cepsyn.1

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.\" Copyright (c) 1997 Entropic Research Laboratory, Inc. All rights reserved.
.\" @(#)cepsyn.1	1.2 9/27/97 ERL
.ds ]W (c) 1997 Entropic Research Laboratory, Inc.
.if n .ds pi pi
.if t .ds pi \(*p
.TH  CEPSYN 1\-ESPS 9/27/97
.SH NAME

cepsyn \- recover sampled data from cepstrum and phase
.SH SYNOPSIS
.B
cepsyn
[
.BI \-r " range1"
[
.BI \-r " range2"
]] [
.BI \-t " output_type"
] [
.BI \-x " debug_level"
] [
.B \-W
]
.I phase_in.fea
.I cepst_in.fea
.I output.sd
.SH DESCRIPTION
.PP
This is one of a pair of programs that lets one
analyze a file of sampled data to obtain cepstrum and phase information,
modify the cepstrum,
and recombine the modified cepstrum with the original phase
to obtain a new sampled-data file.
The program
.IR cepanal (1\-ESPS)
analyzes the sampled data into phase and cepstrum data
in separate output files.
This program performs the inverse transformation,
combining phase and cepstrum data in
.I phase_in.fea
and
.I cepstrum_in.fea
to produce sampled data in
.I output.sd.
.PP
Either input file, but not both, may be "\-", for standard input.
If "\-" is given for the output file, the output is written to the
standard output.
.PP
The input files,
.I phase_in.fea
and
.I cepst_in.fea
should have the same format as the output files of
.IR cepanal (1\-ESPS).
Namely, they are ordinary ESPS files, not of any special FEA subtype,
each containing a single field with data type FLOAT.
The fields are named
.I phase
and
.I cepstrum,
respectively; they must have the same length, namely
.IR "n" "/2 + 1,"
where
.I "n"
is the length of the Fourier transform used in
.I cepanal.
(Thus
.I "n"
is 2 raised to the power
.I order,
where
.I order
is the order of the transform.
See the option
.B \-o
in the man page for
.IR cepanal (1\-ESPS)).
.PP
Each input field implicitly determines a vector
of the full transform length,
.I n,
by symmetry, in the case of
.I cepstrum,
or antisymmetry (mod 2\*(pi), in the case of
.I phase.
The program 
performs a Fast Fourier Transform on each vector of cepstral data from
.I cepst_in.fea,
obtaining a real result (because of the symmetry).
To this it adds an imaginary part
consisting of the vector of phase data from the corresponding frame in
.I phase_in.fea.
It then computes the inverse Fourier transform
of the exponential of the resulting complex quantity,
obtaining frames of sample data,
which it combines to form the contents of an ESPS FEA_SD file,
It normally attempts to compensate at the same time for any windowing
performed by 
.IR cepanal :
it divides the overlapped sum of the sampled-data frames by a similarly
overlapped sum of translated copies of the window function,
obtaining an overlapped average of the frames.
For this to succeed, the latter sum must not contain zeros;
otherwise a message is printed, and the division step is skipped.
This behavior can be modified by the
.B \-W
option (see below).
.SH OPTIONS
.PP
The following options are supported.  Default values are shown in brackets.
.TP
.BI \-r " first" : "last" "\fR [1:(last in file)]"
.TP
.BI \-r " first" :+ "incr"
.TP
.BI \-r " first"
The range of records to be taken from one or both input files.
In the first form, a pair of unsigned integers specifies the range of
records to analyze.
If
.I first
is omitted, the default value of 1 is used.  If
.I last
is omitted, the range extends to the end of the file.
If
.IR last " = " first " + " incr,
the second form (with the plus sign) specifies the same range as the
first form.
The third form (omitting the colon) specifies a single record.
Note that for this program the range is specified in frames,
whereas for
.IR cepanal (1\-ESPS)
it is specified in samples.
.IP
This option may be used at most twice.
If used once, it applies to both input files.
If used twice, it applies to
.I phase_in.fea
the first time and
.I cepst_in.fea
the second time.
If the option is used twice and implies ranges of inconsistent sizes,
a warning message may be issued.
For example 
.BR \-r " 1" : 10
and
.BR \-r " 101" : 120
in the same
.I cepsyn
command will generate a warning of inconsistent
.B \-r
options.
On the other hand two options with one unspecified endpoint, like
.BR \-r " 1" :
and
.BR \-r " 101" : 120,
are not considered inconsistent and will not generate the warning.
.TP
.BI \-t " output_type" "\fR [FLOAT]"
The data type of the output sampled data.
.TP
.BI \-x " debug_level \fR[0]\fP"
A positive value specifies that debugging output is to be printed on
the standard error output.
Larger values result in more output.
For the default value, 0, there is no output.
.TP
.BI \-W
Specifying this option causes the program to ignore the input header item
.I window_type
and assume a rectangular window.
.SH ESPS PARAMETERS
.PP
This program does not access a parameter file.
.SH ESPS COMMON
.PP
The ESPS Common file is not read.
.PP
If Common processing is enabled,
and the output file is not standard output,
the program writes the Common parameters
.I prog,
.I filename,
.I start,
and
.I nan
to record the program's name, the name of the output file,
the starting record number of the output file (always 1),
and the number of points in the output file.
.PP
ESPS Common processing may be disabled
by setting the environment variable USE_ESPS_COMMON to
.I off.
The default ESPS Common file is
.I espscom
in the user's home directory.
This may be overridden
by setting the environment variable ESPSCOM to the desired path.
User feedback of Common processing is determined
by the environment variable ESPS_VERBOSE, with 0 causing no feedback
and increasing levels causing increasingly detailed feedback.
If ESPS_VERBOSE is not defined, a default value of 3 is assumed.
.SH ESPS HEADERS
.PP
The program reads the header items
.I sf,
.I framelen,
.I record_freq,
.I start_time
.I step,
and
.I window_type
from the header of
.I phase_in.fea.
It relies on the phase file for these items
since they are more likely to be preserved intact there
than in the cepstrum file.
However, it also reads certain of the corresponding items from
.I cepst_in.fea
and prints a message in case of inconsistency.
.PP
The program defines the
standard ouput header items
.I start_time
and
.I record_freq
and includes the normal field definition
for a FEA_SD file in the output header (see
.IR init_feasd_hd (3\-ESPS)).
Like most ESPS programs, it includes copies of the input file headers
in the ouput header (see
.IR add_source_file (3\-ESPS)),
and it saves a copy of the command line as a comment in the output
header
(see
.IR add_comment (3\-ESPS)
and
.IR get_cmd_line (3\-ESPS)).
.SH FUTURE CHANGES
.PP
.SH EXAMPLES
.PP
.SH ERRORS AND DIAGNOSTICS
.PP
If an unknown option is specified,
if the
.B \-r
option is used more than two times,
or if the number of file names is wrong,
.I cepsyn
prints a synopsis of command-line usage and exits.
The program exits with an error message if any of the folowing are true:
the output file name is the same as one of the input file names
(but not "\-");
the input file names are the same;
the field
.I phase
in 
.I phase_in.fea
is absent or not FLOAT;
the field
.I cepstrum
in 
.I cepst_in.fea
is absent or not FLOAT;
the fields
.I phase
and
.I cepstrum
have different sizes;
the size of the fields
.I phase
and
.I cepstrum
does not correspond to an integer order
(i.e. is is not of the form
.IR "n" "/2 + 1,"
where
.I n
is a power of 2);
the generic header items
.I frmlen,
.I sf,
and
.I record_freq
in
.I cepst_in.fea
are not all present or do not all have positive numerical values;
a
.B \-r
option specifies a starting record before the beginning of the file
or specifies an empty range of records;
two
.B \-r
options specify ranges with different explicit lengths;
the
.B \-t
option does not specify a valid numeric data type;
an attempt to write an ESPS common file failed.
The program prints a message and continues
if any of the following conditions are encountered:
one of the generic header items
.I frmlen,
.I sf,
and
.I record_freq
in
.I cepst_in.fea
(if present) specifies a value inconsistent with
.I phase_in.fea;
the two input file headers, together with any range options,
specify inconsistent values of
.I start_time;
the end of the input file is reached prematurely
according to an explicitly indicated end of range.
.SH BUGS
.PP
None known.
.SH REFERENCES
.PP
.SH "SEE ALSO"
.na
.IR cepanal (1\-ESPS),
.IR fft (1\-ESPS),
.IR fftcep (1\-ESPS),
.br
.IR fftinv (1\-ESPS),
.IR init_feasd_hd (3\-ESPS),
.br
.IR add_source_file (3\-ESPS),
.IR add_comment (3\-ESPS),
.br
.IR get_cmd_line (3\-ESPS).
.ad
.PP
.SH AUTHOR
.PP
Rod Johnson