NAME

     ilch1 - 1-D Local Cosine - Uniform Bin Width Quantization  -
     Huffman Coding Decompression

SYNOPSIS

     ilch1 [ -Nntap ] [ -Ootap ] [ -rsnrst ] [ -renred ] [ -V ] [
     -? ]

DESCRIPTION

     ilch1 performs local cosine uniform de-quantization  huffman
     de-coding.  The  algorithm  uses  1-D local cosine transform
     algorithm, uniform de-quantization and Huffman de-coding.
     ilch1 gets both its data and  its  parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the compression ratio,  the  trace  local  cosine  transform
     decomposition levels, the time local cosine transform decom-
     position levels and verbose printout, if desired.  In  addi-
     tion,  this  routine  provides  random access to the seismic
     record decompression. In other words, the user  can  specify
     that  among  say  1,000,000  seismic  gathers that have been
     compressed, he can decompress gather n1 to gather n2,  where
     the  integers  n1 and n2 are greater than 1 and smaller than
     1,000,000.

  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).

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

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

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

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

DISCUSSION

     This  code   uses   a   local   cosine-uniform   bin   width
     dequantization-Huffman decoding decompression algorithm. The
     input file is structured so as to contain the seismic header
     lossessly  comperssed  by  gzip,  followed  by a compression
     parameter header (such  as  window  lengths  for  the  local
     cosine   transform,  quantization  bin  widths  and  Huffman
     codes), followed by the  Huffman  coded,  uniform  quantized
     local cosine transform coefficients.

DISCUSSION

     This  product  is  licensed  from  GeoEnergy  Inc.   It   is
     proprietary  to  BP  Amoco and may not be ported to applica-
     tions or locations outside the company without the expressed
     written permission

BUGS

     none known at present

SEE ALSO

     lch1(1)

AUTHOR

     Anthony Vassiliou (GeoEnergy Inc.  918-494-4641),  Joe  Wade
     (socon 421-3324)

COPYRIGHT

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