/* * 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. * */ struct biquad2_state { int32_t gain; int32_t a1; int32_t a2; int32_t b1; int32_t b2; int32_t z1; int32_t z2; }; static inline void biquad2_init(struct biquad2_state *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; } static inline int16_t biquad2(struct biquad2_state *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; }