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/drivers/isdn/mISDN/dsp_biquad.h

http://github.com/mirrors/linux
C Header | 51 lines | 31 code | 7 blank | 13 comment | 0 complexity | 6ded40eaa327fafdd233d28224523105 MD5 | raw file
 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
15struct 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
26static 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
39static 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}