| 1 | /* |
| 2 | * This file is part of the Independent JPEG Group's software. |
| 3 | * |
| 4 | * The authors make NO WARRANTY or representation, either express or implied, |
| 5 | * with respect to this software, its quality, accuracy, merchantability, or |
| 6 | * fitness for a particular purpose. This software is provided "AS IS", and |
| 7 | * you, its user, assume the entire risk as to its quality and accuracy. |
| 8 | * |
| 9 | * This software is copyright (C) 1994-1996, Thomas G. Lane. |
| 10 | * All Rights Reserved except as specified below. |
| 11 | * |
| 12 | * Permission is hereby granted to use, copy, modify, and distribute this |
| 13 | * software (or portions thereof) for any purpose, without fee, subject to |
| 14 | * these conditions: |
| 15 | * (1) If any part of the source code for this software is distributed, then |
| 16 | * this README file must be included, with this copyright and no-warranty |
| 17 | * notice unaltered; and any additions, deletions, or changes to the original |
| 18 | * files must be clearly indicated in accompanying documentation. |
| 19 | * (2) If only executable code is distributed, then the accompanying |
| 20 | * documentation must state that "this software is based in part on the work |
| 21 | * of the Independent JPEG Group". |
| 22 | * (3) Permission for use of this software is granted only if the user accepts |
| 23 | * full responsibility for any undesirable consequences; the authors accept |
| 24 | * NO LIABILITY for damages of any kind. |
| 25 | * |
| 26 | * These conditions apply to any software derived from or based on the IJG |
| 27 | * code, not just to the unmodified library. If you use our work, you ought |
| 28 | * to acknowledge us. |
| 29 | * |
| 30 | * Permission is NOT granted for the use of any IJG author's name or company |
| 31 | * name in advertising or publicity relating to this software or products |
| 32 | * derived from it. This software may be referred to only as "the Independent |
| 33 | * JPEG Group's software". |
| 34 | * |
| 35 | * We specifically permit and encourage the use of this software as the basis |
| 36 | * of commercial products, provided that all warranty or liability claims are |
| 37 | * assumed by the product vendor. |
| 38 | * |
| 39 | * This file contains a fast, not so accurate integer implementation of the |
| 40 | * forward DCT (Discrete Cosine Transform). |
| 41 | * |
| 42 | * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT |
| 43 | * on each column. Direct algorithms are also available, but they are |
| 44 | * much more complex and seem not to be any faster when reduced to code. |
| 45 | * |
| 46 | * This implementation is based on Arai, Agui, and Nakajima's algorithm for |
| 47 | * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in |
| 48 | * Japanese, but the algorithm is described in the Pennebaker & Mitchell |
| 49 | * JPEG textbook (see REFERENCES section in file README). The following code |
| 50 | * is based directly on figure 4-8 in P&M. |
| 51 | * While an 8-point DCT cannot be done in less than 11 multiplies, it is |
| 52 | * possible to arrange the computation so that many of the multiplies are |
| 53 | * simple scalings of the final outputs. These multiplies can then be |
| 54 | * folded into the multiplications or divisions by the JPEG quantization |
| 55 | * table entries. The AA&N method leaves only 5 multiplies and 29 adds |
| 56 | * to be done in the DCT itself. |
| 57 | * The primary disadvantage of this method is that with fixed-point math, |
| 58 | * accuracy is lost due to imprecise representation of the scaled |
| 59 | * quantization values. The smaller the quantization table entry, the less |
| 60 | * precise the scaled value, so this implementation does worse with high- |
| 61 | * quality-setting files than with low-quality ones. |
| 62 | */ |
| 63 | |
| 64 | /** |
| 65 | * @file |
| 66 | * Independent JPEG Group's fast AAN dct. |
| 67 | */ |
| 68 | |
| 69 | #include <stdlib.h> |
| 70 | #include <stdio.h> |
| 71 | #include "libavutil/common.h" |
| 72 | #include "dct.h" |
| 73 | |
| 74 | #define DCTSIZE 8 |
| 75 | #define GLOBAL(x) x |
| 76 | #define RIGHT_SHIFT(x, n) ((x) >> (n)) |
| 77 | |
| 78 | /* |
| 79 | * This module is specialized to the case DCTSIZE = 8. |
| 80 | */ |
| 81 | |
| 82 | #if DCTSIZE != 8 |
| 83 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
| 84 | #endif |
| 85 | |
| 86 | |
| 87 | /* Scaling decisions are generally the same as in the LL&M algorithm; |
| 88 | * see jfdctint.c for more details. However, we choose to descale |
| 89 | * (right shift) multiplication products as soon as they are formed, |
| 90 | * rather than carrying additional fractional bits into subsequent additions. |
| 91 | * This compromises accuracy slightly, but it lets us save a few shifts. |
| 92 | * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) |
| 93 | * everywhere except in the multiplications proper; this saves a good deal |
| 94 | * of work on 16-bit-int machines. |
| 95 | * |
| 96 | * Again to save a few shifts, the intermediate results between pass 1 and |
| 97 | * pass 2 are not upscaled, but are represented only to integral precision. |
| 98 | * |
| 99 | * A final compromise is to represent the multiplicative constants to only |
| 100 | * 8 fractional bits, rather than 13. This saves some shifting work on some |
| 101 | * machines, and may also reduce the cost of multiplication (since there |
| 102 | * are fewer one-bits in the constants). |
| 103 | */ |
| 104 | |
| 105 | #define CONST_BITS 8 |
| 106 | |
| 107 | |
| 108 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
| 109 | * causing a lot of useless floating-point operations at run time. |
| 110 | * To get around this we use the following pre-calculated constants. |
| 111 | * If you change CONST_BITS you may want to add appropriate values. |
| 112 | * (With a reasonable C compiler, you can just rely on the FIX() macro...) |
| 113 | */ |
| 114 | |
| 115 | #if CONST_BITS == 8 |
| 116 | #define FIX_0_382683433 ((int32_t) 98) /* FIX(0.382683433) */ |
| 117 | #define FIX_0_541196100 ((int32_t) 139) /* FIX(0.541196100) */ |
| 118 | #define FIX_0_707106781 ((int32_t) 181) /* FIX(0.707106781) */ |
| 119 | #define FIX_1_306562965 ((int32_t) 334) /* FIX(1.306562965) */ |
| 120 | #else |
| 121 | #define FIX_0_382683433 FIX(0.382683433) |
| 122 | #define FIX_0_541196100 FIX(0.541196100) |
| 123 | #define FIX_0_707106781 FIX(0.707106781) |
| 124 | #define FIX_1_306562965 FIX(1.306562965) |
| 125 | #endif |
| 126 | |
| 127 | |
| 128 | /* We can gain a little more speed, with a further compromise in accuracy, |
| 129 | * by omitting the addition in a descaling shift. This yields an incorrectly |
| 130 | * rounded result half the time... |
| 131 | */ |
| 132 | |
| 133 | #ifndef USE_ACCURATE_ROUNDING |
| 134 | #undef DESCALE |
| 135 | #define DESCALE(x,n) RIGHT_SHIFT(x, n) |
| 136 | #endif |
| 137 | |
| 138 | |
| 139 | /* Multiply a int16_t variable by an int32_t constant, and immediately |
| 140 | * descale to yield a int16_t result. |
| 141 | */ |
| 142 | |
| 143 | #define MULTIPLY(var,const) ((int16_t) DESCALE((var) * (const), CONST_BITS)) |
| 144 | |
| 145 | static av_always_inline void row_fdct(int16_t * data){ |
| 146 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
| 147 | int tmp10, tmp11, tmp12, tmp13; |
| 148 | int z1, z2, z3, z4, z5, z11, z13; |
| 149 | int16_t *dataptr; |
| 150 | int ctr; |
| 151 | |
| 152 | /* Pass 1: process rows. */ |
| 153 | |
| 154 | dataptr = data; |
| 155 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
| 156 | tmp0 = dataptr[0] + dataptr[7]; |
| 157 | tmp7 = dataptr[0] - dataptr[7]; |
| 158 | tmp1 = dataptr[1] + dataptr[6]; |
| 159 | tmp6 = dataptr[1] - dataptr[6]; |
| 160 | tmp2 = dataptr[2] + dataptr[5]; |
| 161 | tmp5 = dataptr[2] - dataptr[5]; |
| 162 | tmp3 = dataptr[3] + dataptr[4]; |
| 163 | tmp4 = dataptr[3] - dataptr[4]; |
| 164 | |
| 165 | /* Even part */ |
| 166 | |
| 167 | tmp10 = tmp0 + tmp3; /* phase 2 */ |
| 168 | tmp13 = tmp0 - tmp3; |
| 169 | tmp11 = tmp1 + tmp2; |
| 170 | tmp12 = tmp1 - tmp2; |
| 171 | |
| 172 | dataptr[0] = tmp10 + tmp11; /* phase 3 */ |
| 173 | dataptr[4] = tmp10 - tmp11; |
| 174 | |
| 175 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
| 176 | dataptr[2] = tmp13 + z1; /* phase 5 */ |
| 177 | dataptr[6] = tmp13 - z1; |
| 178 | |
| 179 | /* Odd part */ |
| 180 | |
| 181 | tmp10 = tmp4 + tmp5; /* phase 2 */ |
| 182 | tmp11 = tmp5 + tmp6; |
| 183 | tmp12 = tmp6 + tmp7; |
| 184 | |
| 185 | /* The rotator is modified from fig 4-8 to avoid extra negations. */ |
| 186 | z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
| 187 | z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
| 188 | z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
| 189 | z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
| 190 | |
| 191 | z11 = tmp7 + z3; /* phase 5 */ |
| 192 | z13 = tmp7 - z3; |
| 193 | |
| 194 | dataptr[5] = z13 + z2; /* phase 6 */ |
| 195 | dataptr[3] = z13 - z2; |
| 196 | dataptr[1] = z11 + z4; |
| 197 | dataptr[7] = z11 - z4; |
| 198 | |
| 199 | dataptr += DCTSIZE; /* advance pointer to next row */ |
| 200 | } |
| 201 | } |
| 202 | |
| 203 | /* |
| 204 | * Perform the forward DCT on one block of samples. |
| 205 | */ |
| 206 | |
| 207 | GLOBAL(void) |
| 208 | ff_fdct_ifast (int16_t * data) |
| 209 | { |
| 210 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
| 211 | int tmp10, tmp11, tmp12, tmp13; |
| 212 | int z1, z2, z3, z4, z5, z11, z13; |
| 213 | int16_t *dataptr; |
| 214 | int ctr; |
| 215 | |
| 216 | row_fdct(data); |
| 217 | |
| 218 | /* Pass 2: process columns. */ |
| 219 | |
| 220 | dataptr = data; |
| 221 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
| 222 | tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7]; |
| 223 | tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7]; |
| 224 | tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6]; |
| 225 | tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6]; |
| 226 | tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5]; |
| 227 | tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5]; |
| 228 | tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4]; |
| 229 | tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4]; |
| 230 | |
| 231 | /* Even part */ |
| 232 | |
| 233 | tmp10 = tmp0 + tmp3; /* phase 2 */ |
| 234 | tmp13 = tmp0 - tmp3; |
| 235 | tmp11 = tmp1 + tmp2; |
| 236 | tmp12 = tmp1 - tmp2; |
| 237 | |
| 238 | dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */ |
| 239 | dataptr[DCTSIZE*4] = tmp10 - tmp11; |
| 240 | |
| 241 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
| 242 | dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */ |
| 243 | dataptr[DCTSIZE*6] = tmp13 - z1; |
| 244 | |
| 245 | /* Odd part */ |
| 246 | |
| 247 | tmp10 = tmp4 + tmp5; /* phase 2 */ |
| 248 | tmp11 = tmp5 + tmp6; |
| 249 | tmp12 = tmp6 + tmp7; |
| 250 | |
| 251 | /* The rotator is modified from fig 4-8 to avoid extra negations. */ |
| 252 | z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
| 253 | z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
| 254 | z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
| 255 | z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
| 256 | |
| 257 | z11 = tmp7 + z3; /* phase 5 */ |
| 258 | z13 = tmp7 - z3; |
| 259 | |
| 260 | dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */ |
| 261 | dataptr[DCTSIZE*3] = z13 - z2; |
| 262 | dataptr[DCTSIZE*1] = z11 + z4; |
| 263 | dataptr[DCTSIZE*7] = z11 - z4; |
| 264 | |
| 265 | dataptr++; /* advance pointer to next column */ |
| 266 | } |
| 267 | } |
| 268 | |
| 269 | /* |
| 270 | * Perform the forward 2-4-8 DCT on one block of samples. |
| 271 | */ |
| 272 | |
| 273 | GLOBAL(void) |
| 274 | ff_fdct_ifast248 (int16_t * data) |
| 275 | { |
| 276 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
| 277 | int tmp10, tmp11, tmp12, tmp13; |
| 278 | int z1; |
| 279 | int16_t *dataptr; |
| 280 | int ctr; |
| 281 | |
| 282 | row_fdct(data); |
| 283 | |
| 284 | /* Pass 2: process columns. */ |
| 285 | |
| 286 | dataptr = data; |
| 287 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
| 288 | tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1]; |
| 289 | tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3]; |
| 290 | tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5]; |
| 291 | tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7]; |
| 292 | tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1]; |
| 293 | tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3]; |
| 294 | tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5]; |
| 295 | tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7]; |
| 296 | |
| 297 | /* Even part */ |
| 298 | |
| 299 | tmp10 = tmp0 + tmp3; |
| 300 | tmp11 = tmp1 + tmp2; |
| 301 | tmp12 = tmp1 - tmp2; |
| 302 | tmp13 = tmp0 - tmp3; |
| 303 | |
| 304 | dataptr[DCTSIZE*0] = tmp10 + tmp11; |
| 305 | dataptr[DCTSIZE*4] = tmp10 - tmp11; |
| 306 | |
| 307 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
| 308 | dataptr[DCTSIZE*2] = tmp13 + z1; |
| 309 | dataptr[DCTSIZE*6] = tmp13 - z1; |
| 310 | |
| 311 | tmp10 = tmp4 + tmp7; |
| 312 | tmp11 = tmp5 + tmp6; |
| 313 | tmp12 = tmp5 - tmp6; |
| 314 | tmp13 = tmp4 - tmp7; |
| 315 | |
| 316 | dataptr[DCTSIZE*1] = tmp10 + tmp11; |
| 317 | dataptr[DCTSIZE*5] = tmp10 - tmp11; |
| 318 | |
| 319 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
| 320 | dataptr[DCTSIZE*3] = tmp13 + z1; |
| 321 | dataptr[DCTSIZE*7] = tmp13 - z1; |
| 322 | |
| 323 | dataptr++; /* advance pointer to next column */ |
| 324 | } |
| 325 | } |
| 326 | |
| 327 | |
| 328 | #undef GLOBAL |
| 329 | #undef CONST_BITS |
| 330 | #undef DESCALE |
| 331 | #undef FIX_0_541196100 |
| 332 | #undef FIX_1_306562965 |