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skills/ck-media-processing/SKILL.md

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+---
+name: ck-media-processing
+description: >
+  Processes audio, video, and images using FFmpeg and ImageMagick pipelines.
+  Activate when user says 'convert video', 'compress image', 'extract audio',
+  'resize images in bulk', 'transcode media', or 'process video file'.
+  Accepts file paths, format targets, quality settings, and filter specifications.
+---
+
+## Overview
+Builds and executes FFmpeg and ImageMagick commands for media conversion, compression, resizing, format conversion, and pipeline processing of audio, video, and image files.
+
+## When to Use
+- Converting between video/audio formats (MP4, WebM, MOV, MP3, AAC, etc.)
+- Compressing or optimizing media files for web delivery
+- Bulk resizing, cropping, or converting images
+- Extracting audio tracks or video frames
+- Applying filters, watermarks, or overlays to media
+- Generating thumbnails or animated GIFs from video
+
+## Don't Use When
+- AI-based image generation is needed (use ck-ai-artist)
+- Video needs programmatic composition with React components (use ck-remotion)
+- Media editing requires a GUI (recommend appropriate desktop software)
+- File is DRM-protected content
+
+## Steps / Instructions
+
+### 1. Identify Task and Tools
+
+| Task | Tool |
+|------|------|
+| Video conversion/compression | FFmpeg |
+| Audio extraction/conversion | FFmpeg |
+| Image resize/crop/convert | ImageMagick (`convert`) or FFmpeg |
+| Bulk image processing | ImageMagick + shell loop |
+| Thumbnails from video | FFmpeg |
+| GIF from video clip | FFmpeg |
+
+### 2. FFmpeg — Common Operations
+
+**Convert video format:**
+```bash
+ffmpeg -i input.mov -c:v libx264 -crf 23 -c:a aac output.mp4
+```
+
+**Compress video (reduce file size):**
+```bash
+# CRF 18-28: lower = better quality, larger file
+ffmpeg -i input.mp4 -c:v libx264 -crf 28 -preset slow -c:a aac -b:a 128k output-compressed.mp4
+```
+
+**Extract audio:**
+```bash
+ffmpeg -i video.mp4 -vn -c:a libmp3lame -q:a 2 audio.mp3
+```
+
+**Trim video clip:**
+```bash
+ffmpeg -i input.mp4 -ss 00:01:30 -to 00:02:45 -c copy clip.mp4
+```
+
+**Extract frames as images:**
+```bash
+# 1 frame per second
+ffmpeg -i video.mp4 -vf fps=1 frames/frame_%04d.png
+
+# Specific frame at timestamp
+ffmpeg -i video.mp4 -ss 00:00:05 -vframes 1 thumbnail.png
+```
+
+**Create GIF from video:**
+```bash
+ffmpeg -i input.mp4 -ss 0 -t 5 -vf "fps=10,scale=480:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" output.gif
+```
+
+**WebM for web (VP9):**
+```bash
+ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus output.webm
+```
+
+### 3. ImageMagick — Common Operations
+
+**Resize image:**
+```bash
+convert input.jpg -resize 800x600 output.jpg
+# Preserve aspect ratio (fit within box):
+convert input.jpg -resize 800x600\> output.jpg
+```
+
+**Convert format:**
+```bash
+convert input.png output.webp
+convert input.bmp output.jpg
+```
+
+**Compress JPEG:**
+```bash
+convert input.jpg -quality 80 output.jpg
+```
+
+**Bulk resize (all PNGs in directory):**
+```bash
+for f in *.png; do
+  convert "$f" -resize 1920x1080\> "resized_$f"
+done
+```
+
+**Add watermark:**
+```bash
+convert input.jpg -gravity SouthEast \
+  \( watermark.png -resize 200x200 \) \
+  -composite output.jpg
+```
+
+**Crop to specific region:**
+```bash
+# WxH+X+Y
+convert input.jpg -crop 400x300+100+50 cropped.jpg
+```
+
+### 4. Check Output Quality
+
+After processing:
+```bash
+# Inspect video metadata
+ffprobe -v quiet -print_format json -show_streams output.mp4
+
+# Check image info
+identify -verbose output.jpg | grep -E "Geometry|Format|Quality|Filesize"
+```
+
+### 5. Batch Processing Script
+
+```bash
+#!/bin/bash
+INPUT_DIR="./raw"
+OUTPUT_DIR="./processed"
+mkdir -p "$OUTPUT_DIR"
+
+for f in "$INPUT_DIR"/*.mp4; do
+  name=$(basename "$f" .mp4)
+  ffmpeg -i "$f" -c:v libx264 -crf 26 -c:a aac \
+    "$OUTPUT_DIR/${name}-compressed.mp4"
+done
+```
+
+## Notes
+- Always test on a single file before batch processing
+- Keep originals — never overwrite input files in place
+- FFmpeg `-c copy` is lossless stream copy (fastest, no re-encode)
+- Use `-y` flag to overwrite output without prompting in scripts
+- Check available encoders: `ffmpeg -encoders | grep -E "video|audio"`