FastRTC Voice Demo

A reference implementation of a browser-based, real-time voice conversation experience. The repository separates a FastAPI/FastRTC backend from a Next.js frontend so the voice pipeline and interface can evolve independently.

What it demonstrates

• microphone capture and browser voice interaction
• FastRTC-powered real-time transport
• speech-to-text and text-to-speech through ElevenLabs
• LLM responses through an OpenAI-compatible API key
• tunable voice-activity detection settings

Architecture

Browser (Next.js) → FastAPI + FastRTC → STT / LLM / TTS providers

The browser UI lives in frontend/fastrtc-demo; the Python backend lives in backend/.

Run locally

1. Configure provider keys

Copy .env.example to .env and supply your own keys:

LLM_API_KEY=...
ELEVENLABS_API_KEY=...

Never commit .env or expose provider keys in a browser client.

2. Start the backend

python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
./run.sh

On Windows, run uvicorn backend.server:app --host 0.0.0.0 --port 8000 after installing dependencies.

3. Start the frontend

cd frontend/fastrtc-demo
npm install
npm run dev

Open the local URL printed by Next.js and allow microphone access when prompted.

Voice tuning

The backend exposes voice-activity detection settings such as speech threshold, silence duration, speech padding, and maximum segment duration. Increase silence duration if the assistant interrupts too quickly; decrease it if responses feel slow.

Operational notes

This is a demonstration project. Running it requires billable third-party API credentials, HTTPS in most production microphone contexts, and a deployment design that keeps provider keys on the server.

License

MIT