libavcodec/mss12.c

   1 /*
   2  * Copyright (c) 2012 Konstantin Shishkov
   3  *
   4  * This file is part of Libav.
   5  *
   6  * Libav 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  * Libav 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 Libav; 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  * Common functions for Microsoft Screen 1 and 2
  24  */
  25
  26 #include "libavutil/intfloat.h"
  27 #include "libavutil/intreadwrite.h"
  28 #include "avcodec.h"
  29 #include "mss12.h"
  30
  31 enum SplitMode {
  32     SPLIT_VERT = 0,
  33     SPLIT_HOR,
  34     SPLIT_NONE
  35 };
  36
  37 static const int sec_order_sizes[4] = { 1, 7, 6, 1 };
  38
  39 enum ContextDirection {
  40     TOP_LEFT = 0,
  41     TOP,
  42     TOP_RIGHT,
  43     LEFT
  44 };
  45
  46 static int model_calc_threshold(Model *m)
  47 {
  48     int thr;
  49
  50     thr = 2 * m->weights[m->num_syms] - 1;
  51     thr = ((thr >> 1) + 4 * m->cum_prob[0]) / thr;
  52
  53     return FFMIN(thr, 0x3FFF);
  54 }
  55
  56 static void model_reset(Model *m)
  57 {
  58     int i;
  59
  60     for (i = 0; i <= m->num_syms; i++) {
  61         m->weights[i]  = 1;
  62         m->cum_prob[i] = m->num_syms - i;
  63     }
  64     m->weights[0] = 0;
  65     for (i = 0; i < m->num_syms; i++)
  66         m->idx2sym[i + 1] = i;
  67 }
  68
  69 static av_cold void model_init(Model *m, int num_syms, int thr_weight)
  70 {
  71     m->num_syms   = num_syms;
  72     m->thr_weight = thr_weight;
  73     m->threshold  = num_syms * thr_weight;
  74 }
  75
  76 static void model_rescale_weights(Model *m)
  77 {
  78     int i;
  79     int cum_prob;
  80
  81     if (m->thr_weight == THRESH_ADAPTIVE)
  82         m->threshold = model_calc_threshold(m);
  83     while (m->cum_prob[0] > m->threshold) {
  84         cum_prob = 0;
  85         for (i = m->num_syms; i >= 0; i--) {
  86             m->cum_prob[i] = cum_prob;
  87             m->weights[i]  = (m->weights[i] + 1) >> 1;
  88             cum_prob      += m->weights[i];
  89         }
  90     }
  91 }
  92
  93 void ff_mss12_model_update(Model *m, int val)
  94 {
  95     int i;
  96
  97     if (m->weights[val] == m->weights[val - 1]) {
  98         for (i = val; m->weights[i - 1] == m->weights[val]; i--);
  99         if (i != val) {
 100             int sym1, sym2;
 101
 102             sym1 = m->idx2sym[val];
 103             sym2 = m->idx2sym[i];
 104
 105             m->idx2sym[val]  = sym2;
 106             m->idx2sym[i]    = sym1;
 107
 108             val = i;
 109         }
 110     }
 111     m->weights[val]++;
 112     for (i = val - 1; i >= 0; i--)
 113         m->cum_prob[i]++;
 114     model_rescale_weights(m);
 115 }
 116
 117 static void pixctx_reset(PixContext *ctx)
 118 {
 119     int i, j;
 120
 121     if (!ctx->special_initial_cache)
 122         for (i = 0; i < ctx->cache_size; i++)
 123             ctx->cache[i] = i;
 124     else {
 125         ctx->cache[0] = 1;
 126         ctx->cache[1] = 2;
 127         ctx->cache[2] = 4;
 128     }
 129
 130     model_reset(&ctx->cache_model);
 131     model_reset(&ctx->full_model);
 132
 133     for (i = 0; i < 15; i++)
 134         for (j = 0; j < 4; j++)
 135             model_reset(&ctx->sec_models[i][j]);
 136 }
 137
 138 static av_cold void pixctx_init(PixContext *ctx, int cache_size,
 139                                 int full_model_syms, int special_initial_cache)
 140 {
 141     int i, j, k, idx;
 142
 143     ctx->cache_size            = cache_size + 4;
 144     ctx->num_syms              = cache_size;
 145     ctx->special_initial_cache = special_initial_cache;
 146
 147     model_init(&ctx->cache_model, ctx->num_syms + 1, THRESH_LOW);
 148     model_init(&ctx->full_model, full_model_syms, THRESH_HIGH);
 149
 150     for (i = 0, idx = 0; i < 4; i++)
 151         for (j = 0; j < sec_order_sizes[i]; j++, idx++)
 152             for (k = 0; k < 4; k++)
 153                 model_init(&ctx->sec_models[idx][k], 2 + i,
 154                            i ? THRESH_LOW : THRESH_ADAPTIVE);
 155 }
 156
 157 static av_always_inline int decode_pixel(ArithCoder *acoder, PixContext *pctx,
 158                                          uint8_t *ngb, int num_ngb, int any_ngb)
 159 {
 160     int i, val, pix;
 161
 162     val = acoder->get_model_sym(acoder, &pctx->cache_model);
 163     if (val < pctx->num_syms) {
 164         if (any_ngb) {
 165             int idx, j;
 166
 167             idx = 0;
 168             for (i = 0; i < pctx->cache_size; i++) {
 169                 for (j = 0; j < num_ngb; j++)
 170                     if (pctx->cache[i] == ngb[j])
 171                         break;
 172                 if (j == num_ngb) {
 173                     if (idx == val)
 174                         break;
 175                     idx++;
 176                 }
 177             }
 178             val = FFMIN(i, pctx->cache_size - 1);
 179         }
 180         pix = pctx->cache[val];
 181     } else {
 182         pix = acoder->get_model_sym(acoder, &pctx->full_model);
 183         for (i = 0; i < pctx->cache_size - 1; i++)
 184             if (pctx->cache[i] == pix)
 185                 break;
 186         val = i;
 187     }
 188     if (val) {
 189         for (i = val; i > 0; i--)
 190             pctx->cache[i] = pctx->cache[i - 1];
 191         pctx->cache[0] = pix;
 192     }
 193
 194     return pix;
 195 }
 196
 197 static int decode_pixel_in_context(ArithCoder *acoder, PixContext *pctx,
 198                                    uint8_t *src, int stride, int x, int y,
 199                                    int has_right)
 200 {
 201     uint8_t neighbours[4];
 202     uint8_t ref_pix[4];
 203     int nlen;
 204     int layer = 0, sub;
 205     int pix;
 206     int i, j;
 207
 208     if (!y) {
 209         memset(neighbours, src[-1], 4);
 210     } else {
 211         neighbours[TOP] = src[-stride];
 212         if (!x) {
 213             neighbours[TOP_LEFT] = neighbours[LEFT] = neighbours[TOP];
 214         } else {
 215             neighbours[TOP_LEFT] = src[-stride - 1];
 216             neighbours[    LEFT] = src[-1];
 217         }
 218         if (has_right)
 219             neighbours[TOP_RIGHT] = src[-stride + 1];
 220         else
 221             neighbours[TOP_RIGHT] = neighbours[TOP];
 222     }
 223
 224     sub = 0;
 225     if (x >= 2 && src[-2] == neighbours[LEFT])
 226         sub  = 1;
 227     if (y >= 2 && src[-2 * stride] == neighbours[TOP])
 228         sub |= 2;
 229
 230     nlen = 1;
 231     ref_pix[0] = neighbours[0];
 232     for (i = 1; i < 4; i++) {
 233         for (j = 0; j < nlen; j++)
 234             if (ref_pix[j] == neighbours[i])
 235                 break;
 236         if (j == nlen)
 237             ref_pix[nlen++] = neighbours[i];
 238     }
 239
 240     switch (nlen) {
 241     case 1:
 242         layer = 0;
 243         break;
 244     case 2:
 245         if (neighbours[TOP] == neighbours[TOP_LEFT]) {
 246             if (neighbours[TOP_RIGHT] == neighbours[TOP_LEFT])
 247                 layer = 1;
 248             else if (neighbours[LEFT] == neighbours[TOP_LEFT])
 249                 layer = 2;
 250             else
 251                 layer = 3;
 252         } else if (neighbours[TOP_RIGHT] == neighbours[TOP_LEFT]) {
 253             if (neighbours[LEFT] == neighbours[TOP_LEFT])
 254                 layer = 4;
 255             else
 256                 layer = 5;
 257         } else if (neighbours[LEFT] == neighbours[TOP_LEFT]) {
 258             layer = 6;
 259         } else {
 260             layer = 7;
 261         }
 262         break;
 263     case 3:
 264         if (neighbours[TOP] == neighbours[TOP_LEFT])
 265             layer = 8;
 266         else if (neighbours[TOP_RIGHT] == neighbours[TOP_LEFT])
 267             layer = 9;
 268         else if (neighbours[LEFT] == neighbours[TOP_LEFT])
 269             layer = 10;
 270         else if (neighbours[TOP_RIGHT] == neighbours[TOP])
 271             layer = 11;
 272         else if (neighbours[TOP] == neighbours[LEFT])
 273             layer = 12;
 274         else
 275             layer = 13;
 276         break;
 277     case 4:
 278         layer = 14;
 279         break;
 280     }
 281
 282     pix = acoder->get_model_sym(acoder,
 283                                 &pctx->sec_models[layer][sub]);
 284     if (pix < nlen)
 285         return ref_pix[pix];
 286     else
 287         return decode_pixel(acoder, pctx, ref_pix, nlen, 1);
 288 }
 289
 290 static int decode_region(ArithCoder *acoder, uint8_t *dst, uint8_t *rgb_pic,
 291                          int x, int y, int width, int height, int stride,
 292                          int rgb_stride, PixContext *pctx, const uint32_t *pal)
 293 {
 294     int i, j, p;
 295     uint8_t *rgb_dst = rgb_pic + x * 3 + y * rgb_stride;
 296
 297     dst += x + y * stride;
 298
 299     for (j = 0; j < height; j++) {
 300         for (i = 0; i < width; i++) {
 301             if (!i && !j)
 302                 p = decode_pixel(acoder, pctx, NULL, 0, 0);
 303             else
 304                 p = decode_pixel_in_context(acoder, pctx, dst + i, stride,
 305                                             i, j, width - i - 1);
 306             dst[i] = p;
 307
 308             if (rgb_pic)
 309                 AV_WB24(rgb_dst + i * 3, pal[p]);
 310         }
 311         dst     += stride;
 312         rgb_dst += rgb_stride;
 313     }
 314
 315     return 0;
 316 }
 317
 318 static void copy_rectangles(MSS12Context const *c,
 319                             int x, int y, int width, int height)
 320 {
 321     int j;
 322
 323     if (c->last_rgb_pic)
 324         for (j = y; j < y + height; j++) {
 325             memcpy(c->rgb_pic      + j * c->rgb_stride + x * 3,
 326                    c->last_rgb_pic + j * c->rgb_stride + x * 3,
 327                    width * 3);
 328             memcpy(c->pal_pic      + j * c->pal_stride + x,
 329                    c->last_pal_pic + j * c->pal_stride + x,
 330                    width);
 331         }
 332 }
 333
 334 static int motion_compensation(MSS12Context const *c,
 335                                int x, int y, int width, int height)
 336 {
 337     if (x + c->mvX < 0 || x + c->mvX + width  > c->avctx->width  ||
 338         y + c->mvY < 0 || y + c->mvY + height > c->avctx->height ||
 339         !c->rgb_pic)
 340         return -1;
 341     else {
 342         uint8_t *dst     = c->pal_pic + x     + y * c->pal_stride;
 343         uint8_t *rgb_dst = c->rgb_pic + x * 3 + y * c->rgb_stride;
 344         uint8_t *src;
 345         uint8_t *rgb_src;
 346         int j;
 347         x += c->mvX;
 348         y += c->mvY;
 349         if (c->last_rgb_pic) {
 350             src     = c->last_pal_pic + x +     y * c->pal_stride;
 351             rgb_src = c->last_rgb_pic + x * 3 + y * c->rgb_stride;
 352         } else {
 353             src     = c->pal_pic + x     + y * c->pal_stride;
 354             rgb_src = c->rgb_pic + x * 3 + y * c->rgb_stride;
 355         }
 356         for (j = 0; j < height; j++) {
 357             memmove(dst, src, width);
 358             memmove(rgb_dst, rgb_src, width * 3);
 359             dst     += c->pal_stride;
 360             src     += c->pal_stride;
 361             rgb_dst += c->rgb_stride;
 362             rgb_src += c->rgb_stride;
 363         }
 364     }
 365     return 0;
 366 }
 367
 368 static int decode_region_masked(MSS12Context const *c, ArithCoder *acoder,
 369                                 uint8_t *dst, int stride, uint8_t *mask,
 370                                 int mask_stride, int x, int y,
 371                                 int width, int height,
 372                                 PixContext *pctx)
 373 {
 374     int i, j, p;
 375     uint8_t *rgb_dst = c->rgb_pic + x * 3 + y * c->rgb_stride;
 376
 377     dst  += x + y * stride;
 378     mask += x + y * mask_stride;
 379
 380     for (j = 0; j < height; j++) {
 381         for (i = 0; i < width; i++) {
 382             if (c->avctx->err_recognition & AV_EF_EXPLODE &&
 383                 ( c->rgb_pic && mask[i] != 0x01 && mask[i] != 0x02 && mask[i] != 0x04 ||
 384                  !c->rgb_pic && mask[i] != 0x80 && mask[i] != 0xFF))
 385                 return -1;
 386
 387             if (mask[i] == 0x02) {
 388                 copy_rectangles(c, x + i, y + j, 1, 1);
 389             } else if (mask[i] == 0x04) {
 390                 if (motion_compensation(c, x + i, y + j, 1, 1))
 391                     return -1;
 392             } else if (mask[i] != 0x80) {
 393                 if (!i && !j)
 394                     p = decode_pixel(acoder, pctx, NULL, 0, 0);
 395                 else
 396                     p = decode_pixel_in_context(acoder, pctx, dst + i, stride,
 397                                                 i, j, width - i - 1);
 398                 dst[i] = p;
 399                 if (c->rgb_pic)
 400                     AV_WB24(rgb_dst + i * 3, c->pal[p]);
 401             }
 402         }
 403         dst     += stride;
 404         mask    += mask_stride;
 405         rgb_dst += c->rgb_stride;
 406     }
 407
 408     return 0;
 409 }
 410
 411 static av_cold void slicecontext_init(SliceContext *sc,
 412                                       int version, int full_model_syms)
 413 {
 414     model_init(&sc->intra_region, 2, THRESH_ADAPTIVE);
 415     model_init(&sc->inter_region, 2, THRESH_ADAPTIVE);
 416     model_init(&sc->split_mode,   3, THRESH_HIGH);
 417     model_init(&sc->edge_mode,    2, THRESH_HIGH);
 418     model_init(&sc->pivot,        3, THRESH_LOW);
 419
 420     pixctx_init(&sc->intra_pix_ctx, 8, full_model_syms, 0);
 421
 422     pixctx_init(&sc->inter_pix_ctx, version ? 3 : 2,
 423                 full_model_syms, version ? 1 : 0);
 424 }
 425
 426 void ff_mss12_slicecontext_reset(SliceContext *sc)
 427 {
 428     model_reset(&sc->intra_region);
 429     model_reset(&sc->inter_region);
 430     model_reset(&sc->split_mode);
 431     model_reset(&sc->edge_mode);
 432     model_reset(&sc->pivot);
 433     pixctx_reset(&sc->intra_pix_ctx);
 434     pixctx_reset(&sc->inter_pix_ctx);
 435 }
 436
 437 static int decode_pivot(SliceContext *sc, ArithCoder *acoder, int base)
 438 {
 439     int val, inv;
 440
 441     inv = acoder->get_model_sym(acoder, &sc->edge_mode);
 442     val = acoder->get_model_sym(acoder, &sc->pivot) + 1;
 443
 444     if (val > 2) {
 445         if ((base + 1) / 2 - 2 <= 0)
 446             return -1;
 447
 448         val = acoder->get_number(acoder, (base + 1) / 2 - 2) + 3;
 449     }
 450
 451     if (val >= base)
 452         return -1;
 453
 454     return inv ? base - val : val;
 455 }
 456
 457 static int decode_region_intra(SliceContext *sc, ArithCoder *acoder,
 458                                int x, int y, int width, int height)
 459 {
 460     MSS12Context const *c = sc->c;
 461     int mode;
 462
 463     mode = acoder->get_model_sym(acoder, &sc->intra_region);
 464
 465     if (!mode) {
 466         int i, j, pix, rgb_pix;
 467         int stride       = c->pal_stride;
 468         int rgb_stride   = c->rgb_stride;
 469         uint8_t *dst     = c->pal_pic + x     + y * stride;
 470         uint8_t *rgb_dst = c->rgb_pic + x * 3 + y * rgb_stride;
 471
 472         pix     = decode_pixel(acoder, &sc->intra_pix_ctx, NULL, 0, 0);
 473         rgb_pix = c->pal[pix];
 474         for (i = 0; i < height; i++, dst += stride, rgb_dst += rgb_stride) {
 475             memset(dst, pix, width);
 476             if (c->rgb_pic)
 477                 for (j = 0; j < width * 3; j += 3)
 478                     AV_WB24(rgb_dst + j, rgb_pix);
 479         }
 480     } else {
 481         return decode_region(acoder, c->pal_pic, c->rgb_pic,
 482                              x, y, width, height, c->pal_stride, c->rgb_stride,
 483                              &sc->intra_pix_ctx, &c->pal[0]);
 484     }
 485
 486     return 0;
 487 }
 488
 489 static int decode_region_inter(SliceContext *sc, ArithCoder *acoder,
 490                                int x, int y, int width, int height)
 491 {
 492     MSS12Context const *c = sc->c;
 493     int mode;
 494
 495     mode = acoder->get_model_sym(acoder, &sc->inter_region);
 496
 497     if (!mode) {
 498         mode = decode_pixel(acoder, &sc->inter_pix_ctx, NULL, 0, 0);
 499
 500         if (c->avctx->err_recognition & AV_EF_EXPLODE &&
 501             ( c->rgb_pic && mode != 0x01 && mode != 0x02 && mode != 0x04 ||
 502              !c->rgb_pic && mode != 0x80 && mode != 0xFF))
 503             return -1;
 504
 505         if (mode == 0x02)
 506             copy_rectangles(c, x, y, width, height);
 507         else if (mode == 0x04)
 508             return motion_compensation(c, x, y, width, height);
 509         else if (mode != 0x80)
 510             return decode_region_intra(sc, acoder, x, y, width, height);
 511     } else {
 512         if (decode_region(acoder, c->mask, NULL,
 513                           x, y, width, height, c->mask_stride, 0,
 514                           &sc->inter_pix_ctx, &c->pal[0]) < 0)
 515             return -1;
 516         return decode_region_masked(c, acoder, c->pal_pic,
 517                                     c->pal_stride, c->mask,
 518                                     c->mask_stride,
 519                                     x, y, width, height,
 520                                     &sc->intra_pix_ctx);
 521     }
 522
 523     return 0;
 524 }
 525
 526 int ff_mss12_decode_rect(SliceContext *sc, ArithCoder *acoder,
 527                          int x, int y, int width, int height)
 528 {
 529     int mode, pivot;
 530
 531     mode = acoder->get_model_sym(acoder, &sc->split_mode);
 532
 533     switch (mode) {
 534     case SPLIT_VERT:
 535         if ((pivot = decode_pivot(sc, acoder, height)) < 1)
 536             return -1;
 537         if (ff_mss12_decode_rect(sc, acoder, x, y, width, pivot))
 538             return -1;
 539         if (ff_mss12_decode_rect(sc, acoder, x, y + pivot, width, height - pivot))
 540             return -1;
 541         break;
 542     case SPLIT_HOR:
 543         if ((pivot = decode_pivot(sc, acoder, width)) < 1)
 544             return -1;
 545         if (ff_mss12_decode_rect(sc, acoder, x, y, pivot, height))
 546             return -1;
 547         if (ff_mss12_decode_rect(sc, acoder, x + pivot, y, width - pivot, height))
 548             return -1;
 549         break;
 550     case SPLIT_NONE:
 551         if (sc->c->keyframe)
 552             return decode_region_intra(sc, acoder, x, y, width, height);
 553         else
 554             return decode_region_inter(sc, acoder, x, y, width, height);
 555     default:
 556         return -1;
 557     }
 558
 559     return 0;
 560 }
 561
 562 av_cold int ff_mss12_decode_init(MSS12Context *c, int version,
 563                                  SliceContext* sc1, SliceContext *sc2)
 564 {
 565     AVCodecContext *avctx = c->avctx;
 566     int i;
 567
 568     if (avctx->extradata_size < 52 + 256 * 3) {
 569         av_log(avctx, AV_LOG_ERROR, "Insufficient extradata size %d\n",
 570                avctx->extradata_size);
 571         return AVERROR_INVALIDDATA;
 572     }
 573
 574     if (AV_RB32(avctx->extradata) < avctx->extradata_size) {
 575         av_log(avctx, AV_LOG_ERROR,
 576                "Insufficient extradata size: expected %d got %d\n",
 577                AV_RB32(avctx->extradata),
 578                avctx->extradata_size);
 579         return AVERROR_INVALIDDATA;
 580     }
 581
 582     avctx->coded_width  = AV_RB32(avctx->extradata + 20);
 583     avctx->coded_height = AV_RB32(avctx->extradata + 24);
 584     if (avctx->coded_width > 4096 || avctx->coded_height > 4096) {
 585         av_log(avctx, AV_LOG_ERROR, "Frame dimensions %dx%d too large",
 586                avctx->coded_width, avctx->coded_height);
 587         return AVERROR_INVALIDDATA;
 588     }
 589
 590     av_log(avctx, AV_LOG_DEBUG, "Encoder version %d.%d\n",
 591            AV_RB32(avctx->extradata + 4), AV_RB32(avctx->extradata + 8));
 592     if (version != AV_RB32(avctx->extradata + 4) > 1) {
 593         av_log(avctx, AV_LOG_ERROR,
 594                "Header version doesn't match codec tag\n");
 595         return -1;
 596     }
 597
 598     c->free_colours = AV_RB32(avctx->extradata + 48);
 599     if ((unsigned)c->free_colours > 256) {
 600         av_log(avctx, AV_LOG_ERROR,
 601                "Incorrect number of changeable palette entries: %d\n",
 602                c->free_colours);
 603         return AVERROR_INVALIDDATA;
 604     }
 605     av_log(avctx, AV_LOG_DEBUG, "%d free colour(s)\n", c->free_colours);
 606
 607     av_log(avctx, AV_LOG_DEBUG, "Display dimensions %dx%d\n",
 608            AV_RB32(avctx->extradata + 12), AV_RB32(avctx->extradata + 16));
 609     av_log(avctx, AV_LOG_DEBUG, "Coded dimensions %dx%d\n",
 610            avctx->coded_width, avctx->coded_height);
 611     av_log(avctx, AV_LOG_DEBUG, "%g frames per second\n",
 612            av_int2float(AV_RB32(avctx->extradata + 28)));
 613     av_log(avctx, AV_LOG_DEBUG, "Bitrate %d bps\n",
 614            AV_RB32(avctx->extradata + 32));
 615     av_log(avctx, AV_LOG_DEBUG, "Max. lead time %g ms\n",
 616            av_int2float(AV_RB32(avctx->extradata + 36)));
 617     av_log(avctx, AV_LOG_DEBUG, "Max. lag time %g ms\n",
 618            av_int2float(AV_RB32(avctx->extradata + 40)));
 619     av_log(avctx, AV_LOG_DEBUG, "Max. seek time %g ms\n",
 620            av_int2float(AV_RB32(avctx->extradata + 44)));
 621
 622     if (version) {
 623         if (avctx->extradata_size < 60 + 256 * 3) {
 624             av_log(avctx, AV_LOG_ERROR,
 625                    "Insufficient extradata size %d for v2\n",
 626                    avctx->extradata_size);
 627             return AVERROR_INVALIDDATA;
 628         }
 629
 630         c->slice_split = AV_RB32(avctx->extradata + 52);
 631         av_log(avctx, AV_LOG_DEBUG, "Slice split %d\n", c->slice_split);
 632
 633         c->full_model_syms = AV_RB32(avctx->extradata + 56);
 634         if (c->full_model_syms < 2 || c->full_model_syms > 256) {
 635             av_log(avctx, AV_LOG_ERROR,
 636                    "Incorrect number of used colours %d\n",
 637                    c->full_model_syms);
 638             return AVERROR_INVALIDDATA;
 639         }
 640         av_log(avctx, AV_LOG_DEBUG, "Used colours %d\n",
 641                c->full_model_syms);
 642     } else {
 643         c->slice_split     = 0;
 644         c->full_model_syms = 256;
 645     }
 646
 647     for (i = 0; i < 256; i++)
 648         c->pal[i] = AV_RB24(avctx->extradata + 52 +
 649                             (version ? 8 : 0) + i * 3);
 650
 651     c->mask_stride = FFALIGN(avctx->width, 16);
 652     c->mask        = av_malloc(c->mask_stride * avctx->height);
 653     if (!c->mask) {
 654         av_log(avctx, AV_LOG_ERROR, "Cannot allocate mask plane\n");
 655         return AVERROR(ENOMEM);
 656     }
 657
 658     sc1->c = c;
 659     slicecontext_init(sc1, version, c->full_model_syms);
 660     if (c->slice_split) {
 661         sc2->c = c;
 662         slicecontext_init(sc2, version, c->full_model_syms);
 663     }
 664     c->corrupted = 1;
 665
 666     return 0;
 667 }
 668
 669 av_cold int ff_mss12_decode_end(MSS12Context *c)
 670 {
 671     av_freep(&c->mask);
 672
 673     return 0;
 674 }