calesthio/openmontage

video-edit

Edit videos locally using ffmpeg. Trim, concat, resize, speed, overlay, extract audio, compress, and convert. Use when: (1) Trimming or cutting video segments, (2) Concatenating multiple clips, (3) Resizing video for social platforms, (4) Extracting or replacing audio, (5) Compressing video, (6) Converting video formats, (7) Getting video info.

First seen Apr 4, 2026

Installation

$ npx skills add calesthio/openmontage --skill video-edit

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More details

Agent compatibility

Declared targets from SKILL.md / docs. Unmarked agents are not listed — the skill may still install via the CLI.

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Repository health

Stars 56.6K
License LICENSE
Default branch main
Open issues 96
Status Active

Package contents

Files included with this skill beyond the listing page.

  • skill md SKILL.md 3,418 B
  • docs SUMMARY.md 3,222 B

History

  1. First seen on skills.sh
  2. First recorded snapshot · 906 installs

SKILL.md

Video Edit

Edit videos locally by running ffmpeg/ffprobe directly. No wrapper scripts needed.

Prerequisites

Install ffmpeg (includes ffprobe):

# macOS
brew install ffmpeg

# Ubuntu/Debian
sudo apt update && sudo apt install -y ffmpeg

# Verify
ffmpeg -version && ffprobe -version

Quick Reference

Get video info

ffprobe -v quiet -print_format json -show_format -show_streams video.mp4

Trim

ffmpeg -y -ss 00:00:30 -to 00:01:45 -i video.mp4 -c copy trimmed.mp4

Concatenate clips

# 1. Create a file list
printf "file '%s'\n" clip1.mp4 clip2.mp4 clip3.mp4 > list.txt

# 2. Concat with stream copy
ffmpeg -y -f concat -safe 0 -i list.txt -c copy joined.mp4

Resize for platform

ffmpeg -y -i video.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black" \
  -c:a copy tiktok.mp4

Change speed

# 2x faster
ffmpeg -y -i video.mp4 -filter:v "setpts=0.5*PTS" -filter:a "atempo=2.0" fast.mp4

# 0.5x (slow motion)
ffmpeg -y -i video.mp4 -filter:v "setpts=2.0*PTS" -filter:a "atempo=0.5" slow.mp4

Extract audio

ffmpeg -y -i video.mp4 -vn -acodec libmp3lame audio.mp3

Replace audio

ffmpeg -y -i video.mp4 -i audio.mp3 -c:v copy -map 0:v:0 -map 1:a:0 -shortest output.mp4

Compress

ffmpeg -y -i video.mp4 -crf 23 -preset medium -c:a copy compressed.mp4

Convert format

ffmpeg -y -i video.mov output.mp4

Add image overlay

# Logo in top-right corner
ffmpeg -y -i video.mp4 -i logo.png \
  -filter_complex "overlay=W-w-10:10" -c:a copy watermarked.mp4

Platform Presets

Platform Resolution Scale + pad filter
TikTok 1080 x 1920 scale=1080:1920:forceoriginalaspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black
YouTube 1920 x 1080 scale=1920:1080:forceoriginalaspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black
Instagram 1080 x 1350 scale=1080:1350:forceoriginalaspect_ratio=decrease,pad=1080:1350:(ow-iw)/2:(oh-ih)/2:black
Square 1080 x 1080 scale=1080:1080:forceoriginalaspect_ratio=decrease,pad=1080:1080:(ow-iw)/2:(oh-ih)/2:black
Twitter/X 1920 x 1080 scale=1920:1080:forceoriginalaspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black

Use the filter with: ffmpeg -y -i input.mp4 -vf "<filter>" -c:a copy output.mp4

Tips

  • Always use -y to overwrite output without prompting.
  • Use -c copy when you only need to cut/join (no re-encoding, very fast).
  • Lower CRF = better quality, larger file. Range 18-28 is typical; 23 is the default.
  • For detailed recipes and flag explanations, see references/operations.md.