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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 | } |