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/* GSL - Generic Sound Layer
* Copyright (C) 2001 Tim Janik
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#ifndef __GSL_FFT_H__
#define __GSL_FFT_H__
#include <gsl/gsldefs.h>
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/**
* gsl_power2_fftac
* @n_values: Number of complex values
* @ri_values_in: Complex sample values [0..n_values*2-1]
* @ri_values_out: Complex frequency values [0..n_values*2-1]
* This function performs a decimation in time fourier transformation
* in forward direction, where the input values are equidistant sampled
* data, and the output values contain the frequency proportions of the
* input.
* The input and output arrays are complex values with real and imaginery
* portions interleaved, adressable in the range [0..2*n_values-1], where
* n_values must be a power of two.
* Frequencies are stored in-order, the K-th output corresponds to the
* frequency K/n_values. (If you want to interpret negative frequencies,
* note that the frequencies -K/n_values and (n_values-K)/n_values are
* equivalent).
* Note that the transformation is performed out of place, the input
* array is not modified, and may not overlap with the output array.
*/
void gsl_power2_fftac (const unsigned int n_values,
const double *ri_values_in,
double *ri_values_out);
/**
* gsl_power2_fftsc
* @n_values: Number of complex values
* @ri_values_in: Complex frequency values [0..n_values*2-1]
* @ri_values_out: Complex sample values [0..n_values*2-1]
* This function performs a decimation in time fourier transformation
* in backwards direction with normalization. As such, this function
* represents the counterpart to gsl_power2_fftac(), that is, a value
* array which is transformed into the frequency domain with
* gsl_power2_fftac() can be reconstructed by issuing gsl_power2_fftsc()
* on the transform.
* Note that the transformation is performed out of place, the input
* array is not modified, and may not overlap with the output array.
*/
void gsl_power2_fftsc (const unsigned int n_values,
const double *ri_values_in,
double *ri_values_out);
/**
* gsl_power2_fftar
* @n_values: Number of complex values
* @r_values_in: Real sample values [0..n_values-1]
* @ri_values_out: Complex frequency values [0..n_values-1]
* Real valued variant of gsl_power2_fftac(), the input array contains
* real valued equidistant sampled data [0..n_values-1], and the output
* array contains the positive frequency half of the complex valued
* fourier transform. Note, that the complex valued fourier transform H
* of a purely real valued set of data, satisfies H(-f) = Conj(H(f)),
* where Conj() denotes the complex conjugate, so that just the positive
* frequency half suffices to describe the entire frequency spectrum.
* Even so, the resulting n_values/2 complex frequencies are one value
* off in storage size, but the resulting frequencies H(0) and
* H(n_values/2) are both real valued, so the real portion of
* H(n_values/2) is stored in ri_values_out[1] (the imaginery part of
* H(0)), so that both r_values_in and ri_values_out can be of size
* n_values.
* Note that the transformation is performed out of place, the input
* array is not modified, and may not overlap with the output array.
*/
void gsl_power2_fftar (const unsigned int n_values,
const double *r_values_in,
double *ri_values_out);
/**
* gsl_power2_fftsr
* @n_values: Number of complex values
* @ri_values_in: Complex frequency values [0..n_values-1]
* @r_values_out: Real sample values [0..n_values-1]
* Real valued variant of gsl_power2_fftsc(), counterpart to
* gsl_power2_fftar(), using the same frequency storage format.
* A real valued data set transformed into the frequency domain
* with gsl_power2_fftar() can be reconstructed using this function.
* Note that the transformation is performed out of place, the input
* array is not modified, and may not overlap with the output array.
*/
void gsl_power2_fftsr (const unsigned int n_values,
const double *ri_values_in,
double *r_values_out);
/* --- convenience wrappers --- */
void gsl_power2_fftar_simple (const unsigned int n_values,
const float *real_values,
float *complex_values);
void gsl_power2_fftsr_simple (const unsigned int n_values,
const float *complex_values,
float *real_values);
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* __GSL_FFT_H__ */
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