isdn/mISDN/dsp_biquad.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * SpanDSP - a series of DSP components for telephony
0004  *
0005  * biquad.h - General telephony bi-quad section routines (currently this just
0006  *            handles canonic/type 2 form)
0007  *
0008  * Written by Steve Underwood <steveu@coppice.org>
0009  *
0010  * Copyright (C) 2001 Steve Underwood
0011  *
0012  * All rights reserved.
0013  */
0014
0015 struct biquad2_state {
0016     int32_t gain;
0017     int32_t a1;
0018     int32_t a2;
0019     int32_t b1;
0020     int32_t b2;
0021
0022     int32_t z1;
0023     int32_t z2;
0024 };
0025
0026 static inline void biquad2_init(struct biquad2_state *bq,
0027                 int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2)
0028 {
0029     bq->gain = gain;
0030     bq->a1 = a1;
0031     bq->a2 = a2;
0032     bq->b1 = b1;
0033     bq->b2 = b2;
0034
0035     bq->z1 = 0;
0036     bq->z2 = 0;
0037 }
0038
0039 static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample)
0040 {
0041     int32_t y;
0042     int32_t z0;
0043
0044     z0 = sample * bq->gain + bq->z1 * bq->a1 + bq->z2 * bq->a2;
0045     y = z0 + bq->z1 * bq->b1 + bq->z2 * bq->b2;
0046
0047     bq->z2 = bq->z1;
0048     bq->z1 = z0 >> 15;
0049     y >>= 15;
0050     return  y;
0051 }