AssemblyAI Text-to-Speech

Overview

AssemblyAITTSService streams text to AssemblyAI’s Streaming TTS WebSocket API and plays the audio as it arrives. Per-word timings drive word-level text output, and interruptions cancel synthesis in flight without reconnecting.

AssemblyAI TTS API Reference

Pipecat’s API methods for AssemblyAI TTS integration

Example Implementation

Complete example with AssemblyAI STT and TTS

AssemblyAI Documentation

Official AssemblyAI documentation

AssemblyAI Dashboard

Manage API keys and cloned voices

Installation

uv add "pipecat-ai[assemblyai]"

Prerequisites

AssemblyAI Account Setup

AssemblyAI Account: Sign up at the AssemblyAI dashboard
API Key: Generate an API key from the dashboard

Required Environment Variables

ASSEMBLYAI_API_KEY: Your AssemblyAI API key for authentication

Configuration

AssemblyAITTSService

str

required

AssemblyAI API key. A temporary token opens a single session, so it can’t carry the service’s reconnects and session renewals.

str

default:"wss://tts.us.assemblyai.com/v1/ws"

Streaming TTS WebSocket URL. Use wss://tts.eu.assemblyai.com/v1/ws to process text and audio in the EU. A cloned voice works only on the host of the zone it was created in.

int

default:"None"

Output sample rate in Hz. When None, uses the pipeline’s output sample rate.

AssemblyAITTSService.Settings

default:"None"

Runtime-configurable settings. See Settings below.

Settings

Runtime-configurable settings passed via the settings constructor argument using AssemblyAITTSService.Settings(...). These can be updated mid-conversation with TTSUpdateSettingsFrame. Changing voice, language, or model reconnects the session. See Service Settings for details.

Parameter	Type	Default	Description
`voice`	`str`	`"49c443a4-8a1d-5f7e-b70b-98bdbd9823c3"`	Voice to speak with, sent as the API’s `voice_id`. Accepts a voice ID, an AssemblyAI library slug such as `aai-jane`, or the slug of a cloned voice shown in the dashboard. Default is Audrey.
`language`	`Language \| str`	`None`	Language the session speaks. When unset, the session speaks the voice’s own language.
`model`	`str`	`None`	Model name, such as `assemblyai-tts-1`. When unset, the session runs the language’s default model.

Usage

Basic Setup

import os

from pipecat.services.assemblyai.tts import AssemblyAITTSService

tts = AssemblyAITTSService(
    api_key=os.getenv("ASSEMBLYAI_API_KEY"),
)

Choosing a Voice

tts = AssemblyAITTSService(
    api_key=os.getenv("ASSEMBLYAI_API_KEY"),
    settings=AssemblyAITTSService.Settings(voice="aai-jane"),
)

Processing Data in the EU

tts = AssemblyAITTSService(
    api_key=os.getenv("ASSEMBLYAI_API_KEY"),
    url="wss://tts.eu.assemblyai.com/v1/ws",
)

Notes

Sentence and token aggregation: With sentence aggregation, each sentence is its own request. With TextAggregationMode.TOKEN, the turn’s text streams as it is generated.
Word timestamps: Per-word timings produce word-level TTSTextFrame output.
Sessions: The service keeps an idle session open, replaces a session before its one-hour limit, and waits as long as the server asks before reconnecting.

Event Handlers

AssemblyAITTSService supports the standard service connection events:

Event	Description
`on_connected`	Connected to AssemblyAI WebSocket
`on_disconnected`	Disconnected from AssemblyAI
`on_connection_error`	WebSocket connection error occurred

@tts.event_handler("on_connected")
async def on_connected(service):
    print("Connected to AssemblyAI")

Get Started

Standards

Pipecat Server

Client SDKs

Pipecat Flows

Pipecat Cloud

CLI

Pipecat Context Hub

AssemblyAI Text-to-Speech

Overview

AssemblyAI TTS API Reference

Example Implementation

AssemblyAI Documentation

AssemblyAI Dashboard

Installation

Prerequisites

AssemblyAI Account Setup

Required Environment Variables

Configuration

AssemblyAITTSService

Settings

Usage

Basic Setup

Choosing a Voice

Processing Data in the EU

Notes

Event Handlers

​Overview

AssemblyAI TTS API Reference

Example Implementation

AssemblyAI Documentation

AssemblyAI Dashboard

​Installation

​Prerequisites

​AssemblyAI Account Setup

​Required Environment Variables

​Configuration

​AssemblyAITTSService

​Settings

​Usage

​Basic Setup

​Choosing a Voice

​Processing Data in the EU

​Notes

​Event Handlers

Overview

Installation

Prerequisites

AssemblyAI Account Setup

Required Environment Variables

Configuration

AssemblyAITTSService

Settings

Usage

Basic Setup

Choosing a Voice

Processing Data in the EU

Notes

Event Handlers