {
   rtc.MediaStream _mediaStream;
 
   VideoTrack(
diff --git a/lib/src/types.dart b/lib/src/types.dart
index 0917e0b..98888aa 100644
--- a/lib/src/types.dart
+++ b/lib/src/types.dart
@@ -7,6 +7,7 @@ typedef CancelListenFunc = Function();
 enum ProtocolVersion {
   protocol2,
   protocol3,
+  protocol4,
 }
 
 enum ConnectionState {