name: ffmpeg
description: Extract audio and transcode MP4 to WebM using ffmpeg.
ffmpeg
Use when
- Extract audio from a video file.
- Transcode an MP4 video to WebM.
Don't use when
- A higher-level video-editing skill or tool is already in use for complex edits.
- The task is purely file transfer or metadata inspection (no transcoding needed).
Outputs
- Output files should be written to
artifacts/ when possible (e.g., artifacts/output.webm).
Templates or Examples
- Use the command blocks below as templates, swapping inputs/outputs and codecs as needed.
Requirements
- Prefer safe defaults and explicit codecs.
- Keep commands minimal and reproducible.
- Use ASCII-only output unless file already uses Unicode.
Commands
Extract audio (MP4 → MP3)
ffmpeg -y -i input.mp4 -vn -c:a libmp3lame -q:a 2 output.mp3
Extract audio (MP4 → WAV, lossless)
ffmpeg -y -i input.mp4 -vn -c:a pcm_s16le -ar 44100 -ac 2 output.wav
Transcode MP4 → WebM (VP9 + Opus)
ffmpeg -y -i input.mp4 -c:v libvpx-vp9 -crf 32 -b:v 0 -row-mt 1 -c:a libopus -b:a 128k output.webm
Transcode MP4 → WebM (VP8 + Vorbis)
ffmpeg -y -i input.mp4 -c:v libvpx -crf 10 -b:v 1M -c:a libvorbis -b:a 128k output.webm
Notes
-y overwrites output files. Remove if you want interactive prompts.- Lower
-crf means higher quality (and larger files).
- If audio-only extraction is desired, use
-vn to drop video.
By