node-fftw

This repo is for nodejs port and bindings with fftw, the fft library.

This repo DOES NOT contain fftw code, you need to install fftw first.

You can download fftw from http://www.fftw.org/download.html

You can install it following http://www.fftw.org/fftw3_doc/Installation-and-Customization.html

Functions:

* discrete fourier transform(dft) using fftw
* real-to-complex, arbitrary dimensions.
* complex-to-complex, arbitrary dimensions.

* inverse dft using fftw, using dft with sign=+1
* chirp z transform, accept only 1d real number, using Bluestein's algorithm.

Examples

* dft and idft : new fftw.dftPlan(isReal, size, sign, flags)
* isReal: indicate real number or complex number. The result is always complex,
* size : an array, the rank of the array indicate the dimension,
the values indicate length of each dimension,
* sign: -1 for dft, +1 for idft,
* flags: the flags passed to fftw.

```js
const fftw = require("./index.js");
const dftPlan = new fftw.dftPlan(true, [16], -1, fftw.flags.FFTW_DESTROY_INPUT);
for(var i = 0; i < 16; i++)
{
dftPlan.in[i] = Math.sin(Math.PI / 4 i) + Math.cos(Math.PI / 4 i);
}

dftPlan.calcAsync(function(plan) {
console.log("dft result", this.out, plan.out);
});
``
* czt : new fftw.cztr1dPlan(inSize, outSize, sampleRate, fstart, fstop, flags)
* inSize: the size of input buffer, 1d real
* outSize: the size of output buffer, 1d complex
* sampleRate: the sample rate
* fstart: the frequency to start calculation,
* fstop: the frequency to stop calculation,
* flags: the flags passed to fftw.
we use w = expi(-2pi (f2 - f1) / (outSize * sampleRate)),
and a = expi(2pi f1 / sampleRate)

``js
const fftw = require("./index.js");
const cztPlan = new fftw.cztr1dPlan(16, 8, 1, 1, 8, fftw.flags.FFTW_DESTROY_INPUT);
for(var i = 0; i < 16; i++)
{
cztPlan.in[i] = Math.sin(Math.PI / 4 i) + Math.cos(Math.PI / 4 i);
}

cztPlan.calcAsync(function(plan){
console.log("czt result", this.out, plan.out);
});
``


Supported flags


``js
const fftw = require("./index.js");
const flags = fftw.flags;
``
* FFTW_MEASURE
* FFTW_DESTROY_INPUT
* FFTW_UNALIGNED
* FFTW_CONSERVE_MEMORY
* FFTW_EXHAUSTIVE
* FFTW_PRESERVE_INPUT
* FFTW_PATIENT
* FFTW_ESTIMATE
* FFTW_WISDOM_ONLY

TODO

* nodejs implementation for sid::complex` compatible complex number
* Testing and bug fix
* fftw wisdom interface
* discrete cos transform (DCT)
* DST
* DHT
* fftw multi thread, openmp and MPI interface
* other fftw functionalities