| 1 | /* |
| 2 | * Copyright (C) 2007 Vitor Sessak <vitor1001@gmail.com> |
| 3 | * |
| 4 | * This file is part of FFmpeg. |
| 5 | * |
| 6 | * FFmpeg is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU Lesser General Public |
| 8 | * License as published by the Free Software Foundation; either |
| 9 | * version 2.1 of the License, or (at your option) any later version. |
| 10 | * |
| 11 | * FFmpeg is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | * Lesser General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU Lesser General Public |
| 17 | * License along with FFmpeg; if not, write to the Free Software |
| 18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 19 | */ |
| 20 | |
| 21 | /** |
| 22 | * @file |
| 23 | * Codebook Generator using the ELBG algorithm |
| 24 | */ |
| 25 | |
| 26 | #include <string.h> |
| 27 | |
| 28 | #include "libavutil/avassert.h" |
| 29 | #include "libavutil/common.h" |
| 30 | #include "libavutil/lfg.h" |
| 31 | #include "elbg.h" |
| 32 | #include "avcodec.h" |
| 33 | |
| 34 | #define DELTA_ERR_MAX 0.1 ///< Precision of the ELBG algorithm (as percentual error) |
| 35 | |
| 36 | /** |
| 37 | * In the ELBG jargon, a cell is the set of points that are closest to a |
| 38 | * codebook entry. Not to be confused with a RoQ Video cell. */ |
| 39 | typedef struct cell_s { |
| 40 | int index; |
| 41 | struct cell_s *next; |
| 42 | } cell; |
| 43 | |
| 44 | /** |
| 45 | * ELBG internal data |
| 46 | */ |
| 47 | typedef struct{ |
| 48 | int error; |
| 49 | int dim; |
| 50 | int numCB; |
| 51 | int *codebook; |
| 52 | cell **cells; |
| 53 | int *utility; |
| 54 | int64_t *utility_inc; |
| 55 | int *nearest_cb; |
| 56 | int *points; |
| 57 | AVLFG *rand_state; |
| 58 | int *scratchbuf; |
| 59 | } elbg_data; |
| 60 | |
| 61 | static inline int distance_limited(int *a, int *b, int dim, int limit) |
| 62 | { |
| 63 | int i, dist=0; |
| 64 | for (i=0; i<dim; i++) { |
| 65 | dist += (a[i] - b[i])*(a[i] - b[i]); |
| 66 | if (dist > limit) |
| 67 | return INT_MAX; |
| 68 | } |
| 69 | |
| 70 | return dist; |
| 71 | } |
| 72 | |
| 73 | static inline void vect_division(int *res, int *vect, int div, int dim) |
| 74 | { |
| 75 | int i; |
| 76 | if (div > 1) |
| 77 | for (i=0; i<dim; i++) |
| 78 | res[i] = ROUNDED_DIV(vect[i],div); |
| 79 | else if (res != vect) |
| 80 | memcpy(res, vect, dim*sizeof(int)); |
| 81 | |
| 82 | } |
| 83 | |
| 84 | static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells) |
| 85 | { |
| 86 | int error=0; |
| 87 | for (; cells; cells=cells->next) |
| 88 | error += distance_limited(centroid, elbg->points + cells->index*elbg->dim, elbg->dim, INT_MAX); |
| 89 | |
| 90 | return error; |
| 91 | } |
| 92 | |
| 93 | static int get_closest_codebook(elbg_data *elbg, int index) |
| 94 | { |
| 95 | int i, pick=0, diff, diff_min = INT_MAX; |
| 96 | for (i=0; i<elbg->numCB; i++) |
| 97 | if (i != index) { |
| 98 | diff = distance_limited(elbg->codebook + i*elbg->dim, elbg->codebook + index*elbg->dim, elbg->dim, diff_min); |
| 99 | if (diff < diff_min) { |
| 100 | pick = i; |
| 101 | diff_min = diff; |
| 102 | } |
| 103 | } |
| 104 | return pick; |
| 105 | } |
| 106 | |
| 107 | static int get_high_utility_cell(elbg_data *elbg) |
| 108 | { |
| 109 | int i=0; |
| 110 | /* Using linear search, do binary if it ever turns to be speed critical */ |
| 111 | uint64_t r; |
| 112 | |
| 113 | if (elbg->utility_inc[elbg->numCB-1] < INT_MAX) { |
| 114 | r = av_lfg_get(elbg->rand_state) % (unsigned int)elbg->utility_inc[elbg->numCB-1] + 1; |
| 115 | } else { |
| 116 | r = av_lfg_get(elbg->rand_state); |
| 117 | r = (av_lfg_get(elbg->rand_state) + (r<<32)) % elbg->utility_inc[elbg->numCB-1] + 1; |
| 118 | } |
| 119 | |
| 120 | while (elbg->utility_inc[i] < r) { |
| 121 | i++; |
| 122 | } |
| 123 | |
| 124 | av_assert2(elbg->cells[i]); |
| 125 | |
| 126 | return i; |
| 127 | } |
| 128 | |
| 129 | /** |
| 130 | * Implementation of the simple LBG algorithm for just two codebooks |
| 131 | */ |
| 132 | static int simple_lbg(elbg_data *elbg, |
| 133 | int dim, |
| 134 | int *centroid[3], |
| 135 | int newutility[3], |
| 136 | int *points, |
| 137 | cell *cells) |
| 138 | { |
| 139 | int i, idx; |
| 140 | int numpoints[2] = {0,0}; |
| 141 | int *newcentroid[2] = { |
| 142 | elbg->scratchbuf + 3*dim, |
| 143 | elbg->scratchbuf + 4*dim |
| 144 | }; |
| 145 | cell *tempcell; |
| 146 | |
| 147 | memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0])); |
| 148 | |
| 149 | newutility[0] = |
| 150 | newutility[1] = 0; |
| 151 | |
| 152 | for (tempcell = cells; tempcell; tempcell=tempcell->next) { |
| 153 | idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>= |
| 154 | distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX); |
| 155 | numpoints[idx]++; |
| 156 | for (i=0; i<dim; i++) |
| 157 | newcentroid[idx][i] += points[tempcell->index*dim + i]; |
| 158 | } |
| 159 | |
| 160 | vect_division(centroid[0], newcentroid[0], numpoints[0], dim); |
| 161 | vect_division(centroid[1], newcentroid[1], numpoints[1], dim); |
| 162 | |
| 163 | for (tempcell = cells; tempcell; tempcell=tempcell->next) { |
| 164 | int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX), |
| 165 | distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)}; |
| 166 | int idx = dist[0] > dist[1]; |
| 167 | newutility[idx] += dist[idx]; |
| 168 | } |
| 169 | |
| 170 | return newutility[0] + newutility[1]; |
| 171 | } |
| 172 | |
| 173 | static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i, |
| 174 | int *newcentroid_p) |
| 175 | { |
| 176 | cell *tempcell; |
| 177 | int *min = newcentroid_i; |
| 178 | int *max = newcentroid_p; |
| 179 | int i; |
| 180 | |
| 181 | for (i=0; i< elbg->dim; i++) { |
| 182 | min[i]=INT_MAX; |
| 183 | max[i]=0; |
| 184 | } |
| 185 | |
| 186 | for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next) |
| 187 | for(i=0; i<elbg->dim; i++) { |
| 188 | min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]); |
| 189 | max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]); |
| 190 | } |
| 191 | |
| 192 | for (i=0; i<elbg->dim; i++) { |
| 193 | int ni = min[i] + (max[i] - min[i])/3; |
| 194 | int np = min[i] + (2*(max[i] - min[i]))/3; |
| 195 | newcentroid_i[i] = ni; |
| 196 | newcentroid_p[i] = np; |
| 197 | } |
| 198 | } |
| 199 | |
| 200 | /** |
| 201 | * Add the points in the low utility cell to its closest cell. Split the high |
| 202 | * utility cell, putting the separate points in the (now empty) low utility |
| 203 | * cell. |
| 204 | * |
| 205 | * @param elbg Internal elbg data |
| 206 | * @param indexes {luc, huc, cluc} |
| 207 | * @param newcentroid A vector with the position of the new centroids |
| 208 | */ |
| 209 | static void shift_codebook(elbg_data *elbg, int *indexes, |
| 210 | int *newcentroid[3]) |
| 211 | { |
| 212 | cell *tempdata; |
| 213 | cell **pp = &elbg->cells[indexes[2]]; |
| 214 | |
| 215 | while(*pp) |
| 216 | pp= &(*pp)->next; |
| 217 | |
| 218 | *pp = elbg->cells[indexes[0]]; |
| 219 | |
| 220 | elbg->cells[indexes[0]] = NULL; |
| 221 | tempdata = elbg->cells[indexes[1]]; |
| 222 | elbg->cells[indexes[1]] = NULL; |
| 223 | |
| 224 | while(tempdata) { |
| 225 | cell *tempcell2 = tempdata->next; |
| 226 | int idx = distance_limited(elbg->points + tempdata->index*elbg->dim, |
| 227 | newcentroid[0], elbg->dim, INT_MAX) > |
| 228 | distance_limited(elbg->points + tempdata->index*elbg->dim, |
| 229 | newcentroid[1], elbg->dim, INT_MAX); |
| 230 | |
| 231 | tempdata->next = elbg->cells[indexes[idx]]; |
| 232 | elbg->cells[indexes[idx]] = tempdata; |
| 233 | tempdata = tempcell2; |
| 234 | } |
| 235 | } |
| 236 | |
| 237 | static void evaluate_utility_inc(elbg_data *elbg) |
| 238 | { |
| 239 | int i; |
| 240 | int64_t inc=0; |
| 241 | |
| 242 | for (i=0; i < elbg->numCB; i++) { |
| 243 | if (elbg->numCB*elbg->utility[i] > elbg->error) |
| 244 | inc += elbg->utility[i]; |
| 245 | elbg->utility_inc[i] = inc; |
| 246 | } |
| 247 | } |
| 248 | |
| 249 | |
| 250 | static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility) |
| 251 | { |
| 252 | cell *tempcell; |
| 253 | |
| 254 | elbg->utility[idx] = newutility; |
| 255 | for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next) |
| 256 | elbg->nearest_cb[tempcell->index] = idx; |
| 257 | } |
| 258 | |
| 259 | /** |
| 260 | * Evaluate if a shift lower the error. If it does, call shift_codebooks |
| 261 | * and update elbg->error, elbg->utility and elbg->nearest_cb. |
| 262 | * |
| 263 | * @param elbg Internal elbg data |
| 264 | * @param idx {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)} |
| 265 | */ |
| 266 | static void try_shift_candidate(elbg_data *elbg, int idx[3]) |
| 267 | { |
| 268 | int j, k, olderror=0, newerror, cont=0; |
| 269 | int newutility[3]; |
| 270 | int *newcentroid[3] = { |
| 271 | elbg->scratchbuf, |
| 272 | elbg->scratchbuf + elbg->dim, |
| 273 | elbg->scratchbuf + 2*elbg->dim |
| 274 | }; |
| 275 | cell *tempcell; |
| 276 | |
| 277 | for (j=0; j<3; j++) |
| 278 | olderror += elbg->utility[idx[j]]; |
| 279 | |
| 280 | memset(newcentroid[2], 0, elbg->dim*sizeof(int)); |
| 281 | |
| 282 | for (k=0; k<2; k++) |
| 283 | for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) { |
| 284 | cont++; |
| 285 | for (j=0; j<elbg->dim; j++) |
| 286 | newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j]; |
| 287 | } |
| 288 | |
| 289 | vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim); |
| 290 | |
| 291 | get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]); |
| 292 | |
| 293 | newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]); |
| 294 | newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]); |
| 295 | |
| 296 | newerror = newutility[2]; |
| 297 | |
| 298 | newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points, |
| 299 | elbg->cells[idx[1]]); |
| 300 | |
| 301 | if (olderror > newerror) { |
| 302 | shift_codebook(elbg, idx, newcentroid); |
| 303 | |
| 304 | elbg->error += newerror - olderror; |
| 305 | |
| 306 | for (j=0; j<3; j++) |
| 307 | update_utility_and_n_cb(elbg, idx[j], newutility[j]); |
| 308 | |
| 309 | evaluate_utility_inc(elbg); |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | /** |
| 314 | * Implementation of the ELBG block |
| 315 | */ |
| 316 | static void do_shiftings(elbg_data *elbg) |
| 317 | { |
| 318 | int idx[3]; |
| 319 | |
| 320 | evaluate_utility_inc(elbg); |
| 321 | |
| 322 | for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++) |
| 323 | if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) { |
| 324 | if (elbg->utility_inc[elbg->numCB-1] == 0) |
| 325 | return; |
| 326 | |
| 327 | idx[1] = get_high_utility_cell(elbg); |
| 328 | idx[2] = get_closest_codebook(elbg, idx[0]); |
| 329 | |
| 330 | if (idx[1] != idx[0] && idx[1] != idx[2]) |
| 331 | try_shift_candidate(elbg, idx); |
| 332 | } |
| 333 | } |
| 334 | |
| 335 | #define BIG_PRIME 433494437LL |
| 336 | |
| 337 | void avpriv_init_elbg(int *points, int dim, int numpoints, int *codebook, |
| 338 | int numCB, int max_steps, int *closest_cb, |
| 339 | AVLFG *rand_state) |
| 340 | { |
| 341 | int i, k; |
| 342 | |
| 343 | if (numpoints > 24*numCB) { |
| 344 | /* ELBG is very costly for a big number of points. So if we have a lot |
| 345 | of them, get a good initial codebook to save on iterations */ |
| 346 | int *temp_points = av_malloc_array(dim, (numpoints/8)*sizeof(int)); |
| 347 | for (i=0; i<numpoints/8; i++) { |
| 348 | k = (i*BIG_PRIME) % numpoints; |
| 349 | memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int)); |
| 350 | } |
| 351 | |
| 352 | avpriv_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state); |
| 353 | avpriv_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state); |
| 354 | |
| 355 | av_free(temp_points); |
| 356 | |
| 357 | } else // If not, initialize the codebook with random positions |
| 358 | for (i=0; i < numCB; i++) |
| 359 | memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim, |
| 360 | dim*sizeof(int)); |
| 361 | |
| 362 | } |
| 363 | |
| 364 | void avpriv_do_elbg(int *points, int dim, int numpoints, int *codebook, |
| 365 | int numCB, int max_steps, int *closest_cb, |
| 366 | AVLFG *rand_state) |
| 367 | { |
| 368 | int dist; |
| 369 | elbg_data elbg_d; |
| 370 | elbg_data *elbg = &elbg_d; |
| 371 | int i, j, k, last_error, steps=0; |
| 372 | int *dist_cb = av_malloc_array(numpoints, sizeof(int)); |
| 373 | int *size_part = av_malloc_array(numCB, sizeof(int)); |
| 374 | cell *list_buffer = av_malloc_array(numpoints, sizeof(cell)); |
| 375 | cell *free_cells; |
| 376 | int best_dist, best_idx = 0; |
| 377 | |
| 378 | elbg->error = INT_MAX; |
| 379 | elbg->dim = dim; |
| 380 | elbg->numCB = numCB; |
| 381 | elbg->codebook = codebook; |
| 382 | elbg->cells = av_malloc_array(numCB, sizeof(cell *)); |
| 383 | elbg->utility = av_malloc_array(numCB, sizeof(int)); |
| 384 | elbg->nearest_cb = closest_cb; |
| 385 | elbg->points = points; |
| 386 | elbg->utility_inc = av_malloc_array(numCB, sizeof(*elbg->utility_inc)); |
| 387 | elbg->scratchbuf = av_malloc_array(5*dim, sizeof(int)); |
| 388 | |
| 389 | elbg->rand_state = rand_state; |
| 390 | |
| 391 | do { |
| 392 | free_cells = list_buffer; |
| 393 | last_error = elbg->error; |
| 394 | steps++; |
| 395 | memset(elbg->utility, 0, numCB*sizeof(int)); |
| 396 | memset(elbg->cells, 0, numCB*sizeof(cell *)); |
| 397 | |
| 398 | elbg->error = 0; |
| 399 | |
| 400 | /* This loop evaluate the actual Voronoi partition. It is the most |
| 401 | costly part of the algorithm. */ |
| 402 | for (i=0; i < numpoints; i++) { |
| 403 | best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX); |
| 404 | for (k=0; k < elbg->numCB; k++) { |
| 405 | dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist); |
| 406 | if (dist < best_dist) { |
| 407 | best_dist = dist; |
| 408 | best_idx = k; |
| 409 | } |
| 410 | } |
| 411 | elbg->nearest_cb[i] = best_idx; |
| 412 | dist_cb[i] = best_dist; |
| 413 | elbg->error += dist_cb[i]; |
| 414 | elbg->utility[elbg->nearest_cb[i]] += dist_cb[i]; |
| 415 | free_cells->index = i; |
| 416 | free_cells->next = elbg->cells[elbg->nearest_cb[i]]; |
| 417 | elbg->cells[elbg->nearest_cb[i]] = free_cells; |
| 418 | free_cells++; |
| 419 | } |
| 420 | |
| 421 | do_shiftings(elbg); |
| 422 | |
| 423 | memset(size_part, 0, numCB*sizeof(int)); |
| 424 | |
| 425 | memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int)); |
| 426 | |
| 427 | for (i=0; i < numpoints; i++) { |
| 428 | size_part[elbg->nearest_cb[i]]++; |
| 429 | for (j=0; j < elbg->dim; j++) |
| 430 | elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] += |
| 431 | elbg->points[i*elbg->dim + j]; |
| 432 | } |
| 433 | |
| 434 | for (i=0; i < elbg->numCB; i++) |
| 435 | vect_division(elbg->codebook + i*elbg->dim, |
| 436 | elbg->codebook + i*elbg->dim, size_part[i], elbg->dim); |
| 437 | |
| 438 | } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) && |
| 439 | (steps < max_steps)); |
| 440 | |
| 441 | av_free(dist_cb); |
| 442 | av_free(size_part); |
| 443 | av_free(elbg->utility); |
| 444 | av_free(list_buffer); |
| 445 | av_free(elbg->cells); |
| 446 | av_free(elbg->utility_inc); |
| 447 | av_free(elbg->scratchbuf); |
| 448 | } |