#include "fft_lib_fftw3.h"
namespace chromaprint {
FFTLib::FFTLib(size_t frame_size) : m_frame_size(frame_size) {
m_window = (FFTW_SCALAR *) fftw_malloc(sizeof(FFTW_SCALAR) * frame_size);
m_input = (FFTW_SCALAR *) fftw_malloc(sizeof(FFTW_SCALAR) * frame_size);
m_output = (FFTW_SCALAR *) fftw_malloc(sizeof(FFTW_SCALAR) * frame_size);
PrepareHammingWindow(m_window, m_window + frame_size, 1.0 / INT16_MAX);
m_plan = fftw_plan_r2r_1d(frame_size, m_input, m_output, FFTW_R2HC, FFTW_ESTIMATE);
}
FFTLib::~FFTLib() {
fftw_destroy_plan(m_plan);
fftw_free(m_output);
fftw_free(m_input);
fftw_free(m_window);
}
void FFTLib::Load(const int16_t *b1, const int16_t *e1, const int16_t *b2, const int16_t *e2) {
auto window = m_window;
auto output = m_input;
ApplyWindow(b1, e1, window, output);
ApplyWindow(b2, e2, window, output);
}
void FFTLib::Compute(FFTFrame &frame) {
fftw_execute(m_plan);
auto output = frame.data();
auto in_ptr = m_output;
auto rev_in_ptr = m_output + m_frame_size - 1;
output[0] = in_ptr[0] * in_ptr[0];
output[m_frame_size / 2] = in_ptr[m_frame_size / 2] * in_ptr[m_frame_size / 2];
in_ptr += 1;
output += 1;
for (size_t i = 1; i < m_frame_size / 2; i++) {
*output++ = in_ptr[0] * in_ptr[0] + rev_in_ptr[0] * rev_in_ptr[0];
in_ptr++;
rev_in_ptr--;
}
}
};