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annotate src/levinson.c @ 5:799b56cbccb6

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EFR2 decoder: add post-processing step from AMR
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 03 Apr 2024 06:09:10 +0000
parents 56410792419a
children
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1 /*************************************************************************
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2 *
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3 * FUNCTION: Levinson()
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4 *
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5 * PURPOSE: Levinson-Durbin algorithm in double precision. To compute the
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6 * LP filter parameters from the speech autocorrelations.
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7 *
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8 * DESCRIPTION:
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9 * R[i] autocorrelations.
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10 * A[i] filter coefficients.
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11 * K reflection coefficients.
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12 * Alpha prediction gain.
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13 *
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14 * Initialisation:
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15 * A[0] = 1
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16 * K = -R[1]/R[0]
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17 * A[1] = K
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18 * Alpha = R[0] * (1-K**2]
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19 *
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20 * Do for i = 2 to M
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21 *
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22 * S = SUM ( R[j]*A[i-j] ,j=1,i-1 ) + R[i]
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23 *
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24 * K = -S / Alpha
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25 *
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26 * An[j] = A[j] + K*A[i-j] for j=1 to i-1
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27 * where An[i] = new A[i]
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28 * An[i]=K
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29 *
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30 * Alpha=Alpha * (1-K**2)
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31 *
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32 * END
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33 *
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34 *************************************************************************/
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35
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36 #include "typedef.h"
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37 #include "basic_op.h"
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38 #include "oper_32b.h"
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39 #include "count.h"
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40
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41 /* Lpc order == 10 */
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42
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43 #define M 10
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44
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45 /* Last A(z) for case of unstable filter */
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46
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47 Word16 old_A[M + 1];
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48
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49 void Levinson (
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50 Word16 Rh[], /* (i) : Rh[m+1] Vector of autocorrelations (msb) */
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51 Word16 Rl[], /* (i) : Rl[m+1] Vector of autocorrelations (lsb) */
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52 Word16 A[], /* (o) : A[m] LPC coefficients (m = 10) */
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53 Word16 rc[] /* (o) : rc[4] First 4 reflection coefficients */
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54
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55 )
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56 {
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57 Word16 i, j;
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58 Word16 hi, lo;
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59 Word16 Kh, Kl; /* reflexion coefficient; hi and lo */
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60 Word16 alp_h, alp_l, alp_exp; /* Prediction gain; hi lo and exponent */
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61 Word16 Ah[M + 1], Al[M + 1]; /* LPC coef. in double prec. */
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62 Word16 Anh[M + 1], Anl[M + 1];/* LPC coef.for next iteration in double
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63 prec. */
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64 Word32 t0, t1, t2; /* temporary variable */
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65
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66 /* K = A[1] = -R[1] / R[0] */
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67
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68 t1 = L_Comp (Rh[1], Rl[1]);
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69 t2 = L_abs (t1); /* abs R[1] */
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70 t0 = Div_32 (t2, Rh[0], Rl[0]); /* R[1]/R[0] */
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71 test ();
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72 if (t1 > 0)
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73 t0 = L_negate (t0); /* -R[1]/R[0] */
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74 L_Extract (t0, &Kh, &Kl); /* K in DPF */
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75
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76 rc[0] = round (t0); move16 ();
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77
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78 t0 = L_shr (t0, 4); /* A[1] in */
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79 L_Extract (t0, &Ah[1], &Al[1]); /* A[1] in DPF */
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80
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81 /* Alpha = R[0] * (1-K**2) */
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82
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83 t0 = Mpy_32 (Kh, Kl, Kh, Kl); /* K*K */
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84 t0 = L_abs (t0); /* Some case <0 !! */
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85 t0 = L_sub ((Word32) 0x7fffffffL, t0); /* 1 - K*K */
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86 L_Extract (t0, &hi, &lo); /* DPF format */
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87 t0 = Mpy_32 (Rh[0], Rl[0], hi, lo); /* Alpha in */
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88
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89 /* Normalize Alpha */
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90
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91 alp_exp = norm_l (t0);
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92 t0 = L_shl (t0, alp_exp);
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93 L_Extract (t0, &alp_h, &alp_l); /* DPF format */
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94
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95 /*--------------------------------------*
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96 * ITERATIONS I=2 to M *
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97 *--------------------------------------*/
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98
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99 for (i = 2; i <= M; i++)
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100 {
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101 /* t0 = SUM ( R[j]*A[i-j] ,j=1,i-1 ) + R[i] */
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102
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103 t0 = 0; move32 ();
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104 for (j = 1; j < i; j++)
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105 {
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106 t0 = L_add (t0, Mpy_32 (Rh[j], Rl[j], Ah[i - j], Al[i - j]));
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107 }
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108 t0 = L_shl (t0, 4);
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109
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110 t1 = L_Comp (Rh[i], Rl[i]);
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111 t0 = L_add (t0, t1); /* add R[i] */
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112
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113 /* K = -t0 / Alpha */
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114
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115 t1 = L_abs (t0);
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116 t2 = Div_32 (t1, alp_h, alp_l); /* abs(t0)/Alpha */
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117 test ();
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118 if (t0 > 0)
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119 t2 = L_negate (t2); /* K =-t0/Alpha */
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120 t2 = L_shl (t2, alp_exp); /* denormalize; compare to Alpha */
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121 L_Extract (t2, &Kh, &Kl); /* K in DPF */
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122
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123 test ();
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124 if (sub (i, 5) < 0)
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125 {
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126 rc[i - 1] = round (t2); move16 ();
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127 }
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128 /* Test for unstable filter. If unstable keep old A(z) */
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129
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130 test ();
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131 if (sub (abs_s (Kh), 32750) > 0)
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132 {
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133 for (j = 0; j <= M; j++)
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134 {
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135 A[j] = old_A[j]; move16 ();
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136 }
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137
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138 for (j = 0; j < 4; j++)
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139 {
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140 rc[j] = 0; move16 ();
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Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
141 }
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
142
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
143 return;
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
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144 }
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
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145 /*------------------------------------------*
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Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
146 * Compute new LPC coeff. -> An[i] *
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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147 * An[j]= A[j] + K*A[i-j] , j=1 to i-1 *
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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148 * An[i]= K *
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Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
149 *------------------------------------------*/
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Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
150
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
151 for (j = 1; j < i; j++)
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Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
152 {
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
153 t0 = Mpy_32 (Kh, Kl, Ah[i - j], Al[i - j]);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
154 t0 = L_mac (t0, Ah[j], 32767);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
155 t0 = L_mac (t0, Al[j], 1);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
156 L_Extract (t0, &Anh[j], &Anl[j]);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
157 }
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
158 t2 = L_shr (t2, 4);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
159 L_Extract (t2, &Anh[i], &Anl[i]);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
160
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
161 /* Alpha = Alpha * (1-K**2) */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
162
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
163 t0 = Mpy_32 (Kh, Kl, Kh, Kl); /* K*K */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
164 t0 = L_abs (t0); /* Some case <0 !! */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
165 t0 = L_sub ((Word32) 0x7fffffffL, t0); /* 1 - K*K */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
166 L_Extract (t0, &hi, &lo); /* DPF format */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
167 t0 = Mpy_32 (alp_h, alp_l, hi, lo);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
168
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
169 /* Normalize Alpha */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
170
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
171 j = norm_l (t0);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
172 t0 = L_shl (t0, j);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
173 L_Extract (t0, &alp_h, &alp_l); /* DPF format */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
174 alp_exp = add (alp_exp, j); /* Add normalization to
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
175 alp_exp */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
176
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
177 /* A[j] = An[j] */
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
178
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
179 for (j = 1; j <= i; j++)
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
180 {
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
181 Ah[j] = Anh[j]; move16 ();
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
182 Al[j] = Anl[j]; move16 ();
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
183 }
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
184 }
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
185
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
186 A[0] = 4096; move16 ();
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
187 for (i = 1; i <= M; i++)
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
188 {
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
189 t0 = L_Comp (Ah[i], Al[i]);
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
190 old_A[i] = A[i] = round (L_shl (t0, 1));move16 (); move16 ();
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
191 }
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
192
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
193 return;
56410792419a src: original EFR source from ETSI
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
194 }