@doot-games/dsp

Pure signal-processing primitives. No audio context, no DOM. Every function takes plain typed arrays, so the whole package is testable in isolation and reusable outside this project.

API

• fft(re, im) in-place iterative radix-2 FFT. re and im are Float32Array of length N (a power of two).
• nextPow2(n) smallest power of two at least n.
• hannWindow(N) returns a periodic Hann window as a Float32Array.
• magnitudes(re, im, out?) magnitude spectrum of the lower half of a transformed frame.
• bandedFlux(mag, prev, loEnd, midEnd) half-wave-rectified spectral flux split into low, mid, and high bands by bin index. Returns { flux, lo, mid, hi }.
• autocorr(signal, minLag, maxLag) autocorrelation over an inclusive lag range, returned as a Float64Array indexed by lag.
• parabolicShift(ym1, y0, yp1) sub-sample peak refinement in [-1, 1].

Example

import { fft, hannWindow, magnitudes } from '@doot-games/dsp';

const N = 1024;
const win = hannWindow(N);
const re = new Float32Array(N), im = new Float32Array(N);
for (let i = 0; i < N; i++) re[i] = sample(i) * win[i];
fft(re, im);
const mag = magnitudes(re, im);