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 29struct 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 40static 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 53static 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} 66