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annotate libtwamr/levinson.c @ 468:4104b0390fab

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author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 13 May 2024 07:21:09 +0000
parents c713061b6edf
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c713061b6edf libtwamr: integrate levinson.c
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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 : levinson.c
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11 * Purpose : Levinson-Durbin algorithm in double precision.
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12 * : To compute the LP filter parameters from the
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13 * : speech autocorrelations.
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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 /*
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19 *****************************************************************************
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20 * MODULE INCLUDE FILE AND VERSION ID
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21 *****************************************************************************
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22 */
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23 #include "namespace.h"
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24 #include "levinson.h"
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25
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26 /*
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27 *****************************************************************************
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28 * INCLUDE FILES
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29 *****************************************************************************
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30 */
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31 #include "typedef.h"
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32 #include "basic_op.h"
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33 #include "oper_32b.h"
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34 #include "no_count.h"
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35 #include "cnst.h"
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36
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37 /*
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38 *****************************************************************************
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39 * LOCAL VARIABLES AND TABLES
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40 *****************************************************************************
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41 */
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42 /*---------------------------------------------------------------*
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43 * Constants (defined in "cnst.h") *
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44 *---------------------------------------------------------------*
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45 * M : LPC order
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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 * PUBLIC PROGRAM CODE
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51 *****************************************************************************
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52 */
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53
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54 /*************************************************************************
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55 *
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56 * Function: Levinson_reset
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57 * Purpose: Initializes state memory to zero
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58 *
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59 **************************************************************************
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60 */
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61 void Levinson_reset (LevinsonState *state)
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62 {
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63 Word16 i;
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64
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65 state->old_A[0] = 4096;
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66 for(i = 1; i < M + 1; i++)
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67 state->old_A[i] = 0;
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68 }
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69
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70 /*************************************************************************
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71 *
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72 * FUNCTION: Levinson()
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73 *
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74 * PURPOSE: Levinson-Durbin algorithm in double precision. To compute the
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75 * LP filter parameters from the speech autocorrelations.
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76 *
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77 * DESCRIPTION:
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78 * R[i] autocorrelations.
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79 * A[i] filter coefficients.
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80 * K reflection coefficients.
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81 * Alpha prediction gain.
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82 *
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83 * Initialisation:
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84 * A[0] = 1
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85 * K = -R[1]/R[0]
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86 * A[1] = K
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87 * Alpha = R[0] * (1-K**2]
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88 *
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89 * Do for i = 2 to M
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90 *
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91 * S = SUM ( R[j]*A[i-j] ,j=1,i-1 ) + R[i]
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92 *
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93 * K = -S / Alpha
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94 *
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95 * An[j] = A[j] + K*A[i-j] for j=1 to i-1
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96 * where An[i] = new A[i]
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97 * An[i]=K
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98 *
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99 * Alpha=Alpha * (1-K**2)
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100 *
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101 * END
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102 *
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103 *************************************************************************/
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104 int Levinson (
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105 LevinsonState *st,
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106 Word16 Rh[], /* i : Rh[m+1] Vector of autocorrelations (msb) */
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107 Word16 Rl[], /* i : Rl[m+1] Vector of autocorrelations (lsb) */
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108 Word16 A[], /* o : A[m] LPC coefficients (m = 10) */
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109 Word16 rc[] /* o : rc[4] First 4 reflection coefficients */
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110 )
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111 {
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112 Word16 i, j;
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113 Word16 hi, lo;
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114 Word16 Kh, Kl; /* reflexion coefficient; hi and lo */
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115 Word16 alp_h, alp_l, alp_exp; /* Prediction gain; hi lo and exponent */
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116 Word16 Ah[M + 1], Al[M + 1]; /* LPC coef. in double prec. */
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117 Word16 Anh[M + 1], Anl[M + 1];/* LPC coef.for next iteration in double
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118 prec. */
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119 Word32 t0, t1, t2; /* temporary variable */
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120
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121 /* K = A[1] = -R[1] / R[0] */
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122
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123 t1 = L_Comp (Rh[1], Rl[1]);
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124 t2 = L_abs (t1); /* abs R[1] */
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125 t0 = Div_32 (t2, Rh[0], Rl[0]); /* R[1]/R[0] */
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126 test ();
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127 if (t1 > 0)
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128 t0 = L_negate (t0); /* -R[1]/R[0] */
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129 L_Extract (t0, &Kh, &Kl); /* K in DPF */
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130
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131 rc[0] = round (t0); move16 ();
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132
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133 t0 = L_shr (t0, 4); /* A[1] in */
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134 L_Extract (t0, &Ah[1], &Al[1]); /* A[1] in DPF */
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135
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136 /* Alpha = R[0] * (1-K**2) */
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137
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138 t0 = Mpy_32 (Kh, Kl, Kh, Kl); /* K*K */
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139 t0 = L_abs (t0); /* Some case <0 !! */
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parents:
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140 t0 = L_sub ((Word32) 0x7fffffffL, t0); /* 1 - K*K */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
141 L_Extract (t0, &hi, &lo); /* DPF format */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
142 t0 = Mpy_32 (Rh[0], Rl[0], hi, lo); /* Alpha in */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
143
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
144 /* Normalize Alpha */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
145
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
146 alp_exp = norm_l (t0);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
147 t0 = L_shl (t0, alp_exp);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
148 L_Extract (t0, &alp_h, &alp_l); /* DPF format */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
149
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
150 /*--------------------------------------*
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
151 * ITERATIONS I=2 to M *
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
152 *--------------------------------------*/
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
153
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
154 for (i = 2; i <= M; i++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
155 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
156 /* t0 = SUM ( R[j]*A[i-j] ,j=1,i-1 ) + R[i] */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
157
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
158 t0 = 0; move32 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
159 for (j = 1; j < i; j++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
160 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
161 t0 = L_add (t0, Mpy_32 (Rh[j], Rl[j], Ah[i - j], Al[i - j]));
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
162 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
163 t0 = L_shl (t0, 4);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
164
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
165 t1 = L_Comp (Rh[i], Rl[i]);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
166 t0 = L_add (t0, t1); /* add R[i] */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
167
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
168 /* K = -t0 / Alpha */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
169
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
170 t1 = L_abs (t0);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
171 t2 = Div_32 (t1, alp_h, alp_l); /* abs(t0)/Alpha */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
172 test ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
173 if (t0 > 0)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
174 t2 = L_negate (t2); /* K =-t0/Alpha */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
175 t2 = L_shl (t2, alp_exp); /* denormalize; compare to Alpha */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
176 L_Extract (t2, &Kh, &Kl); /* K in DPF */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
177
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
178 test ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
179 if (sub (i, 5) < 0)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
180 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
181 rc[i - 1] = round (t2); move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
182 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
183 /* Test for unstable filter. If unstable keep old A(z) */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
184
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
185 test ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
186 if (sub (abs_s (Kh), 32750) > 0)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
187 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
188 for (j = 0; j <= M; j++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
189 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
190 A[j] = st->old_A[j]; move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
191 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
192
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
193 for (j = 0; j < 4; j++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
194 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
195 rc[j] = 0; move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
196 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
197
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
198 return 0;
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
199 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
200 /*------------------------------------------*
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
201 * Compute new LPC coeff. -> An[i] *
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
202 * An[j]= A[j] + K*A[i-j] , j=1 to i-1 *
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
203 * An[i]= K *
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
204 *------------------------------------------*/
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
205
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
206 for (j = 1; j < i; j++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
207 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
208 t0 = Mpy_32 (Kh, Kl, Ah[i - j], Al[i - j]);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
209 t0 = L_add(t0, L_Comp(Ah[j], Al[j]));
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
210 L_Extract (t0, &Anh[j], &Anl[j]);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
211 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
212 t2 = L_shr (t2, 4);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
213 L_Extract (t2, &Anh[i], &Anl[i]);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
214
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
215 /* Alpha = Alpha * (1-K**2) */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
216
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
217 t0 = Mpy_32 (Kh, Kl, Kh, Kl); /* K*K */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
218 t0 = L_abs (t0); /* Some case <0 !! */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
219 t0 = L_sub ((Word32) 0x7fffffffL, t0); /* 1 - K*K */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
220 L_Extract (t0, &hi, &lo); /* DPF format */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
221 t0 = Mpy_32 (alp_h, alp_l, hi, lo);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
222
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
223 /* Normalize Alpha */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
224
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
225 j = norm_l (t0);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
226 t0 = L_shl (t0, j);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
227 L_Extract (t0, &alp_h, &alp_l); /* DPF format */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
228 alp_exp = add (alp_exp, j); /* Add normalization to
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
229 alp_exp */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
230
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
231 /* A[j] = An[j] */
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
232
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
233 for (j = 1; j <= i; j++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
234 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
235 Ah[j] = Anh[j]; move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
236 Al[j] = Anl[j]; move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
237 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
238 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
239
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
240 A[0] = 4096; move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
241 for (i = 1; i <= M; i++)
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
242 {
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
243 t0 = L_Comp (Ah[i], Al[i]);
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
244 st->old_A[i] = A[i] = round (L_shl (t0, 1));move16 (); move16 ();
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
245 }
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
246
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
247 return 0;
c713061b6edf libtwamr: integrate levinson.c
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
248 }