/gemini-tts

name: gemini-tts
description: Generate speech from text using Google Gemini TTS. Use when creating voiceovers, narration, podcasts, or any text-to-speech task. Supports 70+ languages, style/emotion control via natural language prompts, and 30 prebuilt voices. Trigger on "Gemini TTS", "Google TTS", "voiceover", "narration", "text to speech", "speech generation".
license: MIT
compatibility: Requires Node.js 18+, ffmpeg, and internet access. Set GEMINI_API_KEY env var.
metadata: {"openclaw": {"requires": {"env": ["GEMINI_API_KEY"]}, "primaryEnv": "GEMINI_API_KEY"}}

Gemini Text-to-Speech

Generate natural, expressive speech from text using Google Gemini TTS. Supports 70+ languages, 30 prebuilt voices, and style control via natural language prompts and audio tags.

> **Requirements:** Node.js 18+, ffmpeg, `@google/genai` npm package, `GEMINI_API_KEY` env var.

Available Scripts

• **`scripts/generate-tts.mjs`** — All-in-one TTS generator with single-request consistency, silence-based splitting, and automatic trimming.

Quick Start

Single text to speech

npm install @google/genai
GEMINI_API_KEY=your-key node scripts/generate-tts.mjs \
  --text "Hello, welcome to our product!" \
  --output-dir public/vo \
  --voice Kore

Multi-segment voiceover (consistent voice)

Create a `segments.json`:

[
  { "id": "intro", "text": "Welcome to our product launch." },
  { "id": "features", "text": "Here are the three features you will love." },
  { "id": "close", "text": "Get started today at our website." }
]

Run:

GEMINI_API_KEY=your-key node scripts/generate-tts.mjs \
  --segments segments.json \
  --output-dir public/vo \
  --voice Kore \
  --director-notes "Tone: Warm, confident, inspiring. Style: Professional narrator with a vocal smile. Accent: Neutral American English. Pacing: Moderate."

Output (JSON to stdout):

{
  "success": true,
  "segments": [
    { "id": "intro", "file": "public/vo/vo-intro.mp3", "duration": 3.25 },
    { "id": "features", "file": "public/vo/vo-features.mp3", "duration": 4.10 },
    { "id": "close", "file": "public/vo/vo-close.mp3", "duration": 2.80 }
  ],
  "totalDuration": 10.15,
  "fullAudioFile": "public/vo/vo-full.wav"
}

Script Options

| Flag | Default | Description | |------|---------|-------------| | `--segments FILE` | — | JSON file with `[{id, text}]` segment definitions | | `--text TEXT` | — | Single text to generate (alternative to `--segments`) | | `--output-dir DIR` | — | Output directory for audio files (required) | | `--voice NAME` | `Kore` | Prebuilt voice name (see Voices table) | | `--model NAME` | `gemini-3.1-flash-tts-preview` | Gemini TTS model ID | | `--director-notes TEXT` | — | Performance guidance: style, pacing, accent, breathing, articulation. Does not control gender/age (use `--voice` for that). | | `--retries N` | `3` | Max retry attempts for API errors | | `--trim` / `--no-trim` | `--trim` | Trim silence from segment boundaries | | `--format FORMAT` | `mp3` | Output format: `mp3` or `wav` |

Exit Codes

| Code | Meaning | |------|---------| | 0 | Success | | 1 | Missing required arguments or env vars | | 2 | API error after retries exhausted | | 3 | ffmpeg not installed or processing failed | | 4 | File I/O error |

How It Works (Multi-Segment)

Gemini TTS does NOT guarantee voice consistency across separate API requests. The script solves this by:

1. Combining all segments into ONE prompt with `[3 second pause]` markers between them 2. Generating a single continuous audio file in one API call 3. Detecting silence gaps with ffmpeg `silencedetect` using adaptive thresholds (starts at noise=-35dB, d=1.5s, progressively relaxes). If an exact match is found, uses it directly. If a threshold jump occurs (too few → too many), regenerates audio with faster speech pacing to make inter-segment pauses more distinct, then retries detection. 4. Splitting at silence midpoints into individual segment files 5. Trimming residual silence padding (~1.5s per side) from each segment, keeping 0.15s breathing room

Models

| Model | Best For | |-------|----------| | `gemini-3.1-flash-tts-preview` | Latest, most controllable, 200+ audio tags (default) | | `gemini-2.5-flash-preview-tts` | Fast, good quality, general use | | `gemini-2.5-pro-preview-tts` | Highest quality, complex performances |

Voices

30 prebuilt voices:

| Voice | Gender | Character | Pitch | |-------|--------|-----------|-------| | Achernar | Female | Soft | Higher | | Achird | Male | Friendly | Lower middle | | Algenib | Male | Gravelly | Lower | | Algieba | Male | Smooth | Lower | | Alnilam | Male | Firm | Lower middle | | Aoede | Female | Breezy | Middle | | Autonoe | Female | Bright | Middle | | Callirrhoe | Female | Easy-going | Middle | | Charon | Male | Informative | Lower | | Despina | Female | Smooth | Middle | | Enceladus | Male | Breathy | Lower | | Erinome | Female | Clear | Middle | | Fenrir | Male | Excitable | Lower middle | | Gacrux | Female | Mature | Middle | | Iapetus | Male | Clear | Lower middle | | Kore | Female | Firm | Middle | | Laomedeia | Female | Upbeat | Higher | | Leda | Female | Youthful | Higher | | Orus | Male | Firm | Lower middle | | Puck | Male | Upbeat | Middle | | Pulcherrima | Male | Forward | Middle | | Rasalgethi | Male | Informative | Middle | | Sadachbia | Male | Lively | Lower | | Sadaltager | Male | Knowledgeable | Middle | | Schedar | Male | Even | Lower middle | | Sulafat | Female | Warm | Middle | | Umbriel | Male | Easy-going | Lower middle | | Vindemiatrix | Female | Gentle | Middle | | Zephyr | Female | Bright | Higher | | Zubenelgenubi | Male | Casual | Lower middle |

Director's Notes (`--director-notes`)

Performance guidance for the selected voice. Define only what matters — overspecifying limits the model's creativity and can worsen results.

The three most common directions are Style, Pacing, and Accent, but you can include any custom instructions