real_fourier.h (2905B)
1 /* 2 * Copyright (c) 2014 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 #ifndef COMMON_AUDIO_REAL_FOURIER_H_ 12 #define COMMON_AUDIO_REAL_FOURIER_H_ 13 14 #include <stddef.h> 15 16 #include <complex> 17 #include <memory> 18 19 #include "rtc_base/memory/aligned_malloc.h" 20 21 // Uniform interface class for the real DFT and its inverse, for power-of-2 22 // input lengths. Also contains helper functions for buffer allocation, taking 23 // care of any memory alignment requirements the underlying library might have. 24 25 namespace webrtc { 26 27 class RealFourier { 28 public: 29 // Shorthand typenames for the scopers used by the buffer allocation helpers. 30 typedef std::unique_ptr<float[], AlignedFreeDeleter> fft_real_scoper; 31 typedef std::unique_ptr<std::complex<float>[], AlignedFreeDeleter> 32 fft_cplx_scoper; 33 34 // The alignment required for all input and output buffers, in bytes. 35 static const size_t kFftBufferAlignment; 36 37 // Construct a wrapper instance for the given input order, which must be 38 // between 1 and kMaxFftOrder, inclusively. 39 static std::unique_ptr<RealFourier> Create(int fft_order); 40 virtual ~RealFourier() {} 41 42 // Helper to compute the smallest FFT order (a power of 2) which will contain 43 // the given input length. 44 static int FftOrder(size_t length); 45 46 // Helper to compute the input length from the FFT order. 47 static size_t FftLength(int order); 48 49 // Helper to compute the exact length, in complex floats, of the transform 50 // output (i.e. |2^order / 2 + 1|). 51 static size_t ComplexLength(int order); 52 53 // Buffer allocation helpers. The buffers are large enough to hold `count` 54 // floats/complexes and suitably aligned for use by the implementation. 55 // The returned scopers are set up with proper deleters; the caller owns 56 // the allocated memory. 57 static fft_real_scoper AllocRealBuffer(int count); 58 static fft_cplx_scoper AllocCplxBuffer(int count); 59 60 // Main forward transform interface. The output array need only be big 61 // enough for |2^order / 2 + 1| elements - the conjugate pairs are not 62 // returned. Input and output must be properly aligned (e.g. through 63 // AllocRealBuffer and AllocCplxBuffer) and input length must be 64 // |2^order| (same as given at construction time). 65 virtual void Forward(const float* src, std::complex<float>* dest) const = 0; 66 67 // Inverse transform. Same input format as output above, conjugate pairs 68 // not needed. 69 virtual void Inverse(const std::complex<float>* src, float* dest) const = 0; 70 71 virtual int order() const = 0; 72 }; 73 74 } // namespace webrtc 75 76 #endif // COMMON_AUDIO_REAL_FOURIER_H_