fft.1

speech signal process tools

the number of frequencies in the output spectral records is 1 + 2^(order \- 1).
If the \fB\-c\fP option is used or the input data type is complex,
the number of frequencies in the output spectral records is 1 + 2^order.
.TP 
.B \-c
Specifies that complex spectra (type SPTYP_CPLX) be stored in the output
FEA_SPEC file.  
.TP
.B \-z
Specifies that \fIfft\fP operate silently, without issuing various 
warnings. 
.TP
.BI \-x " debug_level" "\fR [0]"
A positive value specifies
that debugging output be printed on the standard error output.
Larger values result in more output.
The default is 0, for no output.
.SH ESPS PARAMETERS
.PP
.PP
The parameter file is not required to be present, as there are 
default parameter values that apply.  If the parameter file 
does exist, the following parameters are read:
.TP
.I "start - integer"
.IP
The first point in the input sampled data file that is processed.  A
value of 1 denotes the first sample in the file.  This is only read
if the \fB\-r\fP and \fB\-p\fP options are not used.
If it is not in the parameter (or Common) file,
the default value of 1 is used.  
.TP
.I "nan - integer"
.IP
The total number of data points to process.  If 
.I nan
is 0,
all points from
.I start
through the end  of the file are processed.
This parameter is not read if the
.B \-r
or
.B \-p
option is used.
(See the discussion under \fB\-r\fP).
.TP
.I "frame_len - integer"
.IP
The number of points in each frame.  This parameter is not read if the
.B \-l
option is specified.  A value of 0 indicates that the transform length
(determined by the fft order) is to be used as a default;
the same default value is used in case
.I frame_len
is specified neither with the
.B \-l
option nor in the parameter file.
.TP
.I "step \- integer"
Initial points of consecutive frames differ by this number of samples.
This parameter is not read if the
.B \-S
option is specified.
If the option is omitted and no value is found in the parameter file,
a default equal to
.I frame_len
is used (resulting in exactly abutted frames).
The same default applies if \fIstep\fP is given the value 0.
.TP
.I "window_type \- string"
The data window to apply to the data.
This parameter is not read if the command-line option
.B \-w
is specified.
If the option is omitted and if no value is found in the parameter file,
the default used is "RECT", for a rectangular window with amplitude one.
Other acceptable values include
"HAMMING", for Hamming, "HANNING" for Hanning, "COS4" for cos^4,
and "TRIANG", for triangular;
see the window(3-ESPSsp) manual page for the complete list.
.TP
.I "order \- integer"
.IP
The order of the fft \- the transform length is 2^order (2 to the order-th
power).  If no value is given in the file, a default value of 10 is used
(transform length 1024).  This value is not read if the command line option
\fB\-o\fP is used.
.PP
The values of parameters obtained from the parameter file are printed
if the environment variable ESPS_VERBOSE is 3 or greater.  The default
value is 3.
.sp 1
.SH EXAMPLE
.PP
The following \fIcsh\fP script demonstrates the use of \fIfft\fP and
other ESPS programs to produce a frequency-zoomed spectrogram
suitable for display by \fIxwaves\fP.
.nf

#!/bin/csh -f

# This script is designed to be used as an xwaves "add_espsf" program.
# To use it with xwaves, send a command like
# 
#   add_espsf name zoom7k.2k menu wave command xwzoomer 7000 2000
# 
# This will add a menu entry to the waveform display menu that will
# produce a zoomed-in spectrogram with a bandwidth of 2kHz and a center
# frequency of 7kHz.  By modifying the "-l" and "-o" options sent to fft
# (see below), you can effectively increase or decrease the frequency
# resolution as needed.  Commands like the one above can either be
# entered directly into the xwaves command window in the "COMMAND (or
# @file)" line, or from an external process via the "send_xwaves"
# program (see eman send_xwaves).
# Note that this script is pretty slow, and can be made VERY slow, if
# the "bandwidth" parameter is not an integral sub-multiple of the input
# file's sample frequency.

if ( $#argv < 5 ) then
  echo Usage: xwzoomer center_freq bandwidth range input.sd output.fspec
endif

# Center Frequency
set cf = $1

# Analysis bandwidth
set bw = $2

# Range of points to include in zoomed analysis (e.g. -r1234:23000)
set range = $3

set input = $4
set output = $5

# Analysis frame interval for FFT (sec)
set frint = .004

set sf = `hditem -i record_freq $input`
set step = `echo $frint $bw \* p q | dc`

set np = `echo $range | sed 's/\-r//' | sed 's/\:/ /'`
set npoints = `echo $np[2] $np[1] - 1 + p q | dc`

echo int new_sample_freq = $bw";" > /tmp/Psfparams

testsd -c -r $sf -p $npoints -f -$cf - | multsd $range -t -z $input - - | \
sfconvert -P/tmp/Psfparams - - | \
/h8/dt/apl/zoomer/fftnew/fft -z -l256 -S $step -o8 -O$cf -wHANNING - - | \
feafunc -fre_spec_val -f- -tBYTE  - - | \
clip -m0:118 -fre_spec_val -f- - $output

.fi
.SH "ESPS COMMON"
.PP
.PP
ESPS Common is read provided that Common processing is enabled and 
that the 
.I filename
entry in Common matches 
.I sd_file,
in which case parameters present in Common override values from
the parameter file, which in turn may be overriden by command
line options (see the discussion in ESPS PARAMETERS and under
each option).  
.PP
If Common processing is enabled and if
.I fea_spec_file
is not standard output, the Common parameters 
.I "filename, prog, start,"
and
.I nan
are written to Common, where 
.I filename
is set to the input 
.I sd_file.
.PP
ESPS Common processing may be disabled by setting the environment variable
USE_ESPS_COMMON to "off".
The default ESPS Common file is .espscom in the user's home directory.
This may be overidden 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
.I fft
reads the value of 
.I common.type
from the input SD file 
.I sd_file.  
.PP
Relevant fields in the type-dependent portion of the 
output file header are filled appropriately.
The standard generic header items required for FEA_SPEC files
are filled in (see \fIFEA_SPEC\fP(5-ESPS) for details).
The generic header item
.I "fft_length"
is set to the length of the fft (2^order), the item
.I "step"
is set to the step size (see \fB\-S\fP), and
the item 
.I input_data,
value either complex or real,
is added.  The CODED generic
header item \fIwindow_type\fP is set according to to the window
type (see \fB\-w\fP).  
.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 processed
plus one half of \fIframe_len\fP.  (Thus, \fIstart_time\fP is middle of
the first frame, which is appropriate since the output data represent
the entire frame; without this adjustment for \fIframe_len\fP,
\fIwaves\fP+ displays would not line up properly.) 
.PP
The generic header item \fIrecord_freq\fP (type DOUBLE) is written in
the output file.  The value is the number of output records per second
of input data.
.SH "FUTURE CHANGES"
.PP
.SH "SEE ALSO"
.PP
.nf
\fIfftinv\fP(1\-\s-1ESPS\s+1), \fIplotspec\fP(1\-\s-1ESPS\s+1), \fIexprompt\fP(1\-\s-1ESPS\s+1), 
\fIexpromptrun\fP(1\-\s-1ESPS\s+1), \fIrefcof\fP(1\-\s-1ESPS\s+1), \fIme_spec\fP(1\-\s-1ESPS\s+1),
\fIxtext\fP(1\-\s-1ESPS\s+1), \fIFEA_SD\fP(5\-ESPS), \fIFEA_SPEC\fP(5\-ESPS), 
\fIESPS\fP(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
Original manual page and program by Rod Johnson; revised by John Shore for 
ESPS 3.0.  Revised by John Shore for windowing and overlapping frames.  
Revised by Rod Johnson for output to FEA_SPEC file. Revised for
FEA_SD input files by David Burton.  \fIxfft\fP by John Shore.