/** * @file 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> #ifndef PI # ifdef M_PI # define PI M_PI # else # define PI 3.14159265358979323846 # endif #endif /* global declarations */ void init_fdct (void); void fdct (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; { register int i, j; 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]; */ s += c[j][0] * block[8 * i + 0]; s += c[j][1] * block[8 * i + 1]; s += c[j][2] * block[8 * i + 2]; s += c[j][3] * block[8 * i + 3]; s += c[j][4] * block[8 * i + 4]; s += c[j][5] * block[8 * i + 5]; s += c[j][6] * block[8 * i + 6]; s += c[j][7] * block[8 * i + 7]; 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]; */ s += c[i][0] * tmp[8 * 0 + j]; s += c[i][1] * tmp[8 * 1 + j]; s += c[i][2] * tmp[8 * 2 + j]; s += c[i][3] * tmp[8 * 3 + j]; s += c[i][4] * tmp[8 * 4 + j]; s += c[i][5] * tmp[8 * 5 + j]; s += c[i][6] * tmp[8 * 6 + j]; s += c[i][7] * tmp[8 * 7 + j]; s*=8.0; block[8 * i + j] = (short)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) */ } } /* perform IDCT matrix multiply for 8x8 coefficient block */ void idct(block) 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; } }