Bookstore author event promo: Seedance 2.5 at 1:1, 480p, 8 s

A square 8-second promo on Seedance 2.5 costs $2.06 at 480p (640 x 640) and $4.63 at 720p (960 x 960) on Sume. For a feed post that plays at phone width, 480p is enough for a first run. Upgrade to 720p for the version you pin to the shop's page.

Why 1:1 and why Seedance 2.5

Event promos are posted to feeds, where a square frame uses more of the screen than a 16:9 frame. Seedance 2.5 lists 1:1 on Sume, along with seven other aspect-ratio values, and takes reference images. Send the book cover as a reference so the cover is the real one. fal's Seedance 2.5 explainer, read 2026-10-08, lists up to 30 images in its reference endpoint.

Generated text on a cover is unreliable. Use a flat scan of the real cover as the reference and check it frame by frame.

Square-frame prices

Sume bills the provider list price times 1.25, rounded up to the cent per job.

What to put in the clip

Keep the event facts out of the prompt.

• Prompt for the mood: a reading chair, warm light, pages turning.
• Add the author name, date and time as text in your editor.
• Run a 4-second test at 480p for $1.03 before the 8-second job.
• Get the author's permission before using their photo as a reference.

Submit it and read the result

Sume reserves the billable amount from your workspace USD balance when the job is submitted, then returns a polling_url. Add the flat cover scan as an image_url entry in input_references once the draft prompt is right. Poll the job until status is completed or failed; a completed job lists its files in unsigned_urls.

import os
import time
import requests

H = {"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"}
body = {
    "model": "seedance-2.5",
    "prompt": "A slow push-in on the scene, soft natural light",
    "duration": 8,
    "resolution": "480p",
    "aspect_ratio": "1:1",
}
r = requests.post("https://api.sume.com/v1/videos", headers=H, json=body, timeout=60)
r.raise_for_status()
url = r.json()["polling_url"]
while True:
    job = requests.get(url, headers=H, timeout=30).json()
    if job["status"] in ("completed", "failed"):
        break
    time.sleep(10)
print(job["status"], job.get("unsigned_urls"))

Limits

Seedance 2.5 on Sume runs 4 to 30 seconds, so there is no 3-second option. fal's page lists 480p and 720p, and the 1080p column follows the Sume catalog, which I did not render. A reference video would raise the bill, as another post in this series shows; images do not.