filter.h

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/*=============================================================================
 *
 *  This software has been released under the terms of the GNU Public
 *  license. See http://www.gnu.org/copyleft/gpl.html for details.
 *
 *  Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
 *
 *=============================================================================
 */

#if !defined _DSP_H
# error "Never use <filter.h> directly; include <dsp.h> instead"
#endif

#ifndef _FILTER_H
#define _FILTER_H       1

/* Design and implementation of different types of digital filters */

/* Flags used for filter design */

/* Filter characteristics */
#define LP          0x00010000 /* Low pass */
#define HP          0x00020000 /* High pass */
#define BP          0x00040000 /* Band pass */
#define BS          0x00080000 /* Band stop */
#define TYPE_MASK   0x000F0000

/* Window types */
#define BOXCAR      0x00000001
#define TRIANG      0x00000002
#define HAMMING     0x00000004
#define HANNING     0x00000008
#define BLACKMAN    0x00000010
#define FLATTOP     0x00000011
#define KAISER      0x00000012
#define WINDOW_MASK 0x0000001F

/* Parallel filter design */
#define FWD         0x00000001 /* Forward indexing of polyphase filter */
#define REW         0x00000002 /* Reverse indexing of polyphase filter */
#define ODD         0x00000010 /* Make filter HP */

/* Exported functions */
extern _ftype_t fir(unsigned int n, _ftype_t* w, _ftype_t* x);

extern _ftype_t* pfir(unsigned int n, unsigned int k, unsigned int xi, _ftype_t** w, _ftype_t** x, _ftype_t* y, unsigned int s);

extern int updateq(unsigned int n, unsigned int xi, _ftype_t* xq, _ftype_t* in);
extern int updatepq(unsigned int n, unsigned int k, unsigned int xi, _ftype_t** xq, _ftype_t* in, unsigned int s);

extern int design_fir(unsigned int n, _ftype_t* w, _ftype_t* fc, unsigned int flags, _ftype_t opt);

extern int design_pfir(unsigned int n, unsigned int k, _ftype_t* w, _ftype_t** pw, _ftype_t g, unsigned int flags);
extern void prewarp(_ftype_t* a, _ftype_t fc, _ftype_t fs);
void bilinear(_ftype_t* a, _ftype_t* b, _ftype_t* k, _ftype_t fs, _ftype_t *coef);

extern int szxform(const _ftype_t* a, const _ftype_t* b, _ftype_t Q, _ftype_t fc, _ftype_t fs, _ftype_t *k, _ftype_t *coef);

/* Add new data to circular queue designed to be used with a FIR
 * filter. xq is the circular queue, in pointing at the new sample, xi
 * current index for xq and n the length of the filter. xq must be n*2
 * long.
 */
#define updateq(n,xi,xq,in)\
  xq[xi]=(xq)[(xi)+(n)]=*(in);\
  xi=(++(xi))&((n)-1);

#endif