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comparison libgsmefr/syn_filt.c @ 53:49dd1ac8e75b

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libgsmefr: import most *.c files from ETSI source
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 25 Nov 2022 16:18:21 +0000
parents
children bb71c5414e71
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52:988fd7ff514f 53:49dd1ac8e75b
1 /*************************************************************************
2 *
3 * FUNCTION: Syn_filt:
4 *
5 * PURPOSE: Perform synthesis filtering through 1/A(z).
6 *
7 *************************************************************************/
8
9 #include "typedef.h"
10 #include "basic_op.h"
11 #include "count.h"
12
13 /* m = LPC order == 10 */
14 #define m 10
15
16 void Syn_filt (
17 Word16 a[], /* (i) : a[m+1] prediction coefficients (m=10) */
18 Word16 x[], /* (i) : input signal */
19 Word16 y[], /* (o) : output signal */
20 Word16 lg, /* (i) : size of filtering */
21 Word16 mem[], /* (i/o) : memory associated with this filtering. */
22 Word16 update /* (i) : 0=no update, 1=update of memory. */
23 )
24 {
25 Word16 i, j;
26 Word32 s;
27 Word16 tmp[80]; /* This is usually done by memory allocation (lg+m) */
28 Word16 *yy;
29
30 /* Copy mem[] to yy[] */
31
32 yy = tmp; move16 ();
33
34 for (i = 0; i < m; i++)
35 {
36 *yy++ = mem[i]; move16 ();
37 }
38
39 /* Do the filtering. */
40
41 for (i = 0; i < lg; i++)
42 {
43 s = L_mult (x[i], a[0]);
44 for (j = 1; j <= m; j++)
45 {
46 s = L_msu (s, a[j], yy[-j]);
47 }
48 s = L_shl (s, 3);
49 *yy++ = round (s); move16 ();
50 }
51
52 for (i = 0; i < lg; i++)
53 {
54 y[i] = tmp[i + m]; move16 ();
55 }
56
57 /* Update of memory if update==1 */
58
59 test ();
60 if (update != 0)
61 {
62 for (i = 0; i < m; i++)
63 {
64 mem[i] = y[lg - m + i]; move16 ();
65 }
66 }
67 return;
68 }