lpc10/deemp.c

   1 /*
   2
   3  * Revision 1.2  1996/08/20  20:23:46  jaf
   4  * Removed all static local variables that were SAVE'd in the Fortran
   5  * code, and put them in struct lpc10_decoder_state that is passed as an
   6  * argument.
   7  *
   8  * Removed init function, since all initialization is now done in
   9  * init_lpc10_decoder_state().
  10  *
  11  * Revision 1.1  1996/08/19  22:32:34  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 deemp_(real *x, integer *n, struct lpc10_decoder_state *st);
  25
  26 /* ***************************************************************** */
  27
  28 /*      DEEMP Version 48 */
  29
  30 /*
  31  * Revision 1.2  1996/08/20  20:23:46  jaf
  32  * Removed all static local variables that were SAVE'd in the Fortran
  33  * code, and put them in struct lpc10_decoder_state that is passed as an
  34  * argument.
  35  *
  36  * Removed init function, since all initialization is now done in
  37  * init_lpc10_decoder_state().
  38  *
  39  * Revision 1.1  1996/08/19  22:32:34  jaf
  40  * Initial revision
  41  * */
  42 /* Revision 1.3  1996/03/20  15:54:37  jaf */
  43 /* Added comments about which indices of array arguments are read or */
  44 /* written. */
  45
  46 /* Added entry INITDEEMP to reinitialize the local state variables, if */
  47 /* desired. */
  48
  49 /* Revision 1.2  1996/03/14  22:11:13  jaf */
  50 /* Comments added explaining which of the local variables of this */
  51 /* subroutine need to be saved from one invocation to the next, and which */
  52 /* do not. */
  53
  54 /* Revision 1.1  1996/02/07 14:44:53  jaf */
  55 /* Initial revision */
  56
  57
  58 /* ***************************************************************** */
  59
  60 /*  De-Emphasize output speech with   1 / ( 1 - .75z**-1 ) */
  61 /*    cascaded with 200 Hz high pass filter */
  62 /*    ( 1 - 1.9998z**-1 + z**-2 ) / ( 1 - 1.75z**-1 + .78z**-2 ) */
  63
  64 /*  WARNING!  The coefficients above may be out of date with the code */
  65 /*  below.  Either that, or some kind of transformation was performed */
  66 /*  on the coefficients above to create the code below. */
  67
  68 /* Input: */
  69 /*  N  - Number of samples */
  70 /* Input/Output: */
  71 /*  X  - Speech */
  72 /*       Indices 1 through N are read before being written. */
  73
  74 /* This subroutine maintains local state from one call to the next.  If */
  75 /* you want to switch to using a new audio stream for this filter, or */
  76 /* reinitialize its state for any other reason, call the ENTRY */
  77 /* INITDEEMP. */
  78
  79 /* Subroutine */ int deemp_(real *x, integer *n, struct lpc10_decoder_state *st)
  80 {
  81     /* Initialized data */
  82
  83     real *dei1;
  84     real *dei2;
  85     real *deo1;
  86     real *deo2;
  87     real *deo3;
  88
  89     /* System generated locals */
  90     integer i__1;
  91     real r__1;
  92
  93     /* Local variables */
  94     integer k;
  95     real dei0;
  96
  97 /*       Arguments */
  98 /*       Local variables that need not be saved */
  99 /*       Local state */
 100 /*       All of the locals saved below were not given explicit initial */
 101 /*       values in the original code.  I think 0 is a safe choice. */
 102     /* Parameter adjustments */
 103     if (x) {
 104         --x;
 105         }
 106
 107     /* Function Body */
 108
 109     dei1 = &(st->dei1);
 110     dei2 = &(st->dei2);
 111     deo1 = &(st->deo1);
 112     deo2 = &(st->deo2);
 113     deo3 = &(st->deo3);
 114
 115     i__1 = *n;
 116     for (k = 1; k <= i__1; ++k) {
 117         dei0 = x[k];
 118         r__1 = x[k] - *dei1 * 1.9998f + *dei2;
 119         x[k] = r__1 + *deo1 * 2.5f - *deo2 * 2.0925f + *deo3 * .585f;
 120         *dei2 = *dei1;
 121         *dei1 = dei0;
 122         *deo3 = *deo2;
 123         *deo2 = *deo1;
 124         *deo1 = x[k];
 125     }
 126     return 0;
 127 } /* deemp_ */