1 files changed, 72 insertions, 0 deletions

diff --git a/xbmc/utils/rfft.cpp b/xbmc/utils/rfft.cpp
new file mode 100644
index 0000000..871eea7
--- /dev/null
+++ b/xbmc/utils/rfft.cpp
@@ -0,0 +1,72 @@
+/*
+ *  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 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] *= 0.5*(1.0-cos(2*M_PI*i/(data.size()-1)));
+}