| name | sfx-beats |
| description | Mix synthesized SFX into a short. Two modes — comedy (CANONICAL, runs after burn-subtitles in the pipeline): Claude marks punchline/irony beats and a vine boom / record scratch lands on each; tension (on request only): riser ending at the first pivot word, low hit at the loudest RMS peak after it, soft outro stinger. All SFX synthesized with stdlib `wave` — no external assets. Comedy mode marks ZERO beats on non-comedic clips and passes through untouched. |
sfx-beats
Sound design is emotional manipulation, not decoration. Two modes:
comedy (canonical — in the per-span chain after burn-subtitles)
Claude reads the clip transcript and marks 0-4 beats where a meme SFX
amplifies the moment:
- boom (vine boom, ~0.8s saturated 90→40Hz sub drop, LOUD on purpose) —
a punchline, absurd claim, or savage line landing.
- scratch (record scratch, ~0.32s back-and-forth filtered noise) — a
wait-WHAT irony pivot.
The "ding" insight/aha-moment bell is RETIRED — comedy mode marks only
punchline (boom) and irony (scratch) beats.
The prompt is explicitly conservative: a boom on a mediocre beat reads as
cringe, so ZERO beats is a valid answer → passthrough copy. Beats are
validated (known types, ≥2.5s apart, inside [1.0, dur-0.5], max 4). Any
Claude/parse failure degrades to passthrough — never fatal. SFX_COMEDY=0
skips the step in the orchestrators.
tension (on request only — NOT in the canonical chain)
- Riser (0.8s noise sweep) — ends exactly on the first pivot word
(
but/therefore/so/...) inside the middle 60% of the clip.
- Hit (50–80Hz transient) — at the highest RMS peak after the riser.
- Stinger (440/660Hz bell) — in the last 0.4s.
Tension SFX sit at -18dBFS under speech; comedy booms run hotter (-7dB peak)
because the boom IS the joke. An alimiter keeps the mix ≤0.97.
Invoke
.claude/skills/sfx-beats/sfx-beats.sh <input> <transcript.json> <out> [mode=tension|comedy] [audio_rms.json] [--pane <tmux>]
mode: tension (default) or comedyaudio_rms.json (tension only): per-second RMS; computed on the fly if omitted--pane: route the comedy Claude call through a long-lived tmux pane
Output
mp4 with video stream-copied and audio AAC 192k after amix with the SFX bed
(or a passthrough copy when nothing is marked). Idempotent via <out>.sfxmeta
(input + transcript mtimes + mode).
How
- comedy:
comedy_prompt.py → run_claude_step → parse_comedy.py →
make_sfx.py renders the marked events into a full-length stereo WAV.
- tension:
plan_sfx.py picks pivot/peak deterministically → same renderer.
