Codebook generator using the ELBG algorithm
[libav.git] / libavcodec / elbg.c
1 /*
2 * Copyright (C) 2007 Vitor <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 cbook_gen.c
23 * Codebook Generator using the ELBG algorithm
24 */
25
26 #include <string.h>
27
28 #include "elbg.h"
29 #include "avcodec.h"
30 #include "random.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];
109 while (elbg->utility_inc[i] < r)
110 i++;
111 return i;
112 }
113
114 /**
115 * Implementation of the simple LBG algorithm for just two codebooks
116 */
117 static int simple_lbg(int dim,
118 int centroid[3][dim],
119 int newutility[3],
120 int *points,
121 cell *cells)
122 {
123 int i, idx;
124 int numpoints[2] = {0,0};
125 int newcentroid[2][dim];
126 cell *tempcell;
127
128 memset(newcentroid, 0, sizeof(newcentroid));
129
130 newutility[0] =
131 newutility[1] = 0;
132
133 for (tempcell = cells; tempcell; tempcell=tempcell->next) {
134 idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>=
135 distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX);
136 numpoints[idx]++;
137 for (i=0; i<dim; i++)
138 newcentroid[idx][i] += points[tempcell->index*dim + i];
139 }
140
141 vect_division(centroid[0], newcentroid[0], numpoints[0], dim);
142 vect_division(centroid[1], newcentroid[1], numpoints[1], dim);
143
144 for (tempcell = cells; tempcell; tempcell=tempcell->next) {
145 int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX),
146 distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)};
147 int idx = dist[0] > dist[1];
148 newutility[idx] += dist[idx];
149 }
150
151 return newutility[0] + newutility[1];
152 }
153
154 static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i,
155 int *newcentroid_p)
156 {
157 cell *tempcell;
158 int min[elbg->dim];
159 int max[elbg->dim];
160 int i;
161
162 for (i=0; i< elbg->dim; i++) {
163 min[i]=INT_MAX;
164 max[i]=0;
165 }
166
167 for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next)
168 for(i=0; i<elbg->dim; i++) {
169 min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]);
170 max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]);
171 }
172
173 for (i=0; i<elbg->dim; i++) {
174 newcentroid_i[i] = min[i] + (max[i] - min[i])/3;
175 newcentroid_p[i] = min[i] + (2*(max[i] - min[i]))/3;
176 }
177 }
178
179 /**
180 * Add the points in the low utility cell to its closest cell. Split the high
181 * utility cell, putting the separed points in the (now empty) low utility
182 * cell.
183 *
184 * @param elbg Internal elbg data
185 * @param indexes {luc, huc, cluc}
186 * @param newcentroid A vector with the position of the new centroids
187 */
188 static void shift_codebook(elbg_data *elbg, int *indexes,
189 int newcentroid[3][elbg->dim])
190 {
191 cell *tempdata;
192 cell **pp = &elbg->cells[indexes[2]];
193
194 while(*pp)
195 pp= &(*pp)->next;
196
197 *pp = elbg->cells[indexes[0]];
198
199 elbg->cells[indexes[0]] = NULL;
200 tempdata = elbg->cells[indexes[1]];
201 elbg->cells[indexes[1]] = NULL;
202
203 while(tempdata) {
204 cell *tempcell2 = tempdata->next;
205 int idx = distance_limited(elbg->points + tempdata->index*elbg->dim,
206 newcentroid[0], elbg->dim, INT_MAX) >
207 distance_limited(elbg->points + tempdata->index*elbg->dim,
208 newcentroid[1], elbg->dim, INT_MAX);
209
210 tempdata->next = elbg->cells[indexes[idx]];
211 elbg->cells[indexes[idx]] = tempdata;
212 tempdata = tempcell2;
213 }
214 }
215
216 static void evaluate_utility_inc(elbg_data *elbg)
217 {
218 int i, inc=0;
219
220 for (i=0; i < elbg->numCB; i++) {
221 if (elbg->numCB*elbg->utility[i] > elbg->error)
222 inc += elbg->utility[i];
223 elbg->utility_inc[i] = inc;
224 }
225 }
226
227
228 static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)
229 {
230 cell *tempcell;
231
232 elbg->utility[idx] = newutility;
233 for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next)
234 elbg->nearest_cb[tempcell->index] = idx;
235 }
236
237 /**
238 * Evaluate if a shift lower the error. If it does, call shift_codebooks
239 * and update elbg->error, elbg->utility and elbg->nearest_cb.
240 *
241 * @param elbg Internal elbg data
242 * @param indexes {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)}
243 */
244 static void try_shift_candidate(elbg_data *elbg, int idx[3])
245 {
246 int j, k, olderror=0, newerror, cont=0;
247 int newutility[3];
248 int newcentroid[3][elbg->dim];
249 cell *tempcell;
250
251 for (j=0; j<3; j++)
252 olderror += elbg->utility[idx[j]];
253
254 memset(newcentroid[2], 0, elbg->dim*sizeof(int));
255
256 for (k=0; k<2; k++)
257 for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) {
258 cont++;
259 for (j=0; j<elbg->dim; j++)
260 newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j];
261 }
262
263 vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim);
264
265 get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]);
266
267 newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]);
268 newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]);
269
270 newerror = newutility[2];
271
272 newerror += simple_lbg(elbg->dim, newcentroid, newutility, elbg->points,
273 elbg->cells[idx[1]]);
274
275 if (olderror > newerror) {
276 shift_codebook(elbg, idx, newcentroid);
277
278 elbg->error += newerror - olderror;
279
280 for (j=0; j<3; j++)
281 update_utility_and_n_cb(elbg, idx[j], newutility[j]);
282
283 evaluate_utility_inc(elbg);
284 }
285 }
286
287 /**
288 * Implementation of the ELBG block
289 */
290 static void do_shiftings(elbg_data *elbg)
291 {
292 int idx[3];
293
294 evaluate_utility_inc(elbg);
295
296 for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++)
297 if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) {
298 if (elbg->utility_inc[elbg->numCB-1] == 0)
299 return;
300
301 idx[1] = get_high_utility_cell(elbg);
302 idx[2] = get_closest_codebook(elbg, idx[0]);
303
304 try_shift_candidate(elbg, idx);
305 }
306 }
307
308 #define BIG_PRIME 433494437LL
309
310 void ff_init_elbg(int *points, int dim, int numpoints, int *codebook,
311 int numCB, int max_steps, int *closest_cb,
312 AVRandomState *rand_state)
313 {
314 int i, k;
315
316 if (numpoints > 24*numCB) {
317 /* ELBG is very costly for a big number of points. So if we have a lot
318 of them, get a good initial codebook to save on iterations */
319 int *temp_points = av_malloc(dim*(numpoints/8)*sizeof(int));
320 for (i=0; i<numpoints/8; i++) {
321 k = (i*BIG_PRIME) % numpoints;
322 memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int));
323 }
324
325 ff_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
326 ff_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
327
328 av_free(temp_points);
329
330 } else // If not, initialize the codebook with random positions
331 for (i=0; i < numCB; i++)
332 memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim,
333 dim*sizeof(int));
334
335 }
336
337 void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
338 int numCB, int max_steps, int *closest_cb,
339 AVRandomState *rand_state)
340 {
341 int dist;
342 elbg_data elbg_d;
343 elbg_data *elbg = &elbg_d;
344 int i, j, k, last_error, steps=0;
345 int *dist_cb = av_malloc(numpoints*sizeof(int));
346 int *size_part = av_malloc(numCB*sizeof(int));
347 cell *list_buffer = av_malloc(numpoints*sizeof(cell));
348 cell *free_cells;
349
350 elbg->error = INT_MAX;
351 elbg->dim = dim;
352 elbg->numCB = numCB;
353 elbg->codebook = codebook;
354 elbg->cells = av_malloc(numCB*sizeof(cell *));
355 elbg->utility = av_malloc(numCB*sizeof(int));
356 elbg->nearest_cb = closest_cb;
357 elbg->points = points;
358 elbg->utility_inc = av_malloc(numCB*sizeof(int));
359
360 elbg->rand_state = rand_state;
361
362 do {
363 free_cells = list_buffer;
364 last_error = elbg->error;
365 steps++;
366 memset(elbg->utility, 0, numCB*sizeof(int));
367 memset(elbg->cells, 0, numCB*sizeof(cell *));
368
369 elbg->error = 0;
370
371 /* This loop evaluate the actual Voronoi partition. It is the most
372 costly part of the algorithm. */
373 for (i=0; i < numpoints; i++) {
374 dist_cb[i] = INT_MAX;
375 for (k=0; k < elbg->numCB; k++) {
376 dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, dist_cb[i]);
377 if (dist < dist_cb[i]) {
378 dist_cb[i] = dist;
379 elbg->nearest_cb[i] = k;
380 }
381 }
382 elbg->error += dist_cb[i];
383 elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
384 free_cells->index = i;
385 free_cells->next = elbg->cells[elbg->nearest_cb[i]];
386 elbg->cells[elbg->nearest_cb[i]] = free_cells;
387 free_cells++;
388 }
389
390 do_shiftings(elbg);
391
392 memset(size_part, 0, numCB*sizeof(int));
393
394 memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
395
396 for (i=0; i < numpoints; i++) {
397 size_part[elbg->nearest_cb[i]]++;
398 for (j=0; j < elbg->dim; j++)
399 elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
400 elbg->points[i*elbg->dim + j];
401 }
402
403 for (i=0; i < elbg->numCB; i++)
404 vect_division(elbg->codebook + i*elbg->dim,
405 elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
406
407 } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
408 (steps < max_steps));
409
410 av_free(dist_cb);
411 av_free(size_part);
412 av_free(elbg->utility);
413 av_free(list_buffer);
414 av_free(elbg->cells);
415 av_free(elbg->utility_inc);
416 }