NAME

     fftpack  - module to do 1D  FFT  of  input  data  and  ouput
     packed  FFT  format  suitable  for  input [after slicing] to
     vfilt3d .

SYNOPSIS

     fftpack [ -Nntap ] [ -Ootap ] [ -nsnstr  ]  [  -nenetr  ]  [
     -rsnrst ] [ -renred ] [ -R ] [ -V ] [ -? ] [ -h ]

DESCRIPTION

     fftpack performs a 1D FFT of the input dataset  and  outputs
     transformed   data  in  packed  format.   When  followed  by
     fdslice | resorter -fdslice  the output is converted to fre-
     quency  slices  suitable  for  input to  vfilt3d .  There is
     provision to access a subset of records and traces  but  the
     routine  will  use  all  samples of the input dataset.  If a
     subset of samples is desired use program  wind .

     fftpack gets both its data and its parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the start and end records and traces, the direction  of  the
     FFT [forward or inverse] and verbose printout, if desired.

  Command line arguments
     -N ntap
          Enter the input data set name or file immediately after
          typing -N unless the input is from a pipe in which case
          the -N entry must be omitted.  This input  file  should
          include the complete path name if the file resides in a
          different directory.  Example -N/b/vsp/dummy tells  the
          program to look for file 'dummy' in directory '/b/vsp'.

     -O otap
          Enter the output data  set  name  or  file  immediately
          after typing -O.  This output file is not required when
          piping the output to another process.  The output  data
          set also requires the full path name (see above).

     -ns nstr
          Enter the start trace number.  The default is the first
          trace of the record.

     -ne netr
          Enter the end trace number. The  default  is  the  last
          trace of the record.

     -rs nrst
          Enter start record number.  Default value is the  first
          record.

     -re nred
          Enter end record number.  Default value is last record.

     -R   Enter the command line  argument  '-R'  to  perform  an
          inverse  1D  FFT of the data.  If this option is chosen
          it is expected that the data was originally transformed
          using  this  routine as the data must be in packed for-
          mat.

     -V   Enter the command line argument '-V' to get  additional
          printout.

     -?   Enter the command line argument '-?'  or   -h   to  get
          online  help.   The  program  terminates after the help
          screen is printed.

BUGS

     A  hdrswap  may be required after the inverse transform when
     used  in  conjunction  with   vfilt3d  as the original trace
     header information will have been lost during all the  slic-
     ing  and  dicing.  If no further processing is required then
     all is probably well.

SEE ALSO

     vfilt3d(1)   qdslice(1)   ttds3d(1)   fkrad(1)    fkshape(1)
     fkkstrip(1)

AUTHOR

     original code Dennis Yanchak  [GUPCO]  USP  Port  by  P.G.A.
     Garossino [APR:3932]

COPYRIGHT

     copyright 2001, Amoco Production Company
               All Rights Reserved
          an affiliate of BP America Inc.