xbmc/utils/rfft.cpp

   1 /*
   2  *  Copyright (C) 2015-2018 Team Kodi
   3  *  This file is part of Kodi - https://kodi.tv
   4  *
   5  *  SPDX-License-Identifier: GPL-2.0-or-later
   6  *  See LICENSES/README.md for more information.
   7  */
   8
   9 #include "rfft.h"
  10
  11 #if defined(TARGET_WINDOWS) && !defined(_USE_MATH_DEFINES)
  12 #define _USE_MATH_DEFINES
  13 #endif
  14 #include <math.h>
  15
  16 RFFT::RFFT(int size, bool windowed) :
  17   m_size(size), m_windowed(windowed)
  18 {
  19   m_cfg = kiss_fftr_alloc(m_size,0,nullptr,nullptr);
  20 }
  21
  22 RFFT::~RFFT()
  23 {
  24   // we don' use kiss_fftr_free here because
  25   // its hardcoded to free and doesn't pay attention
  26   // to SIMD (which might be used during kiss_fftr_alloc
  27   //in the C'tor).
  28   KISS_FFT_FREE(m_cfg);
  29 }
  30
  31 void RFFT::calc(const float* input, float* output)
  32 {
  33   // temporary buffers
  34   std::vector<kiss_fft_scalar> linput(m_size), rinput(m_size);
  35   std::vector<kiss_fft_cpx> loutput(m_size), routput(m_size);
  36
  37   for (size_t i=0;i<m_size;++i)
  38   {
  39     linput[i] = input[2*i];
  40     rinput[i] = input[2*i+1];
  41   }
  42
  43   if (m_windowed)
  44   {
  45     hann(linput);
  46     hann(rinput);
  47   }
  48
  49   // transform channels
  50   kiss_fftr(m_cfg, &linput[0], &loutput[0]);
  51   kiss_fftr(m_cfg, &rinput[0], &routput[0]);
  52
  53   auto&& filter = [&](kiss_fft_cpx& data)
  54   {
  55     return static_cast<double>(sqrt(data.r * data.r + data.i * data.i)) * 2.0 / m_size *
  56            (m_windowed ? sqrt(8.0 / 3.0) : 1.0);
  57   };
  58
  59   // interleave while taking magnitudes and normalizing
  60   for (size_t i=0;i<m_size/2;++i)
  61   {
  62     output[2*i] = filter(loutput[i]);
  63     output[2*i+1] = filter(routput[i]);
  64   }
  65 }
  66
  67 #include <iostream>
  68
  69 void RFFT::hann(std::vector<kiss_fft_scalar>& data)
  70 {
  71   for (size_t i=0;i<data.size();++i)
  72     data[i] *= 0.5f * (1.0f - cos(2.0f * static_cast<float>(M_PI) * i / (data.size() - 1)));
  73 }