1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0-or-later */
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * SpanDSP - a series of DSP components for telephony
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * biquad.h - General telephony bi-quad section routines (currently this just
6*4882a593Smuzhiyun * handles canonic/type 2 form)
7*4882a593Smuzhiyun *
8*4882a593Smuzhiyun * Written by Steve Underwood <steveu@coppice.org>
9*4882a593Smuzhiyun *
10*4882a593Smuzhiyun * Copyright (C) 2001 Steve Underwood
11*4882a593Smuzhiyun *
12*4882a593Smuzhiyun * All rights reserved.
13*4882a593Smuzhiyun */
14*4882a593Smuzhiyun
15*4882a593Smuzhiyun struct biquad2_state {
16*4882a593Smuzhiyun int32_t gain;
17*4882a593Smuzhiyun int32_t a1;
18*4882a593Smuzhiyun int32_t a2;
19*4882a593Smuzhiyun int32_t b1;
20*4882a593Smuzhiyun int32_t b2;
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun int32_t z1;
23*4882a593Smuzhiyun int32_t z2;
24*4882a593Smuzhiyun };
25*4882a593Smuzhiyun
biquad2_init(struct biquad2_state * bq,int32_t gain,int32_t a1,int32_t a2,int32_t b1,int32_t b2)26*4882a593Smuzhiyun static inline void biquad2_init(struct biquad2_state *bq,
27*4882a593Smuzhiyun int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2)
28*4882a593Smuzhiyun {
29*4882a593Smuzhiyun bq->gain = gain;
30*4882a593Smuzhiyun bq->a1 = a1;
31*4882a593Smuzhiyun bq->a2 = a2;
32*4882a593Smuzhiyun bq->b1 = b1;
33*4882a593Smuzhiyun bq->b2 = b2;
34*4882a593Smuzhiyun
35*4882a593Smuzhiyun bq->z1 = 0;
36*4882a593Smuzhiyun bq->z2 = 0;
37*4882a593Smuzhiyun }
38*4882a593Smuzhiyun
biquad2(struct biquad2_state * bq,int16_t sample)39*4882a593Smuzhiyun static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample)
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun int32_t y;
42*4882a593Smuzhiyun int32_t z0;
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun z0 = sample * bq->gain + bq->z1 * bq->a1 + bq->z2 * bq->a2;
45*4882a593Smuzhiyun y = z0 + bq->z1 * bq->b1 + bq->z2 * bq->b2;
46*4882a593Smuzhiyun
47*4882a593Smuzhiyun bq->z2 = bq->z1;
48*4882a593Smuzhiyun bq->z1 = z0 >> 15;
49*4882a593Smuzhiyun y >>= 15;
50*4882a593Smuzhiyun return y;
51*4882a593Smuzhiyun }
52