Fabric/docs/Gemini-TTS.md

Gemini Text-to-Speech (TTS) Guide

Fabric supports Google Gemini's text-to-speech (TTS) capabilities, allowing you to convert text into high-quality audio using various AI-generated voices.

Overview

The Gemini TTS feature in Fabric allows you to:

• Convert text input into audio using Google's Gemini TTS models
• Choose from 30+ different AI voices with varying characteristics
• Generate high-quality WAV audio files
• Integrate TTS generation into your existing Fabric workflows

Usage

Basic TTS Generation

To generate audio from text using TTS:

# Basic TTS with default voice (Kore)
echo "Hello, this is a test of Gemini TTS" | fabric -m gemini-2.5-flash-preview-tts -o output.wav

# Using a specific voice
echo "Hello, this is a test with the Charon voice" | fabric -m gemini-2.5-flash-preview-tts --voice Charon -o output.wav

# Using TTS with a pattern
fabric -p summarize --voice Puck -m gemini-2.5-flash-preview-tts -o summary.wav < document.txt

Voice Selection

Use the --voice flag to specify which voice to use for TTS generation:

fabric -m gemini-2.5-flash-preview-tts --voice Zephyr -o output.wav "Your text here"

If no voice is specified, the default voice "Kore" will be used.

Available Voices

Gemini TTS supports 30+ different voices, each with unique characteristics:

Popular Voices

• Kore - Firm and confident (default)
• Charon - Informative and clear
• Puck - Upbeat and energetic
• Zephyr - Bright and cheerful
• Leda - Youthful and energetic
• Aoede - Breezy and natural

Complete Voice List

• Kore, Charon, Puck, Fenrir, Aoede, Leda, Orus, Zephyr
• Autonoe, Callirhoe, Despina, Erinome, Gacrux, Laomedeia
• Pulcherrima, Sulafat, Vindemiatrix, Achernar, Achird
• Algenib, Algieba, Alnilam, Enceladus, Iapetus, Rasalgethi
• Sadachbia, Zubenelgenubi, Vega, Capella, Lyra

Listing Available Voices

To see all available voices with descriptions:

# List all voices with characteristics
fabric --list-gemini-voices

# List voice names only (for shell completion)
fabric --list-gemini-voices --shell-complete-list

Rate Limits

Google Gemini TTS has usage quotas that vary by plan:

Free Tier

• 15 requests per day per project per TTS model
• Quota resets daily
• Applies to all TTS models (e.g., gemini-2.5-flash-preview-tts)

Rate Limit Errors

If you exceed your quota, you'll see an error like:

Error 429: You exceeded your current quota, please check your plan and billing details

Solutions:

• Wait for daily quota reset (typically at midnight UTC)
• Upgrade to a paid plan for higher limits
• Use TTS generation strategically for important content

For current rate limits and pricing, visit: https://ai.google.dev/gemini-api/docs/rate-limits

Configuration

Command Line Options

• --voice <voice_name> - Specify the TTS voice to use
• -o <filename.wav> - Output audio file (required for TTS models)
• -m <tts_model> - Specify a TTS-capable model (e.g., gemini-2.5-flash-preview-tts)

YAML Configuration

You can also set a default voice in your Fabric configuration file (~/.config/fabric/config.yaml):

voice: "Charon"  # Set your preferred default voice

Requirements

• Valid Google Gemini API key configured in Fabric
• TTS-capable Gemini model (models containing "tts" in the name)
• Audio output must be specified with -o filename.wav

Troubleshooting

Common Issues

Error: "TTS model requires audio output"

• Solution: Always specify an output file with -o filename.wav when using TTS models

Error: "Invalid voice 'X'"

• Solution: Check that the voice name is spelled correctly and matches one of the supported voices listed above

Error: "TTS generation failed"

• Solution: Verify your Gemini API key is valid and you have sufficient quota

Getting Help

For additional help with TTS features:

fabric --help

Technical Details

• Audio Format: WAV files with 24kHz sample rate, 16-bit depth, mono channel
• Language Support: Automatic language detection for 24+ languages
• Model Requirements: Models must contain "tts", "preview-tts", or "text-to-speech" in the name
• Voice Selection: Uses Google's PrebuiltVoiceConfig system for consistent voice quality

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