pztoco.3

speech signal process tools

.\" Copyright (c) 1986-1990 Entropic Speech, Inc.
.\" Copyright (c) 1991 Entropic Research Laboratory, Inc.; All rights reserved
.\" @(#)pztoco.3	1.4 02 Jul 1991 ESI/ERL
.TH pz_to_co 3\-ESPSsp 7/1/91
.ds ]W (c) 1991 Entropic Research Laboratory, Inc.
.SH NAME
.nf
pz_to_co \- convert pole or zero locations to filter coefficients.
pz_to_co_d \- convert pole or zero locations to filter coefficients.

.SH SYNOPSIS
.ft B
.br
int pz_to_co (nroots, real, imag, pnco, co);
.br
int nroots;
.br
double *real, *imag;
.br
float *co;
.br
short *pnco;
.sp
int pz_to_co_d (nroots, real, imag, pnco, co);
.br
int nroots;
.br
double *real, *imag;
.br
double *co;
.br
short *pnco;
.ft
.sp
.SH DESCRIPTION
.I pz_to_co 
and
.I pz_to_co_d
take in
.I nroots
root locations and returns the
coefficients for the expanded polynomial.  The root locations
are specified as complex numbers in rectangular form and are
passed to the function in the 
.I real
and
.I imag
arrays.
The resulting polynomial coefficients (starting with order zero)
are returned in the
.I co
array, and the number of them is returned in the variable
pointed to by
.I pnco.
If a root does not lie on the real axis (i.e. its imaginary part is nonzero)
then its complex conjugate is automatically included, and should not be
specified.  Those roots lying on the
real axis are left as is.
.SH EXAMPLE
.nf

int nzero;
double *real, *imag;
	.
	.
	.

/* This converts a set of zero locations to a filter record. */
/* Assume nzero and the real and imag arrays have been initialized. */

oh->hd.filt->max_num = nzero = NUM_COEFF;
oh->hd.filt->max_den = 0;
frec = allo_filt_rec (oh);

pz_to_co (nzero, real, imag, &(frec->filt_func.nsiz), frec->filt_func.zeros);
 
/* Write the filter record to the output file. */
write_header (oh, fpout);
.fi
.SH DIAGNOSTICS
None.
.SH BUGS
None known.
.SH SEE ALSO
zero_pole (1-ESPS)
.SH AUTHOR
Brian Sublett.  pz_to_co_d added by Bill Byrne.