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1/* SPDX-License-Identifier: GPL-2.0-or-later */2/*3 * SpanDSP - a series of DSP components for telephony4 *5 * biquad.h - General telephony bi-quad section routines (currently this just6 * handles canonic/type 2 form)7 *8 * Written by Steve Underwood <steveu@coppice.org>9 *10 * Copyright (C) 2001 Steve Underwood11 *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}52