Seedance 2.5 API in Python: a 30-second clip with an audio reference

To call Seedance 2.5 by API on Sume, POST model: "seedance-2.5" to /v1/videos with duration up to 30, put reference files in input_references, and poll the job. This post pairs one image with one audio file so the clip follows your music.

Seedance 2.5 on Sume runs 4 to 30 seconds at 480p, 720p and 1080p, and the catalog row accepts image, video and audio references.

The script

Save as seedance.py. It needs pip install requests and SUME_API_KEY in the environment. The loop sleeps ten seconds between polls; a 30-second job can take a while, so a webhook is better in production.

import os, time, requests

H = {"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"}
BASE = "https://api.sume.com/v1/videos"
body = {
    "model": "seedance-2.5",
    "prompt": "A drummer plays in a sunlit loft, the camera circles slowly",
    "duration": 30,
    "resolution": "720p",
    "aspect_ratio": "16:9",
    "input_references": [
        {"type": "image_url", "image_url": {"url": "https://example.com/drummer.png"}},
        {"type": "audio_url", "audio_url": {"url": "https://example.com/groove.mp3"}},
    ],
}
job = requests.post(BASE, headers=H, json=body, timeout=60).json()
while True:
    s = requests.get(job["polling_url"], headers=H, timeout=60).json()
    if s["status"] in ("completed", "failed", "cancelled"):
        break
    time.sleep(10)
if s["status"] != "completed":
    raise SystemExit(s.get("error") or s["status"])
open("seedance.mp4", "wb").write(requests.get(s["unsigned_urls"][0], headers=H, timeout=300).content)
print("cost", s["usage"]["cost"])

What the vendor and the catalog say

ByteDance Seed describes Seedance 2.5 as an audio-video joint generation model that creates videos up to 30 seconds in a single generation, with an option to extend twice (read 2026-10-07). Sume does not expose the extension step, so a Sume job is one generation of 4 to 30 seconds.

Reference rules and cost

Reference videos on Seedance models are billed with a priced allowance: the pricing code assumes 15 seconds of reference video at 60 percent of the clip rate, so budget for it when you add one. The audio reference in this example is not a video, but check GET /v1/videos/models for the accepted types before you rely on a combination.

Because pricing is by token, the safest way to know the cost of a 30-second job is the usage.cost on a finished run, plus the reserve that Sume holds at submit. If the reserve exceeds your balance, the submit returns 402 insufficient_credits.

• Send Idempotency-Key so a retried submit returns the same job.
• No seed: a rerun is a new take.
• Use seedance-2-mini or seedance-2-fast for 4 to 15 second drafts.