Google

The Google Voice implementation in Mastra provides both text-to-speech (TTS) and speech-to-text (STT) capabilities using Google Cloud services. It supports multiple voices, languages, advanced audio configuration options, and both standard API key authentication and Vertex AI mode for enterprise deployments.

Usage Example

import { GoogleVoice } from "@mastra/voice-google";

// Initialize with default configuration (uses GOOGLE_API_KEY environment variable)
const voice = new GoogleVoice();

// Text-to-Speech
const audioStream = await voice.speak("Hello, world!", {
  languageCode: "en-US",
  audioConfig: {
    audioEncoding: "LINEAR16",
  },
});

// Speech-to-Text
const transcript = await voice.listen(audioStream, {
  config: {
    encoding: "LINEAR16",
    languageCode: "en-US",
  },
});

// Get available voices for a specific language
const voices = await voice.getSpeakers({ languageCode: "en-US" });

Constructor Parameters

speechModel?:

GoogleModelConfig

= { apiKey: process.env.GOOGLE_API_KEY }

Configuration for text-to-speech functionality

listeningModel?:

GoogleModelConfig

= { apiKey: process.env.GOOGLE_API_KEY }

Configuration for speech-to-text functionality

speaker?:

string

= 'en-US-Casual-K'

Default voice ID to use for text-to-speech

vertexAI?:

boolean

= false

Enable Vertex AI mode for enterprise deployments. Uses project-based authentication instead of API keys. Requires 'project' to be set.

project?:

string

Google Cloud project ID (required when vertexAI is true). Falls back to GOOGLE_CLOUD_PROJECT environment variable.

location?:

string

= 'us-central1'

Google Cloud region for Vertex AI. Falls back to GOOGLE_CLOUD_LOCATION environment variable.

GoogleModelConfig

apiKey?:

string

Google Cloud API key. Falls back to GOOGLE_API_KEY environment variable. Not used when vertexAI is true.

keyFilename?:

string

Path to service account JSON key file. Falls back to GOOGLE_APPLICATION_CREDENTIALS environment variable.

credentials?:

object

In-memory service account credentials object with client_email and private_key properties.

Methods

speak()

Converts text to speech using Google Cloud Text-to-Speech service.

input:

string | NodeJS.ReadableStream

Text to convert to speech. If a stream is provided, it will be converted to text first.

options?:

object

Speech synthesis options

options.speaker?:

string

Voice ID to use for this request

options.languageCode?:

string

Language code for the voice (e.g., 'en-US'). Defaults to the language code from the speaker ID or 'en-US'

options.audioConfig?:

ISynthesizeSpeechRequest['audioConfig']

= { audioEncoding: 'LINEAR16' }

Audio configuration options from Google Cloud Text-to-Speech API

Returns: Promise<NodeJS.ReadableStream>

listen()

Converts speech to text using Google Cloud Speech-to-Text service.

audioStream:

NodeJS.ReadableStream

Audio stream to transcribe

options?:

object

Recognition options

options.stream?:

boolean

Whether to use streaming recognition

options.config?:

IRecognitionConfig

= { encoding: 'LINEAR16', languageCode: 'en-US' }

Recognition configuration from Google Cloud Speech-to-Text API

Returns: Promise<string>

getSpeakers()

Returns an array of available voice options, where each node contains:

voiceId:

string

Unique identifier for the voice

languageCodes:

string[]

List of language codes supported by this voice

isUsingVertexAI()

Checks if Vertex AI mode is enabled.

Returns: boolean - true if using Vertex AI, false otherwise

getProject()

Gets the configured Google Cloud project ID.

Returns: string | undefined - The project ID or undefined if not set

getLocation()

Gets the configured Google Cloud location/region.

Returns: string - The location (default: 'us-central1')

Authentication

The Google Voice provider supports two authentication methods:

Standard Mode (API Key)

Uses a Google Cloud API key for authentication. Suitable for development and simple use cases.

// Using environment variable (GOOGLE_API_KEY)
const voice = new GoogleVoice();

// Using explicit API key
const voice = new GoogleVoice({
  speechModel: { apiKey: "your-api-key" },
  listeningModel: { apiKey: "your-api-key" },
  speaker: "en-US-Casual-K",
});

Vertex AI Mode (Service Account)

Uses Google Cloud project-based authentication with service accounts. Recommended for production and enterprise deployments.

Benefits:

• Better security (no API keys in code)
• IAM-based access control
• Project-level billing and quotas
• Audit logging
• Enterprise features

Configuration Options:

// Using Application Default Credentials (ADC)
// Set GOOGLE_APPLICATION_CREDENTIALS and GOOGLE_CLOUD_PROJECT env vars
const voice = new GoogleVoice({
  vertexAI: true,
  project: "your-gcp-project",
  location: "us-central1", // Optional, defaults to 'us-central1'
});

// Using service account key file
const voice = new GoogleVoice({
  vertexAI: true,
  project: "your-gcp-project",
  speechModel: {
    keyFilename: "/path/to/service-account.json",
  },
  listeningModel: {
    keyFilename: "/path/to/service-account.json",
  },
});

// Using in-memory credentials
const voice = new GoogleVoice({
  vertexAI: true,
  project: "your-gcp-project",
  speechModel: {
    credentials: {
      client_email: "service-account@project.iam.gserviceaccount.com",
      private_key: "-----BEGIN PRIVATE KEY-----\n...\n-----END PRIVATE KEY-----",
    },
  },
});

Required Permissions:

IAM Roles:

For Text-to-Speech:

• roles/texttospeech.admin - Text-to-Speech Admin (full access)
• roles/texttospeech.editor - Text-to-Speech Editor (create and manage)
• roles/texttospeech.viewer - Text-to-Speech Viewer (read-only)

For Speech-to-Text:

• roles/speech.client - Speech-to-Text Client

OAuth Scopes:

For synchronous Text-to-Speech synthesis:

• https://www.googleapis.com/auth/cloud-platform - Full access to Google Cloud Platform services

For long-audio Text-to-Speech operations:

• locations.longAudioSynthesize - Create long-audio synthesis operations
• operations.get - Get operation status
• operations.list - List operations

Important Notes

1. Authentication: Either a Google Cloud API key (standard mode) or service account credentials (Vertex AI mode) is required.
2. Environment Variables:
   • GOOGLE_API_KEY - API key for standard mode
   • GOOGLE_CLOUD_PROJECT - Project ID for Vertex AI mode
   • GOOGLE_CLOUD_LOCATION - Location for Vertex AI mode (defaults to 'us-central1')
   • GOOGLE_APPLICATION_CREDENTIALS - Path to service account key file
3. The default voice is set to 'en-US-Casual-K'.
4. Both text-to-speech and speech-to-text services use LINEAR16 as the default audio encoding.
5. The speak() method supports advanced audio configuration through the Google Cloud Text-to-Speech API.
6. The listen() method supports various recognition configurations through the Google Cloud Speech-to-Text API.
7. Available voices can be filtered by language code using the getSpeakers() method.
8. Vertex AI mode provides enterprise features including IAM control, audit logs, and project-level billing.