ref: 0616603970338b131a5abe19a0ee825faebf4f85
dir: /lpc10/lpfilt.c/
/* * Revision 1.1 1996/08/19 22:31:35 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 lpfilt_(real *inbuf, real *lpbuf, integer *len, integer *nsamp); /* *********************************************************************** */ /* LPFILT Version 55 */ /* * Revision 1.1 1996/08/19 22:31:35 jaf * Initial revision * */ /* Revision 1.3 1996/03/15 16:53:49 jaf */ /* Just put comment header in standard form. */ /* Revision 1.2 1996/03/12 23:58:06 jaf */ /* Comments added explaining that none of the local variables of this */ /* subroutine need to be saved from one invocation to the next. */ /* Revision 1.1 1996/02/07 14:47:44 jaf */ /* Initial revision */ /* *********************************************************************** */ /* 31 Point Equiripple FIR Low-Pass Filter */ /* Linear phase, delay = 15 samples */ /* Passband: ripple = 0.25 dB, cutoff = 800 Hz */ /* Stopband: atten. = 40. dB, cutoff = 1240 Hz */ /* Inputs: */ /* LEN - Length of speech buffers */ /* NSAMP - Number of samples to filter */ /* INBUF - Input speech buffer */ /* Indices len-nsamp-29 through len are read. */ /* Output: */ /* LPBUF - Low passed speech buffer (must be different array than INBUF) */ /* Indices len+1-nsamp through len are written. */ /* This subroutine has no local state. */ /* Subroutine */ int lpfilt_(real *inbuf, real *lpbuf, integer *len, integer * nsamp) { /* System generated locals */ integer i__1; /* Local variables */ integer j; real t; /* Arguments */ /* Parameters/constants */ /* Local variables that need not be saved */ /* Local state */ /* None */ /* Parameter adjustments */ --lpbuf; --inbuf; /* Function Body */ i__1 = *len; for (j = *len + 1 - *nsamp; j <= i__1; ++j) { t = (inbuf[j] + inbuf[j - 30]) * -.0097201988f; t += (inbuf[j - 1] + inbuf[j - 29]) * -.0105179986f; t += (inbuf[j - 2] + inbuf[j - 28]) * -.0083479648f; t += (inbuf[j - 3] + inbuf[j - 27]) * 5.860774e-4f; t += (inbuf[j - 4] + inbuf[j - 26]) * .0130892089f; t += (inbuf[j - 5] + inbuf[j - 25]) * .0217052232f; t += (inbuf[j - 6] + inbuf[j - 24]) * .0184161253f; t += (inbuf[j - 7] + inbuf[j - 23]) * 3.39723e-4f; t += (inbuf[j - 8] + inbuf[j - 22]) * -.0260797087f; t += (inbuf[j - 9] + inbuf[j - 21]) * -.0455563702f; t += (inbuf[j - 10] + inbuf[j - 20]) * -.040306855f; t += (inbuf[j - 11] + inbuf[j - 19]) * 5.029835e-4f; t += (inbuf[j - 12] + inbuf[j - 18]) * .0729262903f; t += (inbuf[j - 13] + inbuf[j - 17]) * .1572008878f; t += (inbuf[j - 14] + inbuf[j - 16]) * .2247288674f; t += inbuf[j - 15] * .250535965f; lpbuf[j] = t; } return 0; } /* lpfilt_ */