ffmpeg-master – OpenClaw Skill

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name: ffmpeg-master version: 1.0.0 description: Use when performing video/audio processing tasks including transcoding, filtering, streaming, metadata manipulation, or complex filtergraph operations with FFmpeg. triggers:

• ffmpeg
• ffprobe
• video processing
• audio conversion
• codec
• transcoding
• filter_complex
• h264
• h265
• mp4
• mkv
• hardware acceleration role: specialist scope: implementation output-format: shell-command

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FFmpeg Master

Comprehensive guide for professional video and audio manipulation using FFmpeg and FFprobe.

Core Concepts

FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play almost anything that humans and machines have created. It is a command-line tool that processes streams through a complex pipeline of demuxers, decoders, filters, encoders, and muxers.

Common Operations

# Basic Transcoding (MP4 to MKV)
ffmpeg -i input.mp4 output.mkv

# Change Video Codec (to H.265/HEVC)
ffmpeg -i input.mp4 -c:v libx265 -crf 28 -c:a copy output.mp4

# Extract Audio (No Video)
ffmpeg -i input.mp4 -vn -c:a libmp3lame -q:a 2 output.mp3

# Resize/Scale Video
ffmpeg -i input.mp4 -vf "scale=1280:720" output.mp4

# Cut Video (Start at 10s, Duration 30s)
ffmpeg -i input.mp4 -ss 00:00:10 -t 00:00:30 -c copy output.mp4

# Fast Precise Cut (Re-encoding only the cut points is complex, so standard re-encoding is safer for precision)
ffmpeg -ss 00:00:10 -i input.mp4 -to 00:00:40 -c:v libx264 -crf 23 -c:a aac output.mp4

# Concatenate Files (using demuxer)
# Create filelist.txt: file 'part1.mp4' \n file 'part2.mp4'
ffmpeg -f concat -safe 0 -i filelist.txt -c copy output.mp4

# Speed Up/Slow Down Video (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

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Processing Categories & When to Use

Codecs & Quality

Option	Use When
-c:v libx264	Standard H.264 encoding (best compatibility)
-c:v libx265	H.265/HEVC encoding (best compression/quality)
-crf [0-51]	Constant Rate Factor (lower is higher quality, 18-28 recommended)
-preset	Encoding speed vs compression (ultrafast, medium, veryslow)
-c:a copy	Pass-through audio without re-encoding (saves time/quality)

Filters & Manipulation

Filter	Use When
scale	Changing resolution (e.g., scale=1920:-1 for 1080p width)
crop	Removing edges (e.g., crop=w:h:x:y)
transpose	Rotating video (1=90deg CW, 2=90deg CCW)
fps	Changing frame rate (e.g., fps=30)
drawtext	Adding text overlays/watermarks
overlay	Picture-in-picture or adding image watermarks
fade	Adding fade-in/out effects (e.g., fade=in:0:30 for first 30 frames)
volume	Adjusting audio levels (e.g., volume=1.5 for 150% volume)
setpts	Changing video speed (e.g., setpts=0.5*PTS for double speed)
atempo	Changing audio speed without pitch shift (0.5 to 2.0)

Inspection & Metadata

Tool/Option	Use When
ffprobe -v error -show_format -show_streams	Getting detailed technical info of a file
-metadata title="Name"	Setting global metadata tags
-map	Selecting specific streams (e.g., -map 0:v:0 -map 0:a:1)

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Advanced: Complex Filtergraphs

Use filter_complex when you need to process multiple inputs or create non-linear filter chains.

# Example: Adding a watermark at the bottom right
ffmpeg -i input.mp4 -i watermark.png -filter_complex "overlay=main_w-overlay_w-10:main_h-overlay_h-10" output.mp4

# Example: Vertical Stack (2 videos)
ffmpeg -i top.mp4 -i bottom.mp4 -filter_complex "vstack=inputs=2" output.mp4

# Example: Side-by-Side (2 videos)
ffmpeg -i left.mp4 -i right.mp4 -filter_complex "hstack=inputs=2" output.mp4

# Example: Grid (4 videos 2x2)
ffmpeg -i v1.mp4 -i v2.mp4 -i v3.mp4 -i v4.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[top];[2:v][3:v]hstack=inputs=2[bottom];[top][bottom]vstack=inputs=2" output.mp4

# Example: Fade Transition (Simple crossfade between two clips)
# Requires manual offset calculation, using xfade is better
ffmpeg -i input1.mp4 -i input2.mp4 -filter_complex "xfade=transition=fade:duration=1:offset=9" output.mp4

Hardware Acceleration

Platform	Codec	Command
NVIDIA (NVENC)	H.264	-c:v h264_nvenc
Intel (QSV)	H.264	-c:v h264_qsv
Apple (VideoToolbox)	H.265	-c:v hevc_videotoolbox

Constraints & Error Handling

• Stream Mapping: Always use -map for complex files to ensure you get the right audio/subtitle tracks.
• Seeking: Put -ss before -i for fast seeking (input seeking), or after -i for accurate seeking (output seeking).
• Format Support: Ensure the output container (extension) supports the codecs you've chosen.