Agent-Skills.md

Agent Skills: FFmpeg CLI Reference

FFmpeg CLI reference for video and audio processing, format conversion, filtering, and media automation. Use when converting video formats, resizing or cropping video, trimming by time, replacing or extracting audio, mixing audio tracks, overlaying text or images, burning subtitles, creating GIFs, generating thumbnails, building slideshows, changing playback speed, encoding with H264/H265/VP9, setting CRF/bitrate, using GPU acceleration, creating storyboards, or running ffprobe. Covers filter_complex, stream selectors, -map, -c copy, seeking, scale, pad, crop, concat, drawtext, zoompan, xfade.

UncategorizedID: henkisdabro/wookstar-claude-code-plugins/ffmpeg-cli
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Install this agent skill to your local

pnpm dlx add-skill https://github.com/henkisdabro/wookstar-claude-plugins/tree/HEAD/plugins/ffmpeg/skills/ffmpeg-cli

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plugins/ffmpeg/skills/ffmpeg-cli/SKILL.md

Skill Metadata

Name
ffmpeg-cli
Description
FFmpeg CLI reference for video and audio processing, format conversion, filtering, and media automation. Use when converting video formats, resizing or cropping video, trimming by time, replacing or extracting audio, mixing audio tracks, overlaying text or images, burning subtitles, creating GIFs, generating thumbnails, building slideshows, changing playback speed, encoding with H264/H265/VP9, setting CRF/bitrate, using GPU acceleration, creating storyboards, or running ffprobe. Covers filter_complex, stream selectors, -map, -c copy, seeking, scale, pad, crop, concat, drawtext, zoompan, xfade.

FFmpeg CLI Reference

Contents

Dependencies

Verify ffmpeg is installed:

ffmpeg -version

Install if missing:

# macOS
brew install ffmpeg

# Ubuntu/Debian
sudo apt install ffmpeg

# Windows (scoop)
scoop install ffmpeg

Glossary of flags and filters

Filtering reference

| Flag/Filter | Purpose | |---|---| | -vf (also -filter:v) | Video filter | | -af (also -filter:a) | Audio filter | | -filter_complex | Complex filter graph for multi-stream filtering | | [0] | All streams from first input (0-based) | | [0:v] | Video stream from first input | | [1:a] | Audio stream from second input | | 0:v:0 | First input, first video stream | | 0:a:1 | First input, second audio stream | | [name] | Named stream, used with -filter_complex | | -map [name] | Select stream for output | | -y | Auto-overwrite output files without confirmation |

Expression evaluations: if, lte, gte and more.

Converting formats

Remux MP4 to MKV (no re-encoding):

ffmpeg -i input.mp4 -c copy output.mkv

MKV and MP4 are both containers for H264/H265 video and AAC/MP3 audio. Video quality is determined by the codec, not the container. MKV supports multiple video streams; MP4 has wider device support.

Remux MP4 to MOV:

ffmpeg -i input.mp4 -c copy output.mov

Encode MP4 to AVI (re-encodes):

ffmpeg -i input.mp4 output.avi

Resizing and padding

Upscale to 1080x1920, preserve aspect ratio, black padding:

ffmpeg -i input.mp4 -vf "scale=w=1080:h=1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:color=black,setsar=1:1" output.mp4

scale options:

  • force_original_aspect_ratio=decrease - auto-decrease output dimensions to fit aspect ratio
  • force_original_aspect_ratio=increase - auto-increase dimensions
  • scale=w=1080:h=-1 - let ffmpeg pick correct height for aspect ratio
  • scale=w=1080:h=-2 - force dimensions divisible by 2

scale reference

pad options:

  • pad=width:height:x:y:color - x:y is top-left corner position
  • (ow-iw)/2:(oh-ih)/2 centres the video; negative values also centre
  • pad reference

setsar=1:1 ensures 1:1 pixel aspect ratio. Prevents ffmpeg from compensating for ratio changes. setsar reference

Two scaled outputs from one input (horizontal + vertical with logo overlay):

ffmpeg -i input.mp4 -i logo.png \
  -filter_complex "[0:v]split=2[s0][s1]; \
    [s0]scale=w=1920:h=1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=black,setsar=1:1[out1]; \
    [s1]scale=w=720:h=1280:force_original_aspect_ratio=decrease,pad=720:1280:(ow-iw)/2:(oh-ih)/2:color=black,setsar=1:1[s2]; \
    [s2][1]overlay=(main_w-overlay_w)/2:(main_w-overlay_w)/5[out2]" \
  -map [out1] -map 0:a output_youtube.mp4 \
  -map [out2] -map 0:a output_shorts.mp4

Trim by time

ffmpeg -i input.mp4 -ss 00:00:10 -to 00:00:25 output.mp4

For faster but less accurate trimming, see the Input/output seeking section in references/encoding-and-settings.md. For the -c copy trade-offs when trimming, see references/core-concepts.md.

Verification and inspection

List supported formats:

ffmpeg -formats

List supported codecs:

ffmpeg -codecs

ffprobe

ffprobe provides structured metadata about media files.

Show detailed stream information:

ffprobe -show_streams -i input.mp4

Verify moov atom position (faststart):

ffprobe -v trace -i input.mp4

Look for type:'moov' near the beginning of output to confirm faststart is applied.

Reference files

Load these on demand with the Read tool when the task requires deeper coverage.

| File | Topics | |---|---| | references/core-concepts.md | -c copy (remux vs transcode), input/output seeking, encoding quick ref (H264/H265/VP9 CRF ranges), GPU acceleration overview, format=yuv420p, -movflags +faststart | | references/audio-processing.md | Replace audio, extract audio, mix audio, combine MP3 tracks, crossfade, change audio format, merge and normalise | | references/advanced-editing.md | Playback speed, FPS change, jump cuts, video cropping for social, drawtext overlay, subtitles (burn/embed/extract), combine media (overlay, logo, background, concat intro/main/outro, vstack) | | references/asset-generation.md | Image to video, slideshow with fade, Ken Burns (zoompan), GIFs, video compilation with fades, thumbnails (single/multiple/scene), image thumbnails, storyboards (scene tile/keyframe/Nth frame) | | references/encoding-and-settings.md | Optimised daily command, H264 (libx264) deep-dive, H265 (libx265) Apple compat, VP9 (libvpx-vp9) constant quality, 1-pass vs 2-pass, -c copy detailed, seeking detailed, GPU detailed (Nvidia/Intel/AMD) |