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127 satır
5.2 KiB
127 satır
5.2 KiB
/* GSL - Generic Sound Layer
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* Copyright (C) 2001 Tim Janik
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Lesser 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
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* Public License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef __GSL_FFT_H__
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#define __GSL_FFT_H__
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#include <gsl/gsldefs.h>
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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/**
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* gsl_power2_fftac
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* @n_values: Number of complex values
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* @ri_values_in: Complex sample values [0..n_values*2-1]
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* @ri_values_out: Complex frequency values [0..n_values*2-1]
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* This function performs a decimation in time fourier transformation
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* in forward direction, where the input values are equidistant sampled
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* data, and the output values contain the frequency proportions of the
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* input.
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* The input and output arrays are complex values with real and imaginery
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* portions interleaved, adressable in the range [0..2*n_values-1], where
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* n_values must be a power of two.
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* Frequencies are stored in-order, the K-th output corresponds to the
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* frequency K/n_values. (If you want to interpret negative frequencies,
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* note that the frequencies -K/n_values and (n_values-K)/n_values are
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* equivalent).
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* Note that the transformation is performed out of place, the input
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* array is not modified, and may not overlap with the output array.
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*/
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void gsl_power2_fftac (const unsigned int n_values,
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const double *ri_values_in,
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double *ri_values_out);
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/**
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* gsl_power2_fftsc
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* @n_values: Number of complex values
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* @ri_values_in: Complex frequency values [0..n_values*2-1]
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* @ri_values_out: Complex sample values [0..n_values*2-1]
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* This function performs a decimation in time fourier transformation
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* in backwards direction with normalization. As such, this function
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* represents the counterpart to gsl_power2_fftac(), that is, a value
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* array which is transformed into the frequency domain with
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* gsl_power2_fftac() can be reconstructed by issuing gsl_power2_fftsc()
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* on the transform.
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* Note that the transformation is performed out of place, the input
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* array is not modified, and may not overlap with the output array.
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*/
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void gsl_power2_fftsc (const unsigned int n_values,
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const double *ri_values_in,
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double *ri_values_out);
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/**
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* gsl_power2_fftar
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* @n_values: Number of complex values
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* @r_values_in: Real sample values [0..n_values-1]
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* @ri_values_out: Complex frequency values [0..n_values-1]
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* Real valued variant of gsl_power2_fftac(), the input array contains
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* real valued equidistant sampled data [0..n_values-1], and the output
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* array contains the positive frequency half of the complex valued
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* fourier transform. Note, that the complex valued fourier transform H
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* of a purely real valued set of data, satisfies H(-f) = Conj(H(f)),
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* where Conj() denotes the complex conjugate, so that just the positive
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* frequency half suffices to describe the entire frequency spectrum.
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* Even so, the resulting n_values/2 complex frequencies are one value
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* off in storage size, but the resulting frequencies H(0) and
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* H(n_values/2) are both real valued, so the real portion of
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* H(n_values/2) is stored in ri_values_out[1] (the imaginery part of
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* H(0)), so that both r_values_in and ri_values_out can be of size
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* n_values.
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* Note that the transformation is performed out of place, the input
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* array is not modified, and may not overlap with the output array.
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*/
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void gsl_power2_fftar (const unsigned int n_values,
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const double *r_values_in,
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double *ri_values_out);
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/**
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* gsl_power2_fftsr
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* @n_values: Number of complex values
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* @ri_values_in: Complex frequency values [0..n_values-1]
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* @r_values_out: Real sample values [0..n_values-1]
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* Real valued variant of gsl_power2_fftsc(), counterpart to
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* gsl_power2_fftar(), using the same frequency storage format.
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* A real valued data set transformed into the frequency domain
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* with gsl_power2_fftar() can be reconstructed using this function.
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* Note that the transformation is performed out of place, the input
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* array is not modified, and may not overlap with the output array.
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*/
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void gsl_power2_fftsr (const unsigned int n_values,
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const double *ri_values_in,
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double *r_values_out);
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/* --- convenience wrappers --- */
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void gsl_power2_fftar_simple (const unsigned int n_values,
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const float *real_values,
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float *complex_values);
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void gsl_power2_fftsr_simple (const unsigned int n_values,
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const float *complex_values,
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float *real_values);
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#ifdef __cplusplus
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}
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#endif /* __cplusplus */
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#endif /* __GSL_FFT_H__ */ /* vim:set ts=8 sw=2 sts=2: */
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