@audio/synth-osc

Oscillator — band-limited sine/square/saw/triangle, detune, custom wave fn

npm install @audio/synth-osc

import osc from '@audio/synth-osc'

Classic waveform oscillator with cents detune and phase offset, in periodic-function's phase conventions (saw falling, square high on the first half, triangle falling from its peak). Pitched — (freq, opts), the family generator contract.

Square, saw and triangle are band-limited: at each jump in value (saw, square) or slope (triangle) within ±32 samples, the waveform takes the residual of a band-limited step (BLEP; Brandt 2001, Välimäki & Huovilainen 2007) or its integral (BLAMP; Esqueda et al. 2016), a 64-tap Kaiser-windowed sinc (β 10, cutoff 0.47·fs), linear phase, no latency. Measured from 55 Hz to 10 kHz at 44.1 and 48 kHz (2¹⁸-point Blackman-Harris spectra):

| | naive (1.0.x) | band-limited | |---|---|---| | strongest alias below 16 kHz, dB re fundamental (saw) | −54 (55 Hz) to −10 (10 kHz) | under −94 (the analysis floor) | | strongest alias anywhere | −52 to −9 | under −75 | | all aliased power re harmonics | −29 to −5 | −76 to −109 | | harmonics vs the ideal, to 16 kHz | exact, plus aliases | within 0.01 dB; −0.8 dB at 0.45·fs |

wave(type, t, dt) gives one sample of it at phase t advancing dt = f/fs per sample, for oscillators of your own (synth-sfx sweeps its pitch through it).

osc(440, { type: 'sawtooth', detune: -5 })   // → Float32Array

| Param | Default | | |---|---|---| | freq | — | Hz (positional) | | duration | 1 | Seconds | | type | 'sine' | 'sine' | 'square' | 'sawtooth' | 'triangle' | | amp | 0.8 | Peak amplitude | | detune | 0 | Cents | | phase | 0 | Starting phase, 0..1 | | wave | — | Custom waveform fn t => v, overrides type | | fs | 44100 | Sample rate |

Use when: the base oscillator under synth-voice and synth-poly, or any test tone with a classic waveform.

Part of @audio/synth — the synth family umbrella.

MIT © audiojs