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