Real-time Voice Agent

In this tutorial, we’ll create a real-time voice agent that responds to queries via speech in ~500ms. This flexible implementation lets you swap in any Large Language Model (LLM) or Text-to-Speech (TTS) model. It’s ideal for voice-based use cases like customer support bots and receptionists. To create this app, we use PipeCat, a framework that handles component integration, user interruptions, and audio data processing. We’ll demonstrate this by joining a meeting room with our voice agent using Daily (PipeCat’s creators) and deploy the app on Cerebrium for seamless deployment and scaling. Essentially our application will have 3/4 parts:

Your Pipecat agent which acts as the orchestrator
Your Deepgram TTS/STT service (Requires a Deepgram Enterprise account)
A self-hosted LLM using the vLLM framework

The reason we achieve such low latency is that each service is hosted within Cerebrium and so we have no network latency for the requests we make - communication across containers is less than 10ms. Realtime Voice Agents

You can find the final version of the code here If you don’t have a Cerebrium account, you can create one by signing up here and following the documentation here to get set up.

Deepgram deployment

For the sake of conciseness, look at our Partner Services page to see how you can deploy a Deepgram service on Cerebrium. The link is here

You need a Deepgram Enterprise License to do deploy Deegram on Cerebrium else you must use their API endpoint below.

LLM Deployment

For our LLM we deploy a OpenAI compatible Llama-3 endpoint using the vLLM framework - in order to have a low TTFT we deploy a quantized version (RedHatAI/Meta-Llama-3.1-8B-Instruct-quantized.w8a8”). Run cerebrium init llama-llm and add the following code to your cerebrium.toml:

[cerebrium.deployment]
name = "llama-llm"
python_version = "3.11"
docker_base_image_url = "debian:bookworm-slim"
include = ["./*", "main.py", "cerebrium.toml"]
exclude = [".*"]

[cerebrium.hardware]
cpu = 4
memory = 12.0
compute = "ADA_L40"

[cerebrium.scaling]
min_replicas = 1
max_replicas = 5
cooldown = 60

[cerebrium.dependencies.pip]
vllm = "latest"
pydantic = "latest"

Add the following code to your main.py - this uses the vLLM framework and makes it openAI compatible:

import os
import time
import json

from huggingface_hub import login
from pydantic import BaseModel
from vllm import SamplingParams, AsyncLLMEngine
from vllm.engine.arg_utils import AsyncEngineArgs

login(token=os.environ.get("HF_TOKEN"))

engine_args = AsyncEngineArgs(
    model="RedHatAI/Meta-Llama-3.1-8B-Instruct-quantized.w8a8",
    gpu_memory_utilization=0.9,
    max_model_len=8192,
)
engine = AsyncLLMEngine.from_engine_args(engine_args)


class Message(BaseModel):
    role: str
    content: str


def format_chat_prompt(messages: list) -> str:
    formatted_messages = []
    for msg in messages:
        msg_obj = Message(**msg)
        formatted_messages.append(
            f"<|start_header_id|>{msg_obj.role}<|end_header_id|>\n{msg_obj.content}<|eot_id|>"
        )
    return "<|begin_of_text|>" + "".join(formatted_messages) + "<|start_header_id|>assistant<|end_header_id|>"


async def run(
    messages: list,
    model: str,
    run_id: str,
    stream: bool = True,
    temperature: float = 0.8,
    top_p: float = 0.95,
    max_tokens: int = 256,
    stream_options: dict = None,
):
    # Format your prompt for llama-friendly usage:
    prompt = format_chat_prompt(messages)

    sampling_params = SamplingParams(temperature=temperature, top_p=top_p, max_tokens=max_tokens)
    results_generator = engine.generate(prompt, sampling_params, run_id)

    previous_text = ""
    first_chunk = True

    async for output in results_generator:
        prompt_output = output.outputs
        new_text = prompt_output[0].text[len(previous_text) :]
        previous_text = prompt_output[0].text

        # Construct OpenAI-compatible chunk
        chunk = {
            "id": run_id,
            "object": "chat.completion.chunk",
            "created": int(time.time()),
            "model": model,
            "choices": [
                {
                    "index": 0,
                    "delta": {},
                    "finish_reason": None,
                }
            ],
        }

        # Include the role in the first chunk
        if first_chunk:
            chunk["choices"][0]["delta"]["role"] = "assistant"
            first_chunk = False

        # Add new text to the delta if any
        if new_text:
            chunk["choices"][0]["delta"]["content"] = new_text

        # Capture a finish reason if it's provided
        finish_reason = prompt_output[0].finish_reason or None
        if finish_reason and finish_reason != "none":
            chunk["choices"][0]["finish_reason"] = finish_reason

        yield f"data: {json.dumps(chunk)}\n\n"

    # Send the final [DONE] message
    yield "data: [DONE]\n\n"

Make sure to add your HuggingFace token to your Secrets on Cerebrium as HF_TOKEN. The run cerebrium deploy to make it live - you should see it live in your Cerebrium dashboard. We will use your deployment url in the next step. Based on your GPU hardware and replica-concurrency in your cerebrium.toml, you can set how many concurrent calls the LLM can take.

Pipecat setup

In your IDE, run the following command to create our pipecat-agent: cerebrium init pipecat-agent. We will be using the Pipecat framework to orchestrate our services to create a voice agent Add the following pip packages to your cerebrium.toml to create your deployment environment:

[cerebrium.deployment]
# This file was automatically generated by Cerebrium as a starting point for your project.
# You can edit it as you wish.
# If you would like to learn more about your Cerebrium config, please visit https://docs.cerebrium.ai/cerebrium/environments/config-files#config-file-example

[cerebrium.deployment]
name = "pipecat-agent"
python_version = "3.11"
include = ["./*", "main.py", "cerebrium.toml"]
exclude = ["./example_exclude"]

[cerebrium.hardware]
region = "us-east-1"
provider = "aws"
compute = "CPU"
cpu = 6
memory = 12.0

[cerebrium.scaling]
min_replicas = 1 # Note: This incurs a constant cost since at least one instance is always running.
max_replicas = 2
cooldown = 180

[cerebrium.dependencies.pip]
torch = ">=2.0.0"
"pipecat-ai[silero, daily, openai, deepgram, cartesia]" = "==0.0.67"
aiohttp = ">=3.9.4"
torchaudio = ">=2.3.0"
channels = ">=4.0.0"
requests = "==2.32.2"
dotenv = "latest"

You can then add the following code to your main.py:

import asyncio
import os
import subprocess
import sys
import time
from multiprocessing import Process

import aiohttp
import requests
from loguru import logger
from pipecat.frames.frames import LLMMessagesFrame, EndFrame
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.services.deepgram.stt import DeepgramSTTService
from pipecat.services.cartesia.tts import CartesiaTTSService
from deepgram import LiveOptions
from pipecat.services.rime.tts import RimeHttpTTSService, RimeTTSService, Language
from pipecat.services.openai import OpenAILLMService
from pipecat.transports.services.daily import DailyParams, DailyTransport
from pipecat.audio.vad.silero import SileroVADAnalyzer
from pipecat.audio.vad.vad_analyzer import VADParams

from helpers import (
    CustomDeepgramSTTService,
)

from dotenv import load_dotenv

load_dotenv()

logger.remove(0)
logger.add(sys.stderr, level="DEBUG")

deepgram_voice: str = "aura-asteria-en"

async def main(room_url: str, token: str):
    async with aiohttp.ClientSession() as session:
        transport = DailyTransport(
            room_url,
            token,
            "Respond bot",
            DailyParams(
                audio_out_enabled=True,
                audio_in_enabled=True,
                transcription_enabled=False,
                vad_enabled=True,
                vad_analyzer=SileroVADAnalyzer(params=VADParams(stop_secs=0.15)),
                vad_audio_passthrough=True,
            ),
        )

        stt = CustomDeepgramSTTService(
            api_key=os.environ.get("DEEPGRAM_API_KEY"),
            websocket_url="ws://p-xxxxxx-deepgram.tenant-cerebrium-prod.svc.cluster.local/v1/listen",
            live_options=LiveOptions(
                model="nova-2-general",
                language="en-US",
                smart_format=True,
                vad_events=True
            )
        )

        tts = CartesiaTTSService(
            api_key=os.environ.get("CARTESIA_API_KEY"),
            voice_id='97f4b8fb-f2fe-444b-bb9a-c109783a857a',

        )

        llm = OpenAILLMService(
            name="LLM",
            model="RedHatAI/Meta-Llama-3.1-8B-Instruct-quantized.w8a8",
            base_url="http://p-xxxxxx-llama-llm.tenant-cerebrium-prod.svc.cluster.local/run"
        )

        messages = [
            {
                "role": "system",
                "content": "You are a fast, low-latency chatbot. Your goal is to demonstrate voice-driven AI capabilities at human-like speeds. The technology powering you is Daily for transport, Cerebrium for serverless infrastructure, Llama 3 (8-B version) LLM, and Deepgram for speech-to-text and text-to-speech. You are hosted on the east coast of the United States. Respond to what the user said in a creative and helpful way, but keep responses short and legible. Ensure responses contain only words. Check again that you have not included special characters other than '?' or '!'.",
            },
        ]

        tma_in = LLMUserResponseAggregator(messages)
        tma_out = LLMAssistantResponseAggregator(messages)

        pipeline = Pipeline(
            [
                transport.input(),  # Transport user input
                stt,  # Speech-to-text
                tma_in,  # User responses
                llm,  # LLM
                tts,  # TTS
                transport.output(),  # Transport bot output
                tma_out,  # Assistant spoken responses
            ]
        )

        task = PipelineTask(
            pipeline,
            params=PipelineParams(
                allow_interruptions=True,
                enable_metrics=True
            ),
        )

        # When the first participant joins, the bot should introduce itself.
        @transport.event_handler("on_first_participant_joined")
        async def on_first_participant_joined(transport, participant):
            # Kick off the conversation.
            time.sleep(1.5)
            messages.append(
                {
                    "role": "system",
                    "content": "Introduce yourself by saying 'hello, I'm FastBot, how can I help you today?'",
                }
            )
            await task.queue_frame(LLMMessagesFrame(messages))

        # When the participant leaves, we exit the bot.
        @transport.event_handler("on_participant_left")
        async def on_participant_left(transport, participant, reason):
            await task.queue_frame(EndFrame())

        # If the call is ended make sure we quit as well.
        @transport.event_handler("on_call_state_updated")
        async def on_call_state_updated(transport, state):
            if state == "left":
                await task.queue_frame(EndFrame())

        runner = PipelineRunner()

        await runner.run(task)
        await session.close()


async def start_bot(room_url: str, token: str = None):

    try:
        await main(room_url, token)
    except Exception as e:
        logger.error(f"Exception in main: {e}")
        sys.exit(1)  # Exit with a non-zero status code

    return {"message": "session finished"}


def create_room():
    url = "https://api.daily.co/v1/rooms/"
    headers = {
        "Content-Type": "application/json",
        "Authorization": f"Bearer {os.environ.get('DAILY_TOKEN')}",
    }
    data = {
        "properties": {
            "exp": int(time.time()) + 60 * 5,  ##5 mins
            "eject_at_room_exp": True,
        }
    }

    response = requests.post(url, headers=headers, json=data)
    if response.status_code == 200:
        room_info = response.json()
        token = create_token(room_info["name"])
        if token and "token" in token:
            room_info["token"] = token["token"]
        else:
            logger.error("Failed to create token")
            return {
                "message": "There was an error creating your room",
                "status_code": 500,
            }
        return room_info
    else:
        data = response.json()
        if data.get("error") == "invalid-request-error" and "rooms reached" in data.get(
            "info", ""
        ):
            logger.error(
                "We are currently at capacity for this demo. Please try again later."
            )
            return {
                "message": "We are currently at capacity for this demo. Please try again later.",
                "status_code": 429,
            }
        logger.error(f"Failed to create room: {response.status_code}")
        return {"message": "There was an error creating your room", "status_code": 500}


def create_token(room_name: str):
    url = "https://api.daily.co/v1/meeting-tokens"
    headers = {
        "Content-Type": "application/json",
        "Authorization": f"Bearer {os.environ.get('DAILY_TOKEN')}",
    }
    data = {"properties": {"room_name": room_name, "is_owner": True}}

    response = requests.post(url, headers=headers, json=data)
    if response.status_code == 200:
        token_info = response.json()
        return token_info
    else:
        logger.error(f"Failed to create token: {response.status_code}")
        return None


# if __name__ == "__main__":
#     room = create_room()
#     if room and "token" in room:
#         asyncio.run(main(room["url"], room["token"]))
#     else:
#         logger.error("Failed to create room")

There is a lot happening above but below we will give a summary:

We are using the WebRTC functionality from Daily to create our room which you can switch out for Twilio/Telenyx. We then have two functions to create/authenticate our meeting room - create_room() and create_token()
For the Deepgram and LLM service, we use a local url to connect to the services within the Cerebrium cluster. We are working on making this better but for now just edit with your project key.
For TTS, we are using the Cartesia service to showcase how versatile Pipecat is but you can use the TTS service from Deepgram too!

The Daily Python SDK provides event webhooks to trigger functionality based on events like users joining or leaving calls. Add this event handling code to the main() function: This code handles these events:

First participant joins: Bot introduces itself via a conversation message
Additional participants join: Bot listens and responds to all participants
Participant leaves or call ends: Bot terminates itself

Based on your CPU hardware and replica-concurrency in your cerebrium.toml, you can set how many concurrent calls this Pipecat agent can take. Create a .env file within your pipecat-agent folder with the following set:

DAILY_TOKEN=
HF_TOKEN=
DEEPGRAM_API_KEY=
CARTESIA_API_KEY=

Get your Daily developer token from your profile. If you don’t have an account, sign up here (they offer a generous free tier). Navigate to the “developers” tab to get your API key and add it to your Cerebrium Secrets. Daily API Key

To test your voice bot locally, you uncomment that main code at the bottom and then run python main.py. Your code should then work That’s it! You now have a fully functioning AI bot that interacts with users through speech in ~500ms. Imagine the possibilities! Now, let’s create a user interface for the bot.

Deploy to Cerebrium

Deploy the app to Cerebrium by running this command in your terminal: cerebrium deploy We’ll add these endpoints to our frontend interface.

Connect frontend

We created a public fork of the PipeCat frontend to show you a nice demo of this application. You can clone the repo here. Follow the instructions in the README.md and then populate the following variables in your .env.development.local

VITE_SERVER_URL=https://api.cortex.cerebrium.ai/v4/p-xxxxx/<APP_NAME> #This is the base url of your pipecat-agent. Do not include the function names
VITE_SERVER_AUTH= #This is the JWT token you can get from the API Keys section of your Cerebrium Dashboard.

You can now run yarn dev and go to the URL: http://localhost:5173/ to test your application!

Conclusion

This tutorial provides a foundation for implementing voice in your app and extending into image and vision capabilities. PipeCat is an extensible, open-source framework for building voice-enabled apps, while Cerebrium provides seamless deployment and autoscaling with pay-as-you-go compute. Tag us as @cerebriumai to showcase your work and join our Slack or Discord communities for questions and feedback.

Examples

​Deepgram deployment

​LLM Deployment

​Pipecat setup

​Deploy to Cerebrium

​Connect frontend

​Conclusion

Deepgram deployment

LLM Deployment

Pipecat setup

Deploy to Cerebrium

Connect frontend

Conclusion