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comparison libgsmefr/inter_6.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 63ad83f3d821
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52:988fd7ff514f 53:49dd1ac8e75b
1 /*************************************************************************
2 *
3 * FUNCTION: Interpol_6()
4 *
5 * PURPOSE: Interpolating the normalized correlation with 1/6 resolution.
6 *
7 *************************************************************************/
8
9 #include "typedef.h"
10 #include "basic_op.h"
11 #include "count.h"
12
13 #define UP_SAMP 6
14 #define L_INTERPOL 4
15 #define FIR_SIZE (UP_SAMP*L_INTERPOL+1)
16
17 /* 1/6 resolution interpolation filter (-3 dB at 3600 Hz) */
18
19 static const Word16 inter_6[FIR_SIZE] =
20 {
21 29519,
22 28316, 24906, 19838, 13896, 7945, 2755,
23 -1127, -3459, -4304, -3969, -2899, -1561,
24 -336, 534, 970, 1023, 823, 516,
25 220, 0, -131, -194, -215, 0
26 };
27
28 Word16 Interpol_6 ( /* (o) : interpolated value */
29 Word16 *x, /* (i) : input vector */
30 Word16 frac /* (i) : fraction */
31 )
32 {
33 Word16 i, k;
34 Word16 *x1, *x2;
35 const Word16 *c1, *c2;
36 Word32 s;
37
38 test ();
39 if (frac < 0)
40 {
41 frac = add (frac, UP_SAMP);
42 x--;
43 }
44 x1 = &x[0]; move16 ();
45 x2 = &x[1]; move16 ();
46 c1 = &inter_6[frac]; move16 ();
47 c2 = &inter_6[sub (UP_SAMP, frac)]; move16 ();
48
49 s = 0; move32 ();
50 for (i = 0, k = 0; i < L_INTERPOL; i++, k += UP_SAMP)
51 {
52 s = L_mac (s, x1[-i], c1[k]);
53 s = L_mac (s, x2[i], c2[k]);
54 }
55
56 return round (s);
57 }