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.

Quality

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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:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black`
YouTube	1920 x 1080	`scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black`
Instagram	1080 x 1350	`scale=1080:1350:force_original_aspect_ratio=decrease,pad=1080:1350:(ow-iw)/2:(oh-ih)/2:black`
Square	1080 x 1080	`scale=1080:1080:force_original_aspect_ratio=decrease,pad=1080:1080:(ow-iw)/2:(oh-ih)/2:black`
Twitter/X	1920 x 1080	`scale=1920:1080:force_original_aspect_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.

Repository: calesthio/OpenMontage
Path: .agents/skills/video-edit/SKILL.md
Commit: 0af32ce

Last updated: 1 day ago
First committed: 4 months ago

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