/* * Copyright (C) 2007 Vitor Sessak <vitor1001@gmail.com> * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * Codebook Generator using the ELBG algorithm */ #include <string.h> #include "libavutil/avassert.h" #include "libavutil/common.h" #include "libavutil/lfg.h" #include "elbg.h" #include "avcodec.h" #define DELTA_ERR_MAX 0.1 ///< Precision of the ELBG algorithm (as percentual error) /** * In the ELBG jargon, a cell is the set of points that are closest to a * codebook entry. Not to be confused with a RoQ Video cell. */ typedef struct cell_s { int index; struct cell_s *next; } cell; /** * ELBG internal data */ typedef struct{ int error; int dim; int numCB; int *codebook; cell **cells; int *utility; int *utility_inc; int *nearest_cb; int *points; AVLFG *rand_state; int *scratchbuf; } elbg_data; static inline int distance_limited(int *a, int *b, int dim, int limit) { int i, dist=0; for (i=0; i<dim; i++) { dist += (a[i] - b[i])*(a[i] - b[i]); if (dist > limit) return INT_MAX; } return dist; } static inline void vect_division(int *res, int *vect, int div, int dim) { int i; if (div > 1) for (i=0; i<dim; i++) res[i] = ROUNDED_DIV(vect[i],div); else if (res != vect) memcpy(res, vect, dim*sizeof(int)); } static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells) { int error=0; for (; cells; cells=cells->next) error += distance_limited(centroid, elbg->points + cells->index*elbg->dim, elbg->dim, INT_MAX); return error; } static int get_closest_codebook(elbg_data *elbg, int index) { int i, pick=0, diff, diff_min = INT_MAX; for (i=0; i<elbg->numCB; i++) if (i != index) { diff = distance_limited(elbg->codebook + i*elbg->dim, elbg->codebook + index*elbg->dim, elbg->dim, diff_min); if (diff < diff_min) { pick = i; diff_min = diff; } } return pick; } static int get_high_utility_cell(elbg_data *elbg) { int i=0; /* Using linear search, do binary if it ever turns to be speed critical */ int r = av_lfg_get(elbg->rand_state)%elbg->utility_inc[elbg->numCB-1] + 1; while (elbg->utility_inc[i] < r) i++; av_assert2(elbg->cells[i]); return i; } /** * Implementation of the simple LBG algorithm for just two codebooks */ static int simple_lbg(elbg_data *elbg, int dim, int *centroid[3], int newutility[3], int *points, cell *cells) { int i, idx; int numpoints[2] = {0,0}; int *newcentroid[2] = { elbg->scratchbuf + 3*dim, elbg->scratchbuf + 4*dim }; cell *tempcell; memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0])); newutility[0] = newutility[1] = 0; for (tempcell = cells; tempcell; tempcell=tempcell->next) { idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>= distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX); numpoints[idx]++; for (i=0; i<dim; i++) newcentroid[idx][i] += points[tempcell->index*dim + i]; } vect_division(centroid[0], newcentroid[0], numpoints[0], dim); vect_division(centroid[1], newcentroid[1], numpoints[1], dim); for (tempcell = cells; tempcell; tempcell=tempcell->next) { int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX), distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)}; int idx = dist[0] > dist[1]; newutility[idx] += dist[idx]; } return newutility[0] + newutility[1]; } static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i, int *newcentroid_p) { cell *tempcell; int *min = newcentroid_i; int *max = newcentroid_p; int i; for (i=0; i< elbg->dim; i++) { min[i]=INT_MAX; max[i]=0; } for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next) for(i=0; i<elbg->dim; i++) { min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]); max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]); } for (i=0; i<elbg->dim; i++) { int ni = min[i] + (max[i] - min[i])/3; int np = min[i] + (2*(max[i] - min[i]))/3; newcentroid_i[i] = ni; newcentroid_p[i] = np; } } /** * Add the points in the low utility cell to its closest cell. Split the high * utility cell, putting the separate points in the (now empty) low utility * cell. * * @param elbg Internal elbg data * @param indexes {luc, huc, cluc} * @param newcentroid A vector with the position of the new centroids */ static void shift_codebook(elbg_data *elbg, int *indexes, int *newcentroid[3]) { cell *tempdata; cell **pp = &elbg->cells[indexes[2]]; while(*pp) pp= &(*pp)->next; *pp = elbg->cells[indexes[0]]; elbg->cells[indexes[0]] = NULL; tempdata = elbg->cells[indexes[1]]; elbg->cells[indexes[1]] = NULL; while(tempdata) { cell *tempcell2 = tempdata->next; int idx = distance_limited(elbg->points + tempdata->index*elbg->dim, newcentroid[0], elbg->dim, INT_MAX) > distance_limited(elbg->points + tempdata->index*elbg->dim, newcentroid[1], elbg->dim, INT_MAX); tempdata->next = elbg->cells[indexes[idx]]; elbg->cells[indexes[idx]] = tempdata; tempdata = tempcell2; } } static void evaluate_utility_inc(elbg_data *elbg) { int i, inc=0; for (i=0; i < elbg->numCB; i++) { if (elbg->numCB*elbg->utility[i] > elbg->error) inc += elbg->utility[i]; elbg->utility_inc[i] = inc; } } static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility) { cell *tempcell; elbg->utility[idx] = newutility; for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next) elbg->nearest_cb[tempcell->index] = idx; } /** * Evaluate if a shift lower the error. If it does, call shift_codebooks * and update elbg->error, elbg->utility and elbg->nearest_cb. * * @param elbg Internal elbg data * @param idx {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)} */ static void try_shift_candidate(elbg_data *elbg, int idx[3]) { int j, k, olderror=0, newerror, cont=0; int newutility[3]; int *newcentroid[3] = { elbg->scratchbuf, elbg->scratchbuf + elbg->dim, elbg->scratchbuf + 2*elbg->dim }; cell *tempcell; for (j=0; j<3; j++) olderror += elbg->utility[idx[j]]; memset(newcentroid[2], 0, elbg->dim*sizeof(int)); for (k=0; k<2; k++) for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) { cont++; for (j=0; j<elbg->dim; j++) newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j]; } vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim); get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]); newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]); newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]); newerror = newutility[2]; newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points, elbg->cells[idx[1]]); if (olderror > newerror) { shift_codebook(elbg, idx, newcentroid); elbg->error += newerror - olderror; for (j=0; j<3; j++) update_utility_and_n_cb(elbg, idx[j], newutility[j]); evaluate_utility_inc(elbg); } } /** * Implementation of the ELBG block */ static void do_shiftings(elbg_data *elbg) { int idx[3]; evaluate_utility_inc(elbg); for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++) if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) { if (elbg->utility_inc[elbg->numCB-1] == 0) return; idx[1] = get_high_utility_cell(elbg); idx[2] = get_closest_codebook(elbg, idx[0]); if (idx[1] != idx[0] && idx[1] != idx[2]) try_shift_candidate(elbg, idx); } } #define BIG_PRIME 433494437LL void avpriv_init_elbg(int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state) { int i, k; if (numpoints > 24*numCB) { /* ELBG is very costly for a big number of points. So if we have a lot of them, get a good initial codebook to save on iterations */ int *temp_points = av_malloc(dim*(numpoints/8)*sizeof(int)); for (i=0; i<numpoints/8; i++) { k = (i*BIG_PRIME) % numpoints; memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int)); } avpriv_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state); avpriv_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state); av_free(temp_points); } else // If not, initialize the codebook with random positions for (i=0; i < numCB; i++) memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim, dim*sizeof(int)); } void avpriv_do_elbg(int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state) { int dist; elbg_data elbg_d; elbg_data *elbg = &elbg_d; int i, j, k, last_error, steps=0; int *dist_cb = av_malloc(numpoints*sizeof(int)); int *size_part = av_malloc(numCB*sizeof(int)); cell *list_buffer = av_malloc(numpoints*sizeof(cell)); cell *free_cells; int best_dist, best_idx = 0; elbg->error = INT_MAX; elbg->dim = dim; elbg->numCB = numCB; elbg->codebook = codebook; elbg->cells = av_malloc(numCB*sizeof(cell *)); elbg->utility = av_malloc(numCB*sizeof(int)); elbg->nearest_cb = closest_cb; elbg->points = points; elbg->utility_inc = av_malloc(numCB*sizeof(int)); elbg->scratchbuf = av_malloc(5*dim*sizeof(int)); elbg->rand_state = rand_state; do { free_cells = list_buffer; last_error = elbg->error; steps++; memset(elbg->utility, 0, numCB*sizeof(int)); memset(elbg->cells, 0, numCB*sizeof(cell *)); elbg->error = 0; /* This loop evaluate the actual Voronoi partition. It is the most costly part of the algorithm. */ for (i=0; i < numpoints; i++) { best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX); for (k=0; k < elbg->numCB; k++) { dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist); if (dist < best_dist) { best_dist = dist; best_idx = k; } } elbg->nearest_cb[i] = best_idx; dist_cb[i] = best_dist; elbg->error += dist_cb[i]; elbg->utility[elbg->nearest_cb[i]] += dist_cb[i]; free_cells->index = i; free_cells->next = elbg->cells[elbg->nearest_cb[i]]; elbg->cells[elbg->nearest_cb[i]] = free_cells; free_cells++; } do_shiftings(elbg); memset(size_part, 0, numCB*sizeof(int)); memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int)); for (i=0; i < numpoints; i++) { size_part[elbg->nearest_cb[i]]++; for (j=0; j < elbg->dim; j++) elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] += elbg->points[i*elbg->dim + j]; } for (i=0; i < elbg->numCB; i++) vect_division(elbg->codebook + i*elbg->dim, elbg->codebook + i*elbg->dim, size_part[i], elbg->dim); } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) && (steps < max_steps)); av_free(dist_cb); av_free(size_part); av_free(elbg->utility); av_free(list_buffer); av_free(elbg->cells); av_free(elbg->utility_inc); av_free(elbg->scratchbuf); }