Add black frames to the start or end of a video with tpad

Use tpad in a filtergraph. tpad=start_duration=1:stop_duration=2:color=black adds one second of black before the clip and two after, and POST /v1/video-filter returns a new MP4. tpad is on the allowlist; so is pad, which adds border space around the frame rather than time.

Runway's changelog (Aug 10, 2026) says Tool Mode and Edit Studio can export ProRes 4444 or a PNG sequence for an editorial timeline. Editors often want handles on such files. The Sume side is in Video filter, read 2026-10-01.

Does tpad add time or space?

tpad adds time: frames before or after. pad adds space: a border around each frame. For letterboxing use pad; for lead-in black use tpad.

What does the request look like?

Import the clip, then post the graph.

curl -X POST https://api.sume.com/v1/video-filter \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: tpad-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/clip.mp4",
    "filtergraph": "tpad=start_duration=1:stop_duration=2:color=black"
  }'

What about audio and the duration cap?

tpad works on video frames. The docs do not say it pads audio, so play the result and check sync before you ship it. The source must be 300 seconds or less; a longer source is refused with output_duration_exceeded.

Cutting a range is a different tool: trim and setpts are not allowed in a filtergraph. Use video trim at its own per-job rate, then pad.

What are the limits?