Address review: remove UserStartedSpeakingFrame, add explanatory comment

changelog/3429.added.md

@@ -1 +1 @@
-- Added handling for `server_content.interrupted` signal in Gemini Live services for faster interruption response.
+- Added handling for `server_content.interrupted` signal in the Gemini Live service for faster interruption response in the case where there isn't already turn tracking in the pipeline, e.g. local VAD + context aggregators. When there is already turn tracking in the pipeline, the additional interruption does no harm.

src/pipecat/services/google/gemini_live/llm.py

@@ -1199,8 +1199,17 @@ class GeminiLiveLLMService(LLMService):
                         self._check_and_reset_failure_counter()
 
                         if message.server_content and message.server_content.interrupted:
+                            # NOTE: while the service triggers interruptions in
+                            # the specific case of barge-ins, it does *not*
+                            # emit UserStarted/StoppedSpeakingFrames, as the
+                            # Gemini Live API does not give us broadly reliable
+                            # signals to base those off of. Pipelines that
+                            # require turn tracking (like those using context
+                            # aggregators) still need an independent way to
+                            # track turns, such as local Silero VAD in
+                            # combination with the context aggregator default
+                            # turn strategies.
                             logger.debug("Gemini VAD: interrupted signal received")
-                            await self.broadcast_frame(UserStartedSpeakingFrame())
                             await self.push_interruption_task_frame_and_wait()
                         elif message.server_content and message.server_content.model_turn:
                             await self._handle_msg_model_turn(message)