heygen-com--hyperframes/skills/media-use/audio/references/sfx.md

Sound effects (SFX)

Named sound effects, produced by the shared audio engine (scripts/audio.mjs → scripts/lib/sfx.mjs). Provider-gated by the engine's one switch — whether a HeyGen credential is present, decided once (not per cue):

• HeyGen credential present → retrieve every cue from HeyGen's audio library (/v3/audio/sounds, type=sound_effects, min_score=0.4). Search-and-download, not generation. The bundled library is NOT consulted.
• No credential → the bundled 21-file library (assets/sfx/ + manifest.json): match each cue name, copy the matched file into the project. Offline, deterministic, free.

There is no npx hyperframes sfx command. SFX is never generated — it is retrieved (online) or taken from the bundled library (offline).

Cues — request → meta

Each line names the effects it wants: lines[].sfx: ["whoosh", "ui click"]. The engine flattens these into cues, resolves them per the switch, dedupes identical (id, name) pairs (the same effect named twice downloads/copies once), and writes audio_meta.sfx[]:

{
  "id": "3",                       // joins the cue to the caller's model (frame / scene / segment)
  "name": "whoosh",
  "file": "assets/sfx/whoosh.mp3", // downloaded or copied, relative to project root
  "source": "heygen" | "local",    // which route resolved it
  "offset_s": 0,                   // delay from the line's start
  "duration_s": 0.57,
  "volume": 0.35                   // SFX sit UNDER voice + BGM
}

A cue that matches nothing is skipped (recorded as an anomaly); SFX never blocks a render.

HeyGen retrieval (credentialed)

searchSounds(name, "sound_effects", { limit: 3, minScore: 0.4 }) → top hit → assets/sfx/<slug>.mp3. Results are ranked by score (each carries a presigned audio_url, duration, description). The floor is 0.4 because good SFX hits score ~0.5–0.67 — below the API's default 0.7, which would silently drop most named cues (only whoosh/swoosh-family clears 0.7). duration_s comes from the result (else 1.0). Name effects concretely (glass shatter, not dramatic sound); a vague query returns a poor match.

Bundled library (no credential)

21 curated files in assets/sfx/, indexed by manifest.json — { file, duration, description } per key (e.g. whoosh, pop, click, chime, riser, impact-bass-1, glitch-1, typing, …). A cue name resolves by manifest key, file basename, or slug, so whoosh, whoosh.mp3, or "ui click" (→ slug) all match. Matched files are copied into the project's assets/sfx/; duration_s comes from the manifest, so timing is known offline — e.g. riser is 10.03s, so trigger it at climax − 10.03s. The manifest's description field carries placement hints per effect; read assets/sfx/manifest.json for the full set and usage.

Rules

• Volume ~0.35. SFX must sit under narration and BGM, not fight them.
• No match → skip, don't fail. A missing effect logs an anomaly and moves on; never a render blocker.
• Retrieval (credentialed) or bundled library (offline) — never generation. You search HeyGen by text, or match a name against the 21-file manifest.
• One asset per distinct name. Reuse across lines is deduped to a single download/copy, many cues.
• The switch is global, not per cue. With a credential, retrieval handles even the long tail (effects not in the 21); without one, only the 21 bundled names resolve.