annotate libtwamr/a_refl.c @ 478:936a08cc73ce

doc/AMR-library-API: describe the decoder
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 19 May 2024 21:32:31 +0000
parents 07f936338de1
children
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1 /*
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2 ********************************************************************************
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3 *
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4 * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001
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5 * R99 Version 3.3.0
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6 * REL-4 Version 4.1.0
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7 *
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8 ********************************************************************************
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9 *
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10 * File : a_refl.c
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11 * Purpose : Convert from direct form coefficients to
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12 * reflection coefficients
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13 *
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14 ********************************************************************************
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15 */
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16 /*
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17 ********************************************************************************
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18 * MODULE INCLUDE FILE AND VERSION ID
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19 ********************************************************************************
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20 */
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21 #include "namespace.h"
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22 #include "a_refl.h"
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23
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24
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25 /*
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26 ********************************************************************************
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27 * INCLUDE FILES
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28 ********************************************************************************
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29 */
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30 #include "typedef.h"
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31 #include "basic_op.h"
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32 #include "oper_32b.h"
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33 #include "no_count.h"
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34 #include "cnst.h"
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35
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36 /*
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37 ********************************************************************************
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38 * LOCAL VARIABLES AND TABLES
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39 ********************************************************************************
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40 */
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41
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42 /*
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43 ********************************************************************************
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44 * PUBLIC PROGRAM CODE
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45 ********************************************************************************
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46 */
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47 /*
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48 **************************************************************************
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49 *
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50 * Function : A_Refl
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51 *
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52 **************************************************************************
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53 */
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54 void A_Refl(
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55 Word16 a[], /* i : Directform coefficients */
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56 Word16 refl[] /* o : Reflection coefficients */
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57 )
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58 {
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59 /* local variables */
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60 Word16 i,j;
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61 Word16 aState[M];
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62 Word16 bState[M];
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63 Word16 normShift;
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64 Word16 normProd;
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65 Word32 L_acc;
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66 Word16 scale;
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67 Word32 L_temp;
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68 Word16 temp;
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69 Word16 mult;
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70
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71 /* initialize states */
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72 for (i = 0; i < M; i++)
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73 {
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74 aState[i] = a[i]; move16 ();
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75 }
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76
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77 /* backward Levinson recursion */
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78 for (i = M-1; i >= 0; i--)
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79 {
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80 if (sub(abs_s(aState[i]), 4096) >= 0)
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81 {
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82 goto ExitRefl;
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83 }
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84
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85 refl[i] = shl(aState[i], 3);
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86
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87 L_temp = L_mult(refl[i], refl[i]);
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88 L_acc = L_sub(MAX_32, L_temp);
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89
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90 normShift = norm_l(L_acc);
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91 scale = sub(15, normShift);
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92
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93 L_acc = L_shl(L_acc, normShift);
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94 normProd = round(L_acc);
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95
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96 mult = div_s(16384, normProd);
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97
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98 for (j = 0; j < i; j++)
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99 {
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100 L_acc = L_deposit_h(aState[j]);
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101 L_acc = L_msu(L_acc, refl[i], aState[i-j-1]);
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102
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103 temp = round(L_acc);
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104 L_temp = L_mult(mult, temp);
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105 L_temp = L_shr_r(L_temp, scale);
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106
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107 if (L_sub(L_abs(L_temp), 32767) > 0)
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108 {
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109 goto ExitRefl;
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110 }
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111
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112 bState[j] = extract_l(L_temp);
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113 }
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114
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115 for (j = 0; j < i; j++)
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116 {
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117 aState[j] = bState[j]; move16 ();
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118 }
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119 }
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120 return;
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121
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122 ExitRefl:
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123 for (i = 0; i < M; i++)
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124 {
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125 refl[i] = 0; move16 ();
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126 }
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127 }