window.3t

speech signal process tools

.\" Copyright (c) 1987\-1990 Entropic Speech, Inc.
.\" Copyright (c) 1990\-1997 Entropic Research Laboratory, Inc.
.\" All rights reserved.
.\" @(#)window.3t	1.10 01 Oct 1998 ESI/ERL
.ds ]W (c) 1997 Entropic Research Laboratory, Inc.
.TH WINDOW 3\-ESPSsp 01 Oct 1998
.SH NAME

window \- window a data array.
.SH SYNOPSIS
.nf
.ft B
#include <esps/windows.h>
#include <esps/window.h>
.sp
int 
window(nsamp, x, y, type, p)
    long nsamp;
    float *x, *y;
    int type;
    double *p;
.sp
int 
windowd(nsamp, x, y, type, p)
    long nsamp;
    double *x, *y;
    int type;
    double *p;
.sp
int 
windowcf(nsamp, x, y, type, p)
    long nsamp;
    float_cplx *x, *y;
    int type;
    float_cplx *p;
.sp
int 
windowcd(nsamp, x, y, type, p)
    long nsamp;
    double_cplx *x, *y;
    int type;
    double_cplx *p;
.sp
char *window_types[];
.sp
int
win_type_from_name(name);
    char *name;
.ft
.fi
.SH DESCRIPTION
The four functions
.I window,
.I windowd,
.I windowcf,
and
.I windowcd
each take an array of 
.I nsamp
inputs in 
.I x,
window it with the data window indicated by
.I type,
and return the 
.I nsamp
outputs in the
.I y
array.
They differ only in the data types on which they operate.
.PP
The argument
.I p
can be used in two ways.
Either it is a pointer to
parameters needed for the specification of the window,
or it can also be used to specify an arbitrary
user-defined window type.
For example
if a Kaiser window was specified,
.I p
would be a one element vector that contained 
the shape parameter.
In supported window types,
the size of the 
.I p
array is a function of the window type.
In the other case,
.I p
is a vector containing the weighting
function values; it is assumed that
.I p
contains \fInsamp\fP values.
Note that 
.I x
and 
.I y
may be the same array.
.PP
Currently implemented window types are the following:
.sp
.TS
center, tab($), allbox;
c s
c|c
c|n.
WINDOW FUNCTIONS
Type$P Dimension
rectangular (WT_RECT)$0
Hamming (WT_HAMMING)$0
triangular (WT_TRIANG)$0
Hanning (WT_HANNING)$0
Kaiser (WT_KAISER)$1
cos**4 (WT_COS4)$0
arbitrary (WT_ARB)$nsamp
.TE
.sp .35
.PP
When \fIp\fR has dimension zero,
the appropriately cast NULL 
should be passed to the function (see the example below).
.PP
Note that window(3\-ESPS) defines a string array
\fIwindow_types\fR that contains the names of all legal
window functions. The include file \fIwindow.h\fR contains
numerical equivalents for the all these names, and
it also declares the \fIwindow_types\fR array for the user.
.PP
The function
.I win_type_from_name
takes a window-type name without the "WT_" prefix (e.g. "HAMMING") and
returns the corresponding numeric code (e.g. WT_HAMMING).
The function is case-insensitive, so it would also return WT_HAMMIN
for the input "Hamming" or "hamming".
It returns the value of the constant WT_NONE if the input is not
one of the recognized window type names.
See the example below.
.SH EXAMPLE
.nf
#include <esps/window.h>

float x[100], y[100];
long nsamp = 100;
int data_window;
char *window_func = "HAMMING";   /* Use Hamming window*/

FILE *fpin;		/* input file stream pointer */
struct header *ih;		/* input sampled data file header*/


/* get window type from string */

    if ((data_window = win_type_from_name(window_func)) == WT_NONE)
	ERROR_EXIT("Invalid window function specified.");

/* get sampled data */

    get_sd_recf(x, nsamp, ih, fpin);

/* window data */

    if ((window(nsamp, x, y, data_window, (double *) NULL)) != 0)
	ERROR_EXIT("Error in window function");

.fi
.SH DIAGNOSTICS
The windowing functions return 0 if the windowing was done successfully.
.SH BUGS
None known.
.SH SEE ALSO
auto(1\-ESPS), fft(1\-ESPS), refcof(1\-ESPS), 
.br
cross_cor(1\-ESPS)
.SH AUTHOR
Manual page and code by D. Burton.  Complex functions added by B. Byrne.