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
16 #include "common_audio/third_party/ooura/fft_size_256/fft4g.h"
17 #include "rtc_base/checks.h"
18
19 namespace webrtc {
20
21 using std::complex;
22
23 namespace {
24
Conjugate(complex<float> * array,size_t complex_length)25 void Conjugate(complex<float>* array, size_t complex_length) {
26 std::for_each(array, array + complex_length,
27 [=](complex<float>& v) { v = std::conj(v); });
28 }
29
ComputeWorkIpSize(size_t fft_length)30 size_t ComputeWorkIpSize(size_t fft_length) {
31 return static_cast<size_t>(
32 2 + std::ceil(std::sqrt(static_cast<float>(fft_length))));
33 }
34
35 } // namespace
36
RealFourierOoura(int fft_order)37 RealFourierOoura::RealFourierOoura(int fft_order)
38 : order_(fft_order),
39 length_(FftLength(order_)),
40 complex_length_(ComplexLength(order_)),
41 // Zero-initializing work_ip_ will cause rdft to initialize these work
42 // arrays on the first call.
43 work_ip_(new size_t[ComputeWorkIpSize(length_)]()),
44 work_w_(new float[complex_length_]()) {
45 RTC_CHECK_GE(fft_order, 1);
46 }
47
48 RealFourierOoura::~RealFourierOoura() = default;
49
Forward(const float * src,complex<float> * dest) const50 void RealFourierOoura::Forward(const float* src, complex<float>* dest) const {
51 {
52 // This cast is well-defined since C++11. See "Non-static data members" at:
53 // http://en.cppreference.com/w/cpp/numeric/complex
54 auto* dest_float = reinterpret_cast<float*>(dest);
55 std::copy(src, src + length_, dest_float);
56 WebRtc_rdft(length_, 1, dest_float, work_ip_.get(), work_w_.get());
57 }
58
59 // Ooura places real[n/2] in imag[0].
60 dest[complex_length_ - 1] = complex<float>(dest[0].imag(), 0.0f);
61 dest[0] = complex<float>(dest[0].real(), 0.0f);
62 // Ooura returns the conjugate of the usual Fourier definition.
63 Conjugate(dest, complex_length_);
64 }
65
Inverse(const complex<float> * src,float * dest) const66 void RealFourierOoura::Inverse(const complex<float>* src, float* dest) const {
67 {
68 auto* dest_complex = reinterpret_cast<complex<float>*>(dest);
69 // The real output array is shorter than the input complex array by one
70 // complex element.
71 const size_t dest_complex_length = complex_length_ - 1;
72 std::copy(src, src + dest_complex_length, dest_complex);
73 // Restore Ooura's conjugate definition.
74 Conjugate(dest_complex, dest_complex_length);
75 // Restore real[n/2] to imag[0].
76 dest_complex[0] =
77 complex<float>(dest_complex[0].real(), src[complex_length_ - 1].real());
78 }
79
80 WebRtc_rdft(length_, -1, dest, work_ip_.get(), work_w_.get());
81
82 // Ooura returns a scaled version.
83 const float scale = 2.0f / length_;
84 std::for_each(dest, dest + length_, [scale](float& v) { v *= scale; });
85 }
86
order() const87 int RealFourierOoura::order() const {
88 return order_;
89 }
90
91 } // namespace webrtc
92