fir.h
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/*
* SpanDSP - a series of DSP components for telephony
*
* fir.h - General telephony FIR routines
*
* Written by Steve Underwood <[email protected]>
*
* Copyright (C) 2002 Steve Underwood
*
* All rights reserved.
*
*/
/*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2 as published by the
* Free Software Foundation. See the LICENSE file included with
* this program for more details.
*/
#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 = kmalloc(taps*sizeof (int16_t), GFP_KERNEL);
if (fir->history)
memset (fir->history, '\0', taps*sizeof (int16_t));
}
/*- End of function --------------------------------------------------------*/
static inline void fir16_free (fir16_state_t *fir)
{
kfree(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 = kmalloc(taps*sizeof (int16_t), GFP_KERNEL);
if (fir->history)
memset (fir->history, '\0', taps*sizeof (int16_t));
}
/*- End of function --------------------------------------------------------*/
static inline void fir32_free (fir32_state_t *fir)
{
kfree(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 ------------------------------------------------------------*/