text: ////////////////////////////////////////////////////////////////////////////
  //
  //
  //    Project     : VideoNet Ver. 1.0.
  //    Description : Video Conferencing over the LAN.
  //	  Author      :	Vladiimir Novick ( v_novick@yahoo.com )
  //    Date        : 17/12/2005
  //
  //    This is the modified version of tmndecode (H.263 decoder) 
  //    written by Karl & Robert.It was in ANSI C. I have converted into C++
  //    so that it can be integrated into any windows application. I have 
  //    removed some of the files which had display and file storing 
  //    functions.I have removed the unnecessary code and also added some
  //    new files..
  //	  Original library dealt with files. Input & Output , both were files.
  //    I have done some major changes so that it can be used for real time 
  //    decoding process. Now one can use this library for decoding H263 frames. 
  //
  //
  //    File description : 
  //    Name    : Idctref.cpp
  //
  /////////////////////////////////////////////////////////////////////////////
  
  /************************************************************************
   *
   *  idctref.c, inverse DCT, double precision, for tmndecode (H.263 decoder)
   *  Copyright (C) 1996  Telenor R&D, Norway
   *        Karl Olav Lillevold <Karl.Lillevold@nta.no>
   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation; either version 2 of the License, or
   *  (at your option) any later version.
   *
   *  This program is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *  GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License
   *  along with this program; if not, write to the Free Software
   *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   *
   *  Karl Olav Lillevold               <Karl.Lillevold@nta.no>
   *  Telenor Research and Development
   *  P.O.Box 83                        tel.:   +47 63 84 84 00
   *  N-2007 Kjeller, Norway            fax.:   +47 63 81 00 76
   *
   *  Robert Danielsen                  e-mail: Robert.Danielsen@nta.no
   *  Telenor Research and Development  www:    http://www.nta.no/brukere/DVC/
   *  P.O.Box 83                        tel.:   +47 63 84 84 00
   *  N-2007 Kjeller, Norway            fax.:   +47 63 81 00 76
   *  
   ************************************************************************/
  
  /*
   * based on mpeg2decode, (C) 1994, MPEG Software Simulation Group
   * and mpeg2play, (C) 1994 Stefan Eckart
   *                         <stefan@lis.e-technik.tu-muenchen.de>
   *
   */
  
  
  /*  Perform IEEE 1180 reference (64-bit floating point, separable 8x1
   *  direct matrix multiply) Inverse Discrete Cosine Transform
  */
  
  
  /* Here we use math.h to generate constants.  Compiler results may
     vary a little */
  
  #include "Idctref.h"
  
  
  #ifndef PI
  # ifdef M_PI
  #  define PI M_PI
  # else
  #  define PI 3.14159265358979323846
  # endif
  #endif
  
  /* global declarations */
  void init_idctref ();
  void idctref (short *block);
  
  /* private data */
  
  /* cosine transform matrix for 8x1 IDCT */
  static double c[8][8];
  
  /* initialize DCT coefficient matrix */
  
  void init_idctref()
  {
    int freq, time;
    double scale;
  
    for (freq=0; freq < 8; freq++)
    {
      scale = (freq == 0) ? sqrt(0.125) : 0.5;
      for (time=0; time<8; time++)
        c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5));
    }
  }
  
  /* perform IDCT matrix multiply for 8x8 coefficient block */
  
  void idctref(short *block)
  {
    int i, j, k, v;
    double partial_product;
    double tmp[64];
  
    for (i=0; i<8; i++)
      for (j=0; j<8; j++)
      {
        partial_product = 0.0;
  
        for (k=0; k<8; k++)
          partial_product+= c[k][j]*block[8*i+k];
  
        tmp[8*i+j] = partial_product;
      }
  
    /* Transpose operation is integrated into address mapping by switching 
       loop order of i and j */
  
    for (j=0; j<8; j++)
      for (i=0; i<8; i++)
      {
        partial_product = 0.0;
  
        for (k=0; k<8; k++)
          partial_product+= c[k][i]*tmp[8*k+j];
  
        v = (int)floor(partial_product+0.5);
        block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v);
      }
  }
  