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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.     int *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.     int r = av_lfg_get(elbg->rand_state)%elbg->utility_inc[elbg->numCB-1] + 1;
  112.     while (elbg->utility_inc[i] < r)
  113.         i++;
  114.  
  115.     av_assert2(elbg->cells[i]);
  116.  
  117.     return i;
  118. }
  119.  
  120. /**
  121.  * Implementation of the simple LBG algorithm for just two codebooks
  122.  */
  123. static int simple_lbg(elbg_data *elbg,
  124.                       int dim,
  125.                       int *centroid[3],
  126.                       int newutility[3],
  127.                       int *points,
  128.                       cell *cells)
  129. {
  130.     int i, idx;
  131.     int numpoints[2] = {0,0};
  132.     int *newcentroid[2] = {
  133.         elbg->scratchbuf + 3*dim,
  134.         elbg->scratchbuf + 4*dim
  135.     };
  136.     cell *tempcell;
  137.  
  138.     memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0]));
  139.  
  140.     newutility[0] =
  141.     newutility[1] = 0;
  142.  
  143.     for (tempcell = cells; tempcell; tempcell=tempcell->next) {
  144.         idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>=
  145.               distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX);
  146.         numpoints[idx]++;
  147.         for (i=0; i<dim; i++)
  148.             newcentroid[idx][i] += points[tempcell->index*dim + i];
  149.     }
  150.  
  151.     vect_division(centroid[0], newcentroid[0], numpoints[0], dim);
  152.     vect_division(centroid[1], newcentroid[1], numpoints[1], dim);
  153.  
  154.     for (tempcell = cells; tempcell; tempcell=tempcell->next) {
  155.         int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX),
  156.                        distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)};
  157.         int idx = dist[0] > dist[1];
  158.         newutility[idx] += dist[idx];
  159.     }
  160.  
  161.     return newutility[0] + newutility[1];
  162. }
  163.  
  164. static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i,
  165.                               int *newcentroid_p)
  166. {
  167.     cell *tempcell;
  168.     int *min = newcentroid_i;
  169.     int *max = newcentroid_p;
  170.     int i;
  171.  
  172.     for (i=0; i< elbg->dim; i++) {
  173.         min[i]=INT_MAX;
  174.         max[i]=0;
  175.     }
  176.  
  177.     for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next)
  178.         for(i=0; i<elbg->dim; i++) {
  179.             min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]);
  180.             max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]);
  181.         }
  182.  
  183.     for (i=0; i<elbg->dim; i++) {
  184.         int ni = min[i] + (max[i] - min[i])/3;
  185.         int np = min[i] + (2*(max[i] - min[i]))/3;
  186.         newcentroid_i[i] = ni;
  187.         newcentroid_p[i] = np;
  188.     }
  189. }
  190.  
  191. /**
  192.  * Add the points in the low utility cell to its closest cell. Split the high
  193.  * utility cell, putting the separate points in the (now empty) low utility
  194.  * cell.
  195.  *
  196.  * @param elbg         Internal elbg data
  197.  * @param indexes      {luc, huc, cluc}
  198.  * @param newcentroid  A vector with the position of the new centroids
  199.  */
  200. static void shift_codebook(elbg_data *elbg, int *indexes,
  201.                            int *newcentroid[3])
  202. {
  203.     cell *tempdata;
  204.     cell **pp = &elbg->cells[indexes[2]];
  205.  
  206.     while(*pp)
  207.         pp= &(*pp)->next;
  208.  
  209.     *pp = elbg->cells[indexes[0]];
  210.  
  211.     elbg->cells[indexes[0]] = NULL;
  212.     tempdata = elbg->cells[indexes[1]];
  213.     elbg->cells[indexes[1]] = NULL;
  214.  
  215.     while(tempdata) {
  216.         cell *tempcell2 = tempdata->next;
  217.         int idx = distance_limited(elbg->points + tempdata->index*elbg->dim,
  218.                            newcentroid[0], elbg->dim, INT_MAX) >
  219.                   distance_limited(elbg->points + tempdata->index*elbg->dim,
  220.                            newcentroid[1], elbg->dim, INT_MAX);
  221.  
  222.         tempdata->next = elbg->cells[indexes[idx]];
  223.         elbg->cells[indexes[idx]] = tempdata;
  224.         tempdata = tempcell2;
  225.     }
  226. }
  227.  
  228. static void evaluate_utility_inc(elbg_data *elbg)
  229. {
  230.     int i, inc=0;
  231.  
  232.     for (i=0; i < elbg->numCB; i++) {
  233.         if (elbg->numCB*elbg->utility[i] > elbg->error)
  234.             inc += elbg->utility[i];
  235.         elbg->utility_inc[i] = inc;
  236.     }
  237. }
  238.  
  239.  
  240. static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)
  241. {
  242.     cell *tempcell;
  243.  
  244.     elbg->utility[idx] = newutility;
  245.     for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next)
  246.         elbg->nearest_cb[tempcell->index] = idx;
  247. }
  248.  
  249. /**
  250.  * Evaluate if a shift lower the error. If it does, call shift_codebooks
  251.  * and update elbg->error, elbg->utility and elbg->nearest_cb.
  252.  *
  253.  * @param elbg  Internal elbg data
  254.  * @param idx   {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)}
  255.  */
  256. static void try_shift_candidate(elbg_data *elbg, int idx[3])
  257. {
  258.     int j, k, olderror=0, newerror, cont=0;
  259.     int newutility[3];
  260.     int *newcentroid[3] = {
  261.         elbg->scratchbuf,
  262.         elbg->scratchbuf + elbg->dim,
  263.         elbg->scratchbuf + 2*elbg->dim
  264.     };
  265.     cell *tempcell;
  266.  
  267.     for (j=0; j<3; j++)
  268.         olderror += elbg->utility[idx[j]];
  269.  
  270.     memset(newcentroid[2], 0, elbg->dim*sizeof(int));
  271.  
  272.     for (k=0; k<2; k++)
  273.         for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) {
  274.             cont++;
  275.             for (j=0; j<elbg->dim; j++)
  276.                 newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j];
  277.         }
  278.  
  279.     vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim);
  280.  
  281.     get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]);
  282.  
  283.     newutility[2]  = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]);
  284.     newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]);
  285.  
  286.     newerror = newutility[2];
  287.  
  288.     newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points,
  289.                            elbg->cells[idx[1]]);
  290.  
  291.     if (olderror > newerror) {
  292.         shift_codebook(elbg, idx, newcentroid);
  293.  
  294.         elbg->error += newerror - olderror;
  295.  
  296.         for (j=0; j<3; j++)
  297.             update_utility_and_n_cb(elbg, idx[j], newutility[j]);
  298.  
  299.         evaluate_utility_inc(elbg);
  300.     }
  301.  }
  302.  
  303. /**
  304.  * Implementation of the ELBG block
  305.  */
  306. static void do_shiftings(elbg_data *elbg)
  307. {
  308.     int idx[3];
  309.  
  310.     evaluate_utility_inc(elbg);
  311.  
  312.     for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++)
  313.         if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) {
  314.             if (elbg->utility_inc[elbg->numCB-1] == 0)
  315.                 return;
  316.  
  317.             idx[1] = get_high_utility_cell(elbg);
  318.             idx[2] = get_closest_codebook(elbg, idx[0]);
  319.  
  320.             if (idx[1] != idx[0] && idx[1] != idx[2])
  321.                 try_shift_candidate(elbg, idx);
  322.         }
  323. }
  324.  
  325. #define BIG_PRIME 433494437LL
  326.  
  327. void ff_init_elbg(int *points, int dim, int numpoints, int *codebook,
  328.                   int numCB, int max_steps, int *closest_cb,
  329.                   AVLFG *rand_state)
  330. {
  331.     int i, k;
  332.  
  333.     if (numpoints > 24*numCB) {
  334.         /* ELBG is very costly for a big number of points. So if we have a lot
  335.            of them, get a good initial codebook to save on iterations       */
  336.         int *temp_points = av_malloc(dim*(numpoints/8)*sizeof(int));
  337.         for (i=0; i<numpoints/8; i++) {
  338.             k = (i*BIG_PRIME) % numpoints;
  339.             memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int));
  340.         }
  341.  
  342.         ff_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
  343.         ff_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
  344.  
  345.         av_free(temp_points);
  346.  
  347.     } else  // If not, initialize the codebook with random positions
  348.         for (i=0; i < numCB; i++)
  349.             memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim,
  350.                    dim*sizeof(int));
  351.  
  352. }
  353.  
  354. void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
  355.                 int numCB, int max_steps, int *closest_cb,
  356.                 AVLFG *rand_state)
  357. {
  358.     int dist;
  359.     elbg_data elbg_d;
  360.     elbg_data *elbg = &elbg_d;
  361.     int i, j, k, last_error, steps=0;
  362.     int *dist_cb = av_malloc(numpoints*sizeof(int));
  363.     int *size_part = av_malloc(numCB*sizeof(int));
  364.     cell *list_buffer = av_malloc(numpoints*sizeof(cell));
  365.     cell *free_cells;
  366.     int best_dist, best_idx = 0;
  367.  
  368.     elbg->error = INT_MAX;
  369.     elbg->dim = dim;
  370.     elbg->numCB = numCB;
  371.     elbg->codebook = codebook;
  372.     elbg->cells = av_malloc(numCB*sizeof(cell *));
  373.     elbg->utility = av_malloc(numCB*sizeof(int));
  374.     elbg->nearest_cb = closest_cb;
  375.     elbg->points = points;
  376.     elbg->utility_inc = av_malloc(numCB*sizeof(int));
  377.     elbg->scratchbuf = av_malloc(5*dim*sizeof(int));
  378.  
  379.     elbg->rand_state = rand_state;
  380.  
  381.     do {
  382.         free_cells = list_buffer;
  383.         last_error = elbg->error;
  384.         steps++;
  385.         memset(elbg->utility, 0, numCB*sizeof(int));
  386.         memset(elbg->cells, 0, numCB*sizeof(cell *));
  387.  
  388.         elbg->error = 0;
  389.  
  390.         /* This loop evaluate the actual Voronoi partition. It is the most
  391.            costly part of the algorithm. */
  392.         for (i=0; i < numpoints; i++) {
  393.             best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX);
  394.             for (k=0; k < elbg->numCB; k++) {
  395.                 dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist);
  396.                 if (dist < best_dist) {
  397.                     best_dist = dist;
  398.                     best_idx = k;
  399.                 }
  400.             }
  401.             elbg->nearest_cb[i] = best_idx;
  402.             dist_cb[i] = best_dist;
  403.             elbg->error += dist_cb[i];
  404.             elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
  405.             free_cells->index = i;
  406.             free_cells->next = elbg->cells[elbg->nearest_cb[i]];
  407.             elbg->cells[elbg->nearest_cb[i]] = free_cells;
  408.             free_cells++;
  409.         }
  410.  
  411.         do_shiftings(elbg);
  412.  
  413.         memset(size_part, 0, numCB*sizeof(int));
  414.  
  415.         memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
  416.  
  417.         for (i=0; i < numpoints; i++) {
  418.             size_part[elbg->nearest_cb[i]]++;
  419.             for (j=0; j < elbg->dim; j++)
  420.                 elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
  421.                     elbg->points[i*elbg->dim + j];
  422.         }
  423.  
  424.         for (i=0; i < elbg->numCB; i++)
  425.             vect_division(elbg->codebook + i*elbg->dim,
  426.                           elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
  427.  
  428.     } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
  429.             (steps < max_steps));
  430.  
  431.     av_free(dist_cb);
  432.     av_free(size_part);
  433.     av_free(elbg->utility);
  434.     av_free(list_buffer);
  435.     av_free(elbg->cells);
  436.     av_free(elbg->utility_inc);
  437.     av_free(elbg->scratchbuf);
  438. }
  439.