video-editor

name	video-editor
description	Video editing operations using ffmpeg. Use when user needs to: (1) Cut/trim video clips, (2) Merge/join multiple videos, (3) Convert video formats, (4) Extract audio from video, (5) Add subtitles or text overlays, (6) Adjust video speed, (7) Resize/crop video dimensions, (8) Apply filters or effects. Supports common formats like MP4, MOV, AVI, MKV, WebM.

Video Editor (ffmpeg)

Video editing operations for cutting, merging, converting, and processing video files.

Prerequisites

Requires ffmpeg and ffprobe installed:

brew install ffmpeg

Quick Start

Cut/Trim Video

Extract a segment from a video:

{baseDir}/scripts/cut.sh /path/to/input.mp4 --start 00:00:10 --end 00:00:30 --out /path/to/output.mp4

Or use duration instead of end time:

{baseDir}/scripts/cut.sh /path/to/input.mp4 --start 00:01:00 --duration 30 --out /path/to/output.mp4

Merge Videos

Concatenate multiple videos (must have same codec/resolution):

{baseDir}/scripts/merge.sh video1.mp4 video2.mp4 video3.mp4 --out merged.mp4

Convert Format

Convert between video formats:

{baseDir}/scripts/convert.sh input.mov --format mp4 --out output.mp4

Extract Audio

Extract audio track from video:

{baseDir}/scripts/extract-audio.sh input.mp4 --out audio.mp3

Add Subtitles

Burn subtitles into video:

{baseDir}/scripts/add-subtitles.sh input.mp4 subtitles.srt --out output.mp4

Resize Video

Change video resolution:

{baseDir}/scripts/resize.sh input.mp4 --width 1920 --height 1080 --out output.mp4

Or scale proportionally:

{baseDir}/scripts/resize.sh input.mp4 --scale 720 --out output.mp4

Adjust Speed

Speed up or slow down video:

{baseDir}/scripts/speed.sh input.mp4 --rate 2.0 --out output.mp4   # 2x faster
{baseDir}/scripts/speed.sh input.mp4 --rate 0.5 --out output.mp4   # 0.5x slower

Crop Video

Crop to specific region:

{baseDir}/scripts/crop.sh input.mp4 --x 100 --y 100 --width 800 --height 600 --out output.mp4

Common Workflows

Social Media Clip

Cut a segment and resize for Instagram/TikTok:

# First cut the segment
{baseDir}/scripts/cut.sh input.mp4 --start 00:00:15 --duration 15 --out clip.mp4

# Then resize to vertical format
{baseDir}/scripts/resize.sh clip.mp4 --width 1080 --height 1920 --out tiktok.mp4

Extract Highlights

Cut multiple segments and merge:

{baseDir}/scripts/cut.sh input.mp4 --start 00:00:10 --duration 5 --out highlight1.mp4
{baseDir}/scripts/cut.sh input.mp4 --start 00:01:30 --duration 5 --out highlight2.mp4
{baseDir}/scripts/merge.sh highlight1.mp4 highlight2.mp4 --out highlights.mp4

Add Background Music

Replace or mix audio:

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

# Mix audio (video audio at 70%, music at 30%)
ffmpeg -i video.mp4 -i music.mp3 -filter_complex "[0:a]volume=0.7[a0];[1:a]volume=0.3[a1];[a0][a1]amix=inputs=2:duration=first" -c:v copy -shortest output.mp4

Tips

• Quality: Use -crf 18 for high quality, -crf 28 for smaller files (default is 23)
• Presets: Use -preset slow for better compression, -preset fast for quicker encoding
• Hardware acceleration: On Apple Silicon, add -c:v h264_videotoolbox for faster encoding
• Copy mode: Use -c copy to avoid re-encoding (much faster, but limited editing)

Troubleshooting

Merge fails with "Codec mismatch"

Videos must have the same codec, resolution, and frame rate. Re-encode them first:

ffmpeg -i input1.mp4 -c:v libx264 -c:a aac -vf "scale=1920:1080" -r 30 temp1.mp4
ffmpeg -i input2.mp4 -c:v libx264 -c:a aac -vf "scale=1920:1080" -r 30 temp2.mp4
{baseDir}/scripts/merge.sh temp1.mp4 temp2.mp4 --out merged.mp4

Subtitles not showing

Ensure subtitle file format matches extension (.srt, .ass, .vtt). Check encoding:

file -I subtitles.srt  # Should show charset=utf-8

Convert if needed:

iconv -f GBK -t UTF-8 subtitles.srt > subtitles_utf8.srt