1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * SpanDSP - a series of DSP components for telephony
4 *
5 * biquad.h - General telephony bi-quad section routines (currently this just
6 * handles canonic/type 2 form)
7 *
8 * Written by Steve Underwood <steveu@coppice.org>
9 *
10 * Copyright (C) 2001 Steve Underwood
11 *
12 * All rights reserved.
13 */
14
15 struct biquad2_state {
16 int32_t gain;
17 int32_t a1;
18 int32_t a2;
19 int32_t b1;
20 int32_t b2;
21
22 int32_t z1;
23 int32_t z2;
24 };
25
biquad2_init(struct biquad2_state * bq,int32_t gain,int32_t a1,int32_t a2,int32_t b1,int32_t b2)26 static inline void biquad2_init(struct biquad2_state *bq,
27 int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2)
28 {
29 bq->gain = gain;
30 bq->a1 = a1;
31 bq->a2 = a2;
32 bq->b1 = b1;
33 bq->b2 = b2;
34
35 bq->z1 = 0;
36 bq->z2 = 0;
37 }
38
biquad2(struct biquad2_state * bq,int16_t sample)39 static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample)
40 {
41 int32_t y;
42 int32_t z0;
43
44 z0 = sample * bq->gain + bq->z1 * bq->a1 + bq->z2 * bq->a2;
45 y = z0 + bq->z1 * bq->b1 + bq->z2 * bq->b2;
46
47 bq->z2 = bq->z1;
48 bq->z1 = z0 >> 15;
49 y >>= 15;
50 return y;
51 }
52