712c927cec6e0f24667fd17ff6a06d0a8aa5649c
[libav.git] / libavcodec / elbg.c
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 libavcodec/elbg.c
23 * Codebook Generator using the ELBG algorithm
24 */
25
26 #include <string.h>
27
28 #include "libavutil/random.h"
29 #include "elbg.h"
30 #include "avcodec.h"
31
32 #define DELTA_ERR_MAX 0.1 ///< Precision of the ELBG algorithm (as percentual error)
33
34 /**
35 * In the ELBG jargon, a cell is the set of points that are closest to a
36 * codebook entry. Not to be confused with a RoQ Video cell. */
37 typedef struct cell_s {
38 int index;
39 struct cell_s *next;
40 } cell;
41
42 /**
43 * ELBG internal data
44 */
45 typedef struct{
46 int error;
47 int dim;
48 int numCB;
49 int *codebook;
50 cell **cells;
51 int *utility;
52 int *utility_inc;
53 int *nearest_cb;
54 int *points;
55 AVRandomState *rand_state;
56 } elbg_data;
57
58 static inline int distance_limited(int *a, int *b, int dim, int limit)
59 {
60 int i, dist=0;
61 for (i=0; i<dim; i++) {
62 dist += (a[i] - b[i])*(a[i] - b[i]);
63 if (dist > limit)
64 return INT_MAX;
65 }
66
67 return dist;
68 }
69
70 static inline void vect_division(int *res, int *vect, int div, int dim)
71 {
72 int i;
73 if (div > 1)
74 for (i=0; i<dim; i++)
75 res[i] = ROUNDED_DIV(vect[i],div);
76 else if (res != vect)
77 memcpy(res, vect, dim*sizeof(int));
78
79 }
80
81 static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells)
82 {
83 int error=0;
84 for (; cells; cells=cells->next)
85 error += distance_limited(centroid, elbg->points + cells->index*elbg->dim, elbg->dim, INT_MAX);
86
87 return error;
88 }
89
90 static int get_closest_codebook(elbg_data *elbg, int index)
91 {
92 int i, pick=0, diff, diff_min = INT_MAX;
93 for (i=0; i<elbg->numCB; i++)
94 if (i != index) {
95 diff = distance_limited(elbg->codebook + i*elbg->dim, elbg->codebook + index*elbg->dim, elbg->dim, diff_min);
96 if (diff < diff_min) {
97 pick = i;
98 diff_min = diff;
99 }
100 }
101 return pick;
102 }
103
104 static int get_high_utility_cell(elbg_data *elbg)
105 {
106 int i=0;
107 /* Using linear search, do binary if it ever turns to be speed critical */
108 int r = av_random(elbg->rand_state)%(elbg->utility_inc[elbg->numCB-1]-1) + 1;
109 while (elbg->utility_inc[i] < r)
110 i++;
111
112 assert(!elbg->cells[i]);
113
114 return i;
115 }
116
117 /**
118 * Implementation of the simple LBG algorithm for just two codebooks
119 */
120 static int simple_lbg(int dim,
121 int *centroid[3],
122 int newutility[3],
123 int *points,
124 cell *cells)
125 {
126 int i, idx;
127 int numpoints[2] = {0,0};
128 int newcentroid[2][dim];
129 cell *tempcell;
130
131 memset(newcentroid, 0, sizeof(newcentroid));
132
133 newutility[0] =
134 newutility[1] = 0;
135
136 for (tempcell = cells; tempcell; tempcell=tempcell->next) {
137 idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>=
138 distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX);
139 numpoints[idx]++;
140 for (i=0; i<dim; i++)
141 newcentroid[idx][i] += points[tempcell->index*dim + i];
142 }
143
144 vect_division(centroid[0], newcentroid[0], numpoints[0], dim);
145 vect_division(centroid[1], newcentroid[1], numpoints[1], dim);
146
147 for (tempcell = cells; tempcell; tempcell=tempcell->next) {
148 int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX),
149 distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)};
150 int idx = dist[0] > dist[1];
151 newutility[idx] += dist[idx];
152 }
153
154 return newutility[0] + newutility[1];
155 }
156
157 static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i,
158 int *newcentroid_p)
159 {
160 cell *tempcell;
161 int min[elbg->dim];
162 int max[elbg->dim];
163 int i;
164
165 for (i=0; i< elbg->dim; i++) {
166 min[i]=INT_MAX;
167 max[i]=0;
168 }
169
170 for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next)
171 for(i=0; i<elbg->dim; i++) {
172 min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]);
173 max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]);
174 }
175
176 for (i=0; i<elbg->dim; i++) {
177 newcentroid_i[i] = min[i] + (max[i] - min[i])/3;
178 newcentroid_p[i] = min[i] + (2*(max[i] - min[i]))/3;
179 }
180 }
181
182 /**
183 * Add the points in the low utility cell to its closest cell. Split the high
184 * utility cell, putting the separed points in the (now empty) low utility
185 * cell.
186 *
187 * @param elbg Internal elbg data
188 * @param indexes {luc, huc, cluc}
189 * @param newcentroid A vector with the position of the new centroids
190 */
191 static void shift_codebook(elbg_data *elbg, int *indexes,
192 int *newcentroid[3])
193 {
194 cell *tempdata;
195 cell **pp = &elbg->cells[indexes[2]];
196
197 while(*pp)
198 pp= &(*pp)->next;
199
200 *pp = elbg->cells[indexes[0]];
201
202 elbg->cells[indexes[0]] = NULL;
203 tempdata = elbg->cells[indexes[1]];
204 elbg->cells[indexes[1]] = NULL;
205
206 while(tempdata) {
207 cell *tempcell2 = tempdata->next;
208 int idx = distance_limited(elbg->points + tempdata->index*elbg->dim,
209 newcentroid[0], elbg->dim, INT_MAX) >
210 distance_limited(elbg->points + tempdata->index*elbg->dim,
211 newcentroid[1], elbg->dim, INT_MAX);
212
213 tempdata->next = elbg->cells[indexes[idx]];
214 elbg->cells[indexes[idx]] = tempdata;
215 tempdata = tempcell2;
216 }
217 }
218
219 static void evaluate_utility_inc(elbg_data *elbg)
220 {
221 int i, inc=0;
222
223 for (i=0; i < elbg->numCB; i++) {
224 if (elbg->numCB*elbg->utility[i] > elbg->error)
225 inc += elbg->utility[i];
226 elbg->utility_inc[i] = inc;
227 }
228 }
229
230
231 static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)
232 {
233 cell *tempcell;
234
235 elbg->utility[idx] = newutility;
236 for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next)
237 elbg->nearest_cb[tempcell->index] = idx;
238 }
239
240 /**
241 * Evaluate if a shift lower the error. If it does, call shift_codebooks
242 * and update elbg->error, elbg->utility and elbg->nearest_cb.
243 *
244 * @param elbg Internal elbg data
245 * @param indexes {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)}
246 */
247 static void try_shift_candidate(elbg_data *elbg, int idx[3])
248 {
249 int j, k, olderror=0, newerror, cont=0;
250 int newutility[3];
251 int newcentroid[3][elbg->dim];
252 int *newcentroid_ptrs[3];
253 cell *tempcell;
254
255 newcentroid_ptrs[0] = newcentroid[0];
256 newcentroid_ptrs[1] = newcentroid[1];
257 newcentroid_ptrs[2] = newcentroid[2];
258
259 for (j=0; j<3; j++)
260 olderror += elbg->utility[idx[j]];
261
262 memset(newcentroid[2], 0, elbg->dim*sizeof(int));
263
264 for (k=0; k<2; k++)
265 for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) {
266 cont++;
267 for (j=0; j<elbg->dim; j++)
268 newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j];
269 }
270
271 vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim);
272
273 get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]);
274
275 newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]);
276 newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]);
277
278 newerror = newutility[2];
279
280 newerror += simple_lbg(elbg->dim, newcentroid_ptrs, newutility, elbg->points,
281 elbg->cells[idx[1]]);
282
283 if (olderror > newerror) {
284 shift_codebook(elbg, idx, newcentroid_ptrs);
285
286 elbg->error += newerror - olderror;
287
288 for (j=0; j<3; j++)
289 update_utility_and_n_cb(elbg, idx[j], newutility[j]);
290
291 evaluate_utility_inc(elbg);
292 }
293 }
294
295 /**
296 * Implementation of the ELBG block
297 */
298 static void do_shiftings(elbg_data *elbg)
299 {
300 int idx[3];
301
302 evaluate_utility_inc(elbg);
303
304 for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++)
305 if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) {
306 if (elbg->utility_inc[elbg->numCB-1] == 0)
307 return;
308
309 idx[1] = get_high_utility_cell(elbg);
310 idx[2] = get_closest_codebook(elbg, idx[0]);
311
312 if (idx[1] != idx[0] && idx[1] != idx[2])
313 try_shift_candidate(elbg, idx);
314 }
315 }
316
317 #define BIG_PRIME 433494437LL
318
319 void ff_init_elbg(int *points, int dim, int numpoints, int *codebook,
320 int numCB, int max_steps, int *closest_cb,
321 AVRandomState *rand_state)
322 {
323 int i, k;
324
325 if (numpoints > 24*numCB) {
326 /* ELBG is very costly for a big number of points. So if we have a lot
327 of them, get a good initial codebook to save on iterations */
328 int *temp_points = av_malloc(dim*(numpoints/8)*sizeof(int));
329 for (i=0; i<numpoints/8; i++) {
330 k = (i*BIG_PRIME) % numpoints;
331 memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int));
332 }
333
334 ff_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
335 ff_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
336
337 av_free(temp_points);
338
339 } else // If not, initialize the codebook with random positions
340 for (i=0; i < numCB; i++)
341 memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim,
342 dim*sizeof(int));
343
344 }
345
346 void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
347 int numCB, int max_steps, int *closest_cb,
348 AVRandomState *rand_state)
349 {
350 int dist;
351 elbg_data elbg_d;
352 elbg_data *elbg = &elbg_d;
353 int i, j, k, last_error, steps=0;
354 int *dist_cb = av_malloc(numpoints*sizeof(int));
355 int *size_part = av_malloc(numCB*sizeof(int));
356 cell *list_buffer = av_malloc(numpoints*sizeof(cell));
357 cell *free_cells;
358
359 elbg->error = INT_MAX;
360 elbg->dim = dim;
361 elbg->numCB = numCB;
362 elbg->codebook = codebook;
363 elbg->cells = av_malloc(numCB*sizeof(cell *));
364 elbg->utility = av_malloc(numCB*sizeof(int));
365 elbg->nearest_cb = closest_cb;
366 elbg->points = points;
367 elbg->utility_inc = av_malloc(numCB*sizeof(int));
368
369 elbg->rand_state = rand_state;
370
371 do {
372 free_cells = list_buffer;
373 last_error = elbg->error;
374 steps++;
375 memset(elbg->utility, 0, numCB*sizeof(int));
376 memset(elbg->cells, 0, numCB*sizeof(cell *));
377
378 elbg->error = 0;
379
380 /* This loop evaluate the actual Voronoi partition. It is the most
381 costly part of the algorithm. */
382 for (i=0; i < numpoints; i++) {
383 dist_cb[i] = INT_MAX;
384 for (k=0; k < elbg->numCB; k++) {
385 dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, dist_cb[i]);
386 if (dist < dist_cb[i]) {
387 dist_cb[i] = dist;
388 elbg->nearest_cb[i] = k;
389 }
390 }
391 elbg->error += dist_cb[i];
392 elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
393 free_cells->index = i;
394 free_cells->next = elbg->cells[elbg->nearest_cb[i]];
395 elbg->cells[elbg->nearest_cb[i]] = free_cells;
396 free_cells++;
397 }
398
399 do_shiftings(elbg);
400
401 memset(size_part, 0, numCB*sizeof(int));
402
403 memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
404
405 for (i=0; i < numpoints; i++) {
406 size_part[elbg->nearest_cb[i]]++;
407 for (j=0; j < elbg->dim; j++)
408 elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
409 elbg->points[i*elbg->dim + j];
410 }
411
412 for (i=0; i < elbg->numCB; i++)
413 vect_division(elbg->codebook + i*elbg->dim,
414 elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
415
416 } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
417 (steps < max_steps));
418
419 av_free(dist_cb);
420 av_free(size_part);
421 av_free(elbg->utility);
422 av_free(list_buffer);
423 av_free(elbg->cells);
424 av_free(elbg->utility_inc);
425 }