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annotate libgsmefr/residu.c @ 494:aaf4dec8bee0

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libgsmhr1: implement perfect SID detection
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 17 Jun 2024 23:14:19 +0000
parents de9dc80c1312
children
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1 /*************************************************************************
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2 *
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3 * FUNCTION: Residu
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4 *
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5 * PURPOSE: Computes the LP residual.
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6 *
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7 * DESCRIPTION:
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8 * The LP residual is computed by filtering the input speech through
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9 * the LP inverse filter A(z).
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10 *
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11 *************************************************************************/
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12
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13 #include "gsm_efr.h"
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14 #include "typedef.h"
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15 #include "namespace.h"
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16 #include "basic_op.h"
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17 #include "no_count.h"
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18 #include "sig_proc.h"
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20 /* m = LPC order == 10 */
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21 #define m 10
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22
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23 void Residu (
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24 Word16 a[], /* (i) : prediction coefficients */
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25 Word16 x[], /* (i) : speech signal */
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26 Word16 y[], /* (o) : residual signal */
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27 Word16 lg /* (i) : size of filtering */
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28 )
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29 {
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30 Word16 i, j;
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31 Word32 s;
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32
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33 for (i = 0; i < lg; i++)
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34 {
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35 s = L_mult (x[i], a[0]);
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36 for (j = 1; j <= m; j++)
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37 {
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38 s = L_mac (s, a[j], x[i - j]);
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39 }
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40 s = L_shl (s, 3);
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41 y[i] = round (s); move16 ();
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42 }
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43 return;
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44 }