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/*
* 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;
}
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