kopia lustrzana https://github.com/Dsplib/libdspl-2.0
130 wiersze
4.1 KiB
C
130 wiersze
4.1 KiB
C
/*
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* Copyright (c) 2015-2019 Sergey Bakhurin
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* Digital Signal Processing Library [http://dsplib.org]
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*
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* This file is part of libdspl-2.0.
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*
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* is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* DSPL is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with Foobar. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <float.h>
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#include "dspl.h"
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#include "dspl_internal.h"
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup DFT_GROUP
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\fn int fft_shift(double* x, int n, double* y)
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\brief Perform a shift of the vector `x`, for use with the `fft` and `ifft`
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functions, in order
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<a href="http://en.dsplib.org/content/dft_freq/dft_freq.html">
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to move the frequency 0 to the center
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</a> of the vector `y`.
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\param[in] x
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Pointer to the input vector (FFT or IFFT result). \n
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Vector size is `[n x 1]`. \n \n
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\param[in] n
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Input and output vector size. \n \n
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\param[out] y
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Pointer to the output vector with frequency 0 in the center. \n
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Vector size is `[n x 1]`. \n
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Memory must be allocated. \n \n
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\return
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`RES_OK` if function is calculated successfully. \n
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Else \ref ERROR_CODE_GROUP "code error".
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\author Sergey Bakhurin www.dsplib.org
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***************************************************************************** */
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#endif
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#ifdef DOXYGEN_RUSSIAN
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/*! ****************************************************************************
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\ingroup DFT_GROUP
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\fn int fft_shift(double* x, int n, double* y)
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\brief Перестановка спектральных отсчетов дискретного преобразования Фурье
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Функция производит
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<a href="http://ru.dsplib.org/content/dft_freq/dft_freq.html">
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перестановку спектральных отсчетов ДПФ
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</a> и переносит нулевую частоту в центр вектора ДПФ. \n
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Данная функция обрабатывает вещественные входные и выходные вектора
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и может применяться для перестановки
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амплитудного или фазового спектра.
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\param[in] x
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Указатель на исходный вектор ДПФ. \n
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Размер вектора `[n x 1]`. \n \n
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\param[in] n
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Размер ДПФ \f$n\f$ (размер векторов до и после перестановки). \n \n
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\param[out] y
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Указатель на вектор результата перестановки. \n
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Размер вектора `[n x 1]`. \n
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Память должна быть выделена. \n \n
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\return
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`RES_OK` если перестановка произведена успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки". \n
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\author Бахурин Сергей www.dsplib.org
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***************************************************************************** */
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#endif
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int DSPL_API fft_shift(double* x, int n, double* y)
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{
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int n2, r;
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int k;
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double tmp;
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double *buf;
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if(!x || !y)
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return ERROR_PTR;
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if(n<1)
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return ERROR_SIZE;
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r = n%2;
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if(!r)
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{
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n2 = n>>1;
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for(k = 0; k < n2; k++)
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{
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tmp = x[k];
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y[k] = x[k+n2];
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y[k+n2] = tmp;
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}
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}
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else
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{
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n2 = (n+1) >> 1;
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buf = (double*) malloc(n2*sizeof(double));
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memcpy(buf, x, n2*sizeof(double));
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memcpy(y, x+n2, (n2-1)*sizeof(double));
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memcpy(y+n2-1, buf, n2*sizeof(double));
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free(buf);
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}
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return RES_OK;
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}
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