ffmpeg-audio

One ffmpeg shape recurs across the voiceprint, diarization, whisper, and training lanes: mono · 16 kHz · signed-16-bit PCM WAV — ffmpeg -ac 1 -ar 16000 -c:a pcm_s16le. This skill is that convention as a single idempotent CLI, so the same bytes come out every time regardless of who runs it or what container went in.

Defaults are the convention (SR=16000, CH=1, CODEC=pcm_s16le). Change them in one place at the top of ffmpeg_audio.py if a lane ever needs a different target.

Safety model

• Dry-run by default. Every op prints the exact ffmpeg command it would run and changes nothing until --apply.
• Idempotent. An output that already exists and is newer than its input(s) is skipped — re-running a batch is a no-op. --force rebuilds anyway.
• Read-only probe never writes.

The four ops

1. normalize — any audio → mono 16k PCM WAV (the canonical convention).

   python3 ~/.claude/skills/ffmpeg-audio/ffmpeg_audio.py normalize output.m4a -o alice.wav --apply

   Batch a roster with globs + --suffix (no -o):

   python3 .../ffmpeg_audio.py normalize alice.* bob.* carol.* --suffix .16k.wav --apply

2. trim — slice --start/--duration then normalize (the enroll-clip pattern: superwhisper/recordings/<ts>/output.wav → ~/enroll/alice.wav, 22s).

   python3 .../ffmpeg_audio.py trim output.wav --start 0 --duration 22 -o ~/enroll/alice.wav --apply

3. concat — join N inputs into one normalized WAV (filter_complex concat).

   python3 .../ffmpeg_audio.py concat a.wav b.wav c.wav -o joined.wav --apply

4. probe — ffprobe readout (codec · channels · rate · duration). Read-only.

   python3 .../ffmpeg_audio.py probe alice.wav

Reconcile a YAML catalog

For a fixed set of jobs (e.g. the enroll roster), declare them once and reconcile — idempotent, so it's safe to re-run after adding one person.

python3 .../ffmpeg_audio.py reconcile jobs.yaml            # dry-run
python3 .../ffmpeg_audio.py reconcile jobs.yaml --apply    # execute

See examples/enroll_roster.yaml for the shape:

jobs:
  - op: trim
    input: ~/superwhisper/recordings/2026-06-05/output.wav
    start: 0
    duration: 22
    output: ~/enroll/alice.wav
  - op: normalize
    input: ~/recordings/bob.m4a
    output: ~/enroll/bob.wav
  - op: concat
    inputs: [~/clips/a.wav, ~/clips/b.wav]
    output: ~/enroll/merged.wav

Flags

• --apply — actually run ffmpeg (default: dry-run preview)
• --force — rebuild even if the output is up-to-date
• --json — machine-readable result array (for chaining)
• --suffix — output name when -o is omitted (normalize/trim batch mode)

Notes

• macOS: brew install ffmpeg · Ubuntu: apt-get install -y ffmpeg. The script hard-fails on a missing ffmpeg/ffprobe rather than running half a batch.
• Stdlib only for the four ops; reconcile needs PyYAML.
• Output dirs are created as needed. Inputs are glob-expanded (order-preserving, de-duped); a missing input surfaces as a per-job error, never silent.

License

Apache 2.0