ref: 678e9696e73fcc7502fa443364ce1d8f88cb0944
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_ */