chore(llc): improve ice candidate tracing

dogfooding/linux/flutter/generated_plugin_registrant.cc

@@ -9,7 +9,6 @@
 #include <desktop_drop/desktop_drop_plugin.h>
 #include <file_selector_linux/file_selector_plugin.h>
 #include <gtk/gtk_plugin.h>
-#include <media_kit_video/media_kit_video_plugin.h>
 #include <record_linux/record_linux_plugin.h>
 #include <stream_webrtc_flutter/flutter_web_r_t_c_plugin.h>
 #include <url_launcher_linux/url_launcher_plugin.h>
@@ -24,9 +23,6 @@ void fl_register_plugins(FlPluginRegistry* registry) {
   g_autoptr(FlPluginRegistrar) gtk_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "GtkPlugin");
   gtk_plugin_register_with_registrar(gtk_registrar);
-  g_autoptr(FlPluginRegistrar) media_kit_video_registrar =
-      fl_plugin_registry_get_registrar_for_plugin(registry, "MediaKitVideoPlugin");
-  media_kit_video_plugin_register_with_registrar(media_kit_video_registrar);
   g_autoptr(FlPluginRegistrar) record_linux_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "RecordLinuxPlugin");
   record_linux_plugin_register_with_registrar(record_linux_registrar);

dogfooding/linux/flutter/generated_plugins.cmake

@@ -6,7 +6,6 @@ list(APPEND FLUTTER_PLUGIN_LIST
   desktop_drop
   file_selector_linux
   gtk
-  media_kit_video
   record_linux
   stream_webrtc_flutter
   url_launcher_linux

dogfooding/pubspec.yaml

@@ -38,7 +38,7 @@ dependencies:
   rxdart: ^0.28.0
   share_plus: ^13.0.0
   shared_preferences: ^2.5.3
-  stream_chat_flutter: ^10.0.0
+  stream_chat_flutter: ^10.2.0
   stream_video_filters: ^1.4.2
   stream_video_flutter: ^1.4.2
   stream_video_noise_cancellation: ^1.4.2

dogfooding/windows/flutter/generated_plugins.cmake

@@ -11,7 +11,6 @@ list(APPEND FLUTTER_PLUGIN_LIST
   firebase_auth
   firebase_core
   gal
-  media_kit_video
   permission_handler_windows
   record_windows
   share_plus

packages/stream_video/CHANGELOG.md

@@ -1,3 +1,9 @@
+## Upcoming
+
+### 🐞 Fixed
+
+- Serialized remote-description and ICE-candidate handling so a candidate arriving mid-negotiation can no longer be dropped.
+
 ## 1.4.2
 
 ### ✅ Added

packages/stream_video/lib/src/call/stats/trace_tag.dart

@@ -88,6 +88,7 @@ abstract class TraceTag {
   static const String setLocalDescriptionError = 'setLocalDescription.error';
   static const String addIceCandidate = 'addIceCandidate';
   static const String addIceCandidateSuccess = 'addIceCandidate.success';
+  static const String addIceCandidatePending = 'addIceCandidate.pending';
   static const String addIceCandidateError = 'addIceCandidate.error';
 
   // Peer connection factory

packages/stream_video/lib/src/webrtc/peer_connection.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:stream_webrtc_flutter/stream_webrtc_flutter.dart' as rtc;
+import 'package:synchronized/synchronized.dart';
 
 import '../../protobuf/video/sfu/models/models.pbenum.dart';
 import '../../protobuf/video/sfu/signal_rpc/signal.pb.dart';
@@ -10,7 +11,6 @@ import '../logger/impl/tagged_logger.dart';
 import '../models/call_cid.dart';
 import '../sfu/data/models/sfu_error.dart';
 import '../sfu/sfu_client.dart';
-import '../utils/none.dart';
 import '../utils/result.dart';
 import '../utils/standard.dart';
 import 'model/stats/rtc_printable_stats.dart';
@@ -58,6 +58,16 @@ typedef OnTrack =
       rtc.RTCTrackEvent,
     );
 
+enum AddIceCandidateResult {
+  /// The candidate was applied to the peer connection immediately.
+  added,
+
+  /// The remote description was not set yet, so the candidate was buffered
+  /// and will be applied when [StreamPeerConnection.setRemoteDescription]
+  /// completes. This is a normal, deferred-success outcome — not a drop.
+  buffered,
+}
+
 /// Wrapper around the WebRTC connection that contains tracks.
 class StreamPeerConnection extends Disposable {
   /// Creates [StreamPeerConnection] instance.
@@ -121,6 +131,9 @@ class StreamPeerConnection extends Disposable {
 
   final _pendingCandidates = <rtc.RTCIceCandidate>[];
 
+  /// Serializes [setRemoteDescription] and [addIceCandidate]
+  final _candidateLock = Lock();
+
   /// Attempts to restart ICE on the `RTCPeerConnection`.
   /// If the restart fails, this method will trigger onReconnectionNeeded with
   /// the appropriate reconnection strategy based on the error.
@@ -264,17 +277,30 @@ class StreamPeerConnection extends Disposable {
   /// Sets the remote description and adds any pending ice candidates.
   Future<Result<void>> setRemoteDescription(
     rtc.RTCSessionDescription sd,
-  ) async {
-    try {
-      final result = await pc.setRemoteDescription(sd);
-      for (final candidate in _pendingCandidates) {
-        await pc.addCandidate(candidate);
+  ) {
+    return _candidateLock.synchronized(() async {
+      try {
+        await pc.setRemoteDescription(sd);
+      } catch (e, stk) {
+        return Result.failure(VideoErrors.compose(e, stk));
       }
+
+      final pending = List<rtc.RTCIceCandidate>.of(_pendingCandidates);
       _pendingCandidates.clear();
-      return Result.success(result);
-    } catch (e, stk) {
-      return Result.failure(VideoErrors.compose(e, stk));
-    }
+      for (final candidate in pending) {
+        try {
+          await pc.addCandidate(candidate);
+        } catch (e) {
+          _logger.w(
+            () =>
+                '[setRemoteDescription] #$type; dropping candidate '
+                '${candidate.candidate}; failed: $e',
+          );
+        }
+      }
+
+      return const Result.success(null);
+    });
   }
 
   //Sets the local description
@@ -314,20 +340,25 @@ class StreamPeerConnection extends Disposable {
 
   /// Adds an ice candidate to the peer connection.
   ///
-  /// If the peer connection is not yet ready, the candidate is added to a list
-  /// of pending candidates.
-  Future<Result<None>> addIceCandidate(rtc.RTCIceCandidate candidate) async {
-    try {
-      final remoteDescription = await pc.getRemoteDescription();
-      if (remoteDescription == null) {
-        _pendingCandidates.add(candidate);
-        return Result.error('no remoteDescription set');
+  /// If the remote description has not been set yet, the candidate cannot be
+  /// applied immediately, so it is buffered in [_pendingCandidates] and flushed
+  /// by [setRemoteDescription].
+  Future<Result<AddIceCandidateResult>> addIceCandidate(
+    rtc.RTCIceCandidate candidate,
+  ) {
+    return _candidateLock.synchronized(() async {
+      try {
+        final remoteDescription = await pc.getRemoteDescription();
+        if (remoteDescription == null) {
+          _pendingCandidates.add(candidate);
+          return const Result.success(AddIceCandidateResult.buffered);
+        }
+        await pc.addCandidate(candidate);
+        return const Result.success(AddIceCandidateResult.added);
+      } catch (e, stk) {
+        return Result.failure(VideoErrors.compose(e, stk));
       }
-      await pc.addCandidate(candidate);
-      return const Result.success(none);
-    } catch (e, stk) {
-      return Result.failure(VideoErrors.compose(e, stk));
-    }
+    });
   }
 
   /// Adds a local [rtc.MediaStreamTrack] with audio to the current connection.

packages/stream_video/lib/src/webrtc/rtc_manager.dart

@@ -217,13 +217,16 @@ class RtcManager extends Disposable {
     required String iceCandidate,
   }) async {
     final candidate = RtcIceCandidateParser.fromJsonString(iceCandidate);
+    final Result<AddIceCandidateResult>? result;
     if (peerType == StreamPeerType.publisher) {
-      return publisher?.addIceCandidate(candidate) ??
-          Result.error('no publisher created');
+      result = await publisher?.addIceCandidate(candidate);
+      if (result == null) return Result.error('no publisher created');
     } else if (peerType == StreamPeerType.subscriber) {
-      return subscriber.addIceCandidate(candidate);
+      result = await subscriber.addIceCandidate(candidate);
+    } else {
+      return Result.error('unexpected peerType: $peerType');
     }
-    return Result.error('unexpected peerType: $peerType');
+    return result.map((_) => none);
   }
 
   void _onRemoteTrack(StreamPeerConnection pc, rtc.RTCTrackEvent event) {

packages/stream_video/lib/src/webrtc/traced_peer_connection.dart

@@ -9,7 +9,6 @@ import '../call/stats/tracer.dart';
 import '../sfu/data/models/sfu_codec.dart';
 import '../sfu/data/models/sfu_model_mapper_extensions.dart';
 import '../sfu/data/models/sfu_track_type.dart';
-import '../utils/none.dart';
 import '../utils/result.dart';
 import 'model/stats/rtc_codec.dart';
 import 'model/stats/rtc_inbound_rtp_video_stream.dart';
@@ -471,19 +470,25 @@ class TracedStreamPeerConnection extends StreamPeerConnection {
   }
 
   @override
-  Future<Result<None>> addIceCandidate(rtc.RTCIceCandidate candidate) async {
+  Future<Result<AddIceCandidateResult>> addIceCandidate(
+    rtc.RTCIceCandidate candidate,
+  ) async {
     tracer.trace(TraceTag.addIceCandidate, candidate.toMap());
 
     final result = await super.addIceCandidate(candidate);
 
-    if (result.isSuccess) {
-      tracer.trace(TraceTag.addIceCandidateSuccess, null);
-    } else {
-      tracer.trace(
+    result.when(
+      success: (outcome) => tracer.trace(
+        outcome == AddIceCandidateResult.buffered
+            ? TraceTag.addIceCandidatePending
+            : TraceTag.addIceCandidateSuccess,
+        null,
+      ),
+      failure: (error) => tracer.trace(
         TraceTag.addIceCandidateError,
-        result.getErrorOrNull()?.toString(),
-      );
-    }
+        error.toString(),
+      ),
+    );
 
     return result;
   }