ffmpeg-skill

name	ffmpeg-skill
description	Use when user asks to convert, compress, trim, resize, extract audio, add subtitles, create GIFs, or process video/audio files
allowed-tools	Bash(ffmpeg *), Bash(ffprobe *)

FFmpeg Media Processing Skill

FFmpeg is a universal media converter that reads from multiple inputs, applies filters/transformations, and writes to multiple outputs.

When to Use This Skill

Invoke this skill when the user wants to:

• Convert video/audio formats (MP4, MKV, WebM, MP3, etc.)
• Compress or resize videos
• Trim, cut, or merge media files
• Extract audio from video
• Add subtitles or text overlays
• Create GIFs from video
• Adjust speed, rotate, crop, or apply effects
• Stream media (HLS, DASH, RTMP)

Example Inputs/Outputs

User Says	Claude Does
"Convert video.mkv to mp4"	ffmpeg -i video.mkv output.mp4
"Extract audio from movie.mp4"	ffmpeg -i movie.mp4 -vn audio.mp3
"Compress this video"	ffmpeg -i input.mp4 -crf 23 output.mp4
"Make a GIF from the first 5 seconds"	ffmpeg -t 5 -i input.mp4 -vf "fps=10,scale=320:-1" output.gif
"Add subtitles to my video"	ffmpeg -i input.mp4 -vf subtitles=subs.srt output.mp4

Additional Resources

• CONCEPTS.md - Core concepts: video, audio, codecs, containers, processing pipeline
• REFERENCE.md - Complete command reference for all operations
• ADVANCED.md - Streaming (HLS/DASH/RTMP), complex filters, batch processing

---

Synopsis

ffmpeg [global_options] {[input_file_options] -i input_url} ... {[output_file_options] output_url} ...

IMPORTANT: Order matters! Options apply to the next specified file and reset between files.

---

Quick Reference - Main Options

Option	Purpose
-i url	Specify input file
-c copy	Stream copy (no re-encode, fast)
-c:v codec	Set video codec (libx264, libx265, libvpx-vp9)
-c:a codec	Set audio codec (aac, libmp3lame, libopus)
-vf filter	Apply video filter
-af filter	Apply audio filter
-ss time	Seek to position
-t duration	Limit duration
-y	Overwrite output
-vn	No video
-an	No audio

---

Most Common Commands

Convert Format

ffmpeg -i input.mkv output.mp4
ffmpeg -i input.mp4 -c:v libvpx-vp9 -c:a libopus output.webm

Extract Audio

ffmpeg -i video.mp4 -vn -c:a copy audio.aac
ffmpeg -i video.mp4 -vn -c:a libmp3lame -b:a 192k audio.mp3

Compress Video

ffmpeg -i input.mp4 -c:v libx264 -crf 23 -c:a copy output.mp4

Trim/Cut

ffmpeg -ss 00:01:00 -i input.mp4 -t 00:00:30 -c copy output.mp4

Resize

ffmpeg -i input.mp4 -vf scale=1280:720 output.mp4
ffmpeg -i input.mp4 -vf scale=640:-1 output.mp4

Create GIF

ffmpeg -i input.mp4 -vf "fps=10,scale=320:-1" output.gif

Add Text

ffmpeg -i input.mp4 -vf "drawtext=text='Hello':fontsize=36:fontcolor=white:x=(w-text_w)/2:y=(h-text_h)/2" output.mp4

Burn Subtitles

ffmpeg -i input.mp4 -vf "subtitles=subs.srt" output.mp4

Extract Frames

ffmpeg -i input.mp4 -vf fps=1 frame_%04d.png

Speed Up/Slow Down

# 2x speed
ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4

Merge Files

# Create filelist.txt with: file 'part1.mp4' (one per line)
ffmpeg -f concat -safe 0 -i filelist.txt -c copy output.mp4

---

Video Options

Option	Purpose
-r fps	Set frame rate
-s WxH	Set resolution
-crf N	Quality (0-51, lower=better, default 23)
-b:v bitrate	Set video bitrate
-preset name	Encoding speed (ultrafast to veryslow)

Audio Options

Option	Purpose
-ar freq	Sample rate (44100, 48000)
-ac N	Channels (1=mono, 2=stereo)
-b:a bitrate	Audio bitrate

---

Common Filters

Filter	Example	Purpose
scale	scale=1280:720	Resize
crop	crop=640:480:100:50	Crop (w:h:x:y)
transpose	transpose=1	Rotate 90° CW
hflip/vflip	hflip	Mirror
fade	fade=t=in:d=2	Fade in/out
drawtext	drawtext=text='Hi'	Text overlay
subtitles	subtitles=subs.srt	Burn subtitles
overlay	overlay=10:10	Image overlay

---

File Info

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

---

Best Practices

1. Use -c copy when possible (fast, no quality loss)
2. Place -ss before -i for fast seeking
3. Use -y to overwrite without prompts
4. Use -crf 18-28 for quality control
5. Check file info with ffprobe first

---

For complete reference, see REFERENCE.md, CONCEPTS.md, and ADVANCED.md.