real_fourier_ooura.cc (3045B)
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 "common_audio/real_fourier_ooura.h" 12 13 #include <algorithm> 14 #include <cmath> 15 #include <complex> 16 #include <cstddef> 17 18 #include "common_audio/third_party/ooura/fft_size_256/fft4g.h" 19 #include "rtc_base/checks.h" 20 21 namespace webrtc { 22 23 using std::complex; 24 25 namespace { 26 27 void Conjugate(complex<float>* array, size_t complex_length) { 28 std::for_each(array, array + complex_length, 29 [=](complex<float>& v) { v = std::conj(v); }); 30 } 31 32 size_t ComputeWorkIpSize(size_t fft_length) { 33 return static_cast<size_t>( 34 2 + std::ceil(std::sqrt(static_cast<float>(fft_length)))); 35 } 36 37 } // namespace 38 39 RealFourierOoura::RealFourierOoura(int fft_order) 40 : order_(fft_order), 41 length_(FftLength(order_)), 42 complex_length_(ComplexLength(order_)), 43 // Zero-initializing work_ip_ will cause rdft to initialize these work 44 // arrays on the first call. 45 work_ip_(new size_t[ComputeWorkIpSize(length_)]()), 46 work_w_(new float[complex_length_]()) { 47 RTC_CHECK_GE(fft_order, 1); 48 } 49 50 RealFourierOoura::~RealFourierOoura() = default; 51 52 void RealFourierOoura::Forward(const float* src, complex<float>* dest) const { 53 { 54 // This cast is well-defined since C++11. See "Non-static data members" at: 55 // http://en.cppreference.com/w/cpp/numeric/complex 56 auto* dest_float = reinterpret_cast<float*>(dest); 57 std::copy(src, src + length_, dest_float); 58 WebRtc_rdft(length_, 1, dest_float, work_ip_.get(), work_w_.get()); 59 } 60 61 // Ooura places real[n/2] in imag[0]. 62 dest[complex_length_ - 1] = complex<float>(dest[0].imag(), 0.0f); 63 dest[0] = complex<float>(dest[0].real(), 0.0f); 64 // Ooura returns the conjugate of the usual Fourier definition. 65 Conjugate(dest, complex_length_); 66 } 67 68 void RealFourierOoura::Inverse(const complex<float>* src, float* dest) const { 69 { 70 auto* dest_complex = reinterpret_cast<complex<float>*>(dest); 71 // The real output array is shorter than the input complex array by one 72 // complex element. 73 const size_t dest_complex_length = complex_length_ - 1; 74 std::copy(src, src + dest_complex_length, dest_complex); 75 // Restore Ooura's conjugate definition. 76 Conjugate(dest_complex, dest_complex_length); 77 // Restore real[n/2] to imag[0]. 78 dest_complex[0] = 79 complex<float>(dest_complex[0].real(), src[complex_length_ - 1].real()); 80 } 81 82 WebRtc_rdft(length_, -1, dest, work_ip_.get(), work_w_.get()); 83 84 // Ooura returns a scaled version. 85 const float scale = 2.0f / length_; 86 std::for_each(dest, dest + length_, [scale](float& v) { v *= scale; }); 87 } 88 89 int RealFourierOoura::order() const { 90 return order_; 91 } 92 93 } // namespace webrtc