filspectru.3

来自「speech signal process tools」· 3 代码 · 共 70 行

.\" Copyright (c) 1992 Entropic Research Laboratory, Inc.; All rights reserved
.\" @(#)filspectru.3	1.2 27 Sep 1997 ERL
.ds ]W (c) 1992 Entropic Research Laboratory, Inc.
.TH  fil_spectrum 3\-ESPS 27 Sep 1997
.SH NAME

fil_spectrum \- computes FIR, IIR filter spectral response

.SH SYNOPSIS
.nf
.ft B
#include <esps/feafilt.h>
#include <esps/feaspec.h>

int fil_spectrum( spec_rec, mag, phase, filt_rec, fhd, nsamp )
struct feaspec *spec_rec;
double *mag;
double *phase;
struct feafilt *filt_rec;
struct header *fhd;
long nsamp;

.ft
.fi
.SH DESCRIPTION
.PP
\fIfil_spectrum\fR computes the spectral 
response from a FIR or IIR filter as specified 
by \fIfilt_rec\fR.  The number of output points for frequency range from
0 to the Nyquist rate is given by \fInsamp\fR.  Output can be
pointed to by any one of the non-NULL pointers, \fIspec_rec, mag\fR, or
\fIphase\fR.  Output complex spectrum is pointed to by \fIspec_rec\fR,
output linear spectral magnitude response is pointed to by \fImag\fR,
and ouput phase response is pointed to by \fIphase\fR.  \fIfhd\fR is
the file header of the \fIfilt_rec\fR.  Currently \fIfhd\fR is not used
in the function.
.PP
For IIR spectral response, \fInsamp\fR can be an arbitrary number if
poles and zeros coefficients are stored in \fIfilt_rec\fR.  The overall
gain for the IIR pole/zero system equals to
\fIfilt_rec->re_num_coeff[0]\fR.
If \fIfilt_rec->re_num_coeff[0]\fR does not exist, the gain is set to 1.
.PP
For FIR spectral response, \fInsamp\fR must be a power of 2 plus 1.
.SH EXAMPLES
.nf
/* The following computes linear spectral magnitude */

double mag[1025];
struct feafilt *filt_rec;
struct header *fhd;
FILE fp;

get_feafilt_rec( filt_rec, fhd, fp);
fil_spectrum( NULL, mag, NULL, filt_rec, fhd, 1025 );

.PP
.SH ERRORS AND DIAGNOSTICS
The function returns 0 upon success, 1 otherwise.  The function prints
an error message if \fInsamp\fR is not a power of 2 plus 1 when computing
FIR spectral response.
.PP
.SH "SEE ALSO"
.IR filtspec (1\-ESPS),
.IR FEA_FILT (5\-ESPS)
.PP
.SH AUTHOR
.PP
Derek Lin