fftinv.1.tmp

speech signal process tools

.\" Copyright (c) 1987 Entropic Speech, Inc.; all rights reserved
.\" @(#)fftinv.1	1.6 12/13/88 ESI
.TH FFTINV 1\-ESPS 12/13/88
.ds ]W "\fI\s+4\ze\h'0.05'e\s-4\v'-0.4m'\fP\(*p\v'0.4m'\ Entropic Speech, Inc.
.SH "NAME"
fftinv \- Inverse Fast Fourier Transform of ESPS FEA_SPEC file to SD file
.SH "SYNOPSIS"
.B fftinv
[
.BI \-r " range"
] [
.BI \-x " debug_level"
]
.I specfile
.I sdfile
.SH "DESCRIPTION"
.PP
.I Fftinv
takes an input ESPS spectral record file (FEA_SPEC) file, 
.I specfile,
and takes the Fast Fourier Transform of one or more records
segments to produce an ESPS sampled data file (SD) file
.I sdfile.
If the input file name
.I specfile
is replaced by "\-", then stdin is read; similarily, if
.I sdfile
is replaced by "\-", then the output is written to stdout.
.PP
The input FEA_SPEC file must have spectral type SPTYP_CPLX and 
frequency format SPFMT_ASYM_EDGE \- i.e., the full complex 
spectrum is stored.  Such spectral records are produced 
by \fIfft\fP (1\-\s-1ESPS\s+1) using the \fB\-c\fP option.  
.SH "OPTIONS"
.PP
The following options are supported:
.TP
.BI \-r " first" : "last"
.TP
.BI \-r " first\-last"
.TP
.BI \-r " first" :+ "incr"
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 all records from 
.I first
are processed.
.TP
.BI \-x " debug_level\fR[0]\fP"
Specifies that debugging output be printed on stderr; larger values
of 
.I debug_level
result in more output.  The default is for no output.  
.SH "ESPS PARAMETERS"
.PP
The ESPS parameter file is not read.
.SH "ESPS COMMON"
.PP
The ESPS Common file is not read 
or written.
.SH ESPS HEADERS
.PP
The generic header item \fIstart_time\fP (type DOUBLE)
is written in the output file.  
The value written is computed by taking the \fIstart_time\fP value from
the header of the input file (or zero, if such a header item doesn't
exist) and adding to it the offset time (from the
beginning of the input file) of the first point or record processed.
.SH "FUTURE CHANGES"
.PP
.SH "SEE ALSO"
.PP
fft(1\-ESPS), plotsd (1\-ESPS), get_fft_inv (3\-ESPS), SD(5\-ESPS),
FEA_SPEC(5\-ESPS), ESPS(5\-ESPS).
.SH "BUGS"
.PP
.SH "REFERENCES"
.PP
J. W. Cooley and J. W. Tukey, "An Algorithm for the Machine Calculation of
Complex Fourier Series," \fIMath. Computation\fP, Vol. 19, 1965, pp. 297-301.
.sp
Alan V. Oppenheim and Ronald W. Schafer, \fIDigital Signal Processing\fP.
Englewood Cliffs, New Jersey: Prentice-Hall, Inc., 1975.
.SH "AUTHOR"
.PP
manual page and program by John Shore, using library
function by Shankar Narayan.