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/*
** Copyright (C) 2002-2004 Erik de Castro Lopo <erikd@mega-nerd.com>
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program 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 General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "dft_cmp.h"
#include "utils.h"
#ifndef M_PI
#define M_PI 3.14159265358979323846264338
#endif
#define DFT_SPEC_LENGTH (DFT_DATA_LENGTH / 2)
static void dft_magnitude (const double *data, double *spectrum) ;
static double calc_max_spectral_difference (double *spec1, double *spec2) ;
/*--------------------------------------------------------------------------------
** Public functions.
*/
double
dft_cmp (int linenum, double *orig, double *test, int len, double target_snr, int allow_exit)
{ static double orig_spec [DFT_SPEC_LENGTH] ;
static double test_spec [DFT_SPEC_LENGTH] ;
double snr ;
if (! orig || ! test)
{ printf ("Error (line % d) : dft_cmp : Bad input arrays.\n", linenum) ;
return 1 ;
} ;
if (len != DFT_DATA_LENGTH)
{ printf ("Error (line % d) : dft_cmp : Bad input array length.\n", linenum) ;
return 1 ;
} ;
dft_magnitude (orig, orig_spec) ;
dft_magnitude (test, test_spec) ;
snr = calc_max_spectral_difference (orig_spec, test_spec) ;
if (snr > target_snr)
{ printf ("\n\nLine %d: Actual SNR (% 4.1f) > target SNR (% 4.1f).\n\n", linenum, snr, target_snr) ;
oct_save_double (orig, test, len) ;
if (allow_exit)
exit (1) ;
} ;
if (snr < -500.0)
snr = -500.0 ;
return snr ;
} /* dft_cmp */
/*--------------------------------------------------------------------------------
** Quick dirty calculation of magnitude spectrum for real valued data using
** Discrete Fourier Transform. Since the data is real, the DFT is only
** calculated for positive frequencies.
*/
static void
dft_magnitude (const double *data, double *spectrum)
{ static double cos_angle [DFT_DATA_LENGTH] = { 0.0 } ;
static double sin_angle [DFT_DATA_LENGTH] ;
double real_part, imag_part ;
int k, n ;
/* If sine and cosine tables haven't been initialised, do so. */
if (cos_angle [0] == 0.0)
for (n = 0 ; n < DFT_DATA_LENGTH ; n++)
{ cos_angle [n] = cos (2.0 * M_PI * n / DFT_DATA_LENGTH) ;
sin_angle [n] = -1.0 * sin (2.0 * M_PI * n / DFT_DATA_LENGTH) ;
} ;
/* DFT proper. Since the data is real, only generate a half spectrum. */
for (k = 1 ; k < DFT_SPEC_LENGTH ; k++)
{ real_part = 0.0 ;
imag_part = 0.0 ;
for (n = 0 ; n < DFT_DATA_LENGTH ; n++)
{ real_part += data [n] * cos_angle [(k * n) % DFT_DATA_LENGTH] ;
imag_part += data [n] * sin_angle [(k * n) % DFT_DATA_LENGTH] ;
} ;
spectrum [k] = sqrt (real_part * real_part + imag_part * imag_part) ;
} ;
spectrum [k] = 0.0 ;
spectrum [0] = spectrum [1] = spectrum [2] = spectrum [3] = spectrum [4] = 0.0 ;
return ;
} /* dft_magnitude */
static double
calc_max_spectral_difference (double *orig, double *test)
{ double orig_max = 0.0, max_diff = 0.0 ;
int k ;
for (k = 0 ; k < DFT_SPEC_LENGTH ; k++)
{ if (orig_max < orig [k])
orig_max = orig [k] ;
if (max_diff < fabs (orig [k] - test [k]))
max_diff = fabs (orig [k] - test [k]) ;
} ;
if (max_diff < 1e-25)
return -500.0 ;
return 20.0 * log10 (max_diff / orig_max) ;
} /* calc_max_spectral_difference */
/*
** Do not edit or modify anything in this comment block.
** The arch-tag line is a file identity tag for the GNU Arch
** revision control system.
**
** arch-tag: cba7ffe2-bafe-44bd-b57a-15def3408410
*/
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