52 lines
977 B
C
52 lines
977 B
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/*
|
|
* 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.
|
|
*/
|
|
|
|
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;
|
|
}
|