man.diff

来自「speech signal process tools」· DIFF 代码 · 共 147 行

.\" Copyright (c) 1993 Entropic Research Laboratory, Inc.; All rights reserved
.\" @(#)win_filt.1	1.6 9/1/98 ERL
.ds ]W (c) 1993 Entropic Research Laboratory, Inc.
.TH  WIN_FILT 1\-ESPS 9/1/98
.SH NAME

.nf
win_filt \- Designs a FIR filter using Kaiser Windowing
.fi
.SH SYNOPSIS
.B
win_filt
.BI \-P " param_file"
[
.BI \-x " debug_level"
]
file.filter
.SH DESCRIPTION
The program \fIwin_filt\fR designs a linear-phase finite-impulse response
(FIR) filter with its specifications defined in the parameter file 
\fIparam_file\fR.  The filter coefficients are saved in the output file
\fIfile.filter\fR.  If \fIfile.filter\fR is replaced by "-", the 
standard output is written.
.PP
The design method is based on the Kaiser Window -- a \fIsinc\fR function
representing the ideal response is multiplied by a Kaiser window to obtain a
finite length filter.  Type I (symmetric and odd) and type II (symmetric
and even) multiband filter design are supported.
.PP
Also see the shell script \fIxfir_filt(1-ESPS)\fR that is a cover
script for this and other FIR filter design program.  
.PP
Use \fIfiltspec(1-ESPS)\fR to compute the actual filter response; use
\fIplotspec(1-ESPS)\fR to view the response.  For example, 
.PP
\fIfiltspec file.filter - | plotspec -\fR
.PP
The number of output filter taps is determined automatically by 
\fIwin_filt\fR in order to meet the design specification.
.SH OPTIONS
.PP
The following options are supported:
.TP
.BI \-P " param_file \fR[params]\fP"
uses the parameter file 
.I param_file
rather than the default, which is \fIparams\fP. 
.TP
.BI \-x " debug_level \fR[0]\fP"
If 
.I debug_level
is positive,
.I win_filt
prints debugging messages and other information on the standard error
output.  The messages proliferate as the  
.I debug_level
increases.  If \fIdebug_level\fP is 0 (the default), no messages are
printed.  
.SH ESPS PARAMETERS
The following parameters are read from the \fIparam_file\fR.
.TP
.I samp_freq - float
Specifies the sampling frequency of the filter.  This number is used
for scaling the values of \fIband_edge[i]\fR parameters.
.TP
.I nbands - int
Specifies the number of bands.  For example, for a bandpass filter, 
\fInbands\fR is \fI3\fR.
.TP
.I band_edge[i] - float
Specifies the \fIi\fRth cutoff frequency in Hz.  There are \fInbands+1\fR
\fIband_edge[i]\fR parameters.  The first \fIband_edge1\fR must
start with 0, and the last frequency must end with the Nyquist rate.
The cutoff frequency is in the center of the region specified by
\fItrans_band\fR.
For example, for a 8KHz bandpass filter with stopband of 0 to 800 Hz
and 2200 to 4000 Hz, and passband of 1200 to 1800 Hz, 
the parameter \fIBand_edge1\fR is 0, \fIband_edge2\fR is 1000,
\fIband_edge3\fR is 2000, \fIband_edge4\fR is 4000, and
\fItrans_band\fR is 400.  Typically, the filter is 6 dB down at the
band edge of transition.
.TP
.I band[i]_des - float
Specifies desired value for the \fIi\fRth band.  For example, for
a 3-band bandpass filter, \fIband1_des\fR is 0, \fIband2_des\fR is 1,
and \fIband3_des\fR is 0;
.TP
.I rej_db - float
Specifies both the rejection ratio in dB from one passband to
stopband, and the peak error in the passband.
.TP
.I trans_band - float
Specifies the transition bandwidth in Hz from one band to another.
.TP
.I evenflag - int
This is an optional parameter.  If not specified, by default \fIwin_filt\fR
designs a filter with odd filter length; otherwise, a value of 1 forces
even length, and a value of 0 forces odd length.
.PP
.SH ESPS COMMON
No ESPS common parameter processing is used.
.PP
.SH ESPS HEADERS
A new \fIFEA_FILT\fP(5\-ESPS) header is created for the  output  file.   The
program  fills  in  appropriate values in the common part of
the FEA_FILT header as well as the  following  generic  header  items.
.PP
The \fIsamp_freq\fR generic header item contains value of the \fIsamp_freq\fR
parameter.
.PP
The \fItrans_band\fR generic header item contains value of the \fItrans_band\fR
parameter.
.PP
The \fIrej_db\fR generic header item contains value of the \fIrej_db\fR
parameter.
.PP
In addition, the generic header item \fIdelay_samples\fR  (type  DOUBLE) is
added  to the header. \fIDelay_samples\fR  is  equal  to  
(filter length  -  1)/2.   
This represents  the  delay  to  the  center  of  the peak of the
impulse response.

.PP
.SH FUTURE CHANGES
.PP
.SH EXAMPLES
.PP
.SH ERRORS AND DIAGNOSTICS
.PP
.SH BUGS
.PP
None known.
.SH REFERENCES
Oppenheim & Schafer, \fIDiscrete-Time Signal Processing\fR,
Prentice Hall, 1989
.PP
.SH "SEE ALSO"
.nf
\fIxfir_filt\fP(1\-ESPS), \fInotch_filt\fP(1\-ESPS), \fIFEA_FILT\fP(5\-ESPS),
\fIatofilt\fP(1\-ESPS), \fIwmse_filt\fP(1\-ESPS), \fIiir_filt\fP(1\-ESPS), 
\fIsfconvert\fP(1\-ESPS), \fIpkmc_filt\fP(1\-ESPS), 
.nf
.PP
.SH AUTHOR
Derek Lin
.PP