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| 1 : | Isibaar | 3 | /* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */ |
| 2 : | |||
| 3 : | /* | ||
| 4 : | * Disclaimer of Warranty | ||
| 5 : | * | ||
| 6 : | * These software programs are available to the user without any license fee or | ||
| 7 : | * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims | ||
| 8 : | * any and all warranties, whether express, implied, or statuary, including any | ||
| 9 : | * implied warranties or merchantability or of fitness for a particular | ||
| 10 : | * purpose. In no event shall the copyright-holder be liable for any | ||
| 11 : | * incidental, punitive, or consequential damages of any kind whatsoever | ||
| 12 : | * arising from the use of these programs. | ||
| 13 : | * | ||
| 14 : | * This disclaimer of warranty extends to the user of these programs and user's | ||
| 15 : | * customers, employees, agents, transferees, successors, and assigns. | ||
| 16 : | * | ||
| 17 : | * The MPEG Software Simulation Group does not represent or warrant that the | ||
| 18 : | * programs furnished hereunder are free of infringement of any third-party | ||
| 19 : | * patents. | ||
| 20 : | * | ||
| 21 : | * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, | ||
| 22 : | * are subject to royalty fees to patent holders. Many of these patents are | ||
| 23 : | * general enough such that they are unavoidable regardless of implementation | ||
| 24 : | * design. | ||
| 25 : | * | ||
| 26 : | */ | ||
| 27 : | |||
| 28 : | /* This routine is a slow-but-accurate integer implementation of the | ||
| 29 : | * forward DCT (Discrete Cosine Transform). Taken from the IJG software | ||
| 30 : | * | ||
| 31 : | * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT | ||
| 32 : | * on each column. Direct algorithms are also available, but they are | ||
| 33 : | * much more complex and seem not to be any faster when reduced to code. | ||
| 34 : | * | ||
| 35 : | * This implementation is based on an algorithm described in | ||
| 36 : | * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT | ||
| 37 : | * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics, | ||
| 38 : | * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991. | ||
| 39 : | * The primary algorithm described there uses 11 multiplies and 29 adds. | ||
| 40 : | * We use their alternate method with 12 multiplies and 32 adds. | ||
| 41 : | * The advantage of this method is that no data path contains more than one | ||
| 42 : | * multiplication; this allows a very simple and accurate implementation in | ||
| 43 : | * scaled fixed-point arithmetic, with a minimal number of shifts. | ||
| 44 : | * | ||
| 45 : | * The poop on this scaling stuff is as follows: | ||
| 46 : | * | ||
| 47 : | * Each 1-D DCT step produces outputs which are a factor of sqrt(N) | ||
| 48 : | * larger than the true DCT outputs. The final outputs are therefore | ||
| 49 : | * a factor of N larger than desired; since N=8 this can be cured by | ||
| 50 : | * a simple right shift at the end of the algorithm. The advantage of | ||
| 51 : | * this arrangement is that we save two multiplications per 1-D DCT, | ||
| 52 : | * because the y0 and y4 outputs need not be divided by sqrt(N). | ||
| 53 : | * In the IJG code, this factor of 8 is removed by the quantization step | ||
| 54 : | * (in jcdctmgr.c), here it is removed. | ||
| 55 : | * | ||
| 56 : | * We have to do addition and subtraction of the integer inputs, which | ||
| 57 : | * is no problem, and multiplication by fractional constants, which is | ||
| 58 : | * a problem to do in integer arithmetic. We multiply all the constants | ||
| 59 : | * by CONST_SCALE and convert them to integer constants (thus retaining | ||
| 60 : | * CONST_BITS bits of precision in the constants). After doing a | ||
| 61 : | * multiplication we have to divide the product by CONST_SCALE, with proper | ||
| 62 : | * rounding, to produce the correct output. This division can be done | ||
| 63 : | * cheaply as a right shift of CONST_BITS bits. We postpone shifting | ||
| 64 : | * as long as possible so that partial sums can be added together with | ||
| 65 : | * full fractional precision. | ||
| 66 : | * | ||
| 67 : | * The outputs of the first pass are scaled up by PASS1_BITS bits so that | ||
| 68 : | * they are represented to better-than-integral precision. These outputs | ||
| 69 : | * require 8 + PASS1_BITS + 3 bits; this fits in a 16-bit word | ||
| 70 : | * with the recommended scaling. (For 12-bit sample data, the intermediate | ||
| 71 : | * array is INT32 anyway.) | ||
| 72 : | * | ||
| 73 : | * To avoid overflow of the 32-bit intermediate results in pass 2, we must | ||
| 74 : | * have 8 + CONST_BITS + PASS1_BITS <= 26. Error analysis | ||
| 75 : | * shows that the values given below are the most effective. | ||
| 76 : | * | ||
| 77 : | * We can gain a little more speed, with a further compromise in accuracy, | ||
| 78 : | * by omitting the addition in a descaling shift. This yields an incorrectly | ||
| 79 : | * rounded result half the time... | ||
| 80 : | */ | ||
| 81 : | |||
| 82 : | #include "fdct.h" | ||
| 83 : | |||
| 84 : | #define USE_ACCURATE_ROUNDING | ||
| 85 : | |||
| 86 : | #define RIGHT_SHIFT(x, shft) ((x) >> (shft)) | ||
| 87 : | |||
| 88 : | #ifdef USE_ACCURATE_ROUNDING | ||
| 89 : | #define ONE ((int) 1) | ||
| 90 : | #define DESCALE(x, n) RIGHT_SHIFT((x) + (ONE << ((n) - 1)), n) | ||
| 91 : | #else | ||
| 92 : | #define DESCALE(x, n) RIGHT_SHIFT(x, n) | ||
| 93 : | #endif | ||
| 94 : | |||
| 95 : | #define CONST_BITS 13 | ||
| 96 : | #define PASS1_BITS 2 | ||
| 97 : | |||
| 98 : | #define FIX_0_298631336 ((int) 2446) /* FIX(0.298631336) */ | ||
| 99 : | #define FIX_0_390180644 ((int) 3196) /* FIX(0.390180644) */ | ||
| 100 : | #define FIX_0_541196100 ((int) 4433) /* FIX(0.541196100) */ | ||
| 101 : | #define FIX_0_765366865 ((int) 6270) /* FIX(0.765366865) */ | ||
| 102 : | #define FIX_0_899976223 ((int) 7373) /* FIX(0.899976223) */ | ||
| 103 : | #define FIX_1_175875602 ((int) 9633) /* FIX(1.175875602) */ | ||
| 104 : | #define FIX_1_501321110 ((int) 12299) /* FIX(1.501321110) */ | ||
| 105 : | #define FIX_1_847759065 ((int) 15137) /* FIX(1.847759065) */ | ||
| 106 : | #define FIX_1_961570560 ((int) 16069) /* FIX(1.961570560) */ | ||
| 107 : | #define FIX_2_053119869 ((int) 16819) /* FIX(2.053119869) */ | ||
| 108 : | #define FIX_2_562915447 ((int) 20995) /* FIX(2.562915447) */ | ||
| 109 : | #define FIX_3_072711026 ((int) 25172) /* FIX(3.072711026) */ | ||
| 110 : | |||
| 111 : | // function pointer | ||
| 112 : | fdctFuncPtr fdct; | ||
| 113 : | |||
| 114 : | /* | ||
| 115 : | * Perform an integer forward DCT on one block of samples. | ||
| 116 : | */ | ||
| 117 : | |||
| 118 : | void fdct_int32(short * const block) | ||
| 119 : | { | ||
| 120 : | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; | ||
| 121 : | int tmp10, tmp11, tmp12, tmp13; | ||
| 122 : | int z1, z2, z3, z4, z5; | ||
| 123 : | short *blkptr; | ||
| 124 : | int *dataptr; | ||
| 125 : | int data[64]; | ||
| 126 : | int i; | ||
| 127 : | |||
| 128 : | /* Pass 1: process rows. */ | ||
| 129 : | /* Note results are scaled up by sqrt(8) compared to a true DCT; */ | ||
| 130 : | /* furthermore, we scale the results by 2**PASS1_BITS. */ | ||
| 131 : | |||
| 132 : | dataptr = data; | ||
| 133 : | blkptr = block; | ||
| 134 : | for (i = 0; i < 8; i++) | ||
| 135 : | { | ||
| 136 : | tmp0 = blkptr[0] + blkptr[7]; | ||
| 137 : | tmp7 = blkptr[0] - blkptr[7]; | ||
| 138 : | tmp1 = blkptr[1] + blkptr[6]; | ||
| 139 : | tmp6 = blkptr[1] - blkptr[6]; | ||
| 140 : | tmp2 = blkptr[2] + blkptr[5]; | ||
| 141 : | tmp5 = blkptr[2] - blkptr[5]; | ||
| 142 : | tmp3 = blkptr[3] + blkptr[4]; | ||
| 143 : | tmp4 = blkptr[3] - blkptr[4]; | ||
| 144 : | |||
| 145 : | /* Even part per LL&M figure 1 --- note that published figure is faulty; | ||
| 146 : | * rotator "sqrt(2)*c1" should be "sqrt(2)*c6". | ||
| 147 : | */ | ||
| 148 : | |||
| 149 : | tmp10 = tmp0 + tmp3; | ||
| 150 : | tmp13 = tmp0 - tmp3; | ||
| 151 : | tmp11 = tmp1 + tmp2; | ||
| 152 : | tmp12 = tmp1 - tmp2; | ||
| 153 : | |||
| 154 : | dataptr[0] = (tmp10 + tmp11) << PASS1_BITS; | ||
| 155 : | dataptr[4] = (tmp10 - tmp11) << PASS1_BITS; | ||
| 156 : | |||
| 157 : | z1 = (tmp12 + tmp13) * FIX_0_541196100; | ||
| 158 : | dataptr[2] = DESCALE(z1 + tmp13 * FIX_0_765366865, CONST_BITS - PASS1_BITS); | ||
| 159 : | dataptr[6] = DESCALE(z1 + tmp12 * (-FIX_1_847759065), CONST_BITS - PASS1_BITS); | ||
| 160 : | |||
| 161 : | /* Odd part per figure 8 --- note paper omits factor of sqrt(2). | ||
| 162 : | * cK represents cos(K*pi/16). | ||
| 163 : | * i0..i3 in the paper are tmp4..tmp7 here. | ||
| 164 : | */ | ||
| 165 : | |||
| 166 : | z1 = tmp4 + tmp7; | ||
| 167 : | z2 = tmp5 + tmp6; | ||
| 168 : | z3 = tmp4 + tmp6; | ||
| 169 : | z4 = tmp5 + tmp7; | ||
| 170 : | z5 = (z3 + z4) * FIX_1_175875602; /* sqrt(2) * c3 */ | ||
| 171 : | |||
| 172 : | tmp4 *= FIX_0_298631336; /* sqrt(2) * (-c1+c3+c5-c7) */ | ||
| 173 : | tmp5 *= FIX_2_053119869; /* sqrt(2) * ( c1+c3-c5+c7) */ | ||
| 174 : | tmp6 *= FIX_3_072711026; /* sqrt(2) * ( c1+c3+c5-c7) */ | ||
| 175 : | tmp7 *= FIX_1_501321110; /* sqrt(2) * ( c1+c3-c5-c7) */ | ||
| 176 : | z1 *= -FIX_0_899976223; /* sqrt(2) * (c7-c3) */ | ||
| 177 : | z2 *= -FIX_2_562915447; /* sqrt(2) * (-c1-c3) */ | ||
| 178 : | z3 *= -FIX_1_961570560; /* sqrt(2) * (-c3-c5) */ | ||
| 179 : | z4 *= -FIX_0_390180644; /* sqrt(2) * (c5-c3) */ | ||
| 180 : | |||
| 181 : | z3 += z5; | ||
| 182 : | z4 += z5; | ||
| 183 : | |||
| 184 : | dataptr[7] = DESCALE(tmp4 + z1 + z3, CONST_BITS - PASS1_BITS); | ||
| 185 : | dataptr[5] = DESCALE(tmp5 + z2 + z4, CONST_BITS - PASS1_BITS); | ||
| 186 : | dataptr[3] = DESCALE(tmp6 + z2 + z3, CONST_BITS - PASS1_BITS); | ||
| 187 : | dataptr[1] = DESCALE(tmp7 + z1 + z4, CONST_BITS - PASS1_BITS); | ||
| 188 : | |||
| 189 : | dataptr += 8; /* advance pointer to next row */ | ||
| 190 : | blkptr += 8; | ||
| 191 : | } | ||
| 192 : | |||
| 193 : | /* Pass 2: process columns. | ||
| 194 : | * We remove the PASS1_BITS scaling, but leave the results scaled up | ||
| 195 : | * by an overall factor of 8. | ||
| 196 : | */ | ||
| 197 : | |||
| 198 : | dataptr = data; | ||
| 199 : | for (i = 0; i < 8; i++) | ||
| 200 : | { | ||
| 201 : | tmp0 = dataptr[0] + dataptr[56]; | ||
| 202 : | tmp7 = dataptr[0] - dataptr[56]; | ||
| 203 : | tmp1 = dataptr[8] + dataptr[48]; | ||
| 204 : | tmp6 = dataptr[8] - dataptr[48]; | ||
| 205 : | tmp2 = dataptr[16] + dataptr[40]; | ||
| 206 : | tmp5 = dataptr[16] - dataptr[40]; | ||
| 207 : | tmp3 = dataptr[24] + dataptr[32]; | ||
| 208 : | tmp4 = dataptr[24] - dataptr[32]; | ||
| 209 : | |||
| 210 : | /* Even part per LL&M figure 1 --- note that published figure is faulty; | ||
| 211 : | * rotator "sqrt(2)*c1" should be "sqrt(2)*c6". | ||
| 212 : | */ | ||
| 213 : | |||
| 214 : | tmp10 = tmp0 + tmp3; | ||
| 215 : | tmp13 = tmp0 - tmp3; | ||
| 216 : | tmp11 = tmp1 + tmp2; | ||
| 217 : | tmp12 = tmp1 - tmp2; | ||
| 218 : | |||
| 219 : | dataptr[0] = DESCALE(tmp10 + tmp11, PASS1_BITS); | ||
| 220 : | dataptr[32] = DESCALE(tmp10 - tmp11, PASS1_BITS); | ||
| 221 : | |||
| 222 : | z1 = (tmp12 + tmp13) * FIX_0_541196100; | ||
| 223 : | dataptr[16] = DESCALE(z1 + tmp13 * FIX_0_765366865, CONST_BITS + PASS1_BITS); | ||
| 224 : | dataptr[48] = DESCALE(z1 + tmp12 * (-FIX_1_847759065), CONST_BITS + PASS1_BITS); | ||
| 225 : | |||
| 226 : | /* Odd part per figure 8 --- note paper omits factor of sqrt(2). | ||
| 227 : | * cK represents cos(K*pi/16). | ||
| 228 : | * i0..i3 in the paper are tmp4..tmp7 here. | ||
| 229 : | */ | ||
| 230 : | |||
| 231 : | z1 = tmp4 + tmp7; | ||
| 232 : | z2 = tmp5 + tmp6; | ||
| 233 : | z3 = tmp4 + tmp6; | ||
| 234 : | z4 = tmp5 + tmp7; | ||
| 235 : | z5 = (z3 + z4) * FIX_1_175875602; /* sqrt(2) * c3 */ | ||
| 236 : | |||
| 237 : | tmp4 *= FIX_0_298631336; /* sqrt(2) * (-c1+c3+c5-c7) */ | ||
| 238 : | tmp5 *= FIX_2_053119869; /* sqrt(2) * ( c1+c3-c5+c7) */ | ||
| 239 : | tmp6 *= FIX_3_072711026; /* sqrt(2) * ( c1+c3+c5-c7) */ | ||
| 240 : | tmp7 *= FIX_1_501321110; /* sqrt(2) * ( c1+c3-c5-c7) */ | ||
| 241 : | z1 *= -FIX_0_899976223; /* sqrt(2) * (c7-c3) */ | ||
| 242 : | z2 *= -FIX_2_562915447; /* sqrt(2) * (-c1-c3) */ | ||
| 243 : | z3 *= -FIX_1_961570560; /* sqrt(2) * (-c3-c5) */ | ||
| 244 : | z4 *= -FIX_0_390180644; /* sqrt(2) * (c5-c3) */ | ||
| 245 : | |||
| 246 : | z3 += z5; | ||
| 247 : | z4 += z5; | ||
| 248 : | |||
| 249 : | dataptr[56] = DESCALE(tmp4 + z1 + z3, CONST_BITS + PASS1_BITS); | ||
| 250 : | dataptr[40] = DESCALE(tmp5 + z2 + z4, CONST_BITS + PASS1_BITS); | ||
| 251 : | dataptr[24] = DESCALE(tmp6 + z2 + z3, CONST_BITS + PASS1_BITS); | ||
| 252 : | dataptr[8] = DESCALE(tmp7 + z1 + z4, CONST_BITS + PASS1_BITS); | ||
| 253 : | |||
| 254 : | dataptr++; /* advance pointer to next column */ | ||
| 255 : | } | ||
| 256 : | /* descale */ | ||
| 257 : | for (i = 0; i < 64; i++) | ||
| 258 : | block[i] = (short int) DESCALE(data[i], 3); | ||
| 259 : | } | ||
| 260 : |
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