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.

Pricing: $0.14/second. Endpoint: POST /v1/models/alibaba/happy-horse/reference-to-video/runs.

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/models/alibaba/happy-horse/reference-to-video/runs
• 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)

Happy Horse Reference-to-Video API

Endpoint: POST /v1/models/alibaba/happy-horse/reference-to-video/runs

Run the model

Python

import requests

response = requests.post(
    "https://api.runflow.io/v1/models/alibaba/happy-horse/reference-to-video/runs",
    headers={"Authorization": "Bearer RUNFLOW_API_KEY"},
    json={
        "input": {
            "prompt": "character1 walks confidently down a neon-lit Tokyo street at night, cinematic lighting, smooth tracking shot",
            "duration": 5,
            "image_urls": [
                "https://images.unsplash.com/photo-1535713875002-d1d0cf377fde?w=1024&q=80"
            ],
            "resolution": "720p",
            "aspect_ratio": "16:9"
        },
        "callback_url": "https://your-server.com/webhook"
    },
)

data = response.json()
print(data)

Node.js

const response = await fetch(
  "https://api.runflow.io/v1/models/alibaba/happy-horse/reference-to-video/runs",
  {
    method: "POST",
    headers: {
      "Authorization": "Bearer RUNFLOW_API_KEY",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
        "input": {
            "prompt": "character1 walks confidently down a neon-lit Tokyo street at night, cinematic lighting, smooth tracking shot",
            "duration": 5,
            "image_urls": [
                "https://images.unsplash.com/photo-1535713875002-d1d0cf377fde?w=1024&q=80"
            ],
            "resolution": "720p",
            "aspect_ratio": "16:9"
        },
        "callback_url": "https://your-server.com/webhook"
    }),
  }
);

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

cURL

curl -X POST https://api.runflow.io/v1/models/alibaba/happy-horse/reference-to-video/runs \
  -H "Authorization: Bearer $RUNFLOW_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'JSON'
{
    "input": {
        "prompt": "character1 walks confidently down a neon-lit Tokyo street at night, cinematic lighting, smooth tracking shot",
        "duration": 5,
        "image_urls": [
            "https://images.unsplash.com/photo-1535713875002-d1d0cf377fde?w=1024&q=80"
        ],
        "resolution": "720p",
        "aspect_ratio": "16:9"
    },
    "callback_url": "https://your-server.com/webhook"
}
JSON

Request parameters

Parameter	Type	Required	Description
input	object	required	Model input parameters. See “Input schema” below.
callback_url	string | null	optional	Webhook URL - POSTed when the run reaches a terminal state.
metadata	object | null	optional	Arbitrary key-value pairs attached to the run.

Input schema

Field	Type	Required	Allowed values	Description
prompt	string	required	Any	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	Any	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	16:9, 9:16, 1:1, 4:3, 3:4	Aspect ratio of the generated video.
duration	integer	optional	Any	Output video duration in seconds (3-15).
enable_safety_checker	boolean	optional	Any	Enable content moderation for input and output.
resolution	string	optional	720p, 1080p	Output video resolution tier.
seed	integer	optional	Any	Random seed for reproducibility (0-2147483647).

Output schema

Field	Type	Description
outputs	json	Unified output array - one entry per generated artifact with url/type/width/height/duration/etc.
seed	json	Deterministic seed used for generation, or null if the provider doesn’t return one.
timing	json	Provider timing info (inference_ms etc.), or null.
nsfw_detected	json	true if the provider flagged output as NSFW, false if cleared, null if not checked.

Callback payload

When you provide a callback_url, Runflow POSTs to it once the run reaches a terminal state.

Field	Type	Description
event	string	Event type: “run.completed”, “run.failed”, or “run.cancelled”.
run_id	string	The unique identifier of the run.
status	string	Terminal status: “succeeded”, “failed”, or “cancelled”.
output	object | null	The run output. Null if the run failed or was cancelled.
duration_ms	number | null	Total run duration in milliseconds.
created_at	string | null	ISO 8601 timestamp when the run was created.
completed_at	string | null	ISO 8601 timestamp when the run reached terminal state.
metadata	object | null	The metadata object passed at run creation, if any.

• Retries: 3 attempts with exponential backoff (1s, 2s). Retries on 5xx / network errors only.
• Headers: Runflow-Request-Id is always sent. Runflow-Signature is sent if a signing secret is configured.

Additional Resources

• Playground
• API Reference
• Documentation
• OpenAPI

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Run lifecycle

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