Seedance 2.5 延长视频：用 API 制作 1–5 分钟长视频

{
  "model": "dreamina-seedance-2-5",
  "content": [{"type": "text", "text": "A small red paper boat drifts down a winding forest stream at golden hour, slow tracking shot from behind"}],
  "resolution": "480p",
  "ratio": "16:9",
  "duration": 15
}

{
  "model": "dreamina-seedance-2-5",
  "content": [
    {"type": "text", "text": "Continue the shot: the paper boat drifts out of the forest into a wide meadow river, the camera keeps tracking from behind"},
    {"type": "video_url", "video_url": {"url": "https://your-storage.example/segment-1.mp4"}, "role": "reference_video"}
  ],
  "omni_reference_task_type": "extend",
  "resolution": "480p",
  "ratio": "adaptive",
  "duration": 15
}

import os, subprocess, time
import requests

API = "https://api.seedrouter.ai/v1/contents/generations/tasks"
HEADERS = {"Authorization": f"Bearer {os.environ['SEEDROUTER_API_KEY']}"}

def run(body):
    task_id = requests.post(API, json=body, headers=HEADERS).json()["id"]
    while True:
        time.sleep(15)
        task = requests.get(f"{API}/{task_id}", headers=HEADERS).json()
        if task["status"] == "succeeded":
            return task["content"]["video_url"]
        if task["status"] in ("failed", "expired"):
            raise RuntimeError(task)

prompts = [
    "A small red paper boat drifts down a winding forest stream at golden hour, slow tracking shot from behind",
    "Continue the shot: the paper boat drifts out of the forest into a wide meadow river, the camera keeps tracking from behind",
    "Continue the shot: the paper boat floats under an old stone bridge covered in ivy, warm sunset light",
    "Continue the shot: the paper boat drifts onto a calm lake at sunset, the camera slowly rises and pulls back",
]

urls = [run({"model": "dreamina-seedance-2-5", "content": [{"type": "text", "text": prompts[0]}],
             "resolution": "480p", "ratio": "16:9", "duration": 15})]
for prompt in prompts[1:]:
    urls.append(run({"model": "dreamina-seedance-2-5",
                     "content": [{"type": "text", "text": prompt},
                                 {"type": "video_url", "video_url": {"url": urls[-1]}, "role": "reference_video"}],
                     "omni_reference_task_type": "extend",
                     "resolution": "480p", "ratio": "adaptive", "duration": 15}))

with open("list.txt", "w") as f:
    for i, url in enumerate(urls):
        name = f"part{i}.mp4"
        with open(name, "wb") as out:
            out.write(requests.get(url).content)
        f.write(f"file '{name}'\n")
subprocess.run(["ffmpeg", "-f", "concat", "-safe", "0", "-i", "list.txt", "-c", "copy", "long.mp4"], check=True)

video tokens = (output seconds + reference video seconds) × width × height × 24 / 1024