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/lfg.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. */
37typedef struct cell_s {
38    int index;
39    struct cell_s *next;
40} cell;
41
42/**
43 * ELBG internal data
44 */
45typedef 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    AVLFG *rand_state;
56} elbg_data;
57
58static 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
70static 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
81static 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
90static 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
104static 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_lfg_get(elbg->rand_state)%elbg->utility_inc[elbg->numCB-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 */
120static 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
157static 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 */
191static 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
219static 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
231static 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 */
247static 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 */
298static 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
319void ff_init_elbg(int *points, int dim, int numpoints, int *codebook,
320                  int numCB, int max_steps, int *closest_cb,
321                  AVLFG *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
346void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
347                int numCB, int max_steps, int *closest_cb,
348                AVLFG *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    int best_dist, best_idx = 0;
359
360    elbg->error = INT_MAX;
361    elbg->dim = dim;
362    elbg->numCB = numCB;
363    elbg->codebook = codebook;
364    elbg->cells = av_malloc(numCB*sizeof(cell *));
365    elbg->utility = av_malloc(numCB*sizeof(int));
366    elbg->nearest_cb = closest_cb;
367    elbg->points = points;
368    elbg->utility_inc = av_malloc(numCB*sizeof(int));
369
370    elbg->rand_state = rand_state;
371
372    do {
373        free_cells = list_buffer;
374        last_error = elbg->error;
375        steps++;
376        memset(elbg->utility, 0, numCB*sizeof(int));
377        memset(elbg->cells, 0, numCB*sizeof(cell *));
378
379        elbg->error = 0;
380
381        /* This loop evaluate the actual Voronoi partition. It is the most
382           costly part of the algorithm. */
383        for (i=0; i < numpoints; i++) {
384            best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX);
385            for (k=0; k < elbg->numCB; k++) {
386                dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist);
387                if (dist < best_dist) {
388                    best_dist = dist;
389                    best_idx = k;
390                }
391            }
392            elbg->nearest_cb[i] = best_idx;
393            dist_cb[i] = best_dist;
394            elbg->error += dist_cb[i];
395            elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
396            free_cells->index = i;
397            free_cells->next = elbg->cells[elbg->nearest_cb[i]];
398            elbg->cells[elbg->nearest_cb[i]] = free_cells;
399            free_cells++;
400        }
401
402        do_shiftings(elbg);
403
404        memset(size_part, 0, numCB*sizeof(int));
405
406        memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
407
408        for (i=0; i < numpoints; i++) {
409            size_part[elbg->nearest_cb[i]]++;
410            for (j=0; j < elbg->dim; j++)
411                elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
412                    elbg->points[i*elbg->dim + j];
413        }
414
415        for (i=0; i < elbg->numCB; i++)
416            vect_division(elbg->codebook + i*elbg->dim,
417                          elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
418
419    } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
420            (steps < max_steps));
421
422    av_free(dist_cb);
423    av_free(size_part);
424    av_free(elbg->utility);
425    av_free(list_buffer);
426    av_free(elbg->cells);
427    av_free(elbg->utility_inc);
428}
429