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Karsten Keil960366c2008-07-27 01:56:38 +02001/*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * biquad.h - General telephony bi-quad section routines (currently this just
5 * handles canonic/type 2 form)
6 *
7 * Written by Steve Underwood <steveu@coppice.org>
8 *
9 * Copyright (C) 2001 Steve Underwood
10 *
11 * All rights reserved.
12 *
13 * This program is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU General Public License as published by
15 * the Free Software Foundation; either version 2 of the License, or
16 * (at your option) any later version.
17 *
18 * This program is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 * GNU General Public License for more details.
22 *
23 * You should have received a copy of the GNU General Public License
24 * along with this program; if not, write to the Free Software
25 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
26 *
27 */
28
29struct biquad2_state {
30 int32_t gain;
31 int32_t a1;
32 int32_t a2;
33 int32_t b1;
34 int32_t b2;
35
36 int32_t z1;
37 int32_t z2;
38};
39
40static inline void biquad2_init(struct biquad2_state *bq,
41 int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2)
42{
43 bq->gain = gain;
44 bq->a1 = a1;
45 bq->a2 = a2;
46 bq->b1 = b1;
47 bq->b2 = b2;
48
49 bq->z1 = 0;
50 bq->z2 = 0;
51}
52
53static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample)
54{
55 int32_t y;
56 int32_t z0;
57
58 z0 = sample*bq->gain + bq->z1*bq->a1 + bq->z2*bq->a2;
59 y = z0 + bq->z1*bq->b1 + bq->z2*bq->b2;
60
61 bq->z2 = bq->z1;
62 bq->z1 = z0 >> 15;
63 y >>= 15;
64 return y;
65}