Editing

Speed Ramp: Quick and Slow

Cut a rendered action clip with ffmpeg and add fast, slow and frozen parts for a quick-and-slow feel.

Free · No sign-up · Updated 2026-10-27 · By sphereai.work💻Install Claude Code (or Codex, Antigravity) firstThis skill runs best in VS Code with Claude Code, Codex or Antigravity.How to install →

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How to use

1
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2
Unzip and open
Unzip it into a folder and open that folder in VS Code.
3
Just ask
Tell your AI agent ‘Run the automation pipeline in this folder’.

When to use it

All action runs at one speed and feels flat
You want a freeze at the moment of impact
Slow-motion parts stutter or joins jump

Try saying

“펀치 장면에 히트스톱이랑 슬로 넣어줘”Add hit-stop and slow motion to the punch

“착지 장면 퀵앤 슬로우로 바꿔줘”Make the landing quick and slow

What you get

01How to pick the moments
02Commands to cut, retime, freeze and rejoin

Tips

Two or three speed changes are enough in a 30 s short.
Render slow parts at a higher fps for smoother motion.

Get it free now

No sign-up, just one ZIP. Edit it freely for personal or commercial use.

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Installation

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Files and preview

Included files

SKILL.md
README.txt

Preview of SKILL.md

---
name: speed-ramp-quick-slow
description: Simple fast-then-slow speed changes and freeze frames on a rendered action clip with ffmpeg: split, retime, freeze, rejoin. 렌더한 영상에 퀵앤 슬로우 속도 변화 넣기.
---

# Speed Ramp: Quick and Slow

The "quick and slow" look: motion rushes in, slows down at the key moment, then rushes out. This skill does it on a finished render with ffmpeg, so no extra 3D work is needed.

## 1. Plan
- Pick 2-3 moments in a 30-second short: the hero landing, the punch contact, the bully flying away. Do not slow everything; the contrast is what makes it hit.
- For each moment write: start second, end second, speed (for example 0.5 = half speed, 2 = double speed).
- Render that section at a higher frame rate if you can (for example 120 fps) so the slow part stays smooth.

## 2. Cut and retime
1. Cut the clip into parts at the planned seconds: `ffmpeg -i in.mp4 -ss <a> -to <b> -an part1.mp4`.
2. Change the speed of each part with `setpts`:
- half speed: `-vf "setpts=2.0*PTS"`
- double speed: `-vf "setpts=0.5*PTS"`
3. Freeze frame at contact: hold the last frame of a part with `-vf "tpad=stop_mode=clone:stop_duration=0.1"`.
4. Re-encode every part with the same size, fps and codec (`-r 60 -c:v libx264 -pix_fmt yuv420p`).
5. Join with a concat list: `ffmpeg -f concat -safe 0 -i list.txt -c copy out.mp4`.

## 3. Check
- Watch the result at full speed on a phone-size screen.
- The total length still fits the plan (a slow part makes the video longer).

## Output
The retimed clip and the list of moments with their speeds.

---
만든이: sphereai.work (https://sphereai.work)