@qgustavor/stream-audio-fingerprint
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Audio landmark fingerprinting as a JavaScript module
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JavaScript
// Original from: https://www.nayuki.io/page/free-small-fft-in-multiple-languages
// Modified by Chris Cannam: https://code.soundsoftware.ac.uk/projects/js-dsp-test/repository/entry/fft/nayuki-obj/fft.js
/*
* Free FFT and convolution (JavaScript)
*
* Copyright (c) 2014 Project Nayuki
* http://www.nayuki.io/page/free-small-fft-in-multiple-languages
*
* (MIT License)
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
* - The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* - The Software is provided "as is", without warranty of any kind, express or
* implied, including but not limited to the warranties of merchantability,
* fitness for a particular purpose and noninfringement. In no event shall the
* authors or copyright holders be liable for any claim, damages or other
* liability, whether in an action of contract, tort or otherwise, arising from,
* out of or in connection with the Software or the use or other dealings in the
* Software.
*
* Original slightly restructured by Chris Cannam, cannam@all-day-breakfast.com
* Restructured again to use the Typescript variant by Lucas Polito, https://github.com/lpolito
* Typescript from: https://www.nayuki.io/res/free-small-fft-in-multiple-languages/fft.ts
*/
/*
* Construct an object for calculating the discrete Fourier transform (DFT) of size n, where n is a power of 2.
*/
class FFTNayuki {
/**
* @param n Buffer size.
*/
constructor(n) {
this.peakBand = 0;
this.peak = 0;
this.n = n;
this.levels = -1;
for (let i = 0; i < 32; i++) {
if (1 << i === n) {
this.levels = i; // Equal to log2(n)
}
}
if (this.levels === -1) {
throw Error('Length is not a power of 2');
}
// Trigonometric tables
this.cosTable = new Array(n / 2);
this.sinTable = new Array(n / 2);
for (let i = 0; i < n / 2; i++) {
this.cosTable[i] = Math.cos(2 * Math.PI * i / n);
this.sinTable[i] = Math.sin(2 * Math.PI * i / n);
}
this.spectrum = new Array(n / 4);
}
/*
* Computes the discrete Fourier transform (DFT) of the given complex vector, storing the result back into the vector.
* The vector's length must be equal to the size n that was passed to the object constructor, and this must be a power of 2. Uses the Cooley-Tukey decimation-in-time radix-2 algorithm.
*/
forward(real, imag) {
// Bit-reversed addressing permutation
for (let i = 0; i < this.n; i++) {
const j = reverseBits(i, this.levels);
if (j > i) {
let temp = real[i];
real[i] = real[j];
real[j] = temp;
temp = imag[i];
imag[i] = imag[j];
imag[j] = temp;
}
}
// Cooley-Tukey decimation-in-time radix-2 FFT
for (let size = 2; size <= this.n; size *= 2) {
const halfsize = size / 2;
const tablestep = this.n / size;
for (let i = 0; i < this.n; i += size) {
for (let j = i, k = 0; j < i + halfsize; j++, k += tablestep) {
const l = j + halfsize;
const tpre = real[l] * this.cosTable[k] + imag[l] * this.sinTable[k];
const tpim = -real[l] * this.sinTable[k] + imag[l] * this.cosTable[k];
real[l] = real[j] - tpre;
imag[l] = imag[j] - tpim;
real[j] += tpre;
imag[j] += tpim;
}
}
}
this.calculateSpectrum(real, imag);
// Returns the integer whose value is the reverse of the lowest 'bits' bits of the integer 'x'.
function reverseBits(x, bits) {
let y = 0;
for (let i = 0; i < bits; i++) {
y = (y << 1) | (x & 1);
x >>>= 1;
}
return y;
}
}
calculateSpectrum(real, imag) {
// Should this be 4 / buffersize?
const bSi = 4 / this.n;
let mag;
for (let i = 0, N = this.n / 4; i < N; i++) {
mag = bSi * Math.sqrt(real[i] ** 2 + imag[i] ** 2);
if (mag > this.peak) {
this.peakBand = i;
this.peak = mag;
}
this.spectrum[i] = mag;
}
}
}
export default FFTNayuki;