Subversion Repositories Kolibri OS

Rev

Blame | Last modification | View Log | RSS feed

  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 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 separate 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.