add twilio-chatbot example with README.md info how to start app

created twilio_websocket_service.py, TwilioFrameSerializer.py

moved pcm_16000_to_ulaw_8000 and ulaw_8000_to_pcm_16000 to src/pipecat/utils/audio.py
fixed callback on disconnect

src/pipecat/transports/network/fastapi_websocket.py

@@ -0,0 +1,132 @@
+import asyncio
+import io
+import wave
+from fastapi import WebSocket
+
+from typing import Awaitable, Callable
+from pydantic.main import BaseModel
+
+from pipecat.serializers.TwilioFrameSerializer import TwilioFrameSerializer
+from pipecat.frames.frames import AudioRawFrame, StartFrame
+from pipecat.processors.frame_processor import FrameProcessor
+from pipecat.serializers.base_serializer import FrameSerializer
+from pipecat.transports.base_input import BaseInputTransport
+from pipecat.transports.base_output import BaseOutputTransport
+from pipecat.transports.base_transport import BaseTransport, TransportParams
+
+from loguru import logger
+
+
+class FastAPIWebsocketParams(TransportParams):
+    add_wav_header: bool = False
+    audio_frame_size: int = 6400  # 200ms
+    serializer: FrameSerializer = TwilioFrameSerializer()
+
+
+class FastAPIWebsocketCallbacks(BaseModel):
+    on_client_connected: Callable[[WebSocket], Awaitable[None]]
+    on_client_disconnected: Callable[[WebSocket], Awaitable[None]]
+
+
+class FastAPIWebsocketInputTransport(BaseInputTransport):
+
+    def __init__(self, websocket: WebSocket, params: FastAPIWebsocketParams, callbacks: FastAPIWebsocketCallbacks, **kwargs):
+        super().__init__(params, **kwargs)
+
+        self._websocket = websocket
+        self._params = params
+        self._callbacks = callbacks
+
+    async def start(self, frame: StartFrame):
+        await self._callbacks.on_client_connected(self._websocket)
+        await super().start(frame)
+        self._receive_task = self.get_event_loop().create_task(self._receive_messages())
+
+    async def stop(self):
+        await self._websocket.close()
+        await super().stop()
+
+    async def _receive_messages(self):
+        async for message in self._websocket.iter_text():
+            frame = self._params.serializer.deserialize(message)
+
+            if not frame:
+                continue
+
+            if isinstance(frame, AudioRawFrame):
+                self.push_audio_frame(frame)
+
+        await self._callbacks.on_client_disconnected(self._websocket)
+
+class FastAPIWebsocketOutputTransport(BaseOutputTransport):
+
+    def __init__(self, websocket: WebSocket, params: FastAPIWebsocketParams, **kwargs):
+        super().__init__(params, **kwargs)
+
+        self._websocket = websocket
+        self._params = params
+        self._audio_buffer = bytes()
+
+    def write_raw_audio_frames(self, frames: bytes):
+        self._audio_buffer += frames
+        while len(self._audio_buffer) >= self._params.audio_frame_size:
+            frame = AudioRawFrame(
+                audio=self._audio_buffer[:self._params.audio_frame_size],
+                sample_rate=self._params.audio_out_sample_rate,
+                num_channels=self._params.audio_out_channels
+            )
+
+            if self._params.add_wav_header:
+                content = io.BytesIO()
+                ww = wave.open(content, "wb")
+                ww.setsampwidth(2)
+                ww.setnchannels(frame.num_channels)
+                ww.setframerate(frame.sample_rate)
+                ww.writeframes(frame.audio)
+                ww.close()
+                content.seek(0)
+                wav_frame = AudioRawFrame(
+                    content.read(),
+                    sample_rate=frame.sample_rate,
+                    num_channels=frame.num_channels)
+                frame = wav_frame
+
+            payload = self._params.serializer.serialize(frame)
+
+            future = asyncio.run_coroutine_threadsafe(
+                self._websocket.send_json(payload), self.get_event_loop())
+            future.result()
+
+            self._audio_buffer = self._audio_buffer[self._params.audio_frame_size:]
+
+
+class FastAPIWebsocketTransport(BaseTransport):
+
+    def __init__(self, websocket: WebSocket, params: FastAPIWebsocketParams = FastAPIWebsocketParams(), input_name: str | None = None, output_name: str | None = None, loop: asyncio.AbstractEventLoop | None = None):
+        super().__init__(input_name=input_name, output_name=output_name, loop=loop)
+        self._params = params
+
+        self._callbacks = FastAPIWebsocketCallbacks(
+            on_client_connected=self._on_client_connected,
+            on_client_disconnected=self._on_client_disconnected
+        )
+
+        self._input = FastAPIWebsocketInputTransport(websocket, self._params, self._callbacks, name=self._input_name)
+        self._output = FastAPIWebsocketOutputTransport(websocket, self._params, name=self._output_name)
+
+        # Register supported handlers. The user will only be able to register
+        # these handlers.
+        self._register_event_handler("on_client_connected")
+        self._register_event_handler("on_client_disconnected")
+
+    def input(self) -> FrameProcessor:
+        return self._input
+
+    def output(self) -> FrameProcessor:
+        return self._output
+
+    async def _on_client_connected(self, websocket):
+        await self._call_event_handler("on_client_connected", websocket)
+
+    async def _on_client_disconnected(self, websocket):
+        await self._call_event_handler("on_client_disconnected", websocket)