Voice presets for the formant TTS (sound.speech) — named bundles of the synthesis knobs. A caller can pass a preset name, a preset name plus knob overrides, or a bare knob table (see sound.speech).
| knob | description |
|---|---|
f0 | base pitch, Hz |
f0_range | intonation depth: 0 = dead monotone, 1 = natural, >1 theatrical |
speed | speech rate multiplier (1 = normal) |
formant | formant frequency scale = vocal-tract length (≈1.15 reads female, <1 bigger/deeper, >1.2 small creature) |
breath | 0..1, trades voicing for aspiration (1 = full whisper) |
flutter | slow random f0 wobble (0 = dead steady, robotic) |
growl | 0..1, alternate-pitch-period modulation (vocal fry / creak) — the gravelly roughness; 0.2–0.5 is the useful range |
quantize | hold synthesis parameters in blocks of N 5 ms frames — the stepped, quantized "machine voice" effect (0/1 = off) |
gain | output gain |
These presets are deliberately generic (an application maps its characters onto knobs); tuning them is a listening exercise — see tests/sound/manual/speak.lua.