codecs/ilbc/hpInput.c

   1
   2 /******************************************************************
   3
   4     iLBC Speech Coder ANSI-C Source Code
   5
   6     hpInput.c
   7
   8     Copyright (C) The Internet Society (2004).
   9     All Rights Reserved.
  10
  11 ******************************************************************/
  12
  13 #include "constants.h"
  14 #include "hpInput.h"
  15
  16 /*----------------------------------------------------------------*
  17  *  Input high-pass filter
  18  *---------------------------------------------------------------*/
  19
  20 void hpInput(
  21     float *In,  /* (i) vector to filter */
  22     int len,    /* (i) length of vector to filter */
  23     float *Out, /* (o) the resulting filtered vector */
  24     float *mem  /* (i/o) the filter state */
  25 ){
  26     int i;
  27     float *pi, *po;
  28
  29     /* all-zero section*/
  30
  31     pi = &In[0];
  32     po = &Out[0];
  33     for (i=0; i<len; i++) {
  34         *po = hpi_zero_coefsTbl[0] * (*pi);
  35         *po += hpi_zero_coefsTbl[1] * mem[0];
  36         *po += hpi_zero_coefsTbl[2] * mem[1];
  37
  38         mem[1] = mem[0];
  39         mem[0] = *pi;
  40         po++;
  41
  42
  43         pi++;
  44
  45     }
  46
  47     /* all-pole section*/
  48
  49     po = &Out[0];
  50     for (i=0; i<len; i++) {
  51         *po -= hpi_pole_coefsTbl[1] * mem[2];
  52         *po -= hpi_pole_coefsTbl[2] * mem[3];
  53
  54         mem[3] = mem[2];
  55         mem[2] = *po;
  56         po++;
  57     }
  58 }
  59
  60