Audio

Audio processing with ffmpeg. Use this skill when you need to change audio — not just read metadata (use inspect for that).

When to use

This skill — extract audio from video, convert formats, trim/concat timeline edits, loudness normalize, fade, resample, find silence.
inspect — read-only metadata before editing (duration, codecs, sample rate). Always probe first when unsure about input format.
video-transformation — mux normalized or extracted audio back onto video (replace_audio.py and similar ops).
Raw ffmpeg — fine for one-off filter chains, but these scripts return consistent JSON and auto-generate output paths.

Trim with -c copy — trim.py stream-copies for speed. Works for WAV and many containers; can fail or produce glitches on MP3/AAC with frame boundaries. Re-encode with ffmpeg manually if copy fails.
Concat requires matching codecs — concat.py uses the concat demuxer with -c copy. All inputs must share codec, sample rate, and channel layout. Convert/resample first if needed.
Normalize outputs WAV — loudnorm writes PCM WAV. Mux back to video with video-transformation replace_audio.py, or convert with convert.py.
Fade is fixed 1 s in — fade.py applies afade=t=in:st=0:d=1 only. Custom fade curves need raw ffmpeg.
Silence threshold is fixed — silence_detect.py uses noise=-30dB:d=0.5. Pure tones (e.g. test fixtures) may report no silence; real speech/podcast material works best.
Extract vs video extract — extract.py strips video (-vn) to WAV. For video-specific workflows, check video-transformation extract_audio.py too.