# Happy Horse Reference-to-Video

> Generate 1080p video with synchronized native audio from a text prompt and references. Aspect ratios: 16:9, 9:16, 1:1, 4:3, 3:4. Duration: 3–15s.

## Overview

- **Endpoint**: `https://api.runflow.io/v1/run/alibaba/happy-horse/reference-to-video`
- **Model ID**: `alibaba/happy-horse/reference-to-video`
- **Provider**: Alibaba
- **License**: commercial
- **Last Updated**: 2026-04-28

## Pricing

- **Base price**: $0.14/second
- **Note**: Per second of generated video (720p baseline)

### Pricing rules

- **resolution**: $0.28/second

## Input Schema

### `prompt` (string, required)

Text prompt describing the desired video. Reference subjects from your images using ``character1``, ``character2``, ... up to ``character9`` (the order matches the order of ``image_urls``). Max 2500 characters.

### `image_urls` (image_list, required)

Reference images for subject consistency (1-9 images). Formats: JPEG, JPG, PNG, WEBP. Shortest side must be at least 400 px (720P or higher recommended). Max 10 MB each.

### `aspect_ratio` (string, optional)

Aspect ratio of the generated video.
- **Default**: `16:9`

### `duration` (integer, optional)

Output video duration in seconds (3-15).
- **Default**: `5`

### `enable_safety_checker` (boolean, optional)

Enable content moderation for input and output.
- **Default**: `true`

### `resolution` (string, optional)

Output video resolution tier.
- **Default**: `1080p`

### `seed` (integer, optional)

Random seed for reproducibility (0-2147483647).

## Usage Examples

### cURL

```bash
curl -X POST https://api.runflow.io/v1/run/alibaba/happy-horse/reference-to-video \
  -H "Authorization: Bearer $RUNFLOW_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A professional headshot, soft studio lighting"
  }'
```

### Python

```python
import requests

response = requests.post(
    "https://api.runflow.io/v1/run/alibaba/happy-horse/reference-to-video",
    headers={"Authorization": "Bearer RUNFLOW_API_KEY"},
    json={
        "prompt": "A professional headshot, soft studio lighting",
    },
)

data = response.json()
print(data["video"]["url"])
```

### JavaScript

```javascript
const response = await fetch(
  "https://api.runflow.io/v1/run/alibaba/happy-horse/reference-to-video",
  {
    method: "POST",
    headers: {
      "Authorization": "Bearer RUNFLOW_API_KEY",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      prompt: "A professional headshot, soft studio lighting",
    }),
  }
);

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

## Additional Resources

- [Playground](https://www.runflow.io/models/alibaba/happy-horse/reference-to-video)
- [API Reference](https://www.runflow.io/models/alibaba/happy-horse/reference-to-video/api)
- [Documentation](https://docs.runflow.io)
- [OpenAPI](https://api.runflow.io/v1/openapi.json)