Google

Speech-to-text service implementation using Google Cloud’s Speech-to-Text V2 API

Overview

GoogleSTTService provides real-time speech recognition using Google Cloud’s Speech-to-Text V2 API with support for 125+ languages, multiple models, voice activity detection, and advanced features like automatic punctuation and word-level confidence scores.

Google STT API Reference

Pipecat’s API methods for Google Cloud STT integration

Example Implementation

Complete example with Google Cloud services

Google Cloud Documentation

Official Google Cloud Speech-to-Text documentation

Google Cloud Console

Create service accounts and manage API access

Installation

To use Google Cloud Speech services, install the required dependency:

pip install "pipecat-ai[google]"

Prerequisites

Google Cloud Setup

Before using Google Cloud STT services, you need:

1. Google Cloud Account: Sign up at Google Cloud Console
2. Project Setup: Create a project and enable the Speech-to-Text API
3. Service Account: Create a service account with Speech-to-Text permissions
4. Authentication: Set up credentials via service account key or Application Default Credentials

Required Environment Variables

• GOOGLE_APPLICATION_CREDENTIALS: Path to your service account key file (recommended)
• Or use Application Default Credentials for cloud deployments

Configuration

GoogleSTTService

credentials · str · default: "None"

JSON string containing Google Cloud service account credentials.

credentials_path · str · default: "None"

Path to service account credentials JSON file.

location · str · default: "global"

Google Cloud location (e.g., "global", "us-central1"). Non-global locations use regional endpoints.

sample_rate · int · default: "None"

Audio sample rate in Hz. When None, uses the pipeline’s configured sample rate.

params · InputParams · default: "None"

Configuration parameters for the STT service. See InputParams below.

ttfs_p99_latency · float · default: "GOOGLE_TTFS_P99"

P99 latency from speech end to final transcript in seconds. Override for your deployment.

You must provide either credentials (JSON string), credentials_path (file path), or have Application Default Credentials configured. At least one authentication method is required.

InputParams

Parameters passed via the params constructor argument.

Parameter	Type	Default	Description
languages	Language | List[Language]	[Language.EN_US]	Single language or list of recognition languages. First language is primary.
model	str	"latest_long"	Speech recognition model to use.
use_separate_recognition_per_channel	bool	False	Process each audio channel separately.
enable_automatic_punctuation	bool	True	Add punctuation to transcripts.
enable_spoken_punctuation	bool	False	Include spoken punctuation in transcript.
enable_spoken_emojis	bool	False	Include spoken emojis in transcript.
profanity_filter	bool	False	Filter profanity from transcript.
enable_word_time_offsets	bool	False	Include timing information for each word.
enable_word_confidence	bool	False	Include confidence scores for each word.
enable_interim_results	bool	True	Stream partial recognition results.
enable_voice_activity_events	bool	False	Detect voice activity in audio.

Usage

Basic Setup

from pipecat.services.google import GoogleSTTService

stt = GoogleSTTService(
    credentials_path=os.getenv("GOOGLE_APPLICATION_CREDENTIALS"),
)

With Credentials JSON String

import json
from pipecat.services.google import GoogleSTTService

stt = GoogleSTTService(
    credentials=json.dumps(credentials_dict),
    location="us-central1",
)

With Custom Parameters

from pipecat.services.google import GoogleSTTService
from pipecat.transcriptions.language import Language

stt = GoogleSTTService(
    credentials_path=os.getenv("GOOGLE_APPLICATION_CREDENTIALS"),
    params=GoogleSTTService.InputParams(
        languages=[Language.EN_US, Language.ES],
        model="latest_long",
        enable_automatic_punctuation=True,
        enable_word_time_offsets=True,
        enable_word_confidence=True,
    ),
)

Updating Options at Runtime

Google STT supports dynamic option updates via the update_options method:

await stt.update_options(
    languages=[Language.FR],
    model="latest_short",
    enable_automatic_punctuation=False,
)

Notes

• Streaming time limit: Google Cloud STT has a 5-minute streaming limit per connection. The service automatically handles stream reconnection at 4 minutes to provide seamless transcription without interruption.
• Multi-language support: Pass a list of Language values to languages for multi-language recognition. The first language is the primary language.
• Regional endpoints: Use the location parameter to route requests through regional endpoints (e.g., "us-central1", "europe-west1") for data residency requirements. The default "global" endpoint works for most use cases.
• Stream abort on inactivity: If no audio is sent for ~10 seconds (e.g., when audio frames are blocked by an STTMuteFilter), Google automatically closes the stream. The service recovers by automatically reconnecting.
• Authentication priority: The service checks for credentials in this order: credentials (JSON string), credentials_path (file), then Application Default Credentials.

Event Handlers

Google STT supports the standard service connection events:

Event	Description
on_connected	Connected to Google Cloud Speech-to-Text
on_disconnected	Disconnected from Google Cloud Speech-to-Text

@stt.event_handler("on_connected")
async def on_connected(service):
    print("Connected to Google STT")