dsp-collection/signal/Goertzel.js

A collection of JavaScript modules for digital signal processing (written in TypeScript)

import Complex from "../math/Complex.js";
import MutableComplex from "../math/MutableComplex.js";
import ComplexArray from "../math/ComplexArray.js";
export function goertzelSingle(x, relativeFrequency) {
    const n = x.length;
    if (n == 0) {
        throw new Error("Input array must not be empty.");
    }
    const w = 2 * Math.PI / n * relativeFrequency;
    const c = Complex.expj(w);
    const cr2 = c.re * 2;
    let s1 = 0;
    let s2 = 0;
    for (let p = 0; p < n; p++) {
        const s0 = x[p] + cr2 * s1 - s2;
        s2 = s1;
        s1 = s0;
    }
    return new MutableComplex(c.re * s1 - s2, c.im * s1);
}
export function goertzel(x) {
    const n = x.length;
    const a = new ComplexArray(n);
    for (let frequency = 0; frequency < n; frequency++) {
        const c = goertzelSingle(x, frequency);
        a.set(frequency, c);
    }
    return a;
}
export function goertzelSpectrum(x, inclNyquist = false) {
    const n = x.length;
    if (n == 0) {
        throw new Error("Input array must not be empty.");
    }
    const m = (n % 2 == 0 && inclNyquist) ? n / 2 + 1 : Math.ceil(n / 2);
    const a = new ComplexArray(m);
    for (let frequency = 0; frequency < m; frequency++) {
        const c = goertzelSingle(x, frequency);
        if (frequency == 0 || frequency == n / 2) {
            c.divByReal(n);
        }
        else {
            c.mulByReal(2 / n);
        }
        a.set(frequency, c);
    }
    return a;
}
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