fft.hpp

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#pragma once
#include <pffft.h>
 
#include <dsp/common.hpp>
 
 
namespace rack {
namespace dsp {
 

struct RealFFT {
    PFFFT_Setup* setup;
    int length;
 
    RealFFT(size_t length) {
        this->length = length;
        setup = pffft_new_setup(length, PFFFT_REAL);
    }
 
    ~RealFFT() {
        pffft_destroy_setup(setup);
    }

    void rfftUnordered(const float* input, float* output) {
        pffft_transform(setup, input, output, NULL, PFFFT_FORWARD);
    }

    void irfftUnordered(const float* input, float* output) {
        pffft_transform(setup, input, output, NULL, PFFFT_BACKWARD);
    }

    void rfft(const float* input, float* output) {
        pffft_transform_ordered(setup, input, output, NULL, PFFFT_FORWARD);
    }
 
    void irfft(const float* input, float* output) {
        pffft_transform_ordered(setup, input, output, NULL, PFFFT_BACKWARD);
    }

    void scale(float* x) {
        float a = 1.f / length;
        for (int i = 0; i < length; i++) {
            x[i] *= a;
        }
    }
};
 

struct ComplexFFT {
    PFFFT_Setup* setup;
    int length;
 
    ComplexFFT(size_t length) {
        this->length = length;
        setup = pffft_new_setup(length, PFFFT_COMPLEX);
    }
 
    ~ComplexFFT() {
        pffft_destroy_setup(setup);
    }

    void fftUnordered(const float* input, float* output) {
        pffft_transform(setup, input, output, NULL, PFFFT_FORWARD);
    }

    void ifftUnordered(const float* input, float* output) {
        pffft_transform(setup, input, output, NULL, PFFFT_BACKWARD);
    }
 
    void fft(const float* input, float* output) {
        pffft_transform_ordered(setup, input, output, NULL, PFFFT_FORWARD);
    }
 
    void ifft(const float* input, float* output) {
        pffft_transform_ordered(setup, input, output, NULL, PFFFT_BACKWARD);
    }
 
    void scale(float* x) {
        float a = 1.f / length;
        for (int i = 0; i < length; i++) {
            x[2 * i + 0] *= a;
            x[2 * i + 1] *= a;
        }
    }
};
 
 
} // namespace dsp
} // namespace rack