0,0 → 1,463 |
/* |
* 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 |
*/ |
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#include <string.h> |
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#include "libavutil/avassert.h" |
#include "libavutil/common.h" |
#include "libavutil/lfg.h" |
#include "elbg.h" |
#include "avcodec.h" |
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#define DELTA_ERR_MAX 0.1 ///< Precision of the ELBG algorithm (as percentual error) |
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/** |
* 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 elbg_data { |
int error; |
int dim; |
int numCB; |
int *codebook; |
cell **cells; |
int *utility; |
int64_t *utility_inc; |
int *nearest_cb; |
int *points; |
AVLFG *rand_state; |
int *scratchbuf; |
} elbg_data; |
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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; |
} |
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return dist; |
} |
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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)); |
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} |
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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); |
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return error; |
} |
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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; |
} |
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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 */ |
uint64_t r; |
|
if (elbg->utility_inc[elbg->numCB-1] < INT_MAX) { |
r = av_lfg_get(elbg->rand_state) % (unsigned int)elbg->utility_inc[elbg->numCB-1] + 1; |
} else { |
r = av_lfg_get(elbg->rand_state); |
r = (av_lfg_get(elbg->rand_state) + (r<<32)) % elbg->utility_inc[elbg->numCB-1] + 1; |
} |
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while (elbg->utility_inc[i] < r) { |
i++; |
} |
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av_assert2(elbg->cells[i]); |
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return i; |
} |
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/** |
* 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; |
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memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0])); |
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newutility[0] = |
newutility[1] = 0; |
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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]; |
} |
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vect_division(centroid[0], newcentroid[0], numpoints[0], dim); |
vect_division(centroid[1], newcentroid[1], numpoints[1], dim); |
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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]; |
} |
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return newutility[0] + newutility[1]; |
} |
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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; |
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for (i=0; i< elbg->dim; i++) { |
min[i]=INT_MAX; |
max[i]=0; |
} |
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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]); |
} |
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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; |
} |
} |
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/** |
* 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]]; |
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while(*pp) |
pp= &(*pp)->next; |
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*pp = elbg->cells[indexes[0]]; |
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elbg->cells[indexes[0]] = NULL; |
tempdata = elbg->cells[indexes[1]]; |
elbg->cells[indexes[1]] = NULL; |
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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); |
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tempdata->next = elbg->cells[indexes[idx]]; |
elbg->cells[indexes[idx]] = tempdata; |
tempdata = tempcell2; |
} |
} |
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static void evaluate_utility_inc(elbg_data *elbg) |
{ |
int i; |
int64_t inc=0; |
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for (i=0; i < elbg->numCB; i++) { |
if (elbg->numCB*elbg->utility[i] > elbg->error) |
inc += elbg->utility[i]; |
elbg->utility_inc[i] = inc; |
} |
} |
|
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static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility) |
{ |
cell *tempcell; |
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elbg->utility[idx] = newutility; |
for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next) |
elbg->nearest_cb[tempcell->index] = idx; |
} |
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/** |
* 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; |
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for (j=0; j<3; j++) |
olderror += elbg->utility[idx[j]]; |
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memset(newcentroid[2], 0, elbg->dim*sizeof(int)); |
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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]; |
} |
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vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim); |
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get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]); |
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newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]); |
newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]); |
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newerror = newutility[2]; |
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newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points, |
elbg->cells[idx[1]]); |
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if (olderror > newerror) { |
shift_codebook(elbg, idx, newcentroid); |
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elbg->error += newerror - olderror; |
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for (j=0; j<3; j++) |
update_utility_and_n_cb(elbg, idx[j], newutility[j]); |
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evaluate_utility_inc(elbg); |
} |
} |
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/** |
* Implementation of the ELBG block |
*/ |
static void do_shiftings(elbg_data *elbg) |
{ |
int idx[3]; |
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evaluate_utility_inc(elbg); |
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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; |
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idx[1] = get_high_utility_cell(elbg); |
idx[2] = get_closest_codebook(elbg, idx[0]); |
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if (idx[1] != idx[0] && idx[1] != idx[2]) |
try_shift_candidate(elbg, idx); |
} |
} |
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#define BIG_PRIME 433494437LL |
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int 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, ret = 0; |
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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_array(dim, (numpoints/8)*sizeof(int)); |
if (!temp_points) |
return AVERROR(ENOMEM); |
for (i=0; i<numpoints/8; i++) { |
k = (i*BIG_PRIME) % numpoints; |
memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int)); |
} |
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ret = avpriv_init_elbg(temp_points, dim, numpoints / 8, codebook, |
numCB, 2 * max_steps, closest_cb, rand_state); |
if (ret < 0) { |
av_freep(&temp_points); |
return ret; |
} |
ret = avpriv_do_elbg(temp_points, dim, numpoints / 8, codebook, |
numCB, 2 * max_steps, closest_cb, rand_state); |
av_free(temp_points); |
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} 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)); |
return ret; |
} |
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int 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, ret = 0; |
int *dist_cb = av_malloc_array(numpoints, sizeof(int)); |
int *size_part = av_malloc_array(numCB, sizeof(int)); |
cell *list_buffer = av_malloc_array(numpoints, sizeof(cell)); |
cell *free_cells; |
int best_dist, best_idx = 0; |
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elbg->error = INT_MAX; |
elbg->dim = dim; |
elbg->numCB = numCB; |
elbg->codebook = codebook; |
elbg->cells = av_malloc_array(numCB, sizeof(cell *)); |
elbg->utility = av_malloc_array(numCB, sizeof(int)); |
elbg->nearest_cb = closest_cb; |
elbg->points = points; |
elbg->utility_inc = av_malloc_array(numCB, sizeof(*elbg->utility_inc)); |
elbg->scratchbuf = av_malloc_array(5*dim, sizeof(int)); |
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if (!dist_cb || !size_part || !list_buffer || !elbg->cells || |
!elbg->utility || !elbg->utility_inc || !elbg->scratchbuf) { |
ret = AVERROR(ENOMEM); |
goto out; |
} |
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elbg->rand_state = rand_state; |
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do { |
free_cells = list_buffer; |
last_error = elbg->error; |
steps++; |
memset(elbg->utility, 0, numCB*sizeof(int)); |
memset(elbg->cells, 0, numCB*sizeof(cell *)); |
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elbg->error = 0; |
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/* 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++; |
} |
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do_shiftings(elbg); |
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memset(size_part, 0, numCB*sizeof(int)); |
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memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int)); |
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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]; |
} |
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for (i=0; i < elbg->numCB; i++) |
vect_division(elbg->codebook + i*elbg->dim, |
elbg->codebook + i*elbg->dim, size_part[i], elbg->dim); |
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} while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) && |
(steps < max_steps)); |
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out: |
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); |
return ret; |
} |