1/*
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}
66