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5
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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * awgn_tests.c
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2001 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: awgn_tests.c,v 1.12 2006/11/19 14:07:26 steveu Exp $
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26 */
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27
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28 /*! \page awgn_tests_page AWGN tests
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29 \section awgn_tests_page_sec_1 What does it do?
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30 */
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31
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32 #ifdef HAVE_CONFIG_H
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33 #include "config.h"
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34 #endif
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35
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36 #include <stdio.h>
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37 #include <inttypes.h>
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38 #include <stdlib.h>
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39 #include <string.h>
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40 #if defined(HAVE_TGMATH_H)
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41 #include <tgmath.h>
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42 #endif
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43 #if defined(HAVE_MATH_H)
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44 #include <math.h>
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45 #endif
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46 #include <tiffio.h>
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47
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48 #include "spandsp.h"
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49
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50 #if !defined(M_PI)
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51 # define M_PI 3.14159265358979323846 /* pi */
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52 #endif
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53
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54 #define OUT_FILE_NAME "awgn.wav"
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55
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56 /* Some simple sanity tests for the Gaussian noise generation routines */
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57
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58 int main (int argc, char *argv[])
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59 {
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60 int i;
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61 int j;
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62 int clip_high;
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63 int clip_low;
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64 int total_samples;
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65 int idum = 1234567;
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66 int16_t value;
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67 double total;
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68 double x;
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69 double p;
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70 double o;
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71 double error;
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72 int bins[65536];
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73 awgn_state_t noise_source;
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74
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75 /* Generate noise at several RMS levels between -50dBm and 0dBm. Noise is
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76 generated for a large number of samples (1,000,000), and the RMS value
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77 of the noise is calculated along the way. If the resulting level is
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78 close to the requested RMS level, at least the scaling of the noise
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79 should be Ok. At high level some clipping may distort the result a
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80 little. */
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81 for (j = -50; j <= 0; j += 5)
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82 {
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83 clip_high = 0;
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84 clip_low = 0;
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85 total = 0.0;
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86 awgn_init_dbm0(&noise_source, idum, (float) j);
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87 total_samples = 1000000;
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88 for (i = 0; i < total_samples; i++)
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89 {
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90 value = awgn(&noise_source);
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91 if (value == 32767)
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92 clip_high++;
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93 else if (value == -32768)
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94 clip_low++;
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95 total += ((double) value)*((double) value);
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96 }
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97 error = 100.0*(1.0 - sqrt(total/total_samples)/noise_source.rms);
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98 printf("RMS = %.3f (expected %d) %.2f%% error [clipped samples %d+%d]\n",
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99 log10(sqrt(total/total_samples)/32768.0)*20.0 + DBM0_MAX_POWER,
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100 j,
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101 error,
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102 clip_low,
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103 clip_high);
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104 /* We don't check the result at 0dBm0, as there will definitely be a lot of error due to clipping */
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105 if (j < 0 && fabs(error) > 0.2)
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106 {
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107 printf("Test failed.\n");
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108 exit(2);
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109 }
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110 }
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111 /* Now look at the statistical spread of the results, by collecting data in
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112 bins from a large number of samples. Use a fairly high noise level, but
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113 low enough to avoid significant clipping. Use the Gaussian model to
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114 predict the real probability, and present the results for graphing. */
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115 memset(bins, 0, sizeof(bins));
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116 clip_high = 0;
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117 clip_low = 0;
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118 awgn_init_dbm0(&noise_source, idum, -15);
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119 total_samples = 10000000;
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120 for (i = 0; i < total_samples; i++)
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121 {
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122 value = awgn(&noise_source);
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123 if (value == 32767)
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124 clip_high++;
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125 else if (value == -32768)
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126 clip_low++;
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127 bins[value + 32768]++;
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128 }
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129 o = noise_source.rms;
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130 for (i = 0; i < 65536 - 10; i++)
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131 {
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132 x = i - 32768;
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133 /* Find the real probability for this bin */
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134 p = (1.0/(o*sqrt(2.0*M_PI)))*exp(-(x*x)/(2.0*o*o));
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135 /* Now do a little smoothing on the real data to get a reasonably
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136 steady answer */
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137 x = 0;
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138 for (j = 0; j < 10; j++)
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139 x += bins[i + j];
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140 x /= 10.0;
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141 x /= total_samples;
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142 /* Now send it out for graphing. */
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143 printf("%6d %.7f %.7f\n", i - 32768, x, p);
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144 }
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145
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146 printf("Tests passed.\n");
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147 return 0;
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148 }
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149 /*- End of function --------------------------------------------------------*/
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150 /*- End of file ------------------------------------------------------------*/
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