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/*
* Copyright (C) 2015-2018 Team Kodi
* This file is part of Kodi - https://kodi.tv
*
* SPDX-License-Identifier: GPL-2.0-or-later
* See LICENSES/README.md for more information.
*/
#include "rfft.h"
#if defined(TARGET_WINDOWS) && !defined(_USE_MATH_DEFINES)
#define _USE_MATH_DEFINES
#endif
#include <math.h>
RFFT::RFFT(int size, bool windowed) :
m_size(size), m_windowed(windowed)
{
m_cfg = kiss_fftr_alloc(m_size,0,nullptr,nullptr);
}
RFFT::~RFFT()
{
// we don' use kiss_fftr_free here because
// its hardcoded to free and doesn't pay attention
// to SIMD (which might be used during kiss_fftr_alloc
//in the C'tor).
KISS_FFT_FREE(m_cfg);
}
void RFFT::calc(const float* input, float* output)
{
// temporary buffers
std::vector<kiss_fft_scalar> linput(m_size), rinput(m_size);
std::vector<kiss_fft_cpx> loutput(m_size), routput(m_size);
for (size_t i=0;i<m_size;++i)
{
linput[i] = input[2*i];
rinput[i] = input[2*i+1];
}
if (m_windowed)
{
hann(linput);
hann(rinput);
}
// transform channels
kiss_fftr(m_cfg, &linput[0], &loutput[0]);
kiss_fftr(m_cfg, &rinput[0], &routput[0]);
auto&& filter = [&](kiss_fft_cpx& data)
{
return static_cast<double>(sqrt(data.r * data.r + data.i * data.i)) * 2.0 / m_size *
(m_windowed ? sqrt(8.0 / 3.0) : 1.0);
};
// interleave while taking magnitudes and normalizing
for (size_t i=0;i<m_size/2;++i)
{
output[2*i] = filter(loutput[i]);
output[2*i+1] = filter(routput[i]);
}
}
#include <iostream>
void RFFT::hann(std::vector<kiss_fft_scalar>& data)
{
for (size_t i=0;i<data.size();++i)
data[i] *= 0.5f * (1.0f - cos(2.0f * static_cast<float>(M_PI) * i / (data.size() - 1)));
}
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