/* * SpanDSP - a series of DSP components for telephony * * biquad.h - General telephony bi-quad section routines (currently this just *            handles canonic/type 2 form) * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2001 Steve Underwood * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * */typedef struct{    int32_t gain;    int32_t a1;    int32_t a2;    int32_t b1;    int32_t b2;    int32_t z1;    int32_t z2;} biquad2_state_t;static inline void biquad2_init (biquad2_state_t *bq,                	 	 int32_t gain,		                 int32_t a1,            	                 int32_t a2,		                 int32_t b1,		                 int32_t b2){    bq->gain = gain;    bq->a1 = a1;    bq->a2 = a2;    bq->b1 = b1;    bq->b2 = b2;        bq->z1 = 0;    bq->z2 = 0;    }/*- End of function --------------------------------------------------------*/    static inline int16_t biquad2 (biquad2_state_t *bq, int16_t sample){    int32_t y;    int32_t z0;        z0 = sample*bq->gain + bq->z1*bq->a1 + bq->z2*bq->a2;    y = z0 + bq->z1*bq->b1 + bq->z2*bq->b2;    bq->z2 = bq->z1;    bq->z1 = z0 >> 15;    y >>= 15;    return  y;}/*- End of function --------------------------------------------------------*//*- End of file ------------------------------------------------------------*/