/* fdctref.c, forward discrete cosine transform, double precision           *//* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. *//* * Disclaimer of Warranty * * These software programs are available to the user without any license fee or * royalty on an "as is" basis.  The MPEG Software Simulation Group disclaims * any and all warranties, whether express, implied, or statuary, including any * implied warranties or merchantability or of fitness for a particular * purpose.  In no event shall the copyright-holder be liable for any * incidental, punitive, or consequential damages of any kind whatsoever * arising from the use of these programs. * * This disclaimer of warranty extends to the user of these programs and user's * customers, employees, agents, transferees, successors, and assigns. * * The MPEG Software Simulation Group does not represent or warrant that the * programs furnished hereunder are free of infringement of any third-party * patents. * * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, * are subject to royalty fees to patent holders.  Many of these patents are * general enough such that they are unavoidable regardless of implementation * design. * */#include <math.h>#include "config.h"#ifndef PI# ifdef M_PI#  define PI M_PI# else#  define PI 3.14159265358979323846# endif#endif/* global declarations */void init_fdct _ANSI_ARGS_((void));void fdct _ANSI_ARGS_((short *block));/* private data */static double c[8][8]; /* transform coefficients */void init_fdct(){  int i, j;  double s;  for (i=0; i<8; i++)  {    s = (i==0) ? sqrt(0.125) : 0.5;    for (j=0; j<8; j++)      c[i][j] = s * cos((PI/8.0)*i*(j+0.5));  }}void fdct(block)short *block;{  int i, j, k;  double s;  double tmp[64];  for (i=0; i<8; i++)    for (j=0; j<8; j++)    {      s = 0.0;      for (k=0; k<8; k++)        s += c[j][k] * block[8*i+k];      tmp[8*i+j] = s;    }  for (j=0; j<8; j++)    for (i=0; i<8; i++)    {      s = 0.0;      for (k=0; k<8; k++)        s += c[i][k] * tmp[8*k+j];      block[8*i+j] = (int)floor(s+0.499999);      /*       * reason for adding 0.499999 instead of 0.5:       * s is quite often x.5 (at least for i and/or j = 0 or 4)       * and setting the rounding threshold exactly to 0.5 leads to an       * extremely high arithmetic implementation dependency of the result;       * s being between x.5 and x.500001 (which is now incorrectly rounded       * downwards instead of upwards) is assumed to occur less often       * (if at all)       */    }}