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