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annotate libgsmefr/agc.c @ 53:49dd1ac8e75b

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libgsmefr: import most *.c files from ETSI source
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 25 Nov 2022 16:18:21 +0000
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children 7b11cbe99a0e
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49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
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1 /*************************************************************************
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2 *
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3 * FUNCTION: agc
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4 *
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5 * PURPOSE: Scales the postfilter output on a subframe basis by automatic
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6 * control of the subframe gain.
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7 *
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8 * DESCRIPTION:
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9 * sig_out[n] = sig_out[n] * gain[n];
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10 * where gain[n] is the gain at the nth sample given by
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11 * gain[n] = agc_fac * gain[n-1] + (1 - agc_fac) g_in/g_out
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12 * g_in/g_out is the square root of the ratio of energy at the input
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13 * and output of the postfilter.
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14 *
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15 *************************************************************************/
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16
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17 #include "typedef.h"
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18 #include "basic_op.h"
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19 #include "count.h"
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20 #include "sig_proc.h"
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21 #include "cnst.h"
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22
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23 Word16 past_gain; /* initial value of past_gain = 1.0 */
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24
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25 void agc (
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26 Word16 *sig_in, /* (i) : postfilter input signal */
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27 Word16 *sig_out, /* (i/o) : postfilter output signal */
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28 Word16 agc_fac, /* (i) : AGC factor */
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29 Word16 l_trm /* (i) : subframe size */
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30 )
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31 {
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32 Word16 i, exp;
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33 Word16 gain_in, gain_out, g0, gain;
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34 Word32 s;
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35
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36 Word16 temp;
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37
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38 /* calculate gain_out with exponent */
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39
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40 temp = shr (sig_out[0], 2);
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41 s = L_mult (temp, temp);
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42
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43 for (i = 1; i < l_trm; i++)
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44 {
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45 temp = shr (sig_out[i], 2);
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46 s = L_mac (s, temp, temp);
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47 }
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48
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49 test ();
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50 if (s == 0)
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51 {
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52 past_gain = 0; move16 ();
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53 return;
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54 }
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55 exp = sub (norm_l (s), 1);
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56 gain_out = round (L_shl (s, exp));
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57
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58 /* calculate gain_in with exponent */
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59
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60 temp = shr (sig_in[0], 2);
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61 s = L_mult (temp, temp);
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62
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63 for (i = 1; i < l_trm; i++)
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64 {
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65 temp = shr (sig_in[i], 2);
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66 s = L_mac (s, temp, temp);
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67 }
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68
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69 test ();
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70 if (s == 0)
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71 {
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72 g0 = 0; move16 ();
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73 }
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74 else
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75 {
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76 i = norm_l (s);
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77 gain_in = round (L_shl (s, i));
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78 exp = sub (exp, i);
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79
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80 /*---------------------------------------------------*
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81 * g0 = (1-agc_fac) * sqrt(gain_in/gain_out); *
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82 *---------------------------------------------------*/
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83
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84 s = L_deposit_l (div_s (gain_out, gain_in));
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85 s = L_shl (s, 7); /* s = gain_out / gain_in */
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86 s = L_shr (s, exp); /* add exponent */
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87
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88 s = Inv_sqrt (s);
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89 i = round (L_shl (s, 9));
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90
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91 /* g0 = i * (1-agc_fac) */
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92 g0 = mult (i, sub (32767, agc_fac));
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93 }
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94
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95 /* compute gain[n] = agc_fac * gain[n-1]
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96 + (1-agc_fac) * sqrt(gain_in/gain_out) */
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97 /* sig_out[n] = gain[n] * sig_out[n] */
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98
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99 gain = past_gain; move16 ();
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100
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101 for (i = 0; i < l_trm; i++)
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102 {
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103 gain = mult (gain, agc_fac);
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104 gain = add (gain, g0);
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105 sig_out[i] = extract_h (L_shl (L_mult (sig_out[i], gain), 3));
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106 move16 ();
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107 }
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108
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109 past_gain = gain; move16 ();
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110
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111 return;
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112 }
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113
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114 void agc2 (
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115 Word16 *sig_in, /* (i) : postfilter input signal */
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116 Word16 *sig_out, /* (i/o) : postfilter output signal */
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117 Word16 l_trm /* (i) : subframe size */
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118 )
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119 {
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120 Word16 i, exp;
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121 Word16 gain_in, gain_out, g0;
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122 Word32 s;
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123
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124 Word16 temp;
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125
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126 /* calculate gain_out with exponent */
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127
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128 temp = shr (sig_out[0], 2);
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129 s = L_mult (temp, temp);
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130 for (i = 1; i < l_trm; i++)
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131 {
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132 temp = shr (sig_out[i], 2);
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133 s = L_mac (s, temp, temp);
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134 }
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135
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136 test ();
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137 if (s == 0)
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138 {
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139 return;
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140 }
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141 exp = sub (norm_l (s), 1);
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142 gain_out = round (L_shl (s, exp));
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143
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144 /* calculate gain_in with exponent */
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145
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146 temp = shr (sig_in[0], 2);
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147 s = L_mult (temp, temp);
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148 for (i = 1; i < l_trm; i++)
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149 {
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150 temp = shr (sig_in[i], 2);
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151 s = L_mac (s, temp, temp);
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152 }
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153
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154 test ();
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155 if (s == 0)
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156 {
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
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157 g0 = 0; move16 ();
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158 }
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159 else
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160 {
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161 i = norm_l (s);
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162 gain_in = round (L_shl (s, i));
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163 exp = sub (exp, i);
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164
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165 /*---------------------------------------------------*
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166 * g0 = sqrt(gain_in/gain_out); *
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167 *---------------------------------------------------*/
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168
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169 s = L_deposit_l (div_s (gain_out, gain_in));
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170 s = L_shl (s, 7); /* s = gain_out / gain_in */
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parents:
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171 s = L_shr (s, exp); /* add exponent */
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parents:
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172
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173 s = Inv_sqrt (s);
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
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174 g0 = round (L_shl (s, 9));
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
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parents:
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175 }
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parents:
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176
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177 /* sig_out(n) = gain(n) sig_out(n) */
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Mychaela Falconia <falcon@freecalypso.org>
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178
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179 for (i = 0; i < l_trm; i++)
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180 {
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
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181 sig_out[i] = extract_h (L_shl (L_mult (sig_out[i], g0), 3));
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Mychaela Falconia <falcon@freecalypso.org>
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182 move16 ();
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Mychaela Falconia <falcon@freecalypso.org>
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183 }
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
184
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
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185 return;
49dd1ac8e75b libgsmefr: import most *.c files from ETSI source
Mychaela Falconia <falcon@freecalypso.org>
parents:
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186 }