lpc10/lpfilt.c

   1 /*
   2
   3  * Revision 1.1  1996/08/19  22:31:35  jaf
   4  * Initial revision
   5  *
   6
   7 */
   8
   9 /*  -- translated by f2c (version 19951025).
  10    You must link the resulting object file with the libraries:
  11         -lf2c -lm   (in that order)
  12 */
  13
  14 #include "f2c.h"
  15
  16 extern int lpfilt_(real *inbuf, real *lpbuf, integer *len, integer *nsamp);
  17
  18 /* *********************************************************************** */
  19
  20 /*      LPFILT Version 55 */
  21
  22 /*
  23  * Revision 1.1  1996/08/19  22:31:35  jaf
  24  * Initial revision
  25  * */
  26 /* Revision 1.3  1996/03/15  16:53:49  jaf */
  27 /* Just put comment header in standard form. */
  28
  29 /* Revision 1.2  1996/03/12  23:58:06  jaf */
  30 /* Comments added explaining that none of the local variables of this */
  31 /* subroutine need to be saved from one invocation to the next. */
  32
  33 /* Revision 1.1  1996/02/07 14:47:44  jaf */
  34 /* Initial revision */
  35
  36
  37 /* *********************************************************************** */
  38
  39 /*   31 Point Equiripple FIR Low-Pass Filter */
  40 /*     Linear phase, delay = 15 samples */
  41
  42 /*      Passband:  ripple = 0.25 dB, cutoff =  800 Hz */
  43 /*      Stopband:  atten. =  40. dB, cutoff = 1240 Hz */
  44
  45 /* Inputs: */
  46 /*  LEN    - Length of speech buffers */
  47 /*  NSAMP  - Number of samples to filter */
  48 /*  INBUF  - Input speech buffer */
  49 /*           Indices len-nsamp-29 through len are read. */
  50 /* Output: */
  51 /*  LPBUF  - Low passed speech buffer (must be different array than INBUF) */
  52 /*           Indices len+1-nsamp through len are written. */
  53
  54 /* This subroutine has no local state. */
  55
  56 /* Subroutine */ int lpfilt_(real *inbuf, real *lpbuf, integer *len, integer *
  57         nsamp)
  58 {
  59     /* System generated locals */
  60     integer i__1;
  61
  62     /* Local variables */
  63     integer j;
  64     real t;
  65
  66 /*      Arguments */
  67 /*      Parameters/constants */
  68 /*       Local variables that need not be saved */
  69 /*       Local state */
  70 /*       None */
  71     /* Parameter adjustments */
  72     --lpbuf;
  73     --inbuf;
  74
  75     /* Function Body */
  76     i__1 = *len;
  77     for (j = *len + 1 - *nsamp; j <= i__1; ++j) {
  78         t = (inbuf[j] + inbuf[j - 30]) * -.0097201988f;
  79         t += (inbuf[j - 1] + inbuf[j - 29]) * -.0105179986f;
  80         t += (inbuf[j - 2] + inbuf[j - 28]) * -.0083479648f;
  81         t += (inbuf[j - 3] + inbuf[j - 27]) * 5.860774e-4f;
  82         t += (inbuf[j - 4] + inbuf[j - 26]) * .0130892089f;
  83         t += (inbuf[j - 5] + inbuf[j - 25]) * .0217052232f;
  84         t += (inbuf[j - 6] + inbuf[j - 24]) * .0184161253f;
  85         t += (inbuf[j - 7] + inbuf[j - 23]) * 3.39723e-4f;
  86         t += (inbuf[j - 8] + inbuf[j - 22]) * -.0260797087f;
  87         t += (inbuf[j - 9] + inbuf[j - 21]) * -.0455563702f;
  88         t += (inbuf[j - 10] + inbuf[j - 20]) * -.040306855f;
  89         t += (inbuf[j - 11] + inbuf[j - 19]) * 5.029835e-4f;
  90         t += (inbuf[j - 12] + inbuf[j - 18]) * .0729262903f;
  91         t += (inbuf[j - 13] + inbuf[j - 17]) * .1572008878f;
  92         t += (inbuf[j - 14] + inbuf[j - 16]) * .2247288674f;
  93         t += inbuf[j - 15] * .250535965f;
  94         lpbuf[j] = t;
  95     }
  96     return 0;
  97 } /* lpfilt_ */
  98