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annotate libgsmefr/syn_filt.c @ 550:de333989a12b

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document gsm[e]fr-decode-tw5[-r] utilities
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 05 Oct 2024 02:16:48 +0000
parents bb71c5414e71
children
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1 /*************************************************************************
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2 *
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3 * FUNCTION: Syn_filt:
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4 *
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5 * PURPOSE: Perform synthesis filtering through 1/A(z).
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6 *
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7 *************************************************************************/
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8
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9 #include "gsm_efr.h"
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10 #include "typedef.h"
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11 #include "namespace.h"
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12 #include "basic_op.h"
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13 #include "no_count.h"
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14 #include "sig_proc.h"
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16 /* m = LPC order == 10 */
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17 #define m 10
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18
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19 void Syn_filt (
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20 Word16 a[], /* (i) : a[m+1] prediction coefficients (m=10) */
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21 Word16 x[], /* (i) : input signal */
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22 Word16 y[], /* (o) : output signal */
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23 Word16 lg, /* (i) : size of filtering */
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24 Word16 mem[], /* (i/o) : memory associated with this filtering. */
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25 Word16 update /* (i) : 0=no update, 1=update of memory. */
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26 )
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27 {
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28 Word16 i, j;
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29 Word32 s;
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30 Word16 tmp[80]; /* This is usually done by memory allocation (lg+m) */
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31 Word16 *yy;
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33 /* Copy mem[] to yy[] */
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35 yy = tmp; move16 ();
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37 for (i = 0; i < m; i++)
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38 {
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39 *yy++ = mem[i]; move16 ();
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40 }
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42 /* Do the filtering. */
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44 for (i = 0; i < lg; i++)
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45 {
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46 s = L_mult (x[i], a[0]);
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47 for (j = 1; j <= m; j++)
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48 {
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49 s = L_msu (s, a[j], yy[-j]);
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50 }
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51 s = L_shl (s, 3);
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52 *yy++ = round (s); move16 ();
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53 }
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55 for (i = 0; i < lg; i++)
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56 {
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57 y[i] = tmp[i + m]; move16 ();
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58 }
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60 /* Update of memory if update==1 */
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61
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62 test ();
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63 if (update != 0)
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64 {
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65 for (i = 0; i < m; i++)
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66 {
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67 mem[i] = y[lg - m + i]; move16 ();
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68 }
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69 }
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70 return;
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71 }