# LTX-2 19b Extend Video — API Reference

Model ID: `model_ltx-2-19b-extend-video`

---

## Authentication

Scenario API uses HTTP Basic Auth. Encode your credentials in Base64 and pass them as the `Authorization` header.

```
Authorization: Basic base64("<API_KEY>:<API_SECRET>")
```

- **API_KEY** and **API_SECRET** are found in your [Scenario Project Settings](https://app.scenario.com/team&tab=project_api_keys) under API Keys.
- In shell: `$(echo -n '<API_KEY>:<API_SECRET>' | base64)`
- In JavaScript: `btoa("<API_KEY>:<API_SECRET>")`
- In Python: `base64.b64encode(f"{api_key}:{api_secret}".encode()).decode()`

---

## Generate

**Endpoint:** `POST https://api.cloud.scenario.com/v1/generate/custom/model_ltx-2-19b-extend-video`

### Parameters

| Parameter | Type | Required | Default | Description |
|-----------|------|----------|---------|-------------|
| `prompt` | string | yes | - | Text prompt describing how the video should continue |
| `videoStrength` | number | - | `1` | Video conditioning strength. Higher = more faithful to input video motion/style. |
| `extendDuration` | number | - | `4` | Duration of new video to generate in seconds. Additional duration added after the input video. |
| `contextDuration` | number | - | - | Seconds from input video to use as context. Leave empty to use entire video. |
| `aspectRatio` | string | - | `auto` | Video aspect ratio. 'Match Input' detects from input video. |
| `resolution` | string | - | `auto` | Video resolution. 'Match Input' replicates input video dimensions (recommended for extend). |
| `width` | number | - | - | Explicit video width in pixels. Must be used with height. Rounded to multiple of 64. |
| `height` | number | - | - | Explicit video height in pixels. Must be used with width. Rounded to multiple of 64. |
| `fps` | number | - | - | Output frame rate (1-60 fps). Leave empty to match input video. |
| `numInferenceSteps` | number | - | `40` | Number of denoising steps (more = higher quality, slower) |
| `guidanceScale` | number | - | `3` | Classifier-free guidance scale (higher = more prompt adherence) |
| `cameraMotion` | string | - | `none` | Camera movement type in the generated continuation |
| `cameraMotionStrength` | number | - | `1` | Strength of camera motion |
| `generateAudio` | boolean | - | `true` | Whether to generate synchronized audio |
| `audioStrength` | number | - | `1` | Audio conditioning strength (0-1). Higher preserves more input audio characteristics. |
| `enhancePrompt` | boolean | - | `false` | Enhance the prompt for better video generation |
| `seed` | number | - | - | Random seed for reproducibility. Leave blank for random. |
| `negativePrompt` | string | - | - | What to avoid in generation |

### Example Requests

**cURL**

```bash
curl -X POST "https://api.cloud.scenario.com/v1/generate/custom/model_ltx-2-19b-extend-video" \
  -H "Authorization: Basic $(echo -n '<API_KEY>:<API_SECRET>' | base64)" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'EOF'
{
  "prompt": "A fantasy landscape",
  "videoStrength": 1,
  "extendDuration": 4,
  "aspectRatio": "auto",
  "resolution": "auto",
  "numInferenceSteps": 40,
  "guidanceScale": 3,
  "cameraMotion": "none",
  "cameraMotionStrength": 1,
  "generateAudio": true,
  "audioStrength": 1,
  "enhancePrompt": false
}
EOF
```

**Python**

```python
import requests
import base64

api_key = "<API_KEY>"
api_secret = "<API_SECRET>"
token = base64.b64encode(f"{api_key}:{api_secret}".encode()).decode()

url = "https://api.cloud.scenario.com/v1/generate/custom/model_ltx-2-19b-extend-video"
headers = {
    "Authorization": f"Basic {token}",
    "Content-Type": "application/json"
}
payload = {
    "prompt": "A fantasy landscape",
    "videoStrength": 1,
    "extendDuration": 4,
    "aspectRatio": "auto",
    "resolution": "auto",
    "numInferenceSteps": 40,
    "guidanceScale": 3,
    "cameraMotion": "none",
    "cameraMotionStrength": 1,
    "generateAudio": True,
    "audioStrength": 1,
    "enhancePrompt": False
}

response = requests.post(url, headers=headers, json=payload)
print(response.json())
```

**JavaScript**

```javascript
const token = btoa("<API_KEY>:<API_SECRET>");

const body = {
  "prompt": "A fantasy landscape",
  "videoStrength": 1,
  "extendDuration": 4,
  "aspectRatio": "auto",
  "resolution": "auto",
  "numInferenceSteps": 40,
  "guidanceScale": 3,
  "cameraMotion": "none",
  "cameraMotionStrength": 1,
  "generateAudio": true,
  "audioStrength": 1,
  "enhancePrompt": false
};

const response = await fetch(
  "https://api.cloud.scenario.com/v1/generate/custom/model_ltx-2-19b-extend-video",
  {
    method: "POST",
    headers: {
      "Authorization": `Basic ${token}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify(body),
  }
);

const data = await response.json();
console.log(data);
```

---

## Retrieve Results

After submitting a generation request, you receive a `jobId`. Poll the job status endpoint until the job completes.

**Endpoint:** `GET https://api.cloud.scenario.com/v1/jobs/{jobId}`

**Headers:**
```
Authorization: Basic base64("<API_KEY>:<API_SECRET>")
```

Poll until `job.status` is `"success"`. The generated asset IDs are in `job.metadata.assetIds`.

**Example response:**
```json
{
  "job": {
    "jobId": "job_abc123",
    "status": "success",
    "metadata": {
      "assetIds": [
        "asset_abc123"
      ]
    }
  }
}
```

> **Important:** Generated asset URLs are **temporary** and expire after a short period. Download and store any images you wish to keep before the URL expires. More info: [Content Delivery Network (CDN)](https://docs.scenario.com/docs/content-delivery-network-cdn).

---

*Generated by [Scenario](https://app.scenario.com)*