google-gemini-media

What this skill does

# Gemini Multimodal Media (Image/Video/Speech) Skill

## 1. Goals and scope

This Skill consolidates six Gemini API capabilities into reusable workflows and implementation templates:

- Image generation (Nano Banana: text-to-image, image editing, multi-turn iteration)
- Image understanding (caption/VQA/classification/comparison, multi-image prompts; supports inline and Files API)
- Video generation (Veo 3.1: text-to-video, aspect ratio/resolution control, reference-image guidance, first/last frames, video extension, native audio)
- Video understanding (upload/inline/YouTube URL; summaries, Q&A, timestamped evidence)
- Speech generation (Gemini native TTS: single-speaker and multi-speaker; controllable style/accent/pace/tone)
- Audio understanding (upload/inline; description, transcription, time-range transcription, token counting)

> Convention: This Skill follows the official Google Gen AI SDK (Node.js/REST) as the main line; currently only Node.js/REST examples are provided. If your project already wraps other languages or frameworks, map this Skill's request structure, model selection, and I/O spec to your wrapper layer.

---

## 2. Quick routing (decide which capability to use)

1) **Do you need to produce images?**
- Need to generate images from scratch or edit based on an image -> use **Nano Banana image generation** (see Section 5)

2) **Do you need to understand images?**
- Need recognition, description, Q&A, comparison, or info extraction -> use **Image understanding** (see Section 6)

3) **Do you need to produce video?**
- Need to generate an 8-second video (optionally with native audio) -> use **Veo 3.1 video generation** (see Section 7)

4) **Do you need to understand video?**
- Need summaries/Q&A/segment extraction with timestamps -> use **Video understanding** (see Section 8)

5) **Do you need to read text aloud?**
- Need controllable narration, podcast/audiobook style, etc. -> use **Speech generation (TTS)** (see Section 9)

6) **Do you need to understand audio?**
- Need audio descriptions, transcription, time-range transcription, token counting -> use **Audio understanding** (see Section 10)

---

## 3. Unified engineering constraints and I/O spec (must read)

### 3.0 Prerequisites (dependencies and tools)

- Node.js 18+ (match your project version)
- Install SDK (example):
```bash
npm install @google/genai
```
- REST examples only need `curl`; if you need to parse image Base64, install `jq` (optional).

### 3.1 Authentication and environment variables

- Put your API key in `GEMINI_API_KEY`
- REST requests use `x-goog-api-key: $GEMINI_API_KEY`

### 3.2 Two file input modes: Inline vs Files API

**Inline (embedded bytes/Base64)**
- Pros: shorter call chain, good for small files.
- Key constraint: total request size (text prompt + system instructions + embedded bytes) typically has a ~20MB ceiling.

**Files API (upload then reference)**
- Pros: good for large files, reusing the same file, or multi-turn conversations.
- Typical flow:
  1. `files.upload(...)` (SDK) or `POST /upload/v1beta/files` (REST resumable)
  2. Use `file_data` / `file_uri` in `generateContent`

> Engineering suggestion: implement `ensure_file_uri()` so that when a file exceeds a threshold (for example 10-15MB warning) or is reused, you automatically route through the Files API.

### 3.3 Unified handling of binary media outputs

- **Images**: usually returned as `inline_data` (Base64) in response parts; in the SDK use `part.as_image()` or decode Base64 and save as PNG/JPG.
- **Speech (TTS)**: usually returns **PCM** bytes (Base64); save as `.pcm` or wrap into `.wav` (commonly 24kHz, 16-bit, mono).
- **Video (Veo)**: long-running async task; poll the operation; download the file (or use the returned URI).

---

## 4. Model selection matrix (choose by scenario)

> Important: model names, versions, limits, and quotas can change over time. Verify against official docs before use. Last updated: 2026-01-22.

### 4.1 Image generation (Nano Banana)
- **gemini-2.5-flash-image**: optimized for speed/throughput; good for frequent, low-latency generation/editing.
- **gemini-3-pro-image-preview**: stronger instruction following and high-fidelity text rendering; better for professional assets and complex edits.

### 4.2 General image/video/audio understanding
- Docs use `gemini-3-flash-preview` for image, video, and audio understanding (choose stronger models as needed for quality/cost).

### 4.3 Video generation (Veo)
- Example model: `veo-3.1-generate-preview` (generates 8-second video and can natively generate audio).

### 4.4 Speech generation (TTS)
- Example model: `gemini-2.5-flash-preview-tts` (native TTS, currently in preview).

---

## 5. Image generation (Nano Banana)

### 5.1 Text-to-Image

**SDK (Node.js) minimal template**
```js
import { GoogleGenAI } from "@google/genai";
import * as fs from "node:fs";

const ai = new GoogleGenAI({ apiKey: process.env.GEMINI_API_KEY });

const response = await ai.models.generateContent({
  model: "gemini-2.5-flash-image",
  contents:
    "Create a picture of a nano banana dish in a fancy restaurant with a Gemini theme",
});

const parts = response.candidates?.[0]?.content?.parts ?? [];
for (const part of parts) {
  if (part.text) console.log(part.text);
  if (part.inlineData?.data) {
    fs.writeFileSync("out.png", Buffer.from(part.inlineData.data, "base64"));
  }
}
```

**REST (with imageConfig) minimal template**
```bash
curl -s -X POST   "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-image:generateContent"   -H "x-goog-api-key: $GEMINI_API_KEY"   -H "Content-Type: application/json"   -d '{
    "contents":[{"parts":[{"text":"Create a picture of a nano banana dish in a fancy restaurant with a Gemini theme"}]}],
    "generationConfig": {"imageConfig": {"aspectRatio":"16:9"}}
  }'
```

**REST image parsing (Base64 decode)**
```bash
curl -s -X POST "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-image:generateContent" \
  -H "x-goog-api-key: $GEMINI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contents":[{"parts":[{"text":"A minimal studio product shot of a nano banana"}]}]}' \
  | jq -r '.candidates[0].content.parts[] | select(.inline_data) | .inline_data.data' \
  | base64 --decode > out.png

# macOS can use: base64 -D > out.png
```

### 5.2 Text-and-Image-to-Image

Use case: given an image, **add/remove/modify elements**, change style, color grading, etc.

**SDK (Node.js) minimal template**
```js
import { GoogleGenAI } from "@google/genai";
import * as fs from "node:fs";

const ai = new GoogleGenAI({ apiKey: process.env.GEMINI_API_KEY });

const prompt =
  "Add a nano banana on the table, keep lighting consistent, cinematic tone.";
const imageBase64 = fs.readFileSync("input.png").toString("base64");

const response = await ai.models.generateContent({
  model: "gemini-2.5-flash-image",
  contents: [
    { text: prompt },
    { inlineData: { mimeType: "image/png", data: imageBase64 } },
  ],
});

const parts = response.candidates?.[0]?.content?.parts ?? [];
for (const part of parts) {
  if (part.inlineData?.data) {
    fs.writeFileSync("edited.png", Buffer.from(part.inlineData.data, "base64"));
  }
}
```

### 5.3 Multi-turn image iteration (Multi-turn editing)

Best practice: use chat for continuous iteration (for example: generate first, then "only edit a specific region/element", then "make variants in the same style").  
To output mixed "text + image" results, set `response_modalities` to `["TEXT", "IMAGE"]`.

### 5.4 ImageConfig

You can set in `generationConfig.imageConfig` or the SDK config:
- `aspectRatio`: e.g. `16:9`, `1:1`.
- `imageSize`: e.g. `2K`, `4K` (higher resolution is usually slower/more expensive and model support can vary).

---

## 6. Image understanding (Image Understanding)

### 6.1 Two ways to provide input images

- **Inline image data**: suitable for small files (total request size < 20MB).
- **Files API upload**: better for large files or