> ## Documentation Index
> Fetch the complete documentation index at: https://plivo.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Deepgram + OpenAI + Cartesia

> Build voice agents with Deepgram STT, OpenAI GPT-4o, and Cartesia TTS

Build a voice agent using Deepgram for speech recognition, OpenAI GPT-4o for conversation, and Cartesia for text-to-speech synthesis.

**Best for:** Low latency applications requiring expressive, controllable voices.

***

## Prerequisites

| Service      | What You Need                                                     |
| ------------ | ----------------------------------------------------------------- |
| **Plivo**    | Auth ID, Auth Token, Voice-enabled phone number                   |
| **Deepgram** | API key from [console.deepgram.com](https://console.deepgram.com) |
| **OpenAI**   | API key from [platform.openai.com](https://platform.openai.com)   |
| **Cartesia** | API key from [play.cartesia.ai](https://play.cartesia.ai)         |

***

## Installation

```bash theme={null}
pip install "pipecat-ai[deepgram,openai,cartesia]"
```

***

## Environment Variables

```env theme={null}
# Plivo credentials
PLIVO_AUTH_ID=your_auth_id
PLIVO_AUTH_TOKEN=your_auth_token
PLIVO_PHONE_NUMBER=+1234567890

# AI service credentials
DEEPGRAM_API_KEY=your_deepgram_key
OPENAI_API_KEY=sk-your_openai_key
CARTESIA_API_KEY=your_cartesia_key
```

***

## Pipeline Configuration

```python theme={null}
from pipecat.services.deepgram import DeepgramSTTService
from pipecat.services.openai import OpenAILLMService
from pipecat.services.cartesia import CartesiaTTSService

# Speech-to-Text
stt = DeepgramSTTService(
    api_key=os.getenv("DEEPGRAM_API_KEY"),
    # Optional: Use Deepgram Flux for better turn detection
    # from pipecat.services.deepgram import DeepgramFluxSTTService
)

# Language Model
llm = OpenAILLMService(
    api_key=os.getenv("OPENAI_API_KEY"),
    model="gpt-4o",
)

# Text-to-Speech
tts = CartesiaTTSService(
    api_key=os.getenv("CARTESIA_API_KEY"),
    voice_id="your_voice_id",  # Browse voices at play.cartesia.ai
)
```

***

## Service Details

### Deepgram STT

Real-time speech recognition with interim results and language detection.

| Option                   | Description                               |
| ------------------------ | ----------------------------------------- |
| `DeepgramSTTService`     | Standard WebSocket transcription          |
| `DeepgramFluxSTTService` | Enhanced turn detection for conversations |

**Tip:** Use `DeepgramFluxSTTService` with `ExternalUserTurnStrategies` for better conversation flow.

### OpenAI LLM

Chat completion with GPT-4o supporting streaming responses and function calling.

| Model         | Description              |
| ------------- | ------------------------ |
| `gpt-4o`      | Most capable, multimodal |
| `gpt-4o-mini` | Faster, cost-effective   |
| `gpt-4-turbo` | Previous generation      |

### Cartesia TTS

Real-time voice synthesis with word-level timing and interruption handling.

| Feature        | Method                   |
| -------------- | ------------------------ |
| Spell out text | `SPELL("ABC")`           |
| Add emotion    | `EMOTION_TAG("SARCASM")` |
| Insert pause   | `PAUSE_TAG(0.5)`         |
| Adjust speed   | `SPEED_TAG(1.2)`         |
| Adjust volume  | `VOLUME_TAG(0.8)`        |

***

## Quick Start

### Inbound Calls

```bash theme={null}
git clone https://github.com/pipecat-ai/pipecat-examples.git
cd pipecat-examples/plivo-chatbot/inbound

# Configure environment
cp env.example .env
# Edit .env with your credentials

# Start server
uv sync && uv run server.py

# Expose with ngrok (development)
ngrok http 7860
```

Configure your Plivo number's Answer URL to your ngrok URL.

### Outbound Calls

```bash theme={null}
cd pipecat-examples/plivo-chatbot/outbound

cp env.example .env
uv sync && uv run server.py

# Initiate a call
curl -X POST http://localhost:7860/start \
  -H "Content-Type: application/json" \
  -d '{"phone_number": "+1234567890"}'
```

***

## Related

* [Pipecat Overview](overview) - Architecture and setup
* [Deepgram Docs](https://docs.pipecat.ai/server/services/stt/deepgram) - STT configuration
* [OpenAI Docs](https://docs.pipecat.ai/server/services/llm/openai) - LLM configuration
* [Cartesia Docs](https://docs.pipecat.ai/server/services/tts/cartesia) - TTS configuration