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2 /******************************************************************
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4 iLBC Speech Coder ANSI-C Source Code
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11 gainquant.c
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13 Copyright (C) The Internet Society (2004).
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14 All Rights Reserved.
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15
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16 ******************************************************************/
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17
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18 #include <string.h>
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19 #include <math.h>
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20 #include "constants.h"
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21 #include "filter.h"
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22
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23 /*----------------------------------------------------------------*
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24 * quantizer for the gain in the gain-shape coding of residual
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25 *---------------------------------------------------------------*/
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26
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27 float gainquant( /* (o) quantized gain value */
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28 float in, /* (i) gain value */
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29 float maxIn, /* (i) maximum of gain value */
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30 int cblen, /* (i) number of quantization indices */
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31 int *index /* (o) quantization index */
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32 )
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33 {
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34 int i, tindex;
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35 float minmeasure, measure, *cb, scale;
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36
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37 /* ensure a lower bound on the scaling factor */
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38
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39 scale = maxIn;
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40
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41 if (scale < 0.1) {
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42 scale = (float) 0.1;
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43 }
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44
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45 /* select the quantization table */
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46
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47 if (cblen == 8) {
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48 cb = gain_sq3Tbl;
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49 } else if (cblen == 16) {
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50 cb = gain_sq4Tbl;
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51 } else {
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52 cb = gain_sq5Tbl;
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53 }
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54
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55 /* select the best index in the quantization table */
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56
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57 minmeasure = 10000000.0;
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58 tindex = 0;
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59 for (i = 0; i < cblen; i++) {
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60
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61
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62
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63
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64
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65 measure = (in - scale * cb[i]) * (in - scale * cb[i]);
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66
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67 if (measure < minmeasure) {
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68 tindex = i;
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69 minmeasure = measure;
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70 }
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71 }
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72 *index = tindex;
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73
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74 /* return the quantized value */
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75
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76 return scale * cb[tindex];
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77 }
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78
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79 /*----------------------------------------------------------------*
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80 * decoder for quantized gains in the gain-shape coding of
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81 * residual
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82 *---------------------------------------------------------------*/
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83
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84 float gaindequant( /* (o) quantized gain value */
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85 int index, /* (i) quantization index */
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86 float maxIn, /* (i) maximum of unquantized gain */
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87 int cblen /* (i) number of quantization indices */
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88 )
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89 {
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90 float scale;
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91
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92 /* obtain correct scale factor */
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93
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94 scale = (float) fabs(maxIn);
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95
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96 if (scale < 0.1) {
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97 scale = (float) 0.1;
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98 }
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99
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100 /* select the quantization table and return the decoded value */
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101
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102 if (cblen == 8) {
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103 return scale * gain_sq3Tbl[index];
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104 } else if (cblen == 16) {
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105 return scale * gain_sq4Tbl[index];
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106 } else if (cblen == 32) {
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107 return scale * gain_sq5Tbl[index];
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108 }
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109
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110 return 0.0;
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111 }
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