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