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960366cf KK |
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 | ||
29 | struct 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 | ||
40 | static 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 | ||
53 | static 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 | } |