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comparison libtwamr/pre_proc.c @ 397:9b699f30e6f3

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libtwamr: integrate pre_proc.c
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 06 May 2024 19:02:44 +0000
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396:38ee82480462 397:9b699f30e6f3
1 /*
2 ********************************************************************************
3 *
4 * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001
5 * R99 Version 3.3.0
6 * REL-4 Version 4.1.0
7 *
8 ********************************************************************************
9 *
10 * File : pre_proc.c
11 * Purpose : Preprocessing of input speech.
12 *
13 ********************************************************************************
14 */
15
16 /*
17 ********************************************************************************
18 * MODULE INCLUDE FILE AND VERSION ID
19 ********************************************************************************
20 */
21 #include "namespace.h"
22 #include "pre_proc.h"
23
24 /*
25 ********************************************************************************
26 * INCLUDE FILES
27 ********************************************************************************
28 */
29 #include "typedef.h"
30 #include "basic_op.h"
31 #include "oper_32b.h"
32 #include "no_count.h"
33
34 /*
35 ********************************************************************************
36 * LOCAL VARIABLES AND TABLES
37 ********************************************************************************
38 */
39 /* filter coefficients (fc = 80 Hz, coeff. b[] is divided by 2) */
40 static const Word16 b[3] = {1899, -3798, 1899};
41 static const Word16 a[3] = {4096, 7807, -3733};
42
43 /*
44 ********************************************************************************
45 * PUBLIC PROGRAM CODE
46 ********************************************************************************
47 */
48
49 /*************************************************************************
50 *
51 * Function: Pre_Process_reset
52 * Purpose: Initializes state memory to zero
53 *
54 **************************************************************************
55 */
56 void Pre_Process_reset (Pre_ProcessState *state)
57 {
58 state->y2_hi = 0;
59 state->y2_lo = 0;
60 state->y1_hi = 0;
61 state->y1_lo = 0;
62 state->x0 = 0;
63 state->x1 = 0;
64 }
65
66 /*************************************************************************
67 *
68 * FUNCTION: Pre_Process()
69 *
70 * PURPOSE: Preprocessing of input speech.
71 *
72 * DESCRIPTION:
73 * - 2nd order high pass filtering with cut off frequency at 80 Hz.
74 * - Divide input by two.
75 *
76 *
77 * Algorithm:
78 *
79 * y[i] = b[0]*x[i]/2 + b[1]*x[i-1]/2 + b[2]*x[i-2]/2
80 * + a[1]*y[i-1] + a[2]*y[i-2];
81 *
82 *
83 * Input is divided by two in the filtering process.
84 *
85 *************************************************************************/
86 int Pre_Process (
87 Pre_ProcessState *st,
88 Word16 signal[], /* input/output signal */
89 Word16 lg) /* lenght of signal */
90 {
91 Word16 i, x2;
92 Word32 L_tmp;
93
94 for (i = 0; i < lg; i++)
95 {
96 x2 = st->x1; move16 ();
97 st->x1 = st->x0; move16 ();
98 st->x0 = signal[i]; move16 ();
99
100 /* y[i] = b[0]*x[i]/2 + b[1]*x[i-1]/2 + b140[2]*x[i-2]/2 */
101 /* + a[1]*y[i-1] + a[2] * y[i-2]; */
102
103 L_tmp = Mpy_32_16 (st->y1_hi, st->y1_lo, a[1]);
104 L_tmp = L_add (L_tmp, Mpy_32_16 (st->y2_hi, st->y2_lo, a[2]));
105 L_tmp = L_mac (L_tmp, st->x0, b[0]);
106 L_tmp = L_mac (L_tmp, st->x1, b[1]);
107 L_tmp = L_mac (L_tmp, x2, b[2]);
108 L_tmp = L_shl (L_tmp, 3);
109 signal[i] = round (L_tmp); move16 ();
110
111 st->y2_hi = st->y1_hi; move16 ();
112 st->y2_lo = st->y1_lo; move16 ();
113 L_Extract (L_tmp, &st->y1_hi, &st->y1_lo);
114 }
115 return 0;
116 }