libaf/filter.h

   1 /*=============================================================================
   2 //
   3 //  This software has been released under the terms of the GNU General Public
   4 //  license. See http://www.gnu.org/copyleft/gpl.html for details.
   5 //
   6 //  Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
   7 //
   8 //=============================================================================
   9 */
  10
  11 #if !defined _DSP_H
  12 # error "Never use <filter.h> directly; include <dsp.h> instead"
  13 #endif
  14
  15 #ifndef _FILTER_H
  16 #define _FILTER_H       1
  17
  18
  19 // Design and implementation of different types of digital filters
  20
  21
  22 // Flags used for filter design
  23
  24 // Filter characteristics
  25 #define LP          0x00010000 // Low pass
  26 #define HP          0x00020000 // High pass
  27 #define BP          0x00040000 // Band pass
  28 #define BS          0x00080000 // Band stop
  29 #define TYPE_MASK   0x000F0000
  30
  31 // Window types
  32 #define BOXCAR      0x00000001
  33 #define TRIANG      0x00000002
  34 #define HAMMING     0x00000004
  35 #define HANNING     0x00000008
  36 #define BLACKMAN    0x00000010
  37 #define FLATTOP     0x00000011
  38 #define KAISER      0x00000012
  39 #define WINDOW_MASK 0x0000001F
  40
  41 // Parallel filter design
  42 #define FWD         0x00000001 // Forward indexing of polyphase filter
  43 #define REW         0x00000002 // Reverse indexing of polyphase filter
  44 #define ODD         0x00000010 // Make filter HP
  45
  46 // Exported functions
  47 extern _ftype_t af_filter_fir(unsigned int n, _ftype_t* w, _ftype_t* x);
  48
  49 extern _ftype_t* af_filter_pfir(unsigned int n, unsigned int k, unsigned int xi, _ftype_t** w, _ftype_t** x, _ftype_t* y, unsigned int s);
  50
  51 //extern int af_filter_updateq(unsigned int n, unsigned int xi, _ftype_t* xq, _ftype_t* in);
  52 extern int af_filter_updatepq(unsigned int n, unsigned int k, unsigned int xi, _ftype_t** xq, _ftype_t* in, unsigned int s);
  53
  54 extern int af_filter_design_fir(unsigned int n, _ftype_t* w, _ftype_t* fc, unsigned int flags, _ftype_t opt);
  55
  56 extern int af_filter_design_pfir(unsigned int n, unsigned int k, _ftype_t* w, _ftype_t** pw, _ftype_t g, unsigned int flags);
  57
  58 extern int af_filter_szxform(_ftype_t* a, _ftype_t* b, _ftype_t Q, _ftype_t fc, _ftype_t fs, _ftype_t *k, _ftype_t *coef);
  59
  60 /* Add new data to circular queue designed to be used with a FIR
  61    filter. xq is the circular queue, in pointing at the new sample, xi
  62    current index for xq and n the length of the filter. xq must be n*2
  63    long.
  64 */
  65 #define af_filter_updateq(n,xi,xq,in)\
  66   xq[xi]=(xq)[(xi)+(n)]=*(in);\
  67   xi=(++(xi))&((n)-1);
  68
  69 #endif