Runway Gen-4.5 Image-to-Video

POST Base URL: https://api.hiapi.ai /v1/tasks

Image, video, and audio models are called through theUnified Async API POST /v1/tasks endpoint; only the input fields differ (see input parameters below).

Model summary

Model ID	runway-gen-4.5/image-to-video
Type	Video generation (image-to-video)
Endpoint	POST /v1/tasks
Pricing	See HiAPI Pricing

First-frame guided, fixed 720p, 5, 8 or 10 second clips, in landscape, portrait, 4:3, 3:4 or square.

Production guidance

For production, pass callback.url at the top level of the request body so HiAPI can notify your service when the task reaches a terminal state.
GET /v1/tasks/:id is better for local debugging, low-volume jobs, or fallback reconciliation if a callback is missed.
Use callback.when=final. Both success and fail are terminal states, so your service should deduplicate by taskId.

Best suited for

Animate stills

First-frame guided — bring product shots, illustrations and photos to life.

image_urlsprompt

Multiple frame shapes

Landscape, portrait, 4:3, 3:4 or square for each platform.

aspect_ratio

5/8/10 second clips

Pick the clip length you need.

duration

Request parameters

POST https://api.hiapi.ai/v1/tasks

# Create an async task — returns taskId immediately (generation runs async)
# Replace YOUR_API_KEY with your account API key
curl -X POST "https://api.hiapi.ai/v1/tasks" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "runway-gen-4.5/image-to-video",
  "input": {
    "prompt": "The steam locomotive thunders forward across the stone bridge, white steam streaming back from the chimney, wheels turning, the camera tracks smoothly alongside in warm golden hour light",
    "image_urls": [
      "https://dev-static.hiapi.ai/gallery/2026/10/30fa8d9dc2f623dd.jpg"
    ],
    "duration": 5,
    "aspect_ratio": "16:9"
  }
}'

import requests, json

# Business params — fields vary by model (see the model page)
payload = json.loads(r'''
{
  "model": "runway-gen-4.5/image-to-video",
  "input": {
    "prompt": "The steam locomotive thunders forward across the stone bridge, white steam streaming back from the chimney, wheels turning, the camera tracks smoothly alongside in warm golden hour light",
    "image_urls": [
      "https://dev-static.hiapi.ai/gallery/2026/10/30fa8d9dc2f623dd.jpg"
    ],
    "duration": 5,
    "aspect_ratio": "16:9"
  }
}
''')

# Create an async task — returns taskId immediately (generation runs async)
resp = requests.post(
    "https://api.hiapi.ai/v1/tasks",
    headers={"Authorization": "Bearer YOUR_API_KEY", "Content-Type": "application/json"},
    json=payload,
)
print(resp.json())  # Returns { code, message, data: { taskId } }

// Create an async task — returns taskId immediately (generation runs async)
// Replace YOUR_API_KEY with your account API key
const resp = await fetch("https://api.hiapi.ai/v1/tasks", {
  method: "POST",
  headers: {
    "Authorization": "Bearer YOUR_API_KEY",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
  "model": "runway-gen-4.5/image-to-video",
  "input": {
    "prompt": "The steam locomotive thunders forward across the stone bridge, white steam streaming back from the chimney, wheels turning, the camera tracks smoothly alongside in warm golden hour light",
    "image_urls": [
      "https://dev-static.hiapi.ai/gallery/2026/10/30fa8d9dc2f623dd.jpg"
    ],
    "duration": 5,
    "aspect_ratio": "16:9"
  }
}),
});
console.log(await resp.json()); // Returns { code, message, data: { taskId } }

model string required

Fixed value runway-gen-4.5/image-to-video.

example runway-gen-4.5/image-to-video

input object required

Video generation settings.

prompt string required

Describe the motion and camera movement. Max 1000 characters.

image_urls string[] required

Image used as the first frame of the video; one image only. jpeg/png/webp (SVG not supported), max 10MB.

duration enum optional

Video length in seconds: 5, 8 or 10.

default 5 enum: 5810

aspect_ratio enum optional

Aspect ratio of the generated video, for example landscape 16:9 or portrait 9:16. The first frame is center-cropped to this ratio.

default 16:9 enum: 16:99:164:33:41:1

callback object optional

Optional callback configuration. When set, HiAPI notifies your service when the task reaches a terminal state.

url string required

Required when callback is set; HTTPS URL that receives terminal task notifications.

example https://your-domain.com/hiapi/callback

when enum optional

Callback trigger timing. Use final.

default final enum: final

Example requests

Steam locomotive (16:9, 5s)

First-frame guidance with a smooth tracking shot.

Request body

{
  "model": "runway-gen-4.5/image-to-video",
  "input": {
    "prompt": "The steam locomotive thunders forward across the stone bridge, white steam streaming back from the chimney, wheels turning, the camera tracks smoothly alongside in warm golden hour light",
    "image_urls": [
      "https://dev-static.hiapi.ai/gallery/2026/10/30fa8d9dc2f623dd.jpg"
    ],
    "duration": 5,
    "aspect_ratio": "16:9"
  }
}

Getting the result

The response returns a taskId immediately without waiting for generation to finish.
In production, prefer waiting for callback.url to receive the terminal notification. For local debugging, poll GET /v1/tasks/:id.
When status=success, download the generated video from output[].url.
When status=fail, fix the request based on the returned error instead of retrying the same invalid payload.

FAQ

Can I change the resolution?

No. Output is fixed at 720p.

What if the aspect ratio differs from the first frame?

The image is center-cropped to aspect_ratio, so keep the main subject near the center.

I only have text, no image?

Use runway-gen-4.5/text-to-video.