@thi.ng/dsp/osc-additive.js

Composable signal generators, oscillators, filters, FFT, spectrum, windowing & related DSP utils

import { identity } from "@thi.ng/api/fn";
import { gibbs } from "./anti-alias.js";
import { sin } from "./osc-sin.js";
const additive = (osc, freqFn, ampFn, n) => {
  const fcache = [];
  const acache = [];
  for (let i = 1; i <= n; i++) {
    fcache.push(freqFn(i));
    acache.push(ampFn(i));
  }
  return (phase, freq, amp = 1, dc = 0) => {
    let y = 0;
    for (let i = 0; i < n; i++) {
      y += osc(phase, freq * fcache[i], acache[i]);
    }
    return dc + amp * y;
  };
};
const squareAdditive = (n = 8, useGibbs = true) => additive(
  sin,
  (i) => 2 * (i - 1) + 1,
  (i) => 1 / (2 * (i - 1) + 1) * (useGibbs ? gibbs(n, i) : 1),
  n
);
const sawAdditive = (n = 8, useGibbs = true) => additive(sin, identity, (i) => 1 / i * (useGibbs ? gibbs(n, i) : 1), n);
export {
  additive,
  sawAdditive,
  squareAdditive
};