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Diffstat (limited to 'third_party/webrtc/src/webrtc/common_audio/signal_processing/include/real_fft.h')
| -rw-r--r-- | third_party/webrtc/src/webrtc/common_audio/signal_processing/include/real_fft.h | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/third_party/webrtc/src/webrtc/common_audio/signal_processing/include/real_fft.h b/third_party/webrtc/src/webrtc/common_audio/signal_processing/include/real_fft.h new file mode 100644 index 00000000..e7942f04 --- /dev/null +++ b/third_party/webrtc/src/webrtc/common_audio/signal_processing/include/real_fft.h @@ -0,0 +1,97 @@ +/* + * Copyright (c) 2012 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#ifndef WEBRTC_COMMON_AUDIO_SIGNAL_PROCESSING_INCLUDE_REAL_FFT_H_ +#define WEBRTC_COMMON_AUDIO_SIGNAL_PROCESSING_INCLUDE_REAL_FFT_H_ + +#include "webrtc/typedefs.h" + +// For ComplexFFT(), the maximum fft order is 10; +// for OpenMax FFT in ARM, it is 12; +// WebRTC APM uses orders of only 7 and 8. +enum {kMaxFFTOrder = 10}; + +struct RealFFT; + +#ifdef __cplusplus +extern "C" { +#endif + +struct RealFFT* WebRtcSpl_CreateRealFFT(int order); +void WebRtcSpl_FreeRealFFT(struct RealFFT* self); + +// Compute an FFT for a real-valued signal of length of 2^order, +// where 1 < order <= MAX_FFT_ORDER. Transform length is determined by the +// specification structure, which must be initialized prior to calling the FFT +// function with WebRtcSpl_CreateRealFFT(). +// The relationship between the input and output sequences can +// be expressed in terms of the DFT, i.e.: +// x[n] = (2^(-scalefactor)/N) . SUM[k=0,...,N-1] X[k].e^(jnk.2.pi/N) +// n=0,1,2,...N-1 +// N=2^order. +// The conjugate-symmetric output sequence is represented using a CCS vector, +// which is of length N+2, and is organized as follows: +// Index: 0 1 2 3 4 5 . . . N-2 N-1 N N+1 +// Component: R0 0 R1 I1 R2 I2 . . . R[N/2-1] I[N/2-1] R[N/2] 0 +// where R[n] and I[n], respectively, denote the real and imaginary components +// for FFT bin 'n'. Bins are numbered from 0 to N/2, where N is the FFT length. +// Bin index 0 corresponds to the DC component, and bin index N/2 corresponds to +// the foldover frequency. +// +// Input Arguments: +// self - pointer to preallocated and initialized FFT specification structure. +// real_data_in - the input signal. For an ARM Neon platform, it must be +// aligned on a 32-byte boundary. +// +// Output Arguments: +// complex_data_out - the output complex signal with (2^order + 2) 16-bit +// elements. For an ARM Neon platform, it must be different +// from real_data_in, and aligned on a 32-byte boundary. +// +// Return Value: +// 0 - FFT calculation is successful. +// -1 - Error with bad arguments (NULL pointers). +int WebRtcSpl_RealForwardFFT(struct RealFFT* self, + const int16_t* real_data_in, + int16_t* complex_data_out); + +// Compute the inverse FFT for a conjugate-symmetric input sequence of length of +// 2^order, where 1 < order <= MAX_FFT_ORDER. Transform length is determined by +// the specification structure, which must be initialized prior to calling the +// FFT function with WebRtcSpl_CreateRealFFT(). +// For a transform of length M, the input sequence is represented using a packed +// CCS vector of length M+2, which is explained in the comments for +// WebRtcSpl_RealForwardFFTC above. +// +// Input Arguments: +// self - pointer to preallocated and initialized FFT specification structure. +// complex_data_in - the input complex signal with (2^order + 2) 16-bit +// elements. For an ARM Neon platform, it must be aligned on +// a 32-byte boundary. +// +// Output Arguments: +// real_data_out - the output real signal. For an ARM Neon platform, it must +// be different to complex_data_in, and aligned on a 32-byte +// boundary. +// +// Return Value: +// 0 or a positive number - a value that the elements in the |real_data_out| +// should be shifted left with in order to get +// correct physical values. +// -1 - Error with bad arguments (NULL pointers). +int WebRtcSpl_RealInverseFFT(struct RealFFT* self, + const int16_t* complex_data_in, + int16_t* real_data_out); + +#ifdef __cplusplus +} +#endif + +#endif // WEBRTC_COMMON_AUDIO_SIGNAL_PROCESSING_INCLUDE_REAL_FFT_H_ |