FreeCalypso > hg > gsm-codec-lib

annotate libgsmefr/agc.c @ 282:9ee8ad3d4d30

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frtest: rm gsmfr-hand-test and gsmfr-max-out utils These hack programs were never properly documented and were written only as part of a debug chase, in pursuit of a bug that ultimately turned out to be in our then-hacky patch to osmo-bts-sysmo, before beginning of proper patches in Osmocom. These hack programs need to be dropped from the present sw package because they depend on old libgsm, and we are eliminating that dependency.
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 14 Apr 2024 05:44:47 +0000
parents 7b11cbe99a0e
children
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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 "gsm_efr.h"
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18 #include "typedef.h"
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19 #include "namespace.h"
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20 #include "basic_op.h"
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21 #include "no_count.h"
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22 #include "cnst.h"
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23 #include "dec_state.h"
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24 #include "sig_proc.h"
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25
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26 void agc (
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27 struct EFR_decoder_state *st,
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28 Word16 *sig_in, /* (i) : postfilter input signal */
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29 Word16 *sig_out, /* (i/o) : postfilter output signal */
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30 Word16 agc_fac, /* (i) : AGC factor */
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31 Word16 l_trm /* (i) : subframe size */
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32 )
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33 {
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34 Word16 i, exp;
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35 Word16 gain_in, gain_out, g0, gain;
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36 Word32 s;
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37
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38 Word16 temp;
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39
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40 /* calculate gain_out with exponent */
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41
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42 temp = shr (sig_out[0], 2);
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43 s = L_mult (temp, temp);
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45 for (i = 1; i < l_trm; i++)
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46 {
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47 temp = shr (sig_out[i], 2);
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48 s = L_mac (s, temp, temp);
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49 }
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50
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51 if (s == 0)
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52 {
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53 st->past_gain = 0;
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54 return;
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55 }
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56 exp = sub (norm_l (s), 1);
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57 gain_out = round (L_shl (s, exp));
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58
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59 /* calculate gain_in with exponent */
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61 temp = shr (sig_in[0], 2);
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62 s = L_mult (temp, temp);
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63
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64 for (i = 1; i < l_trm; i++)
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65 {
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66 temp = shr (sig_in[i], 2);
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67 s = L_mac (s, temp, temp);
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68 }
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70 if (s == 0)
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71 {
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72 g0 = 0;
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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 = st->past_gain;
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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 }
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107
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108 st->past_gain = gain;
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109
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110 return;
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111 }
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112
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113 void agc2 (
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114 Word16 *sig_in, /* (i) : postfilter input signal */
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115 Word16 *sig_out, /* (i/o) : postfilter output signal */
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116 Word16 l_trm /* (i) : subframe size */
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117 )
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118 {
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119 Word16 i, exp;
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120 Word16 gain_in, gain_out, g0;
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121 Word32 s;
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122
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123 Word16 temp;
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124
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125 /* calculate gain_out with exponent */
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126
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127 temp = shr (sig_out[0], 2);
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128 s = L_mult (temp, temp);
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129 for (i = 1; i < l_trm; i++)
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130 {
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131 temp = shr (sig_out[i], 2);
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132 s = L_mac (s, temp, temp);
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133 }
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134
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135 test ();
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136 if (s == 0)
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137 {
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138 return;
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139 }
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140 exp = sub (norm_l (s), 1);
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141 gain_out = round (L_shl (s, exp));
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142
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143 /* calculate gain_in with exponent */
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144
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145 temp = shr (sig_in[0], 2);
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146 s = L_mult (temp, temp);
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147 for (i = 1; i < l_trm; i++)
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148 {
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149 temp = shr (sig_in[i], 2);
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150 s = L_mac (s, temp, temp);
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151 }
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152
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153 test ();
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154 if (s == 0)
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155 {
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156 g0 = 0; move16 ();
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157 }
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158 else
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159 {
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160 i = norm_l (s);
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161 gain_in = round (L_shl (s, i));
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162 exp = sub (exp, i);
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163
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164 /*---------------------------------------------------*
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165 * g0 = sqrt(gain_in/gain_out); *
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166 *---------------------------------------------------*/
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167
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168 s = L_deposit_l (div_s (gain_out, gain_in));
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169 s = L_shl (s, 7); /* s = gain_out / gain_in */
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170 s = L_shr (s, exp); /* add exponent */
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171
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172 s = Inv_sqrt (s);
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173 g0 = round (L_shl (s, 9));
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174 }
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175
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176 /* sig_out(n) = gain(n) sig_out(n) */
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177
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178 for (i = 0; i < l_trm; i++)
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179 {
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180 sig_out[i] = extract_h (L_shl (L_mult (sig_out[i], g0), 3));
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181 move16 ();
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182 }
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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183
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184 return;
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Mychaela Falconia <falcon@freecalypso.org>
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185 }