Video Editor

Perform video editing tasks with ffmpeg, including cutting, merging, converting formats, extracting audio, adding subtitles, resizing, cropping, adjusting sp...

Security Scan

The skill's files and instructions match its stated purpose (ffmpeg-based video editing); there are no hidden network endpoints, credential requests, or surprising install steps, though a few small system utilities used by the scripts are not declared in metadata.

Purpose & Capability

Name/description, SKILL.md, and the included shell scripts all focus on ffmpeg-based editing (cut, merge, convert, extract audio, subtitles, resize, crop, speed). The declared required binaries (ffmpeg, ffprobe) are appropriate for the stated purpose; scripts perform only video/audio processing using ffmpeg.

Instruction Scope

Runtime instructions direct the agent to run the included scripts and ffmpeg commands; the scripts operate only on user-supplied file paths and temporary files. Minor scope issues: scripts call common system utilities that are not listed in metadata (realpath, mktemp, bc). The SKILL.md troubleshooting examples also reference external utilities (file, iconv). There are no instructions to read unrelated files, access credentials, or send data off-host.

Install Mechanism

No custom install routine or remote downloads are present. The metadata suggests installing ffmpeg via a well-known brew formula (ffmpeg). This is proportionate and expected for an ffmpeg-based skill.

Credentials

The skill requires no environment variables or credentials. Scripts do not attempt to read env vars or secret/config files. Credential access is not requested or implied.

Persistence & Privilege

always is false and the skill does not request persistent system-wide privileges or modify other skills. It is user-invocable and can be invoked autonomously per platform defaults, which is normal for a utility skill.

Assessment

This skill appears coherent and focused on ffmpeg-based editing with no hidden network calls or secret access. Before installing or running: (1) verify ffmpeg/ffprobe are installed (brew install ffmpeg or your distro package); (2) inspect the included scripts (they are plain shell and call ffmpeg); (3) ensure small utilities used by scripts (realpath, mktemp, bc) exist on your system or adjust the scripts; (4) run operations on trusted or sandboxed files first (ffmpeg processes input media and malformed files can crash tools); and (5) note the source/homepage is unspecified — if provenance matters, request a named maintainer or upstream link before wider use.

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