ref: 79f515914c96e04a3be3b20bbc5c71459e4b8915
dir: /lpc10/hp100.c/
/*
* Revision 1.2 1996/08/20 20:28:05 jaf
* Removed all static local variables that were SAVE'd in the Fortran
* code, and put them in struct lpc10_encoder_state that is passed as an
* argument.
*
* Removed init function, since all initialization is now done in
* init_lpc10_encoder_state().
*
* Revision 1.1 1996/08/19 22:32:04 jaf
* Initial revision
*
*/
/* -- translated by f2c (version 19951025).
You must link the resulting object file with the libraries:
-lf2c -lm (in that order)
*/
#include "f2c.h"
extern int hp100_(real *speech, integer *start, integer *end,
struct lpc10_encoder_state *st);
extern int inithp100_(void);
/* ********************************************************************* */
/* HP100 Version 55 */
/* ********************************************************************* */
/* 100 Hz High Pass Filter */
/* Jan 92 - corrected typo (1.937148 to 1.935715), */
/* rounded coefficients to 7 places, */
/* corrected and merged gain (.97466**4), */
/* merged numerator into first two sections. */
/* Input: */
/* start, end - Range of samples to filter */
/* Input/Output: */
/* speech(end) - Speech data. */
/* Indices start through end are read and modified. */
/* This subroutine maintains local state from one call to the next. If */
/* you want to switch to using a new audio stream for this filter, or */
/* reinitialize its state for any other reason, call the ENTRY */
/* INITHP100. */
/* Subroutine */ int hp100_(real *speech, integer *start, integer *end,
struct lpc10_encoder_state *st)
{
/* Temporary local copies of variables in lpc10_encoder_state.
I've only created these because it might cause the loop below
to execute a bit faster to access local variables, rather than
variables in the lpc10_encoder_state structure. It is just a
guess that it will be faster. */
real z11;
real z21;
real z12;
real z22;
/* System generated locals */
integer i__1;
/* Local variables */
integer i__;
real si, err;
/* Arguments */
/* Local variables that need not be saved */
/* Local state */
/* Parameter adjustments */
if (speech) {
--speech;
}
/* Function Body */
z11 = st->z11;
z21 = st->z21;
z12 = st->z12;
z22 = st->z22;
i__1 = *end;
for (i__ = *start; i__ <= i__1; ++i__) {
si = speech[i__];
err = si + z11 * 1.859076f - z21 * .8648249f;
si = err - z11 * 2.f + z21;
z21 = z11;
z11 = err;
err = si + z12 * 1.935715f - z22 * .9417004f;
si = err - z12 * 2.f + z22;
z22 = z12;
z12 = err;
speech[i__] = si * .902428f;
}
st->z11 = z11;
st->z21 = z21;
st->z12 = z12;
st->z22 = z22;
return 0;
} /* hp100_ */