/*
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* SpanDSP - a series of DSP components for telephony
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*
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* biquad.h - General telephony bi-quad section routines (currently this just
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* handles canonic/type 2 form)
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2001 Steve Underwood
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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struct biquad2_state {
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int32_t gain;
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int32_t a1;
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int32_t a2;
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int32_t b1;
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int32_t b2;
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int32_t z1;
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int32_t z2;
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};
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static inline void biquad2_init(struct biquad2_state *bq,
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int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2)
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{
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bq->gain = gain;
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bq->a1 = a1;
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bq->a2 = a2;
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bq->b1 = b1;
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bq->b2 = b2;
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bq->z1 = 0;
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bq->z2 = 0;
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}
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static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample)
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{
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int32_t y;
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int32_t z0;
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z0 = sample * bq->gain + bq->z1 * bq->a1 + bq->z2 * bq->a2;
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y = z0 + bq->z1 * bq->b1 + bq->z2 * bq->b2;
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bq->z2 = bq->z1;
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bq->z1 = z0 >> 15;
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y >>= 15;
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return y;
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}
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