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/*
* SpanDSP - a series of DSP components for telephony
*
* fir.h - General telephony FIR routines
*
* Written by Steve Underwood <steveu@coppice.org>
*
* Copyright (C) 2002 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.
*
*/
#if !defined(_FIR_H_)
#define _FIR_H_
typedef struct
{
int taps;
int curr_pos;
int16_t *coeffs;
int16_t *history;
} fir16_state_t;
typedef struct
{
int taps;
int curr_pos;
int32_t *coeffs;
int16_t *history;
} fir32_state_t;
static inline void fir16_create (fir16_state_t *fir,
int16_t *coeffs,
int taps)
{
fir->taps = taps;
fir->curr_pos = taps - 1;
fir->coeffs = coeffs;
fir->history = MALLOC (taps*sizeof (int16_t));
if (fir->history)
memset (fir->history, '\0', taps*sizeof (int16_t));
}
/*- End of function --------------------------------------------------------*/
static inline void fir16_free (fir16_state_t *fir)
{
FREE (fir->history);
}
/*- End of function --------------------------------------------------------*/
static inline int16_t fir16 (fir16_state_t *fir, int16_t sample)
{
int i;
int offset1;
int offset2;
int32_t y;
fir->history[fir->curr_pos] = sample;
offset2 = fir->curr_pos + 1;
offset1 = fir->taps - offset2;
y = 0;
for (i = fir->taps - 1; i >= offset1; i--)
y += fir->coeffs[i]*fir->history[i - offset1];
for ( ; i >= 0; i--)
y += fir->coeffs[i]*fir->history[i + offset2];
if (fir->curr_pos <= 0)
fir->curr_pos = fir->taps;
fir->curr_pos--;
return y >> 15;
}
/*- End of function --------------------------------------------------------*/
static inline void fir32_create (fir32_state_t *fir,
int32_t *coeffs,
int taps)
{
fir->taps = taps;
fir->curr_pos = taps - 1;
fir->coeffs = coeffs;
fir->history = MALLOC (taps*sizeof (int16_t));
if (fir->history)
memset (fir->history, '\0', taps*sizeof (int16_t));
}
/*- End of function --------------------------------------------------------*/
static inline void fir32_free (fir32_state_t *fir)
{
FREE (fir->history);
}
/*- End of function --------------------------------------------------------*/
static inline int16_t fir32 (fir32_state_t *fir, int16_t sample)
{
int i;
int offset1;
int offset2;
int32_t y;
fir->history[fir->curr_pos] = sample;
offset2 = fir->curr_pos + 1;
offset1 = fir->taps - offset2;
y = 0;
for (i = fir->taps - 1; i >= offset1; i--)
y += fir->coeffs[i]*fir->history[i - offset1];
for ( ; i >= 0; i--)
y += fir->coeffs[i]*fir->history[i + offset2];
if (fir->curr_pos <= 0)
fir->curr_pos = fir->taps;
fir->curr_pos--;
return y >> 15;
}
/*- End of function --------------------------------------------------------*/
#endif
/*- End of file ------------------------------------------------------------*/
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