76 lines
2.9 KiB
C
76 lines
2.9 KiB
C
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/*
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* Copyright (c) 2014 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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#ifndef WEBRTC_COMMON_AUDIO_REAL_FOURIER_H_
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#define WEBRTC_COMMON_AUDIO_REAL_FOURIER_H_
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#include <complex>
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#include <memory>
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#include "webrtc/system_wrappers/include/aligned_malloc.h"
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// Uniform interface class for the real DFT and its inverse, for power-of-2
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// input lengths. Also contains helper functions for buffer allocation, taking
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// care of any memory alignment requirements the underlying library might have.
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namespace webrtc {
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class RealFourier {
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public:
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// Shorthand typenames for the scopers used by the buffer allocation helpers.
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typedef std::unique_ptr<float[], AlignedFreeDeleter> fft_real_scoper;
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typedef std::unique_ptr<std::complex<float>[], AlignedFreeDeleter>
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fft_cplx_scoper;
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// The alignment required for all input and output buffers, in bytes.
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static const size_t kFftBufferAlignment;
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// Construct a wrapper instance for the given input order, which must be
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// between 1 and kMaxFftOrder, inclusively.
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static std::unique_ptr<RealFourier> Create(int fft_order);
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virtual ~RealFourier() {};
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// Helper to compute the smallest FFT order (a power of 2) which will contain
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// the given input length.
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static int FftOrder(size_t length);
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// Helper to compute the input length from the FFT order.
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static size_t FftLength(int order);
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// Helper to compute the exact length, in complex floats, of the transform
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// output (i.e. |2^order / 2 + 1|).
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static size_t ComplexLength(int order);
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// Buffer allocation helpers. The buffers are large enough to hold |count|
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// floats/complexes and suitably aligned for use by the implementation.
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// The returned scopers are set up with proper deleters; the caller owns
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// the allocated memory.
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static fft_real_scoper AllocRealBuffer(int count);
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static fft_cplx_scoper AllocCplxBuffer(int count);
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// Main forward transform interface. The output array need only be big
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// enough for |2^order / 2 + 1| elements - the conjugate pairs are not
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// returned. Input and output must be properly aligned (e.g. through
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// AllocRealBuffer and AllocCplxBuffer) and input length must be
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// |2^order| (same as given at construction time).
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virtual void Forward(const float* src, std::complex<float>* dest) const = 0;
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// Inverse transform. Same input format as output above, conjugate pairs
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// not needed.
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virtual void Inverse(const std::complex<float>* src, float* dest) const = 0;
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virtual int order() const = 0;
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};
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} // namespace webrtc
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#endif // WEBRTC_COMMON_AUDIO_REAL_FOURIER_H_
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