blob: b6049c938b830cd55f4ec2b669203c60c54d50ac
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 percentage 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 elbg_data { |
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 separated 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 | int 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, ret = 0; |
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 | if (!temp_points) |
348 | return AVERROR(ENOMEM); |
349 | for (i=0; i<numpoints/8; i++) { |
350 | k = (i*BIG_PRIME) % numpoints; |
351 | memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int)); |
352 | } |
353 | |
354 | ret = avpriv_init_elbg(temp_points, dim, numpoints / 8, codebook, |
355 | numCB, 2 * max_steps, closest_cb, rand_state); |
356 | if (ret < 0) { |
357 | av_freep(&temp_points); |
358 | return ret; |
359 | } |
360 | ret = avpriv_do_elbg(temp_points, dim, numpoints / 8, codebook, |
361 | numCB, 2 * max_steps, closest_cb, rand_state); |
362 | av_free(temp_points); |
363 | |
364 | } else // If not, initialize the codebook with random positions |
365 | for (i=0; i < numCB; i++) |
366 | memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim, |
367 | dim*sizeof(int)); |
368 | return ret; |
369 | } |
370 | |
371 | int avpriv_do_elbg(int *points, int dim, int numpoints, int *codebook, |
372 | int numCB, int max_steps, int *closest_cb, |
373 | AVLFG *rand_state) |
374 | { |
375 | int dist; |
376 | elbg_data elbg_d; |
377 | elbg_data *elbg = &elbg_d; |
378 | int i, j, k, last_error, steps = 0, ret = 0; |
379 | int *dist_cb = av_malloc_array(numpoints, sizeof(int)); |
380 | int *size_part = av_malloc_array(numCB, sizeof(int)); |
381 | cell *list_buffer = av_malloc_array(numpoints, sizeof(cell)); |
382 | cell *free_cells; |
383 | int best_dist, best_idx = 0; |
384 | |
385 | elbg->error = INT_MAX; |
386 | elbg->dim = dim; |
387 | elbg->numCB = numCB; |
388 | elbg->codebook = codebook; |
389 | elbg->cells = av_malloc_array(numCB, sizeof(cell *)); |
390 | elbg->utility = av_malloc_array(numCB, sizeof(int)); |
391 | elbg->nearest_cb = closest_cb; |
392 | elbg->points = points; |
393 | elbg->utility_inc = av_malloc_array(numCB, sizeof(*elbg->utility_inc)); |
394 | elbg->scratchbuf = av_malloc_array(5*dim, sizeof(int)); |
395 | |
396 | if (!dist_cb || !size_part || !list_buffer || !elbg->cells || |
397 | !elbg->utility || !elbg->utility_inc || !elbg->scratchbuf) { |
398 | ret = AVERROR(ENOMEM); |
399 | goto out; |
400 | } |
401 | |
402 | elbg->rand_state = rand_state; |
403 | |
404 | do { |
405 | free_cells = list_buffer; |
406 | last_error = elbg->error; |
407 | steps++; |
408 | memset(elbg->utility, 0, numCB*sizeof(int)); |
409 | memset(elbg->cells, 0, numCB*sizeof(cell *)); |
410 | |
411 | elbg->error = 0; |
412 | |
413 | /* This loop evaluate the actual Voronoi partition. It is the most |
414 | costly part of the algorithm. */ |
415 | for (i=0; i < numpoints; i++) { |
416 | best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX); |
417 | for (k=0; k < elbg->numCB; k++) { |
418 | dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist); |
419 | if (dist < best_dist) { |
420 | best_dist = dist; |
421 | best_idx = k; |
422 | } |
423 | } |
424 | elbg->nearest_cb[i] = best_idx; |
425 | dist_cb[i] = best_dist; |
426 | elbg->error += dist_cb[i]; |
427 | elbg->utility[elbg->nearest_cb[i]] += dist_cb[i]; |
428 | free_cells->index = i; |
429 | free_cells->next = elbg->cells[elbg->nearest_cb[i]]; |
430 | elbg->cells[elbg->nearest_cb[i]] = free_cells; |
431 | free_cells++; |
432 | } |
433 | |
434 | do_shiftings(elbg); |
435 | |
436 | memset(size_part, 0, numCB*sizeof(int)); |
437 | |
438 | memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int)); |
439 | |
440 | for (i=0; i < numpoints; i++) { |
441 | size_part[elbg->nearest_cb[i]]++; |
442 | for (j=0; j < elbg->dim; j++) |
443 | elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] += |
444 | elbg->points[i*elbg->dim + j]; |
445 | } |
446 | |
447 | for (i=0; i < elbg->numCB; i++) |
448 | vect_division(elbg->codebook + i*elbg->dim, |
449 | elbg->codebook + i*elbg->dim, size_part[i], elbg->dim); |
450 | |
451 | } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) && |
452 | (steps < max_steps)); |
453 | |
454 | out: |
455 | av_free(dist_cb); |
456 | av_free(size_part); |
457 | av_free(elbg->utility); |
458 | av_free(list_buffer); |
459 | av_free(elbg->cells); |
460 | av_free(elbg->utility_inc); |
461 | av_free(elbg->scratchbuf); |
462 | return ret; |
463 | } |
464 |