115 lines
3.3 KiB
C
115 lines
3.3 KiB
C
/*
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$Log: lpfilt.c,v $
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Revision 1.1 2004/05/04 11:16:43 csoutheren
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Initial version
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Revision 1.1 2000/06/05 04:45:12 robertj
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Added LPC-10 2400bps codec
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* Revision 1.1 1996/08/19 22:31:35 jaf
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* Initial revision
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*
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*/
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#ifdef P_R_O_T_O_T_Y_P_E_S
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extern int lpfilt_(real *inbuf, real *lpbuf, integer *len, integer *nsamp);
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#endif
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/* -- translated by f2c (version 19951025).
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You must link the resulting object file with the libraries:
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-lf2c -lm (in that order)
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*/
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#include "f2c.h"
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/* *********************************************************************** */
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/* LPFILT Version 55 */
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/* $Log: lpfilt.c,v $
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* Revision 1.1 2004/05/04 11:16:43 csoutheren
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* Initial version
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*
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* Revision 1.1 2000/06/05 04:45:12 robertj
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* Added LPC-10 2400bps codec
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*
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* Revision 1.1 1996/08/19 22:31:35 jaf
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* Initial revision
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*
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*/
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/* Revision 1.3 1996/03/15 16:53:49 jaf */
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/* Just put comment header in standard form. */
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/* Revision 1.2 1996/03/12 23:58:06 jaf */
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/* Comments added explaining that none of the local variables of this */
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/* subroutine need to be saved from one invocation to the next. */
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/* Revision 1.1 1996/02/07 14:47:44 jaf */
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/* Initial revision */
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/* *********************************************************************** */
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/* 31 Point Equiripple FIR Low-Pass Filter */
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/* Linear phase, delay = 15 samples */
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/* Passband: ripple = 0.25 dB, cutoff = 800 Hz */
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/* Stopband: atten. = 40. dB, cutoff = 1240 Hz */
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/* Inputs: */
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/* LEN - Length of speech buffers */
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/* NSAMP - Number of samples to filter */
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/* INBUF - Input speech buffer */
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/* Indices len-nsamp-29 through len are read. */
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/* Output: */
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/* LPBUF - Low passed speech buffer (must be different array than INBUF) */
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/* Indices len+1-nsamp through len are written. */
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/* This subroutine has no local state. */
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/* Subroutine */ int lpfilt_(real *inbuf, real *lpbuf, integer *len, integer *
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nsamp)
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{
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/* System generated locals */
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integer i__1;
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/* Local variables */
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integer j;
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real t;
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/* Arguments */
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/* Parameters/constants */
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/* Local variables that need not be saved */
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/* Local state */
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/* None */
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/* Parameter adjustments */
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--lpbuf;
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--inbuf;
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/* Function Body */
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i__1 = *len;
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for (j = *len + 1 - *nsamp; j <= i__1; ++j) {
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t = (inbuf[j] + inbuf[j - 30]) * -.0097201988f;
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t += (inbuf[j - 1] + inbuf[j - 29]) * -.0105179986f;
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t += (inbuf[j - 2] + inbuf[j - 28]) * -.0083479648f;
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t += (inbuf[j - 3] + inbuf[j - 27]) * 5.860774e-4f;
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t += (inbuf[j - 4] + inbuf[j - 26]) * .0130892089f;
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t += (inbuf[j - 5] + inbuf[j - 25]) * .0217052232f;
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t += (inbuf[j - 6] + inbuf[j - 24]) * .0184161253f;
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t += (inbuf[j - 7] + inbuf[j - 23]) * 3.39723e-4f;
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t += (inbuf[j - 8] + inbuf[j - 22]) * -.0260797087f;
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t += (inbuf[j - 9] + inbuf[j - 21]) * -.0455563702f;
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t += (inbuf[j - 10] + inbuf[j - 20]) * -.040306855f;
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t += (inbuf[j - 11] + inbuf[j - 19]) * 5.029835e-4f;
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t += (inbuf[j - 12] + inbuf[j - 18]) * .0729262903f;
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t += (inbuf[j - 13] + inbuf[j - 17]) * .1572008878f;
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t += (inbuf[j - 14] + inbuf[j - 16]) * .2247288674f;
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t += inbuf[j - 15] * .250535965f;
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lpbuf[j] = t;
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}
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return 0;
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} /* lpfilt_ */
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