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annotate src/syn_filt.c @ 2:c511bfb36c2a

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beginning of EFR2 decoder, using AMR version of AGC module
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 03 Apr 2024 05:47:51 +0000
parents 56410792419a
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 "typedef.h"
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10 #include "basic_op.h"
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11 #include "count.h"
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12
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13 /* m = LPC order == 10 */
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14 #define m 10
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15
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16 void Syn_filt (
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17 Word16 a[], /* (i) : a[m+1] prediction coefficients (m=10) */
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18 Word16 x[], /* (i) : input signal */
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19 Word16 y[], /* (o) : output signal */
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20 Word16 lg, /* (i) : size of filtering */
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21 Word16 mem[], /* (i/o) : memory associated with this filtering. */
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22 Word16 update /* (i) : 0=no update, 1=update of memory. */
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23 )
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24 {
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25 Word16 i, j;
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26 Word32 s;
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27 Word16 tmp[80]; /* This is usually done by memory allocation (lg+m) */
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28 Word16 *yy;
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29
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30 /* Copy mem[] to yy[] */
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31
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32 yy = tmp; move16 ();
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33
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34 for (i = 0; i < m; i++)
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35 {
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36 *yy++ = mem[i]; move16 ();
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37 }
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38
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39 /* Do the filtering. */
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40
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41 for (i = 0; i < lg; i++)
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42 {
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43 s = L_mult (x[i], a[0]);
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44 for (j = 1; j <= m; j++)
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45 {
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46 s = L_msu (s, a[j], yy[-j]);
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47 }
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48 s = L_shl (s, 3);
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49 *yy++ = round (s); move16 ();
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50 }
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51
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52 for (i = 0; i < lg; i++)
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53 {
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54 y[i] = tmp[i + m]; move16 ();
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55 }
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56
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57 /* Update of memory if update==1 */
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58
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59 test ();
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60 if (update != 0)
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61 {
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62 for (i = 0; i < m; i++)
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63 {
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64 mem[i] = y[lg - m + i]; move16 ();
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65 }
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66 }
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67 return;
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68 }