Improvements for the SmallWebRTCTransport:

- Wait until the pipeline is ready before triggering the `connected` event.
  - Queue messages if the data channel is not ready.
  - Update the aiortc dependency to fix an issue where the 'video/rtx' MIME type
    was incorrectly handled as a codec retransmission.
  - Avoid initial video delays.

CHANGELOG.md

@@ -16,6 +16,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   producer. These processors can be useful to push frames from one part of a
   pipeline to a different one (e.g. when using `ParallelPipeline`).
 
+- Improvements for the `SmallWebRTCTransport`:
+  - Wait until the pipeline is ready before triggering the `connected` event.
+  - Queue messages if the data channel is not ready.
+  - Update the aiortc dependency to fix an issue where the 'video/rtx' MIME type 
+    was incorrectly handled as a codec retransmission.
+  - Avoid initial video delays.
+
 ### Fixed
 
 - Fixed `SmallWebRTCTransport` to support dynamic values for

src/pipecat/transports/network/webrtc_connection.py

@@ -16,6 +16,7 @@ from pipecat.utils.base_object import BaseObject
 
 try:
     from aiortc import RTCConfiguration, RTCIceServer, RTCPeerConnection, RTCSessionDescription
+    from aiortc.rtcrtpreceiver import RemoteStreamTrack
 except ModuleNotFoundError as e:
     logger.error(f"Exception: {e}")
     logger.error("In order to use the SmallWebRTC, you need to `pip install pipecat-ai[webrtc]`.")
@@ -71,12 +72,21 @@ class SmallWebRTCConnection(BaseObject):
         self._data_channel = None
         self._renegotiation_in_progress = False
         self._last_received_time = None
+        self._message_queue = []
 
     def _setup_listeners(self):
         @self._pc.on("datachannel")
         def on_datachannel(channel):
             self._data_channel = channel
 
+            # Flush queued messages once the data channel is open
+            @channel.on("open")
+            async def on_open():
+                logger.debug("Data channel is open, flushing queued messages")
+                while self._message_queue:
+                    message = self._message_queue.pop(0)
+                    self._data_channel.send(message)
+
             @channel.on("message")
             async def on_message(message):
                 try:
@@ -138,6 +148,17 @@ class SmallWebRTCConnection(BaseObject):
     async def initialize(self, sdp: str, type: str):
         await self._create_answer(sdp, type)
 
+    async def discard_old_frames(self, remote_track: RemoteStreamTrack):
+        if not hasattr(remote_track, "_queue") or not isinstance(
+            remote_track._queue, asyncio.Queue
+        ):
+            print("Warning: _queue does not exist or has changed in aiortc.")
+            return
+        logger.debug("Discarding old frames")
+        while not remote_track._queue.empty():
+            remote_track._queue.get_nowait()  # Remove the oldest frame
+            remote_track._queue.task_done()
+
     async def connect(self):
         self._connect_invoked = True
         # If we already connected, trigger again the connected event
@@ -145,6 +166,9 @@ class SmallWebRTCConnection(BaseObject):
             await self._call_event_handler("connected")
             # We are renegotiating here, because likely we have loose the first video frames
             # and aiortc does not handle that pretty well.
+            remove_video_track = self.video_input_track()
+            if isinstance(remove_video_track, RemoteStreamTrack):
+                await self.discard_old_frames(remove_video_track)
             self.ask_to_renegotiate()
 
     async def renegotiate(self, sdp: str, type: str, restart_pc: bool = False):
@@ -203,6 +227,7 @@ class SmallWebRTCConnection(BaseObject):
     async def close(self):
         if self._pc:
             await self._pc.close()
+        self._message_queue.clear()
 
     def get_answer(self):
         if not self._answer:
@@ -216,6 +241,9 @@ class SmallWebRTCConnection(BaseObject):
 
     async def _handle_new_connection_state(self):
         state = self._pc.connectionState
+        if state == "connected" and not self._connect_invoked:
+            # We are going to wait until the pipeline is ready before triggering the event
+            return
         logger.debug(f"Connection state changed to: {state}")
         await self._call_event_handler(state)
         if state == "failed":
@@ -264,9 +292,12 @@ class SmallWebRTCConnection(BaseObject):
         return self._tracks
 
     def send_app_message(self, message: Any):
-        if self._data_channel:
-            json_message = json.dumps(message)
+        json_message = json.dumps(message)
+        if self._data_channel and self._data_channel.readyState == "open":
             self._data_channel.send(json_message)
+        else:
+            logger.debug("Data channel not ready, queuing message")
+            self._message_queue.append(json_message)
 
     def ask_to_renegotiate(self):
         if self._renegotiation_in_progress: