openverse-sfx: Free Licensed Sound Design for Video, Verified by Measurement

You cannot hear. Every decision in this skill is made by measurement (librosa, ffmpeg ebur128, waveform plots) and verified on the exported file - never by feel, and never tell the user it sounds good. Hand them a short list of timestamps to check with headphones instead.

All audio comes from Openverse (https://api.openverse.org): 5.2M free audio files, no API key, $0. Never synthesize music or sound effects in code - no sine-wave beeps, no noise bursts. Use real licensed recordings only.

Critical Rules

1. License filter is mandatory. Only use Openverse results with license=cc0,by,pdm and source=freesound,jamendo. scripts/sfx_search.py enforces this - do not bypass it.
2. One search per kind of sound. Anonymous Openverse use is limited to ~200 searches/day. Search once per sound kind ("whoosh", "ui pop", "upbeat loop") and pick from the shortlist. Do not re-search with rephrased queries.
3. credits.txt is not optional. CC BY audio is only legal to use with credit. Every downloaded file's attribution field goes into credits.txt verbatim. scripts/sfx_fetch.py does this automatically. CC0/PDM need nothing, but log them anyway.
4. Prerequisites first. If missing, install before starting: ffmpeg, and pip install librosa matplotlib numpy scipy.
5. Measure the exported MP4, never the pre-export WAV. AAC compression and mono phone playback change the result; only the shipped file counts.

Workflow