dsp-collection/filter/FirFilterWin.js

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

import * as WindowFunctions from "../signal/WindowFunctions.js";
import { goertzelSingle } from "../signal/Goertzel.js";
import * as ArrayUtils from "../utils/ArrayUtils.js";
export function createWindowKernel(f, width, symetric = true) {
    const nudge = symetric ? 1 : 0;
    const a1 = Float64Array.from({ length: width }, (_x, i) => f(i / (width - nudge)));
    const sum = ArrayUtils.sum(a1);
    const a2 = a1.map(x => x / sum);
    return a2;
}
export function createLpFilterKernel(windowFunctionId, normFirstMinFreq) {
    const descr = WindowFunctions.getFunctionDescrById(windowFunctionId);
    const width = Math.round(descr.firstMinPos / normFirstMinFreq);
    if (width < 3) {
        throw new Error("Filter parameters out of range.");
    }
    return createWindowKernel(descr.f, width);
}
export function calcFreqRespAt(kernel, normFreq) {
    const relFreq = normFreq * kernel.length;
    return goertzelSingle(kernel, relFreq);
}
function reflectIndex(i, n) {
    if (i >= 0 && i < n) {
        return i;
    }
    if (n <= 1) {
        return 0;
    }
    const period = 2 * (n - 1);
    const t = (i % period + period) % period;
    return (t < n) ? t : period - t;
}
export function applyFirKernelAt(signal, pos, kernel) {
    if (pos < 0 || pos >= signal.length) {
        return NaN;
    }
    const width = kernel.length;
    const m = Math.floor(kernel.length / 2);
    const p0 = pos - m;
    let acc = 0;
    for (let i = 0; i < width; i++) {
        const p = reflectIndex(p0 + i, signal.length);
        acc += signal[p] * kernel[i];
    }
    return acc;
}
export function applyFirKernel(signal, kernel) {
    const out = new Float64Array(signal.length);
    for (let i = 0; i < signal.length; i++) {
        out[i] = applyFirKernelAt(signal, i, kernel);
    }
    return out;
}
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