synthesize-sfx-ffmpeg

Purpose

Generate atomic SFX (bell dings, bag thuds, punch impacts, whooshes, risers, sub-bass drops, breath, droplet pings) from scratch using ffmpeg sine waves + exponential decay envelopes + optional reverb. The synthesized output is indistinguishable from a stock library in a finished mix at -14 LUFS and ships in zero API calls.

Use this atom when:

• FAL's fal-ai/elevenlabs/sound-effects endpoint is broken upstream (returns invalid_model_id: eleven_text_to_sound_v0 — see LEARNINGS.md #24).
• The brief is for fight-card / sports / action SFX where stock libraries sound generic.
• The composition needs precise SFX timing (synthesized output lets you target exact decay times, harmonic stacks, attack curves).
• Cost matters — synthesis is $0.

Pairs with:

• add-sound-effects (the higher-level "place SFX hits at marked timestamps" atom — composes this atom's outputs).
• create-music-elevenlabs (the music bed that SFX layer over).

Inputs