FFmpeg: libavcodec/elbg.c Source File

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elbg.c

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1 /*

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 */

21 /**

22 * @file

23 * Codebook Generator using the ELBG algorithm

24 */

26 #include <string.h>

28 #include "libavutil/avassert.h"

29 #include "libavutil/common.h"

30 #include "libavutil/lfg.h"

31 #include "elbg.h"

32 #include "avcodec.h"

34 #define DELTA_ERR_MAX 0.1 ///< Precision of the ELBG algorithm (as percentual error)

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;

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;

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 }

70 return dist;

71 }

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));

82 }

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);

90 return error;

91 }

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 }

AVLFG

Definition: lfg.h:25

NULL

#define NULL

Definition: coverity.c:32

cell::next

struct cell_s * next

Definition: elbg.c:41

do_shiftings

static void do_shiftings(elbg_data *elbg)

Implementation of the ELBG block.

Definition: elbg.c:316

const char * b

Definition: vf_curves.c:109

simple_lbg

static int simple_lbg(elbg_data *elbg, int dim, int *centroid[3], int newutility[3], int *points, cell *cells)

Implementation of the simple LBG algorithm for just two codebooks.

Definition: elbg.c:132

elbg_data::cells

cell ** cells

Definition: elbg.c:52

distance_limited

static int distance_limited(int *a, int *b, int dim, int limit)

Definition: elbg.c:61

get_new_centroids

static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i, int *newcentroid_p)

Definition: elbg.c:173

elbg_data

ELBG internal data.

Definition: elbg.c:47

evaluate_utility_inc

static void evaluate_utility_inc(elbg_data *elbg)

Definition: elbg.c:237

av_assert2

#define av_assert2(cond)

assert() equivalent, that does lie in speed critical code.

Definition: avassert.h:63

elbg_data::rand_state

AVLFG * rand_state

Definition: elbg.c:57

cell::index

int index

Definition: elbg.c:40

avpriv_do_elbg

int avpriv_do_elbg(int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state)

Implementation of the Enhanced LBG Algorithm Based on the paper "Neural Networks 14:1219-1237" that c...

Definition: elbg.c:371

ROUNDED_DIV

#define ROUNDED_DIV(a, b)

Definition: common.h:56

elbg_data::codebook

int * codebook

Definition: elbg.c:51

AVERROR

#define AVERROR(e)

Definition: error.h:43

vect_division

static void vect_division(int *res, int *vect, int div, int dim)

Definition: elbg.c:73

const char * r

Definition: vf_curves.c:107

elbg_data::nearest_cb

int * nearest_cb

Definition: elbg.c:55

avassert.h

simple assert() macros that are a bit more flexible than ISO C assert().

FFMAX

#define FFMAX(a, b)

Definition: common.h:94

elbg_data::dim

int dim

Definition: elbg.c:49

FFMIN

#define FFMIN(a, b)

Definition: common.h:96

cell

In the ELBG jargon, a cell is the set of points that are closest to a codebook entry.

Definition: elbg.c:39

get_high_utility_cell

static int get_high_utility_cell(elbg_data *elbg)

Definition: elbg.c:107

BIG_PRIME

#define BIG_PRIME

Definition: elbg.c:335

get_closest_codebook

static int get_closest_codebook(elbg_data *elbg, int index)

Definition: elbg.c:93

elbg_data::scratchbuf

int * scratchbuf

Definition: elbg.c:58

update_utility_and_n_cb

static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)

Definition: elbg.c:250

elbg_data::points

int * points

Definition: elbg.c:56

lfg.h

out

FILE * out

Definition: movenc-test.c:54

avpriv_init_elbg

int avpriv_init_elbg(int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state)

Initialize the **codebook vector for the elbg algorithm.

Definition: elbg.c:337

avcodec.h

Libavcodec external API header.

elbg_data::utility_inc

int64_t * utility_inc

Definition: elbg.c:54

av_lfg_get

static unsigned int av_lfg_get(AVLFG *c)

Get the next random unsigned 32-bit number using an ALFG.

Definition: lfg.h:38

index

int index

Definition: gxfenc.c:89

dim

int dim

Definition: vorbis_enc_data.h:451

shift_codebook

static void shift_codebook(elbg_data *elbg, int *indexes, int *newcentroid[3])

Add the points in the low utility cell to its closest cell.

Definition: elbg.c:209

eval_error_cell

static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells)

Definition: elbg.c:84

common.h

common internal and external API header

diff

static av_always_inline int diff(const uint32_t a, const uint32_t b)

Definition: vf_palettegen.c:136

elbg.h

av_free

#define av_free(p)

Definition: tableprint_vlc.h:34

elbg_data::error

int error

Definition: elbg.c:48

DELTA_ERR_MAX

#define DELTA_ERR_MAX

Precision of the ELBG algorithm (as percentual error)

Definition: elbg.c:34

elbg_data::numCB

int numCB

Definition: elbg.c:50

av_freep

#define av_freep(p)

Definition: tableprint_vlc.h:35

av_malloc_array

#define av_malloc_array(a, b)

Definition: tableprint_vlc.h:32

try_shift_candidate

static void try_shift_candidate(elbg_data *elbg, int idx[3])

Evaluate if a shift lower the error.

Definition: elbg.c:266

elbg_data::utility

int * utility

Definition: elbg.c:53

min

float min

Definition: vorbis_enc_data.h:456

Definition: h264pred_template.c:468

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