Agent skill

media-processing

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Install this agent skill to your Project

npx add-skill https://github.com/wollfoo/setup-factory/tree/main/skills/media-processing

SKILL.md

Media Processing Skill

Process video, audio, and images using FFmpeg and ImageMagick command-line tools for conversion, optimization, streaming, and manipulation tasks.

When to Use This Skill

Use when:

  • Converting media formats (video, audio, images)
  • Encoding video with codecs (H.264, H.265, VP9, AV1)
  • Processing images (resize, crop, effects, watermarks)
  • Extracting audio from video
  • Creating streaming manifests (HLS/DASH)
  • Generating thumbnails and previews
  • Batch processing media files
  • Optimizing file sizes and quality
  • Applying filters and effects
  • Creating composite images or videos

Tool Selection Guide

FFmpeg: Video/Audio Processing

Use FFmpeg for:

  • Video encoding, conversion, transcoding
  • Audio extraction, conversion, mixing
  • Live streaming (RTMP, HLS, DASH)
  • Video filters (scale, crop, rotate, overlay)
  • Hardware-accelerated encoding
  • Media file inspection (ffprobe)
  • Frame extraction, concatenation
  • Codec selection and optimization

ImageMagick: Image Processing

Use ImageMagick for:

  • Image format conversion (PNG, JPEG, WebP, GIF)
  • Resizing, cropping, transformations
  • Batch image processing (mogrify)
  • Visual effects (blur, sharpen, sepia)
  • Text overlays and watermarks
  • Image composition and montages
  • Color adjustments, filters
  • Thumbnail generation

Decision Matrix

Task Tool Why
Video encoding FFmpeg Native video codec support
Audio extraction FFmpeg Direct stream manipulation
Image resize ImageMagick Optimized for still images
Batch images ImageMagick mogrify for in-place edits
Video thumbnails FFmpeg Frame extraction built-in
GIF creation FFmpeg or ImageMagick FFmpeg for video source, ImageMagick for images
Streaming FFmpeg Live streaming protocols
Image effects ImageMagick Rich filter library

Installation

macOS

bash
brew install ffmpeg imagemagick

Ubuntu/Debian

bash
sudo apt-get install ffmpeg imagemagick

Windows

bash
# Using winget
winget install ffmpeg
winget install ImageMagick.ImageMagick

# Or download binaries
# FFmpeg: https://ffmpeg.org/download.html
# ImageMagick: https://imagemagick.org/script/download.php

Verify Installation

bash
ffmpeg -version
ffprobe -version
magick -version
# or
convert -version

Quick Start Examples

Video Conversion

bash
# Convert format (copy streams, fast)
ffmpeg -i input.mkv -c copy output.mp4

# Re-encode with H.264
ffmpeg -i input.avi -c:v libx264 -crf 22 -c:a aac output.mp4

# Resize video to 720p
ffmpeg -i input.mp4 -vf scale=-1:720 -c:a copy output.mp4

Audio Extraction

bash
# Extract audio (no re-encoding)
ffmpeg -i video.mp4 -vn -c:a copy audio.m4a

# Convert to MP3
ffmpeg -i video.mp4 -vn -q:a 0 audio.mp3

Image Processing

bash
# Convert format
magick input.png output.jpg

# Resize maintaining aspect ratio
magick input.jpg -resize 800x600 output.jpg

# Create square thumbnail
magick input.jpg -resize 200x200^ -gravity center -extent 200x200 thumb.jpg

Batch Image Resize

bash
# Resize all JPEGs to 800px width
mogrify -resize 800x -quality 85 *.jpg

# Output to separate directory
mogrify -path ./output -resize 800x600 *.jpg

Video Thumbnail

bash
# Extract frame at 5 seconds
ffmpeg -ss 00:00:05 -i video.mp4 -vframes 1 -vf scale=320:-1 thumb.jpg

HLS Streaming

bash
# Generate HLS playlist
ffmpeg -i input.mp4 \
  -c:v libx264 -preset fast -crf 22 -g 48 \
  -c:a aac -b:a 128k \
  -f hls -hls_time 6 -hls_playlist_type vod \
  playlist.m3u8

Image Watermark

bash
# Add watermark to corner
magick input.jpg watermark.png -gravity southeast \
  -geometry +10+10 -composite output.jpg

Common Workflows

Optimize Video for Web

bash
# H.264 with good compression
ffmpeg -i input.mp4 \
  -c:v libx264 -preset slow -crf 23 \
  -c:a aac -b:a 128k \
  -movflags +faststart \
  output.mp4

Create Responsive Images

bash
# Generate multiple sizes
for size in 320 640 1024 1920; do
  magick input.jpg -resize ${size}x -quality 85 "output-${size}w.jpg"
done

Extract Video Segment

bash
# From 1:30 to 3:00 (re-encode for precision)
ffmpeg -i input.mp4 -ss 00:01:30 -to 00:03:00 \
  -c:v libx264 -c:a aac output.mp4

Batch Image Optimization

bash
# Convert PNG to optimized JPEG
mogrify -path ./optimized -format jpg -quality 85 -strip *.png

Video GIF Creation

bash
# High quality GIF with palette
ffmpeg -i input.mp4 -vf "fps=15,scale=640:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" output.gif

Image Blur Effect

bash
# Gaussian blur
magick input.jpg -gaussian-blur 0x8 output.jpg

Advanced Techniques

Multi-Pass Video Encoding

bash
# Pass 1 (analysis)
ffmpeg -y -i input.mkv -c:v libx264 -b:v 2600k -pass 1 -an -f null /dev/null

# Pass 2 (encoding)
ffmpeg -i input.mkv -c:v libx264 -b:v 2600k -pass 2 -c:a aac output.mp4

Hardware-Accelerated Encoding

bash
# NVIDIA NVENC
ffmpeg -hwaccel cuda -i input.mp4 -c:v h264_nvenc -preset fast -crf 22 output.mp4

# Intel QuickSync
ffmpeg -hwaccel qsv -c:v h264_qsv -i input.mp4 -c:v h264_qsv output.mp4

Complex Image Pipeline

bash
# Resize, crop, border, adjust
magick input.jpg \
  -resize 1000x1000^ \
  -gravity center \
  -crop 1000x1000+0+0 +repage \
  -bordercolor black -border 5x5 \
  -brightness-contrast 5x10 \
  -quality 90 \
  output.jpg

Video Filter Chains

bash
# Scale, denoise, watermark
ffmpeg -i video.mp4 -i logo.png \
  -filter_complex "[0:v]scale=1280:720,hqdn3d[v];[v][1:v]overlay=10:10" \
  -c:a copy output.mp4

Animated GIF from Images

bash
# Create with delay
magick -delay 100 -loop 0 frame*.png animated.gif

# Optimize size
magick animated.gif -fuzz 5% -layers Optimize optimized.gif

Media Analysis

Inspect Video Properties

bash
# Detailed JSON output
ffprobe -v quiet -print_format json -show_format -show_streams input.mp4

# Get resolution
ffprobe -v error -select_streams v:0 \
  -show_entries stream=width,height \
  -of csv=s=x:p=0 input.mp4

Image Information

bash
# Basic info
identify image.jpg

# Detailed format
identify -verbose image.jpg

# Custom format
identify -format "%f: %wx%h %b\n" image.jpg

Performance Tips

  1. Use CRF for quality control - Better than bitrate for video
  2. Copy streams when possible - Avoid re-encoding with -c copy
  3. Hardware acceleration - GPU encoding 5-10x faster
  4. Appropriate presets - Balance speed vs compression
  5. Batch with mogrify - In-place image processing
  6. Strip metadata - Reduce file size with -strip
  7. Progressive JPEG - Better web loading with -interlace Plane
  8. Limit memory - Prevent crashes on large batches
  9. Test on samples - Verify settings before batch
  10. Parallel processing - Use GNU Parallel for multiple files

Reference Documentation

Detailed guides in references/:

  • ffmpeg-encoding.md - Video/audio codecs, quality optimization, hardware acceleration
  • ffmpeg-streaming.md - HLS/DASH, live streaming, adaptive bitrate
  • ffmpeg-filters.md - Video/audio filters, complex filtergraphs
  • imagemagick-editing.md - Format conversion, effects, transformations
  • imagemagick-batch.md - Batch processing, mogrify, parallel operations
  • format-compatibility.md - Format support, codec recommendations

Common Parameters

FFmpeg Video

  • -c:v - Video codec (libx264, libx265, libvpx-vp9)
  • -crf - Quality (0-51, lower=better, 23=default)
  • -preset - Speed/compression (ultrafast to veryslow)
  • -b:v - Video bitrate (e.g., 2M, 2500k)
  • -vf - Video filters

FFmpeg Audio

  • -c:a - Audio codec (aac, mp3, opus)
  • -b:a - Audio bitrate (e.g., 128k, 192k)
  • -ar - Sample rate (44100, 48000)

ImageMagick Geometry

  • 800x600 - Fit within (maintains aspect)
  • 800x600! - Force exact size
  • 800x600^ - Fill (may crop)
  • 800x - Width only
  • x600 - Height only
  • 50% - Scale percentage

Troubleshooting

FFmpeg "Unknown encoder"

bash
# Check available encoders
ffmpeg -encoders | grep h264

# Install codec libraries
sudo apt-get install libx264-dev libx265-dev

ImageMagick "not authorized"

bash
# Edit policy file
sudo nano /etc/ImageMagick-7/policy.xml
# Change <policy domain="coder" rights="none" pattern="PDF" />
# to <policy domain="coder" rights="read|write" pattern="PDF" />

Memory errors

bash
# Limit memory usage
ffmpeg -threads 4 input.mp4 output.mp4
magick -limit memory 2GB -limit map 4GB input.jpg output.jpg

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