| 1 | /**
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| 2 | * @file fdctref.c
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| 3 | * forward discrete cosine transform, double precision.
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| 4 | */
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| 5 |
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| 6 | /* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */
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| 7 |
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| 8 | /*
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| 9 | * Disclaimer of Warranty
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| 10 | *
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| 11 | * These software programs are available to the user without any license fee or
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| 12 | * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims
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| 13 | * any and all warranties, whether express, implied, or statuary, including any
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| 14 | * implied warranties or merchantability or of fitness for a particular
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| 15 | * purpose. In no event shall the copyright-holder be liable for any
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| 16 | * incidental, punitive, or consequential damages of any kind whatsoever
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| 17 | * arising from the use of these programs.
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| 18 | *
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| 19 | * This disclaimer of warranty extends to the user of these programs and user's
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| 20 | * customers, employees, agents, transferees, successors, and assigns.
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| 21 | *
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| 22 | * The MPEG Software Simulation Group does not represent or warrant that the
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| 23 | * programs furnished hereunder are free of infringement of any third-party
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| 24 | * patents.
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| 25 | *
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| 26 | * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,
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| 27 | * are subject to royalty fees to patent holders. Many of these patents are
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| 28 | * general enough such that they are unavoidable regardless of implementation
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| 29 | * design.
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| 30 | *
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| 31 | */
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| 32 |
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| 33 | #include <math.h>
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| 34 |
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| 35 | #ifndef PI
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| 36 | # ifdef M_PI
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| 37 | # define PI M_PI
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| 38 | # else
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| 39 | # define PI 3.14159265358979323846
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| 40 | # endif
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| 41 | #endif
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| 42 |
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| 43 | /* global declarations */
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| 44 | void init_fdct (void);
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| 45 | void fdct (short *block);
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| 46 |
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| 47 | /* private data */
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| 48 | static double c[8][8]; /* transform coefficients */
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| 49 |
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| 50 | void init_fdct()
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| 51 | {
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| 52 | int i, j;
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| 53 | double s;
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| 54 |
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| 55 | for (i=0; i<8; i++)
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| 56 | {
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| 57 | s = (i==0) ? sqrt(0.125) : 0.5;
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| 58 |
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| 59 | for (j=0; j<8; j++)
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| 60 | c[i][j] = s * cos((PI/8.0)*i*(j+0.5));
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| 61 | }
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| 62 | }
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| 63 |
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| 64 | void fdct(block)
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| 65 | short *block;
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| 66 | {
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| 67 | register int i, j;
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| 68 | double s;
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| 69 | double tmp[64];
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| 70 |
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| 71 | for(i = 0; i < 8; i++)
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| 72 | for(j = 0; j < 8; j++)
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| 73 | {
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| 74 | s = 0.0;
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| 75 |
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| 76 | /*
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| 77 | * for(k = 0; k < 8; k++)
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| 78 | * s += c[j][k] * block[8 * i + k];
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| 79 | */
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| 80 | s += c[j][0] * block[8 * i + 0];
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| 81 | s += c[j][1] * block[8 * i + 1];
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| 82 | s += c[j][2] * block[8 * i + 2];
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| 83 | s += c[j][3] * block[8 * i + 3];
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| 84 | s += c[j][4] * block[8 * i + 4];
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| 85 | s += c[j][5] * block[8 * i + 5];
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| 86 | s += c[j][6] * block[8 * i + 6];
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| 87 | s += c[j][7] * block[8 * i + 7];
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| 88 |
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| 89 | tmp[8 * i + j] = s;
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| 90 | }
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| 91 |
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| 92 | for(j = 0; j < 8; j++)
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| 93 | for(i = 0; i < 8; i++)
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| 94 | {
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| 95 | s = 0.0;
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| 96 |
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| 97 | /*
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| 98 | * for(k = 0; k < 8; k++)
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| 99 | * s += c[i][k] * tmp[8 * k + j];
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| 100 | */
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| 101 | s += c[i][0] * tmp[8 * 0 + j];
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| 102 | s += c[i][1] * tmp[8 * 1 + j];
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| 103 | s += c[i][2] * tmp[8 * 2 + j];
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| 104 | s += c[i][3] * tmp[8 * 3 + j];
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| 105 | s += c[i][4] * tmp[8 * 4 + j];
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| 106 | s += c[i][5] * tmp[8 * 5 + j];
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| 107 | s += c[i][6] * tmp[8 * 6 + j];
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| 108 | s += c[i][7] * tmp[8 * 7 + j];
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| 109 | s*=8.0;
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| 110 |
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| 111 | block[8 * i + j] = (short)floor(s + 0.499999);
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| 112 | /*
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| 113 | * reason for adding 0.499999 instead of 0.5:
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| 114 | * s is quite often x.5 (at least for i and/or j = 0 or 4)
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| 115 | * and setting the rounding threshold exactly to 0.5 leads to an
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| 116 | * extremely high arithmetic implementation dependency of the result;
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| 117 | * s being between x.5 and x.500001 (which is now incorrectly rounded
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| 118 | * downwards instead of upwards) is assumed to occur less often
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| 119 | * (if at all)
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| 120 | */
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| 121 | }
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| 122 | }
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| 123 |
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| 124 | /* perform IDCT matrix multiply for 8x8 coefficient block */
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| 125 |
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| 126 | void idct(block)
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| 127 | short *block;
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| 128 | {
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| 129 | int i, j, k, v;
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| 130 | double partial_product;
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| 131 | double tmp[64];
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| 132 |
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| 133 | for (i=0; i<8; i++)
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| 134 | for (j=0; j<8; j++)
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| 135 | {
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| 136 | partial_product = 0.0;
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| 137 |
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| 138 | for (k=0; k<8; k++)
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| 139 | partial_product+= c[k][j]*block[8*i+k];
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| 140 |
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| 141 | tmp[8*i+j] = partial_product;
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| 142 | }
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| 143 |
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| 144 | /* Transpose operation is integrated into address mapping by switching
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| 145 | loop order of i and j */
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| 146 |
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| 147 | for (j=0; j<8; j++)
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| 148 | for (i=0; i<8; i++)
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| 149 | {
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| 150 | partial_product = 0.0;
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| 151 |
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| 152 | for (k=0; k<8; k++)
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| 153 | partial_product+= c[k][i]*tmp[8*k+j];
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| 154 |
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| 155 | v = (int) floor(partial_product+0.5);
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| 156 | block[8*i+j] = v;
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| 157 | }
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| 158 | }
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