118 lines
2.9 KiB
C
118 lines
2.9 KiB
C
/*
|
|
* 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 Lesser General Public License version 2.1,
|
|
* as published by the Free Software Foundation.
|
|
*
|
|
* 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 Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
*
|
|
* $Id: biquad.h,v 1.14 2008/04/17 14:26:59 steveu Exp $
|
|
*/
|
|
|
|
/*! \page biquad_page Bi-quadratic filter sections
|
|
\section biquad_page_sec_1 What does it do?
|
|
???.
|
|
|
|
\section biquad_page_sec_2 How does it work?
|
|
???.
|
|
*/
|
|
|
|
#if !defined(_SPANDSP_BIQUAD_H_)
|
|
#define _SPANDSP_BIQUAD_H_
|
|
|
|
typedef struct
|
|
{
|
|
int32_t gain;
|
|
int32_t a1;
|
|
int32_t a2;
|
|
int32_t b1;
|
|
int32_t b2;
|
|
|
|
int32_t z1;
|
|
int32_t z2;
|
|
|
|
#if FIRST_ORDER_NOISE_SHAPING
|
|
int32_t residue;
|
|
#elif SECOND_ORDER_NOISE_SHAPING
|
|
int32_t residue1;
|
|
int32_t residue2;
|
|
#endif
|
|
} biquad2_state_t;
|
|
|
|
#if defined(__cplusplus)
|
|
extern "C"
|
|
{
|
|
#endif
|
|
|
|
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;
|
|
|
|
#if FIRST_ORDER_NOISE_SHAPING
|
|
bq->residue = 0;
|
|
#elif SECOND_ORDER_NOISE_SHAPING
|
|
bq->residue1 = 0;
|
|
bq->residue2 = 0;
|
|
#endif
|
|
}
|
|
/*- 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;
|
|
#if FIRST_ORDER_NOISE_SHAPING
|
|
y += bq->residue;
|
|
bq->residue = y & 0x7FFF;
|
|
#elif SECOND_ORDER_NOISE_SHAPING
|
|
y += (2*bq->residue1 - bq->residue2);
|
|
bq->residue2 = bq->residue1;
|
|
bq->residue1 = y & 0x7FFF;
|
|
#endif
|
|
y >>= 15;
|
|
return (int16_t) y;
|
|
}
|
|
/*- End of function --------------------------------------------------------*/
|
|
|
|
#if defined(__cplusplus)
|
|
}
|
|
#endif
|
|
|
|
#endif
|
|
/*- End of file ------------------------------------------------------------*/
|