Migrate from Seedance

H3 video task API · /api/v3

Keep the Ark calling pattern

H3 implements the text-to-video and single-first-frame image-to-video subset of the Ark video task protocol. Keep the paths, authentication, content structure and polling flow, while changing the service address, model ID and supported presets.

Integration item	Migration change
Base URL	`https://fablun.com/api/v3`
API Key	Replace with your Fablun customer key.
model	Use h3-pro or h3-standard; Seedance model IDs are not accepted.
SDK methods	Keep Ark.content_generation.tasks create / get / list / delete.
Reading results	Read id on creation; read status and content.video_url on retrieval.
Input parameters	text / one first_frame; explicitly set supported resolution and duration.

SDK client

Python · Verified SDK 5.0.55

from volcenginesdkarkruntime import Ark
import os

client = Ark(
    base_url="https://fablun.com/api/v3",
    api_key=os.environ["ARK_API_KEY"],
)

Compatibility scope

Item	Current H3 scope
Models and inputs	Two H3 model IDs, text and a single first-frame URL / data URL. Check availability before use.
Specifications	480p / 720p; 1:1, 3:4, 4:3, 16:9 and 9:16; optional audio. Check the model table for duration.
Tasks and retries	Four task operations, six states and idempotent retries. Queue limits and fair scheduling follow Fablun's rules.
Link lifetime	One hour after completion; different from Volcengine's retention policy.
SDK	Verified with volcengine-ark-runtime 5.0.55. New arkruntime versions and newer Seedance features are outside this verification scope.
Not supported	1080p, custom aspect ratios, multimodal references, draft mode and flex.

Protocol compatibility does not imply identical model capabilities, limits, pricing, retention or scheduling to Seedance. Unsupported parameters return errors.

Official protocol referencesVolcengine Ark · Create video generation tasks Volcengine Ark · Video generation tutorial

First and last frames

H3 Pro supports first and last frames for 5-second videos at 480p or 720p, with 1:1, 3:4, 4:3, 16:9 and 9:16 aspect ratios. Supply one image per role; last_frame requires first_frame. A pair is billed as one video, with the usual cancellation, moderation and callback flow. return_last_frame is a separate output option and remains unsupported.

{
  "model": "h3-pro",
  "content": [
    {
      "type": "text",
      "text": "A red ball rolls from left to right."
    },
    {
      "type": "image_url",
      "image_url": {
        "url": "https://YOUR_IMAGE_HOST/first-frame.jpg"
      },
      "role": "first_frame"
    },
    {
      "type": "image_url",
      "image_url": {
        "url": "https://YOUR_IMAGE_HOST/last-frame.jpg"
      },
      "role": "last_frame"
    }
  ],
  "resolution": "720p",
  "duration": 5,
  "ratio": "16:9",
  "generate_audio": true
}