Vidu Q4 cover_url and watermarked_url vs Sume's poll response

A finished Vidu Q4 Preview task returns three URLs: url, cover_url and watermarked_url, each valid for 24 hours. A completed Sume video job returns unsigned_urls and a usage object. Its documented response has no cover image or watermarked copy, so a poster still is a separate, small job.

What comes back on each side?

The Vidu list is from the image-to-video page. The Sume list is from the poll response in the video generation docs.

How do you get a poster from a Sume clip?

Use Video frames. It extracts stills at times you name from one media.sume.com clip and returns durable image artifacts at the source size, as jpeg by default or png. It does not fetch from the open internet, so the docs tell you to import the clip first with POST /v1/media-imports.

The job is billed by its own compute, and you send an Idempotency-Key so a retry does not queue a second extract.

What request asks for the first frame and a mid frame?

Replace the example URL with your own media.sume.com clip.

curl -X POST https://api.sume.com/v1/video-frames \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: poster-001" \
  -d '{"video_url": "https://media.sume.com/artifacts/artf_demo/clip.mp4", "at": [0, 2.5], "format": "jpeg"}'

What about the watermark?

The request table in the video docs lists model, prompt, duration, resolution, aspect_ratio, size, frame_images, input_references, generate_audio, seed, callback_url and provider. There is no watermark switch to port, so there is nothing to map from Vidu's marked copy.