86 lines
2.8 KiB
C++
86 lines
2.8 KiB
C++
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/*
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* Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/common_audio/real_fourier_ooura.h"
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#include <cmath>
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#include <algorithm>
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#include "webrtc/base/checks.h"
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#include "webrtc/common_audio/fft4g.h"
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namespace webrtc {
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using std::complex;
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namespace {
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void Conjugate(complex<float>* array, size_t complex_length) {
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std::for_each(array, array + complex_length,
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[=](complex<float>& v) { v = std::conj(v); });
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}
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size_t ComputeWorkIpSize(size_t fft_length) {
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return static_cast<size_t>(2 + std::ceil(std::sqrt(
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static_cast<float>(fft_length))));
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}
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} // namespace
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RealFourierOoura::RealFourierOoura(int fft_order)
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: order_(fft_order),
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length_(FftLength(order_)),
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complex_length_(ComplexLength(order_)),
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// Zero-initializing work_ip_ will cause rdft to initialize these work
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// arrays on the first call.
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work_ip_(new size_t[ComputeWorkIpSize(length_)]()),
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work_w_(new float[complex_length_]()) {
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RTC_CHECK_GE(fft_order, 1);
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}
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void RealFourierOoura::Forward(const float* src, complex<float>* dest) const {
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{
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// This cast is well-defined since C++11. See "Non-static data members" at:
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// http://en.cppreference.com/w/cpp/numeric/complex
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auto dest_float = reinterpret_cast<float*>(dest);
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std::copy(src, src + length_, dest_float);
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WebRtc_rdft(length_, 1, dest_float, work_ip_.get(), work_w_.get());
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}
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// Ooura places real[n/2] in imag[0].
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dest[complex_length_ - 1] = complex<float>(dest[0].imag(), 0.0f);
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dest[0] = complex<float>(dest[0].real(), 0.0f);
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// Ooura returns the conjugate of the usual Fourier definition.
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Conjugate(dest, complex_length_);
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}
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void RealFourierOoura::Inverse(const complex<float>* src, float* dest) const {
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{
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auto dest_complex = reinterpret_cast<complex<float>*>(dest);
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// The real output array is shorter than the input complex array by one
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// complex element.
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const size_t dest_complex_length = complex_length_ - 1;
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std::copy(src, src + dest_complex_length, dest_complex);
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// Restore Ooura's conjugate definition.
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Conjugate(dest_complex, dest_complex_length);
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// Restore real[n/2] to imag[0].
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dest_complex[0] = complex<float>(dest_complex[0].real(),
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src[complex_length_ - 1].real());
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}
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WebRtc_rdft(length_, -1, dest, work_ip_.get(), work_w_.get());
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// Ooura returns a scaled version.
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const float scale = 2.0f / length_;
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std::for_each(dest, dest + length_, [scale](float& v) { v *= scale; });
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}
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} // namespace webrtc
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