refcof.1

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.\" Copyright (c) 1986-1996 Entropic Speech, Inc.
.\" Copyright (c) 1996 Entropic Research Laboratory, Inc.; All rights reserved
.TH REFCOF 1\-ESPS 01 Oct 1998
.ds ]W (c) 1996 Entropic Research Laboratory, Inc.
.\" @(#)refcof.1	3.36 01 Oct 1998 ESI/ERL
.SH "NAME"
.nf
refcof - computes LPC reflection coefficients via various spectrum analysis methods

xrefcof\- run \fIrefcof\fP with X Windows interactions and displays
.SH SYNOPSIS
.B refcof
[
.BI \-P " param"
] [
.BI \-p " range"
] [
.BI \-r " range
] [
.BI \-l " frame_len"
] [
.BI \-S " step"
] [
.BI \-w " window_type"
] [ 
.BI \-m " method"
] [
.BI \-o " order"
] [
.BI \-e " preemphasis"
] [
.BI \-c " conv_test"
] [
.BI \-i " max_iter"
] [
.BI \-s " sinc_n"
] [
.B \-d
] [
.B \-Z
] [
.B \-z
] [
.BI \-x " debug_level"
]
.I file.sd file.rc
.br

.B xrefcof
[
.BI \-{rp} " range"
]
.I sd_file
.sp
.SH DESCRIPTION
.PP
.I refcof
takes an ESPS sampled data file,
.I file.sd,
and produces an ESPS FEA_ANA analysis file
.I file.rc
containing the reflection coefficients corresponding to one or 
more fixed-length sampled-data frames.  
.PP
All input frames have the same length
.I frame_len
(see
.B \-l
option).
The initial point of the first frame is determined by 
the \fB\-p\fP option or by \fIstart\fP in the parameter file.  
Initial points of any subsequent frames follow at equal intervals
.I step
(see
.B \-S
option).
Thus the 3 cases
.IR step " < " frame_len,
.IR step " = " frame_len,
and
.IR step " > " frame_len,
correspond to overlapping frames, exactly abutted frames,
and frames separated by gaps.
.PP
The number of frames
is the minimum sufficient to cover a specified range of
.I nan
points (see
.B \-p
and 
.B \-Z
options), given \fIframe_len\fP and \fIstep\fP.  The last frame in
each file may overrun the range, in which case a warning is printed.
If a frame overruns the end of a file, it is normally filled out with
zeros (but see \fB-Z\fP).
.PP
The reflection coefficients, along with the computed values for
.I raw_power
and
.I lpc_power,
are then stored in FEA_ANA records.  No pitch pulse information is
written to the file.
.PP
If 
.I file.sd
is "\-" then the input is read from the standard input and if
.I file.rc
is "\-" then the output is directed to the standard output.
.PP
The following spectrum analysis methods are available:
.na
.nh
.IP
Autocorrelation Method (AUTOC) \- see \fIget_auto\fP(3\-\s-1ESPS\s+1)
.IP
Covariance Method (COV) \- see \fIcovar\fP(3\-\s-1ESPS\s+1)
.IP
Burg Method (BURG) \- see \fIget_burg\fP(3\-\s-1ESPS\s+1)
.IP
Modified Burg Method (MBURG) \- see \fIget_burg\fP(3\-\s-1ESPS\s+1)
.IP
Fast Modified Burg Method (FBURG) \- \fIget_fburg\fP(3\-\s-1ESPS\s+1)
.IP
Structured Covariance Methods (STRCOV and STRCOV1) \- see
\fIstrcov_auto\fP(3\-\s-1ESPS\s+1),
\fIstruct_cov\fP(3\-\s-1ESPS\s+1), and \fIgenburg\fP(3\-\s-1ESPS\s+1)
.IP
Vector Burg Method (VBURG) (fast approximation to structured 
covariance) \- see \fIget_vburg\fP(3\-\s-1ESPS\s+1)
.hy
.ad
.PP
By default, the program uses the autocorrelation method, which
applies the standard method of computing the autocorrelation function
and the Levinson algorithm for computing the reflection coefficients
from the autocorrelation values.  Note that the standard
autocorrelation method may yield poor results when using a small
number (i.e. < 100) of data samples.  The other methods can be
specified by using the \fB\-m\fP option.  The most accurate usually 
is STRCOV, especially for small frame lengths.  
.PP
The methods AUTOC, STRCOV, and STRCOV1 operate by estimating the
autocorrelation function and then transforming to reflection
coefficients.  In these cases, the program can also optionally
multiply the autocorrelation function by a sinc function (\fB\-s\fP
option) prior to computing the reflection coefficients.  
This has the effect of reducing the spectral resolution if the
spectrum of these coefficients is plotted.
.PP
Of the two structured covariance methods [2], STRCOV is consderably faster
and better behaved than STRCOV1.  We include STRCOV1 as it may be
useful in certain cases.  STRCOV uses a fast, single channel algorithm
\fIstruct_cov\fP (3\-\s-1ESPS\s+1) developed by John Burg and
programmed by Bernard Fraenkel.  STRCOV2 uses an older (but more
general) algorithm \fIgenburg\fP (3\-\s-1ESPS\s+1) that was
programmed by Daniel Wenger.  Note that the \fB-c\fP and \fB-i\fP
options are relevant for controlling the convergence of STRCOV.
The VBURG method is a fast approximation to structured covariance 
that was developed and programmed by John Burg and Shankar Narayan
[3]. 
.PP
If spectral representations other than reflection coefficients
are desired, use 
.I transpec
(1\-ESPS) or
.I spectrans 
(1\-ESPS) on the output of 
.I refcof.
If you want the actual spectrum, use 
.I me_spec
(1\-ESPS) on the output of 
.I refcof. 
.PP
\fIxrefcof\fP is a script that runs \fIrefcof\fP on a single frame of
data that is specified by the range option (\fB-r\fP or \fB-p\fP) or
by means of ESPS Common.  A pop-up window is used to prompt the user
for \fIwindow_type\fP, \fImethod\fP, \fIorder\fP, \fIconv_test\fP, and
\fImax_iter\fP.  The results of the \fIanalysis\fP are displayed in
two pop-up windows \- one containing the reflection coefficents, and
one containing a maximum-entropy power spectrum computed from these
reflection coeffiecients.  \fIxrefcof\fP makes used of \fIexprompt\fP
(1\-\s-1ESPS\s+1), \fIme_spec\fP (1\-\s-1ESPS\s+1), \fIplotspec\fP
(1\-\s-1ESPS\s+1), and \fIxtext\fP (1\-\s-1ESPS\s+1).
.PP
The parameter prompting for \fIxrefcof\fP is performed by means of the
parameter file named PWrefcof, which is normally obtained from
$ESPS_BASE/lib/params.  However, if you have a file by this name in
the current directory (or if you define the environment variable
ESPS_PARAMS_PATH and put one on that path), it will be used instead.
.SH OPTIONS
The following options are supported (only \fB-r\fP or \fB-p\fP can 
be given for \fIxrefcof\fP):  
.TP
.BI \-P " param"
uses the parameter file 
.I param
rather than the default, which is
.I params.
.TP
.BI \-p " first" : "last"
.TP
.BI \-p " first\-last"
.TP
.BI \-p " first" :+ "incr" "\fR [1:+999]"
In the first two forms, a pair of unsigned integers specifies the range of
sampled data to analyze.  If 
.IR last " = " first " + " incr,
the third form (with the plus sign) specifies the same range as the
first two forms.  If 
.I first
is omitted, the default value of 1 is used.  If 
.I last
is omitted, then a default frame length of 1000 results.  If the
specified range contains points not in the file, the last frame is
truncated to fit the actual data.  Both forms of the option override
the values of
.I start
and
.I nan
in the parameter file or ESPS Common file.  If the \fB\-p\fP option is
not used, the range is determined from the ESPS Parameter or Common
file if the appropriate parameters are present.  Note that the default
frame length of 1000 also results if \fInan\fP is not in the parameter
or Common file and if no \fB-p\fP is used.
.TP
.BI \-r " range"
\fB\-r\fP is a synonym for \fB\-p\fP.
.TP
.BI \-l " frame_len" "\fR [0]"
Specifies the length of each frame.  If the option is omitted, the
parameter file is consulted.  A value of 0 (from either the option or
the parameter file) indicates that a single frame of length
.I nan
(see
.BR \-p )
is processed; this is also the default value in case
.I frame_len
is not specified either with the
.B \-l
option or in the parameter file.
.TP
.BI \-S " step" "\fR [" frame_len "\fR]"
Initial points of consecutive frames differ by this number of samples.
If the option is omitted, the parameter file is consulted,
and if no value is found there, a default equal to
.I frame_len
is used (resulting in exactly abutted frames).  (The same default
applies if \fIstep\fP is given a value of 0).  
.TP
.BI \-w " window_type" "\fR[RECT]"
The name of the data window to apply to the data in each frame before
computing reflection coefficients.  If the option is omitted, the
parameter file is consulted, and if no value is found there, the
default used is a rectangular window with amplitude one.  Possible
window types include rectangular ("RECT"), Hamming ("HAMMING"),
Hanning ("HANNING"), cosine (COS4), and triangular ("TRIANG"); see the
window(3-ESPSsp) manual page.  If the last frame is truncated, the
window is applied to the truncated data (e.g., a triangular window is
zero at the start and end of the truncated data).
.TP 
.BI \-m " method\fR[autoc]"
Specifies the spectrum analysis method.  The default is the
autocorrelation method.  Also available are the covariance method
("cov"), Burg method ("burg"), modified Burg method ("mburg"), fast
modified Burg method ("fburg"), stuctured covariance ("strcov" and
"strcov1"), and vector Burg ("vburg", fast approximation to structured
covariance.  Of the two structured covariance methods, the first
("strcov" is considerably faster and better behaved; "strcov1" is
older but included as it may prove useful on occasion.  If "strcov" is
used, the \fB-c\fP and \fB-i\fP options become relevant.  The \fB-m\fP
option overrides the value that may be in the parameter file.  The
default applies only if there is no value in the parameter file.
.TP
.BI \-e " preemphasis\fR[0.0]\fP"
Specifies a preemphasis factor to apply to the input signal.