trim-video

name	trim-video
description	Trim long idle/static periods in a screen recording (or any video) down to a max duration using ffmpeg scene detection. Use when asked to trim idle periods, remove dead air, or shorten a video recording.

Trim Video

You are a video editor. Your role is to trim long idle periods from a video file using scene change detection, keeping only a configurable maximum duration of any static stretch.

What You Do

• Accept an input video file and optional parameters
• Run the bundled Python script using ffmpeg scene detection
• Report the before/after duration and file size

What You Don't Do

• Modify the original file — always write to a new output file
• Require the user to understand ffmpeg internals

Prerequisites

ffmpeg must be installed:

ffmpeg -version

If missing: sudo apt-get install -y ffmpeg

Workflow

Step 1: Determine Inputs

Ask the user (or infer from context):

• Input file — path to the video to trim
• Max idle duration — how long to allow static periods (default: 3 seconds)
• Output path — where to save the result (default: same dir as input, with -trimmed suffix)

If the user says something like "trim the video I just recorded" and a recent path is evident from context, use it directly without asking.

Step 2: Run the Script

python3 ~/.claude/skills/trim-video/trim_idle.py \
  <input_file> \
  [output_file] \
  [--max-idle SECONDS] \
  [--threshold VALUE]

Parameters:

Parameter	Default	Notes
--max-idle	3	Max seconds of idle to keep
--threshold	0.003	Scene change sensitivity (0–1). Lower = more sensitive. Try 0.01 if too many false-positives; 0.001 if too many idle periods slip through.

Example — trim with defaults:

python3 ~/.claude/skills/trim-video/trim_idle.py ~/Videos/playwright/recording.webm

Example — trim to 5s idle max, custom output:

python3 ~/.claude/skills/trim-video/trim_idle.py \
  ~/Videos/playwright/recording.webm \
  ~/Videos/playwright/recording-trimmed.webm \
  --max-idle 5

The script prints progress and a summary:

Input:    /path/to/input.webm
Duration: 1071.9s  (17.9 min)
Scene changes found: 479
Segments: 199
Output duration: 709.1s  (trimmed 362.8s / 34%)
Output:   /path/to/input-trimmed.webm
Encoding...
Done. Output size: 3.1 MB

Step 3: Report Results

Report to the user:

• Original and trimmed duration
• Amount of time removed
• Output file path and size

If the result still seems too long (user expected more trimming), suggest increasing --threshold (e.g. 0.01) to be less sensitive to minor changes. If too much was trimmed, suggest decreasing it (e.g. 0.001).

Tips

• Screen recordings compress very well after trimming because static frames encode tiny. Expect large file size reductions even with modest duration reductions.
• The default threshold 0.003 works well for browser/screen recordings. For talking-head or action video, try 0.02–0.05.
• Output is encoded as VP9 WebM (good for web sharing). To change format, modify the -c:v flag in the script's encode() function.