YouTube Shorts Align tool: continue a scene from the last frame

The Align tool in YouTube's Shorts camera overlays your previous frame with adjustable transparency so you can line up the next shot, which helps with match cuts and transitions. To get the same continuity from generated video, take the last frame of clip one with Sume's video frames route and send it as the first_frame of the next POST /v1/videos request.

The Align tool is described on Enhance your Shorts, read on 2026-10-02, as an overlay-transparency tool for frame alignment. Sume's routes are from Video frames and Video Generation.

What does the Align tool do?

The help page lists Align among the recording tools, described as overlay transparency for frame alignment. It sits with Speed, Timer, Filters, Effects and Green screen. The page does not give more steps, so there is nothing on it about how the overlay is chosen or whether it works across separately recorded segments.

How do you get the last frame of a clip?

POST /v1/video-frames takes at[], and every value must be at least 0 and less than the clip's duration; a value at or past it fails with frame_time_out_of_range. So read the duration first. A probe-only video inspect (frames: false) returns it for free, and then you ask for a time a little under it.

curl -X POST https://api.sume.com/v1/video-frames \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: last-frame-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/clip1.mp4",
    "at": [4.9],
    "format": "png"
  }'

How do you continue the scene?

When the extract is ready, frames[0].url is a durable media.sume.com image. Pass it to POST /v1/videos as a frame_images entry with frame_type: "first_frame", set aspect_ratio to 9:16, and describe what happens next in the prompt. The new clip starts on the picture where clip one ended.

This gives continuity of the image, not of motion: the second clip starts from a still, so any movement in progress at the cut will reset. Pick a cut point where the subject is calm.

What are the limits?

Video frames accepts clips up to 300 seconds and 24 frames per call. Generated clips are capped per model: check supported_durations on GET /v1/videos/models, since limits are not uniform, so read it for the model you use. For a three-minute Short you will chain several clips and assemble them, as in our Timeline post.

Sume does not upload the result to YouTube, so the last step is yours in Studio.