Starting the base output transport only after starting the small webrtc transport.

CHANGELOG.md

@@ -5,6 +5,15 @@ All notable changes to **Pipecat** will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- Added real-time throttling to the `BaseOutputTransport` when using audio mixer
+  to ensure audio frames (including silence) are emitted at the correct intervals. 
+  This prevents unnecessary CPU usage and avoids flooding the output with silent 
+  frames when no new audio is available.
+
 ## [0.0.66] - 2025-05-02
 
 ### Added

src/pipecat/transports/base_output.py

@@ -435,6 +435,9 @@ class BaseOutputTransport(FrameProcessor):
             async def with_mixer(vad_stop_secs: float) -> AsyncGenerator[Frame, None]:
                 last_frame_time = 0
                 silence = b"\x00" * self._audio_chunk_size
+                # chunk duration in seconds
+                chunk_duration = (10 * self._params.audio_out_10ms_chunks) / 1000.0
+                next_frame_time = time.time()
                 while True:
                     try:
                         frame = self._audio_queue.get_nowait()
@@ -454,6 +457,11 @@ class BaseOutputTransport(FrameProcessor):
                             num_channels=self._params.audio_out_channels,
                         )
                         yield frame
+                    # Throttle frame generation to maintain real-time pacing and avoid flooding with silence
+                    wait = next_frame_time - time.time()
+                    if wait > 0:
+                        await asyncio.sleep(wait)
+                    next_frame_time += chunk_duration
 
             if self._mixer:
                 return with_mixer(BOT_VAD_STOP_SECS)

src/pipecat/transports/network/small_webrtc.py

@@ -484,9 +484,10 @@ class SmallWebRTCOutputTransport(BaseOutputTransport):
         self._params = params
 
     async def start(self, frame: StartFrame):
-        await super().start(frame)
         await self._client.setup(self._params, frame)
         await self._client.connect()
+        # Parent start.
+        await super().start(frame)
 
     async def stop(self, frame: EndFrame):
         await super().stop(frame)