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

examples/twilio-chatbot/test_bot.py

@@ -0,0 +1,88 @@
+import aiohttp
+import os
+import sys
+
+from pipecat.frames.frames import LLMMessagesFrame, Frame, AudioRawFrame
+from pipecat.pipeline.pipeline import Pipeline
+from pipecat.pipeline.runner import PipelineRunner
+from pipecat.pipeline.task import PipelineParams, PipelineTask
+from pipecat.processors.aggregators.llm_response import (
+    LLMAssistantResponseAggregator,
+    LLMUserResponseAggregator
+)
+from pipecat.processors.frame_processor import FrameProcessor, FrameDirection
+
+from pipecat.services.openai import OpenAILLMService
+from pipecat.services.deepgram import DeepgramSTTService
+from pipecat.services.elevenlabs import ElevenLabsTTSService
+from pipecat.transports.network.fastapi_websocket import FastAPIWebsocketTransport, FastAPIWebsocketParams
+from pipecat.vad.silero import SileroVADAnalyzer
+
+from loguru import logger
+
+from dotenv import load_dotenv
+load_dotenv(override=True)
+
+logger.remove(0)
+logger.add(sys.stderr, level="DEBUG")
+
+
+async def run_bot(websocket_client):
+    async with aiohttp.ClientSession() as session:
+        transport = FastAPIWebsocketTransport(
+            websocket=websocket_client,
+            params=FastAPIWebsocketParams(
+                audio_in_enabled=True,
+                audio_out_enabled=True,
+                add_wav_header=False,
+                transcription_enabled=False,
+                vad_enabled=True,
+                vad_analyzer=SileroVADAnalyzer(),
+                vad_audio_passthrough=True
+            )
+        )
+
+        llm = OpenAILLMService(
+            api_key=os.getenv("OPENAI_API_KEY"),
+            model="gpt-4o")
+
+        stt = DeepgramSTTService(api_key=os.getenv('DEEPGRAM_API_KEY'))
+
+        tts = ElevenLabsTTSService(
+            aiohttp_session=session,
+            api_key=os.getenv("ELEVENLABS_API_KEY"),
+            voice_id=os.getenv("ELEVENLABS_VOICE_ID"),
+        )
+
+        messages = [
+            {
+                "role": "system",
+                "content": "You are a helpful LLM in a WebRTC call. Your goal is to demonstrate your capabilities in a succinct way. Your output will be converted to audio so don't include special characters in your answers. Respond to what the user said in a creative and helpful way.",
+            },
+        ]
+
+        tma_in = LLMUserResponseAggregator(messages)
+        tma_out = LLMAssistantResponseAggregator(messages)
+
+        pipeline = Pipeline([
+            transport.input(),   # Websocket input from client
+            stt,                 # Speech-To-Text
+            tma_in,              # User responses
+            llm,                 # LLM
+            tts,                 # Text-To-Speech
+            transport.output(),  # Websocket output to client
+            tma_out              # LLM responses
+        ])
+
+        task = PipelineTask(pipeline, params=PipelineParams(allow_interruptions=True))
+
+        @transport.event_handler("on_client_connected")
+        async def on_client_connected(transport, client):
+            # Kick off the conversation.
+            messages.append(
+                {"role": "system", "content": "Please introduce yourself to the user."})
+            await task.queue_frames([LLMMessagesFrame(messages)])
+
+        runner = PipelineRunner(handle_sigint=False)
+
+        await runner.run(task)