kopia lustrzana https://github.com/Dsplib/libdspl-2.0
913 wiersze
27 KiB
C
913 wiersze
27 KiB
C
/*
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* Copyright (c) 2015-2024 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 <stdio.h>
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#include <math.h>
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#include "dspl.h"
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/* Window functions */
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int win_bartlett (double *w, int n, int win_type);
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int win_bartlett_hann (double *w, int n, int win_type);
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int win_blackman (double *w, int n, int win_type);
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int win_blackman_harris (double *w, int n, int win_type);
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int win_blackman_nuttall(double *w, int n, int win_type);
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int win_cheby (double *w, int n, double param);
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int win_cos (double *w, int n, int win_type);
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int win_flat_top (double *w, int n, int win_type);
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int win_gaussian (double *w, int n, int win_type, double sigma);
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int win_hamming (double *w, int n, int win_type);
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int win_hann (double *w, int n, int win_type);
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int win_kaiser (double* w, int n, int win_type, double param);
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int win_lanczos (double *w, int n, int win_type);
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int win_nuttall (double *w, int n, int win_type);
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int win_rect (double *w, int n);
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup WIN_GROUP
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\brief Window function calculation
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The function calculates a periodic or symmetric window function
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according to parameter `win_type`. \n
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A periodic window function is used for spectral analysis,
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and a symmetric window function can be used to design FIR filters.
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\param [in,out] w
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Pointer to the window. \n
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Vector size is `[n x 1]`. \n
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Memory must be allocated. \n
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The calculated window function will be placed at the given address. \n \n
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\param [in] n
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Size of window function `w` vector. \n \n
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\param [in] win_type
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Combination of flags for specifying the type of window function. \n
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Combination of `DSPL_WIN_MASK | DSPL_WIN_SYM_MASK` bit masks
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is used to set the window type.\n
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Bit mask `DSPL_WIN_MASK` sets the window type.
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Can be one of follow: \n
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\verbatim
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-------------------------------------------------------------------------
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win_type | Description
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-----------------------------|-------------------------------------------
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DSPL_WIN_BARTLETT | Nonparametric Bartlett window
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-----------------------------|-------------------------------------------
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DSPL_WIN_BARTLETT_HANN | Nonparametric Bartlett-Hann window
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-----------------------------|-------------------------------------------
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DSPL_WIN_BLACKMAN | Nonparametric Blackman window
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-----------------------------|-------------------------------------------
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DSPL_WIN_BLACKMAN_HARRIS | Nonparametric Blackman-Harris window
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-----------------------------|-------------------------------------------
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DSPL_WIN_BLACKMAN_NUTTALL | Nonparametric Blackman-Nuttall
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-----------------------------|-------------------------------------------
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DSPL_WIN_CHEBY | Parametric Dolph-Chebyshev window.
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| Parametr `win_param` sets sidelobe attenuation
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| level in dB.
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-----------------------------|-------------------------------------------
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DSPL_WIN_COS | Nonparametric Cosine window
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-----------------------------|-------------------------------------------
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DSPL_WIN_FLAT_TOP | Nonparametric maxflat window
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-----------------------------|-------------------------------------------
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DSPL_WIN_GAUSSIAN | Nonparametric Gauss window
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-----------------------------|-------------------------------------------
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DSPL_WIN_HAMMING | Nonparametric Hamming window
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-----------------------------|-------------------------------------------
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DSPL_WIN_HANN | Nonparametric Hann window
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-----------------------------|-------------------------------------------
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DSPL_WIN_KAISER | Parametric Kaiser window
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-----------------------------|-------------------------------------------
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DSPL_WIN_LANCZOS | Nonparametric Lanczos window
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-----------------------------|-------------------------------------------
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DSPL_WIN_NUTTALL | Nonparametric Nuttall window
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-----------------------------|-------------------------------------------
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DSPL_WIN_RECT | Nonparametric rectangular window
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-------------------------------------------------------------------------
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\endverbatim
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\n
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Bit mask `DSPL_WIN_SYM_MASK` sets window function symmetry: \n
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\verbatim
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-------------------------------------------------------------------------
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DSPL_WIN_SYM_MASK | Description
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-----------------------------|-------------------------------------------
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DSPL_WIN_SYMMETRIC | Symmetry window (default value)
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DSPL_WIN_PERIODIC | Periodic window
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-------------------------------------------------------------------------
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\endverbatim
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\n \n
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\param [in] param
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Window function parameter. \n
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This parameter is using only to parametric window functions,
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and ignored for nonparametric windows. \n
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\n
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\return
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`RES_OK` if window function is calculated successfully. \n
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Else \ref ERROR_CODE_GROUP "error code".
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The following program calculates 64 samples window functions,
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draws their spectrum when using the bin indices of
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the discrete Fourier transform along the frequency axis.
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\include windows_test.c
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A personal graph is displayed for each type of window function.
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Rectangular window
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\image html win_rect.png
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\n
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\n
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Nonparametric windows
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\image html win_bartlett.png
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\image html win_flattop.png
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\image html win_bartletthann.png
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\image html win_hann.png
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\image html win_hamming.png
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\image html win_lanczos.png
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\image html win_blackman.png
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\image html win_blackmanharris.png
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\image html win_blackmannuttall.png
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\image html win_cos.png
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\image html win_nuttall.png
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\n
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\n
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Parametric Dolph-Chebyshev windows
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\image html win_cheby50.png
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\image html win_cheby80.png
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\image html win_cheby120.png
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\n
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\n
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Parametric Gaussian windows
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\image html win_gaussian0p5.png
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\image html win_gaussian0p3.png
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\n
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\n
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Parametric Kaiser windows
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\image html win_kaiser4p0.png
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\image html win_kaiser8p0.png
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\image html win_kaiser12p0.png
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\n
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\n
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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 WIN_GROUP
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\brief Расчет функции оконного взвешивания
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Функция рассчитывает периодическую или симметричную оконную функцию
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в соответствии с параметром `win_type`. \n
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Периодическая оконная функция используется для спектрального анализа,
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а симметричная оконная функция может быть использована для синтеза
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КИХ-фильтров.
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\param [in,out] w
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Указатель на вектор оконной функции. \n
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Размер вектора `[n x 1]`. \n
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Память должна быть выделена. \n
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Рассчитанная оконная функция будет помещена по данному адресу. \n \n
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\param [in] n
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Размер вектора `w` оконной функции. \n \n
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\param [in] win_type
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Комбинация флагов для задания типа оконной функции. \n
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Для задания типа окна используется комбинация битовых масок
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`DSPL_WIN_MASK | DSPL_WIN_SYM_MASK`. \n
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Маска `DSPL_WIN_MASK` задает тип оконной функции.
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Может принимать следующие значения: \n
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\verbatim
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-------------------------------------------------------------------------
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Значение DSPL_WIN_MASK | Описание
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-----------------------------|-------------------------------------------
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DSPL_WIN_BARTLETT | Непараметрическое окно Бартлетта
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-----------------------------|-------------------------------------------
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DSPL_WIN_BARTLETT_HANN | Непараметрическое окно Бартлетта-Ханна
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-----------------------------|-------------------------------------------
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DSPL_WIN_BLACKMAN | Непараметрическое окно Блэкмана
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-----------------------------|-------------------------------------------
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DSPL_WIN_BLACKMAN_HARRIS | Непараметрическое окно Блэкмана-Харриса
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-----------------------------|-------------------------------------------
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DSPL_WIN_BLACKMAN_NUTTALL | Непараметрическое окно Блэкмана-Натталла
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-----------------------------|-------------------------------------------
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DSPL_WIN_CHEBY | Параметрическое окно Дольф-Чебышева.
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| Данное окно всегда является симметричным и
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| игнорирует параметр DSPL_WIN_SYM_MASK .
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| Параметр param задает уровень боковых
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| лепестков в дБ.
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-----------------------------|-------------------------------------------
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DSPL_WIN_COS | Непараметрическое косинус-окно
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-----------------------------|-------------------------------------------
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DSPL_WIN_FLAT_TOP | Непараметрическое окно с максимально
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| плоской вершиной
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-----------------------------|-------------------------------------------
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DSPL_WIN_GAUSSIAN | Параметрическое окно Гаусса
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-----------------------------|-------------------------------------------
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DSPL_WIN_HAMMING | Непараметрическое окно Хемминга
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-----------------------------|-------------------------------------------
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DSPL_WIN_HANN | Непараметрическое окно Ханна
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-----------------------------|-------------------------------------------
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DSPL_WIN_KAISER | Параметрическое окно Кайзера
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-----------------------------|-------------------------------------------
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DSPL_WIN_LANCZOS | Непараметрическое окно Ланкзоса
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-----------------------------|-------------------------------------------
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DSPL_WIN_NUTTALL | Непараметрическое окно Натталла
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-----------------------------|-------------------------------------------
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DSPL_WIN_RECT | Непараметрическое прямоугольное окно
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-------------------------------------------------------------------------
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\endverbatim
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\n
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Маска `DSPL_WIN_SYM_MASK` задает симметричное
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или периодическое окно: \n
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\verbatim
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-------------------------------------------------------------------------
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Значение DSPL_WIN_SYM_MASK | Описание
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-----------------------------|-------------------------------------------
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DSPL_WIN_SYMMETRIC | Симметричное окно (по умолчанию)
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DSPL_WIN_PERIODIC | Периодическое окно
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-------------------------------------------------------------------------
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\endverbatim
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\n \n
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\param [in] param
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Параметр окна. \n
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Данный параметр применяется только для параметрических оконных функций. \n
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Для непараметрических окон игнорируется. \n\n
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\return
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`RES_OK` если оконная функция рассчитана успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки".
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Следующая программа производит расчет оконных функций длительности 64 отсчета,
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строит их спектральную плотность при использовании по оси частот индексы бинов
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дискретного преобразования Фурье.
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\include windows_test.c
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Для каждого вида оконной функция выводится персональный график.
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Прямоугольное окно
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\image html win_rect.png
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\n
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\n
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Непраметрические окна
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\image html win_bartlett.png
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\image html win_flattop.png
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\image html win_bartletthann.png
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\image html win_hann.png
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\image html win_hamming.png
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\image html win_lanczos.png
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\image html win_blackman.png
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\image html win_blackmanharris.png
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\image html win_blackmannuttall.png
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\image html win_cos.png
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\image html win_nuttall.png
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\n
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\n
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Параметрические окна Дольф-Чебышева
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\image html win_cheby50.png
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\image html win_cheby80.png
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\image html win_cheby120.png
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\n
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\n
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Параметрические окна Гаусса
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\image html win_gaussian0p5.png
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\image html win_gaussian0p3.png
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\n
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\n
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Параметрические окна Кайзера
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\image html win_kaiser4p0.png
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\image html win_kaiser8p0.png
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\image html win_kaiser12p0.png
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\n
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\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 window(double* w, int n, int win_type, double param)
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{
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switch(win_type & DSPL_WIN_MASK)
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{
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case DSPL_WIN_BARTLETT:
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return win_bartlett(w, n, win_type);
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case DSPL_WIN_BARTLETT_HANN:
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return win_bartlett_hann(w, n, win_type);
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case DSPL_WIN_BLACKMAN:
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return win_blackman(w, n, win_type);
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case DSPL_WIN_BLACKMAN_HARRIS:
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return win_blackman_harris(w, n, win_type);
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case DSPL_WIN_BLACKMAN_NUTTALL:
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return win_blackman_nuttall(w, n, win_type);
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case DSPL_WIN_CHEBY:
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return win_cheby(w, n, param);
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case DSPL_WIN_FLAT_TOP:
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return win_flat_top(w, n, win_type);
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case DSPL_WIN_GAUSSIAN:
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return win_gaussian(w, n, win_type, param);
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case DSPL_WIN_HAMMING:
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return win_hamming(w, n, win_type);
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case DSPL_WIN_HANN:
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return win_hann(w, n, win_type);
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case DSPL_WIN_KAISER:
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return win_kaiser(w, n, win_type, param);
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case DSPL_WIN_LANCZOS:
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return win_lanczos(w, n, win_type);
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case DSPL_WIN_NUTTALL:
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return win_nuttall(w, n, win_type);
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case DSPL_WIN_RECT:
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return win_rect(w, n);
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case DSPL_WIN_COS:
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return win_cos(w, n, win_type);
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default:
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return ERROR_WIN_TYPE;
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}
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return RES_OK;
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}
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/******************************************************************************
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Barlett window function
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*******************************************************************************/
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int win_bartlett(double *w, int n, int win_type)
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{
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double x = 0.0;
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int i;
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if(!w)
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return ERROR_PTR;
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if(n<2)
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return ERROR_SIZE;
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switch(win_type & DSPL_WIN_SYM_MASK)
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{
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case DSPL_WIN_SYMMETRIC: x = (double)(n-1); break;
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case DSPL_WIN_PERIODIC : x = (double)n; break;
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default: return ERROR_WIN_SYM;
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}
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for(i = 0; i < n; i++)
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{
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w[i] = 2.0 / x * (x * 0.5-fabs((double)i - x * 0.5));
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}
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return RES_OK;
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}
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/******************************************************************************
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Barlett - Hann window function
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******************************************************************************/
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int win_bartlett_hann(double *w, int n, int win_type)
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{
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double y;
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double x = 0.0;
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int i;
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if(!w)
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return ERROR_PTR;
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if(n<2)
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return ERROR_SIZE;
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switch(win_type & DSPL_WIN_SYM_MASK)
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{
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case DSPL_WIN_SYMMETRIC: x = 1.0/(double)(n-1); break;
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case DSPL_WIN_PERIODIC : x = 1.0/(double)n; break;
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default: return ERROR_WIN_SYM;
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}
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y = 0.0;
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for(i = 0; i<n; i++)
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{
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w[i] = 0.62 - 0.48 * fabs(y-0.5)-0.38*cos(M_2PI*y);
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y += x;
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}
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return RES_OK;
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}
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/******************************************************************************
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Blackman window function
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******************************************************************************/
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int win_blackman(double *w, int n, int win_type)
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{
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double y;
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double x = 0.0;
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int i;
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if(!w)
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return ERROR_PTR;
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if(n<2)
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return ERROR_SIZE;
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switch(win_type & DSPL_WIN_SYM_MASK)
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{
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case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
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case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
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default: return ERROR_WIN_SYM;
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}
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y = 0.0;
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for(i = 0; i<n; i++)
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{
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w[i] = 0.42 - 0.5* cos(y)+0.08*cos(2.0*y);
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y += x;
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}
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return RES_OK;
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}
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/******************************************************************************
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Blackman - Harris window function
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******************************************************************************/
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int win_blackman_harris(double *w, int n, int win_type)
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{
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double y;
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double x = 0.0;
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double a0 = 0.35875;
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double a1 = 0.48829;
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double a2 = 0.14128;
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double a3 = 0.01168;
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int i;
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if(!w)
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return ERROR_PTR;
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if(n<2)
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return ERROR_SIZE;
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switch(win_type & DSPL_WIN_SYM_MASK)
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{
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case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i<n; i++)
|
||
{
|
||
w[i] = a0 - a1* cos(y)+a2*cos(2.0*y)-a3*cos(3.0*y);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Blackman - Nuttull window function
|
||
******************************************************************************/
|
||
int win_blackman_nuttall(double *w, int n, int win_type)
|
||
{
|
||
double y;
|
||
double x = 0.0;
|
||
double a0 = 0.3635819;
|
||
double a1 = 0.4891775;
|
||
double a2 = 0.1365995;
|
||
double a3 = 0.0106411;
|
||
int i;
|
||
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i<n; i++)
|
||
{
|
||
w[i] = a0 - a1* cos(y)+a2*cos(2.0*y)-a3*cos(3.0*y);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Chebyshev parametric window function
|
||
param sets spectrum sidelobes level in dB
|
||
ATTENTION! ONLY SYMMETRIC WINDOW
|
||
*******************************************************************************/
|
||
int win_cheby(double *w, int n, double param)
|
||
{
|
||
int k, i, m;
|
||
double z, dz, sum = 0, wmax=0, r1, x0, chx, chy, in;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
if(param <= 0.0)
|
||
return ERROR_WIN_PARAM;
|
||
|
||
r1 = pow(10, param/20);
|
||
x0 = cosh((1.0/(double)(n-1)) * acosh(r1));
|
||
|
||
/* check window length even or odd */
|
||
if(n%2==0)
|
||
{
|
||
dz = 0.5;
|
||
m = n/2-1;
|
||
}
|
||
else
|
||
{
|
||
m = (n-1)/2;
|
||
dz = 0.0;
|
||
}
|
||
|
||
for(k = 0; k < m+2; k++)
|
||
{
|
||
z = (double)(k - m) - dz;
|
||
sum = 0;
|
||
|
||
for(i = 1; i <= m; i++)
|
||
{
|
||
in = (double)i / (double)n;
|
||
chx = x0 * cos(M_PI * in);
|
||
cheby_poly1(&chx, 1, n-1, &chy);
|
||
sum += chy * cos(2.0 * z * M_PI * in);
|
||
}
|
||
|
||
w[k] = r1 + 2.0 * sum;
|
||
w[n-1-k] = w[k];
|
||
|
||
/* max value calculation */
|
||
if(w[k]>wmax)
|
||
wmax=w[k];
|
||
}
|
||
|
||
/* normalization */
|
||
for(k=0; k < n; k++)
|
||
w[k] /= wmax;
|
||
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Cosine window function
|
||
******************************************************************************/
|
||
int win_cos(double *w, int n, int win_type)
|
||
{
|
||
double y;
|
||
double x = 0.0;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i<n; i++)
|
||
{
|
||
w[i] = sin(y);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Flat - Top window function
|
||
******************************************************************************/
|
||
int win_flat_top(double *w, int n, int win_type)
|
||
{
|
||
double y;
|
||
double x = 0.0;
|
||
double a0 = 1.0;
|
||
double a1 = 1.93;
|
||
double a2 = 1.29;
|
||
double a3 = 0.388;
|
||
double a4 = 0.032;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i<n; i++)
|
||
{
|
||
w[i] = a0 - a1* cos(y)+a2*cos(2.0*y)-a3*cos(3.0*y)+a4*cos(4.0*y);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Gaussian window function
|
||
******************************************************************************/
|
||
int win_gaussian(double *w, int n, int win_type, double alpha)
|
||
{
|
||
double a = 0.0;
|
||
double y;
|
||
double sigma;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: a = (double)(n-1)*0.5; break;
|
||
case DSPL_WIN_PERIODIC : a = (double)(n)*0.5; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
|
||
sigma = 1.0 / (alpha * a);
|
||
for(i = 0; i<n; i++)
|
||
{
|
||
y = ((double)i - a)*sigma;
|
||
w[i] = exp(-0.5*y*y);
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Hamming window function
|
||
******************************************************************************/
|
||
int win_hamming(double *w, int n, int win_type)
|
||
{
|
||
double x = 0.0;
|
||
double y;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i < n; i++)
|
||
{
|
||
w[i] = 0.54-0.46*cos(y);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Hann window function
|
||
******************************************************************************/
|
||
int win_hann(double *w, int n, int win_type)
|
||
{
|
||
double x = 0.0;
|
||
double y;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i < n; i++)
|
||
{
|
||
w[i] = 0.5*(1-cos(y));
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
/******************************************************************************
|
||
Kaiser window function
|
||
******************************************************************************/
|
||
int win_kaiser(double* w, int n, int win_type, double param)
|
||
{
|
||
double num, den, x, y, L;
|
||
int i, err;
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: L = (double)(n-1) / 2.0; break;
|
||
case DSPL_WIN_PERIODIC : L = (double)n / 2.0; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
err = bessel_i0(¶m, 1, &den);
|
||
if(err != RES_OK)
|
||
return err;
|
||
for(i = 0; i < n; i++)
|
||
{
|
||
x = 2.0*((double)i - L) / (double)n;
|
||
y = param * sqrt(1.0 - x*x);
|
||
err = bessel_i0(&y, 1, &num);
|
||
if(err != RES_OK)
|
||
return err;
|
||
w[i] = num / den;
|
||
}
|
||
return err;
|
||
}
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Lanczos window function
|
||
******************************************************************************/
|
||
int win_lanczos(double *w, int n, int win_type)
|
||
{
|
||
double y;
|
||
double x = 0.0;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i < n; i++)
|
||
{
|
||
if((y - M_PI)==0.0)
|
||
w[i] = 1.0;
|
||
else
|
||
w[i] = sin(y - M_PI)/(y - M_PI);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
|
||
}
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Nuttall window function
|
||
******************************************************************************/
|
||
int win_nuttall(double *w, int n, int win_type)
|
||
{
|
||
double y;
|
||
double x = 0.0;
|
||
double a0 = 0.355768;
|
||
double a1 = 0.487396;
|
||
double a2 = 0.144232;
|
||
double a3 = 0.012604;
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
switch(win_type & DSPL_WIN_SYM_MASK)
|
||
{
|
||
case DSPL_WIN_SYMMETRIC: x = M_2PI/(double)(n-1); break;
|
||
case DSPL_WIN_PERIODIC : x = M_2PI/(double)n; break;
|
||
default: return ERROR_WIN_SYM;
|
||
}
|
||
|
||
y = 0.0;
|
||
for(i = 0; i < n; i++)
|
||
{
|
||
w[i] = a0 - a1* cos(y)+a2*cos(2.0*y)-a3*cos(3.0*y);
|
||
y += x;
|
||
}
|
||
return RES_OK;
|
||
}
|
||
|
||
|
||
|
||
|
||
|
||
/******************************************************************************
|
||
Rectangle window function
|
||
******************************************************************************/
|
||
int win_rect(double *w, int n)
|
||
{
|
||
int i;
|
||
|
||
if(!w)
|
||
return ERROR_PTR;
|
||
if(n<2)
|
||
return ERROR_SIZE;
|
||
|
||
for(i = 0; i < n; i++)
|
||
w[i] = 1.0;
|
||
return RES_OK;
|
||
}
|
||
|