lpc10/hp100.c

   1 /*
   2
   3  * Revision 1.2  1996/08/20  20:28:05  jaf
   4  * Removed all static local variables that were SAVE'd in the Fortran
   5  * code, and put them in struct lpc10_encoder_state that is passed as an
   6  * argument.
   7  *
   8  * Removed init function, since all initialization is now done in
   9  * init_lpc10_encoder_state().
  10  *
  11  * Revision 1.1  1996/08/19  22:32:04  jaf
  12  * Initial revision
  13  *
  14
  15 */
  16
  17 /*  -- translated by f2c (version 19951025).
  18    You must link the resulting object file with the libraries:
  19         -lf2c -lm   (in that order)
  20 */
  21
  22 #include "f2c.h"
  23
  24 extern int hp100_(real *speech, integer *start, integer *end,
  25                   struct lpc10_encoder_state *st);
  26 extern int inithp100_(void);
  27
  28 /* ********************************************************************* */
  29
  30 /*      HP100 Version 55 */
  31
  32 /* ********************************************************************* */
  33
  34 /*    100 Hz High Pass Filter */
  35
  36 /* Jan 92 - corrected typo (1.937148 to 1.935715), */
  37 /*          rounded coefficients to 7 places, */
  38 /*          corrected and merged gain (.97466**4), */
  39 /*          merged numerator into first two sections. */
  40
  41 /* Input: */
  42 /*  start, end - Range of samples to filter */
  43 /* Input/Output: */
  44 /*  speech(end) - Speech data. */
  45 /*                Indices start through end are read and modified. */
  46
  47 /* This subroutine maintains local state from one call to the next.  If */
  48 /* you want to switch to using a new audio stream for this filter, or */
  49 /* reinitialize its state for any other reason, call the ENTRY */
  50 /* INITHP100. */
  51 /* Subroutine */ int hp100_(real *speech, integer *start, integer *end,
  52         struct lpc10_encoder_state *st)
  53 {
  54     /* Temporary local copies of variables in lpc10_encoder_state.
  55        I've only created these because it might cause the loop below
  56        to execute a bit faster to access local variables, rather than
  57        variables in the lpc10_encoder_state structure.  It is just a
  58        guess that it will be faster. */
  59
  60     real z11;
  61     real z21;
  62     real z12;
  63     real z22;
  64
  65     /* System generated locals */
  66     integer i__1;
  67
  68     /* Local variables */
  69     integer i__;
  70     real si, err;
  71
  72 /*       Arguments */
  73 /*       Local variables that need not be saved */
  74 /*       Local state */
  75     /* Parameter adjustments */
  76     if (speech) {
  77         --speech;
  78         }
  79
  80     /* Function Body */
  81
  82     z11 = st->z11;
  83     z21 = st->z21;
  84     z12 = st->z12;
  85     z22 = st->z22;
  86
  87     i__1 = *end;
  88     for (i__ = *start; i__ <= i__1; ++i__) {
  89         si = speech[i__];
  90         err = si + z11 * 1.859076f - z21 * .8648249f;
  91         si = err - z11 * 2.f + z21;
  92         z21 = z11;
  93         z11 = err;
  94         err = si + z12 * 1.935715f - z22 * .9417004f;
  95         si = err - z12 * 2.f + z22;
  96         z22 = z12;
  97         z12 = err;
  98         speech[i__] = si * .902428f;
  99     }
 100
 101     st->z11 = z11;
 102     st->z21 = z21;
 103     st->z12 = z12;
 104     st->z22 = z22;
 105
 106     return 0;
 107 } /* hp100_ */