Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #include "webrtc/common_audio/real_fourier_ooura.h"
      12             : 
      13             : #include <cmath>
      14             : #include <algorithm>
      15             : 
      16             : #include "webrtc/base/checks.h"
      17             : #include "webrtc/common_audio/fft4g.h"
      18             : 
      19             : namespace webrtc {
      20             : 
      21             : using std::complex;
      22             : 
      23             : namespace {
      24             : 
      25           0 : void Conjugate(complex<float>* array, size_t complex_length) {
      26           0 :   std::for_each(array, array + complex_length,
      27           0 :                 [=](complex<float>& v) { v = std::conj(v); });
      28           0 : }
      29             : 
      30           0 : size_t ComputeWorkIpSize(size_t fft_length) {
      31           0 :   return static_cast<size_t>(2 + std::ceil(std::sqrt(
      32           0 :       static_cast<float>(fft_length))));
      33             : }
      34             : 
      35             : }  // namespace
      36             : 
      37           0 : RealFourierOoura::RealFourierOoura(int fft_order)
      38             :     : order_(fft_order),
      39           0 :       length_(FftLength(order_)),
      40           0 :       complex_length_(ComplexLength(order_)),
      41             :       // Zero-initializing work_ip_ will cause rdft to initialize these work
      42             :       // arrays on the first call.
      43           0 :       work_ip_(new size_t[ComputeWorkIpSize(length_)]()),
      44           0 :       work_w_(new float[complex_length_]()) {
      45           0 :   RTC_CHECK_GE(fft_order, 1);
      46           0 : }
      47             : 
      48           0 : void RealFourierOoura::Forward(const float* src, complex<float>* dest) const {
      49             :   {
      50             :     // This cast is well-defined since C++11. See "Non-static data members" at:
      51             :     // http://en.cppreference.com/w/cpp/numeric/complex
      52           0 :     auto dest_float = reinterpret_cast<float*>(dest);
      53           0 :     std::copy(src, src + length_, dest_float);
      54           0 :     WebRtc_rdft(length_, 1, dest_float, work_ip_.get(), work_w_.get());
      55             :   }
      56             : 
      57             :   // Ooura places real[n/2] in imag[0].
      58           0 :   dest[complex_length_ - 1] = complex<float>(dest[0].imag(), 0.0f);
      59           0 :   dest[0] = complex<float>(dest[0].real(), 0.0f);
      60             :   // Ooura returns the conjugate of the usual Fourier definition.
      61           0 :   Conjugate(dest, complex_length_);
      62           0 : }
      63             : 
      64           0 : void RealFourierOoura::Inverse(const complex<float>* src, float* dest) const {
      65             :   {
      66           0 :     auto dest_complex = reinterpret_cast<complex<float>*>(dest);
      67             :     // The real output array is shorter than the input complex array by one
      68             :     // complex element.
      69           0 :     const size_t dest_complex_length = complex_length_ - 1;
      70           0 :     std::copy(src, src + dest_complex_length, dest_complex);
      71             :     // Restore Ooura's conjugate definition.
      72           0 :     Conjugate(dest_complex, dest_complex_length);
      73             :     // Restore real[n/2] to imag[0].
      74           0 :     dest_complex[0] = complex<float>(dest_complex[0].real(),
      75           0 :                                      src[complex_length_ - 1].real());
      76             :   }
      77             : 
      78           0 :   WebRtc_rdft(length_, -1, dest, work_ip_.get(), work_w_.get());
      79             : 
      80             :   // Ooura returns a scaled version.
      81           0 :   const float scale = 2.0f / length_;
      82           0 :   std::for_each(dest, dest + length_, [scale](float& v) { v *= scale; });
      83           0 : }
      84             : 
      85             : }  // namespace webrtc