libavcodec/h264_refs.c

   1 /*
   2  * H.26L/H.264/AVC/JVT/14496-10/... reference picture handling
   3  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * Libav is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with Libav; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * H.264 / AVC / MPEG4 part10  reference picture handling.
  25  * @author Michael Niedermayer <michaelni@gmx.at>
  26  */
  27
  28 #include "internal.h"
  29 #include "avcodec.h"
  30 #include "h264.h"
  31 #include "golomb.h"
  32
  33 #include <assert.h>
  34
  35 #define COPY_PICTURE(dst, src) \
  36 do {\
  37     *(dst) = *(src);\
  38     (dst)->f.extended_data = (dst)->f.data;\
  39     (dst)->tf.f = &(dst)->f;\
  40 } while (0)
  41
  42
  43 static void pic_as_field(Picture *pic, const int parity){
  44     int i;
  45     for (i = 0; i < 4; ++i) {
  46         if (parity == PICT_BOTTOM_FIELD)
  47             pic->f.data[i] += pic->f.linesize[i];
  48         pic->reference      = parity;
  49         pic->f.linesize[i] *= 2;
  50     }
  51     pic->poc= pic->field_poc[parity == PICT_BOTTOM_FIELD];
  52 }
  53
  54 static int split_field_copy(Picture *dest, Picture *src, int parity, int id_add)
  55 {
  56     int match = !!(src->reference & parity);
  57
  58     if (match) {
  59         COPY_PICTURE(dest, src);
  60         if (parity != PICT_FRAME) {
  61             pic_as_field(dest, parity);
  62             dest->pic_id *= 2;
  63             dest->pic_id += id_add;
  64         }
  65     }
  66
  67     return match;
  68 }
  69
  70 static int build_def_list(Picture *def, int def_len,
  71                           Picture **in, int len, int is_long, int sel)
  72 {
  73     int  i[2] = { 0 };
  74     int index = 0;
  75
  76     while ((i[0] < len || i[1] < len) && index < def_len) {
  77         while (i[0] < len && !(in[i[0]] && (in[i[0]]->reference & sel)))
  78             i[0]++;
  79         while (i[1] < len && !(in[i[1]] && (in[i[1]]->reference & (sel ^ 3))))
  80             i[1]++;
  81         if (i[0] < len && index < def_len) {
  82             in[i[0]]->pic_id = is_long ? i[0] : in[i[0]]->frame_num;
  83             split_field_copy(&def[index++], in[i[0]++], sel, 1);
  84         }
  85         if (i[1] < len && index < def_len) {
  86             in[i[1]]->pic_id = is_long ? i[1] : in[i[1]]->frame_num;
  87             split_field_copy(&def[index++], in[i[1]++], sel ^ 3, 0);
  88         }
  89     }
  90
  91     return index;
  92 }
  93
  94 static int add_sorted(Picture **sorted, Picture **src, int len, int limit, int dir)
  95 {
  96     int i, best_poc;
  97     int out_i = 0;
  98
  99     for (;;) {
 100         best_poc = dir ? INT_MIN : INT_MAX;
 101
 102         for (i = 0; i < len; i++) {
 103             const int poc = src[i]->poc;
 104             if (((poc > limit) ^ dir) && ((poc < best_poc) ^ dir)) {
 105                 best_poc      = poc;
 106                 sorted[out_i] = src[i];
 107             }
 108         }
 109         if (best_poc == (dir ? INT_MIN : INT_MAX))
 110             break;
 111         limit = sorted[out_i++]->poc - dir;
 112     }
 113     return out_i;
 114 }
 115
 116 int ff_h264_fill_default_ref_list(H264Context *h)
 117 {
 118     int i, len;
 119
 120     if (h->slice_type_nos == AV_PICTURE_TYPE_B) {
 121         Picture *sorted[32];
 122         int cur_poc, list;
 123         int lens[2];
 124
 125         if (FIELD_PICTURE(h))
 126             cur_poc = h->cur_pic_ptr->field_poc[h->picture_structure == PICT_BOTTOM_FIELD];
 127         else
 128             cur_poc = h->cur_pic_ptr->poc;
 129
 130         for (list = 0; list < 2; list++) {
 131             len  = add_sorted(sorted,       h->short_ref, h->short_ref_count, cur_poc, 1 ^ list);
 132             len += add_sorted(sorted + len, h->short_ref, h->short_ref_count, cur_poc, 0 ^ list);
 133             assert(len <= 32);
 134
 135             len  = build_def_list(h->default_ref_list[list], FF_ARRAY_ELEMS(h->default_ref_list[0]),
 136                                   sorted, len, 0, h->picture_structure);
 137             len += build_def_list(h->default_ref_list[list] + len,
 138                                   FF_ARRAY_ELEMS(h->default_ref_list[0]) - len,
 139                                   h->long_ref, 16, 1, h->picture_structure);
 140
 141             if (len < h->ref_count[list])
 142                 memset(&h->default_ref_list[list][len], 0, sizeof(Picture) * (h->ref_count[list] - len));
 143             lens[list] = len;
 144         }
 145
 146         if (lens[0] == lens[1] && lens[1] > 1) {
 147             for (i = 0; i < lens[0] &&
 148                         h->default_ref_list[0][i].f.buf[0]->buffer ==
 149                         h->default_ref_list[1][i].f.buf[0]->buffer; i++);
 150             if (i == lens[0]) {
 151                 Picture tmp;
 152                 COPY_PICTURE(&tmp, &h->default_ref_list[1][0]);
 153                 COPY_PICTURE(&h->default_ref_list[1][0], &h->default_ref_list[1][1]);
 154                 COPY_PICTURE(&h->default_ref_list[1][1], &tmp);
 155             }
 156         }
 157     } else {
 158         len  = build_def_list(h->default_ref_list[0], FF_ARRAY_ELEMS(h->default_ref_list[0]),
 159                               h->short_ref, h->short_ref_count, 0, h->picture_structure);
 160         len += build_def_list(h->default_ref_list[0] + len,
 161                               FF_ARRAY_ELEMS(h->default_ref_list[0]) - len,
 162                               h-> long_ref, 16, 1, h->picture_structure);
 163
 164         if (len < h->ref_count[0])
 165             memset(&h->default_ref_list[0][len], 0, sizeof(Picture) * (h->ref_count[0] - len));
 166     }
 167 #ifdef TRACE
 168     for (i = 0; i < h->ref_count[0]; i++) {
 169         tprintf(h->avctx, "List0: %s fn:%d 0x%p\n",
 170                 (h->default_ref_list[0][i].long_ref ? "LT" : "ST"),
 171                 h->default_ref_list[0][i].pic_id,
 172                 h->default_ref_list[0][i].f.data[0]);
 173     }
 174     if (h->slice_type_nos == AV_PICTURE_TYPE_B) {
 175         for (i = 0; i < h->ref_count[1]; i++) {
 176             tprintf(h->avctx, "List1: %s fn:%d 0x%p\n",
 177                     (h->default_ref_list[1][i].long_ref ? "LT" : "ST"),
 178                     h->default_ref_list[1][i].pic_id,
 179                     h->default_ref_list[1][i].f.data[0]);
 180         }
 181     }
 182 #endif
 183     return 0;
 184 }
 185
 186 static void print_short_term(H264Context *h);
 187 static void print_long_term(H264Context *h);
 188
 189 /**
 190  * Extract structure information about the picture described by pic_num in
 191  * the current decoding context (frame or field). Note that pic_num is
 192  * picture number without wrapping (so, 0<=pic_num<max_pic_num).
 193  * @param pic_num picture number for which to extract structure information
 194  * @param structure one of PICT_XXX describing structure of picture
 195  *                      with pic_num
 196  * @return frame number (short term) or long term index of picture
 197  *         described by pic_num
 198  */
 199 static int pic_num_extract(H264Context *h, int pic_num, int *structure)
 200 {
 201     *structure = h->picture_structure;
 202     if (FIELD_PICTURE(h)) {
 203         if (!(pic_num & 1))
 204             /* opposite field */
 205             *structure ^= PICT_FRAME;
 206         pic_num >>= 1;
 207     }
 208
 209     return pic_num;
 210 }
 211
 212 int ff_h264_decode_ref_pic_list_reordering(H264Context *h)
 213 {
 214     int list, index, pic_structure, i;
 215
 216     print_short_term(h);
 217     print_long_term(h);
 218
 219     for (list = 0; list < h->list_count; list++) {
 220         for (i = 0; i < h->ref_count[list]; i++)
 221             COPY_PICTURE(&h->ref_list[list][i], &h->default_ref_list[list][i]);
 222
 223         if (get_bits1(&h->gb)) {
 224             int pred = h->curr_pic_num;
 225
 226             for (index = 0; ; index++) {
 227                 unsigned int reordering_of_pic_nums_idc = get_ue_golomb_31(&h->gb);
 228                 unsigned int pic_id;
 229                 int i;
 230                 Picture *ref = NULL;
 231
 232                 if (reordering_of_pic_nums_idc == 3)
 233                     break;
 234
 235                 if (index >= h->ref_count[list]) {
 236                     av_log(h->avctx, AV_LOG_ERROR, "reference count overflow\n");
 237                     return -1;
 238                 }
 239
 240                 if (reordering_of_pic_nums_idc < 3) {
 241                     if (reordering_of_pic_nums_idc < 2) {
 242                         const unsigned int abs_diff_pic_num = get_ue_golomb(&h->gb) + 1;
 243                         int frame_num;
 244
 245                         if (abs_diff_pic_num > h->max_pic_num) {
 246                             av_log(h->avctx, AV_LOG_ERROR, "abs_diff_pic_num overflow\n");
 247                             return -1;
 248                         }
 249
 250                         if (reordering_of_pic_nums_idc == 0)
 251                             pred -= abs_diff_pic_num;
 252                         else
 253                             pred += abs_diff_pic_num;
 254                         pred &= h->max_pic_num - 1;
 255
 256                         frame_num = pic_num_extract(h, pred, &pic_structure);
 257
 258                         for (i = h->short_ref_count - 1; i >= 0; i--) {
 259                             ref = h->short_ref[i];
 260                             assert(ref->reference);
 261                             assert(!ref->long_ref);
 262                             if (ref->frame_num == frame_num &&
 263                                 (ref->reference & pic_structure))
 264                                 break;
 265                         }
 266                         if (i >= 0)
 267                             ref->pic_id = pred;
 268                     } else {
 269                         int long_idx;
 270                         pic_id = get_ue_golomb(&h->gb); //long_term_pic_idx
 271
 272                         long_idx = pic_num_extract(h, pic_id, &pic_structure);
 273
 274                         if (long_idx > 31) {
 275                             av_log(h->avctx, AV_LOG_ERROR, "long_term_pic_idx overflow\n");
 276                             return -1;
 277                         }
 278                         ref = h->long_ref[long_idx];
 279                         assert(!(ref && !ref->reference));
 280                         if (ref && (ref->reference & pic_structure)) {
 281                             ref->pic_id = pic_id;
 282                             assert(ref->long_ref);
 283                             i = 0;
 284                         } else {
 285                             i = -1;
 286                         }
 287                     }
 288
 289                     if (i < 0) {
 290                         av_log(h->avctx, AV_LOG_ERROR, "reference picture missing during reorder\n");
 291                         memset(&h->ref_list[list][index], 0, sizeof(Picture)); //FIXME
 292                     } else {
 293                         for (i = index; i + 1 < h->ref_count[list]; i++) {
 294                             if (ref->long_ref == h->ref_list[list][i].long_ref &&
 295                                 ref->pic_id   == h->ref_list[list][i].pic_id)
 296                                 break;
 297                         }
 298                         for (; i > index; i--) {
 299                             COPY_PICTURE(&h->ref_list[list][i], &h->ref_list[list][i - 1]);
 300                         }
 301                         COPY_PICTURE(&h->ref_list[list][index], ref);
 302                         if (FIELD_PICTURE(h)) {
 303                             pic_as_field(&h->ref_list[list][index], pic_structure);
 304                         }
 305                     }
 306                 } else {
 307                     av_log(h->avctx, AV_LOG_ERROR, "illegal reordering_of_pic_nums_idc\n");
 308                     return -1;
 309                 }
 310             }
 311         }
 312     }
 313     for (list = 0; list < h->list_count; list++) {
 314         for (index = 0; index < h->ref_count[list]; index++) {
 315             if (!h->ref_list[list][index].f.buf[0]) {
 316                 av_log(h->avctx, AV_LOG_ERROR, "Missing reference picture\n");
 317                 if (h->default_ref_list[list][0].f.buf[0])
 318                     COPY_PICTURE(&h->ref_list[list][index], &h->default_ref_list[list][0]);
 319                 else
 320                     return -1;
 321             }
 322         }
 323     }
 324
 325     return 0;
 326 }
 327
 328 void ff_h264_fill_mbaff_ref_list(H264Context *h)
 329 {
 330     int list, i, j;
 331     for (list = 0; list < 2; list++) { //FIXME try list_count
 332         for (i = 0; i < h->ref_count[list]; i++) {
 333             Picture *frame = &h->ref_list[list][i];
 334             Picture *field = &h->ref_list[list][16 + 2 * i];
 335             COPY_PICTURE(field, frame);
 336             for (j = 0; j < 3; j++)
 337                 field[0].f.linesize[j] <<= 1;
 338             field[0].reference = PICT_TOP_FIELD;
 339             field[0].poc       = field[0].field_poc[0];
 340             COPY_PICTURE(field + 1, field);
 341             for (j = 0; j < 3; j++)
 342                 field[1].f.data[j] += frame->f.linesize[j];
 343             field[1].reference = PICT_BOTTOM_FIELD;
 344             field[1].poc       = field[1].field_poc[1];
 345
 346             h->luma_weight[16 + 2 * i][list][0] = h->luma_weight[16 + 2 * i + 1][list][0] = h->luma_weight[i][list][0];
 347             h->luma_weight[16 + 2 * i][list][1] = h->luma_weight[16 + 2 * i + 1][list][1] = h->luma_weight[i][list][1];
 348             for (j = 0; j < 2; j++) {
 349                 h->chroma_weight[16 + 2 * i][list][j][0] = h->chroma_weight[16 + 2 * i + 1][list][j][0] = h->chroma_weight[i][list][j][0];
 350                 h->chroma_weight[16 + 2 * i][list][j][1] = h->chroma_weight[16 + 2 * i + 1][list][j][1] = h->chroma_weight[i][list][j][1];
 351             }
 352         }
 353     }
 354 }
 355
 356 /**
 357  * Mark a picture as no longer needed for reference. The refmask
 358  * argument allows unreferencing of individual fields or the whole frame.
 359  * If the picture becomes entirely unreferenced, but is being held for
 360  * display purposes, it is marked as such.
 361  * @param refmask mask of fields to unreference; the mask is bitwise
 362  *                anded with the reference marking of pic
 363  * @return non-zero if pic becomes entirely unreferenced (except possibly
 364  *         for display purposes) zero if one of the fields remains in
 365  *         reference
 366  */
 367 static inline int unreference_pic(H264Context *h, Picture *pic, int refmask)
 368 {
 369     int i;
 370     if (pic->reference &= refmask) {
 371         return 0;
 372     } else {
 373         for(i = 0; h->delayed_pic[i]; i++)
 374             if(pic == h->delayed_pic[i]){
 375                 pic->reference = DELAYED_PIC_REF;
 376                 break;
 377             }
 378         return 1;
 379     }
 380 }
 381
 382 /**
 383  * Find a Picture in the short term reference list by frame number.
 384  * @param frame_num frame number to search for
 385  * @param idx the index into h->short_ref where returned picture is found
 386  *            undefined if no picture found.
 387  * @return pointer to the found picture, or NULL if no pic with the provided
 388  *                 frame number is found
 389  */
 390 static Picture *find_short(H264Context *h, int frame_num, int *idx)
 391 {
 392     int i;
 393
 394     for (i = 0; i < h->short_ref_count; i++) {
 395         Picture *pic = h->short_ref[i];
 396         if (h->avctx->debug & FF_DEBUG_MMCO)
 397             av_log(h->avctx, AV_LOG_DEBUG, "%d %d %p\n", i, pic->frame_num, pic);
 398         if (pic->frame_num == frame_num) {
 399             *idx = i;
 400             return pic;
 401         }
 402     }
 403     return NULL;
 404 }
 405
 406 /**
 407  * Remove a picture from the short term reference list by its index in
 408  * that list.  This does no checking on the provided index; it is assumed
 409  * to be valid. Other list entries are shifted down.
 410  * @param i index into h->short_ref of picture to remove.
 411  */
 412 static void remove_short_at_index(H264Context *h, int i)
 413 {
 414     assert(i >= 0 && i < h->short_ref_count);
 415     h->short_ref[i] = NULL;
 416     if (--h->short_ref_count)
 417         memmove(&h->short_ref[i], &h->short_ref[i + 1],
 418                 (h->short_ref_count - i) * sizeof(Picture*));
 419 }
 420
 421 /**
 422  *
 423  * @return the removed picture or NULL if an error occurs
 424  */
 425 static Picture *remove_short(H264Context *h, int frame_num, int ref_mask)
 426 {
 427     Picture *pic;
 428     int i;
 429
 430     if (h->avctx->debug & FF_DEBUG_MMCO)
 431         av_log(h->avctx, AV_LOG_DEBUG, "remove short %d count %d\n", frame_num, h->short_ref_count);
 432
 433     pic = find_short(h, frame_num, &i);
 434     if (pic) {
 435         if (unreference_pic(h, pic, ref_mask))
 436             remove_short_at_index(h, i);
 437     }
 438
 439     return pic;
 440 }
 441
 442 /**
 443  * Remove a picture from the long term reference list by its index in
 444  * that list.
 445  * @return the removed picture or NULL if an error occurs
 446  */
 447 static Picture *remove_long(H264Context *h, int i, int ref_mask)
 448 {
 449     Picture *pic;
 450
 451     pic = h->long_ref[i];
 452     if (pic) {
 453         if (unreference_pic(h, pic, ref_mask)) {
 454             assert(h->long_ref[i]->long_ref == 1);
 455             h->long_ref[i]->long_ref = 0;
 456             h->long_ref[i]           = NULL;
 457             h->long_ref_count--;
 458         }
 459     }
 460
 461     return pic;
 462 }
 463
 464 void ff_h264_remove_all_refs(H264Context *h)
 465 {
 466     int i;
 467
 468     for (i = 0; i < 16; i++) {
 469         remove_long(h, i, 0);
 470     }
 471     assert(h->long_ref_count == 0);
 472
 473     for (i = 0; i < h->short_ref_count; i++) {
 474         unreference_pic(h, h->short_ref[i], 0);
 475         h->short_ref[i] = NULL;
 476     }
 477     h->short_ref_count = 0;
 478 }
 479
 480 /**
 481  * print short term list
 482  */
 483 static void print_short_term(H264Context *h)
 484 {
 485     uint32_t i;
 486     if (h->avctx->debug & FF_DEBUG_MMCO) {
 487         av_log(h->avctx, AV_LOG_DEBUG, "short term list:\n");
 488         for (i = 0; i < h->short_ref_count; i++) {
 489             Picture *pic = h->short_ref[i];
 490             av_log(h->avctx, AV_LOG_DEBUG, "%d fn:%d poc:%d %p\n",
 491                    i, pic->frame_num, pic->poc, pic->f.data[0]);
 492         }
 493     }
 494 }
 495
 496 /**
 497  * print long term list
 498  */
 499 static void print_long_term(H264Context *h)
 500 {
 501     uint32_t i;
 502     if (h->avctx->debug & FF_DEBUG_MMCO) {
 503         av_log(h->avctx, AV_LOG_DEBUG, "long term list:\n");
 504         for (i = 0; i < 16; i++) {
 505             Picture *pic = h->long_ref[i];
 506             if (pic) {
 507                 av_log(h->avctx, AV_LOG_DEBUG, "%d fn:%d poc:%d %p\n",
 508                        i, pic->frame_num, pic->poc, pic->f.data[0]);
 509             }
 510         }
 511     }
 512 }
 513
 514 static int check_opcodes(MMCO *mmco1, MMCO *mmco2, int n_mmcos)
 515 {
 516     int i;
 517
 518     for (i = 0; i < n_mmcos; i++) {
 519         if (mmco1[i].opcode != mmco2[i].opcode)
 520             return -1;
 521     }
 522
 523     return 0;
 524 }
 525
 526 int ff_generate_sliding_window_mmcos(H264Context *h, int first_slice)
 527 {
 528     MMCO mmco_temp[MAX_MMCO_COUNT], *mmco = first_slice ? h->mmco : mmco_temp;
 529     int mmco_index = 0, i;
 530
 531     assert(h->long_ref_count + h->short_ref_count <= h->sps.ref_frame_count);
 532
 533     if (h->short_ref_count &&
 534         h->long_ref_count + h->short_ref_count == h->sps.ref_frame_count &&
 535         !(FIELD_PICTURE(h) && !h->first_field && h->cur_pic_ptr->reference)) {
 536         mmco[0].opcode        = MMCO_SHORT2UNUSED;
 537         mmco[0].short_pic_num = h->short_ref[h->short_ref_count - 1]->frame_num;
 538         mmco_index            = 1;
 539         if (FIELD_PICTURE(h)) {
 540             mmco[0].short_pic_num *= 2;
 541             mmco[1].opcode         = MMCO_SHORT2UNUSED;
 542             mmco[1].short_pic_num  = mmco[0].short_pic_num + 1;
 543             mmco_index             = 2;
 544         }
 545     }
 546
 547     if (first_slice) {
 548         h->mmco_index = mmco_index;
 549     } else if (!first_slice && mmco_index >= 0 &&
 550                (mmco_index != h->mmco_index ||
 551                 (i = check_opcodes(h->mmco, mmco_temp, mmco_index)))) {
 552         av_log(h->avctx, AV_LOG_ERROR,
 553                "Inconsistent MMCO state between slices [%d, %d, %d]\n",
 554                mmco_index, h->mmco_index, i);
 555         return AVERROR_INVALIDDATA;
 556     }
 557     return 0;
 558 }
 559
 560 int ff_h264_execute_ref_pic_marking(H264Context *h, MMCO *mmco, int mmco_count)
 561 {
 562     int i, av_uninit(j);
 563     int current_ref_assigned = 0, err = 0;
 564     Picture *av_uninit(pic);
 565
 566     if ((h->avctx->debug & FF_DEBUG_MMCO) && mmco_count == 0)
 567         av_log(h->avctx, AV_LOG_DEBUG, "no mmco here\n");
 568
 569     for (i = 0; i < mmco_count; i++) {
 570         int av_uninit(structure), av_uninit(frame_num);
 571         if (h->avctx->debug & FF_DEBUG_MMCO)
 572             av_log(h->avctx, AV_LOG_DEBUG, "mmco:%d %d %d\n", h->mmco[i].opcode,
 573                    h->mmco[i].short_pic_num, h->mmco[i].long_arg);
 574
 575         if (mmco[i].opcode == MMCO_SHORT2UNUSED ||
 576             mmco[i].opcode == MMCO_SHORT2LONG) {
 577             frame_num = pic_num_extract(h, mmco[i].short_pic_num, &structure);
 578             pic       = find_short(h, frame_num, &j);
 579             if (!pic) {
 580                 if (mmco[i].opcode != MMCO_SHORT2LONG ||
 581                     !h->long_ref[mmco[i].long_arg]    ||
 582                     h->long_ref[mmco[i].long_arg]->frame_num != frame_num) {
 583                     av_log(h->avctx, AV_LOG_ERROR, "mmco: unref short failure\n");
 584                     err = AVERROR_INVALIDDATA;
 585                 }
 586                 continue;
 587             }
 588         }
 589
 590         switch (mmco[i].opcode) {
 591         case MMCO_SHORT2UNUSED:
 592             if (h->avctx->debug & FF_DEBUG_MMCO)
 593                 av_log(h->avctx, AV_LOG_DEBUG, "mmco: unref short %d count %d\n",
 594                        h->mmco[i].short_pic_num, h->short_ref_count);
 595             remove_short(h, frame_num, structure ^ PICT_FRAME);
 596             break;
 597         case MMCO_SHORT2LONG:
 598                 if (h->long_ref[mmco[i].long_arg] != pic)
 599                     remove_long(h, mmco[i].long_arg, 0);
 600
 601                 remove_short_at_index(h, j);
 602                 h->long_ref[ mmco[i].long_arg ] = pic;
 603                 if (h->long_ref[mmco[i].long_arg]) {
 604                     h->long_ref[mmco[i].long_arg]->long_ref = 1;
 605                     h->long_ref_count++;
 606                 }
 607             break;
 608         case MMCO_LONG2UNUSED:
 609             j   = pic_num_extract(h, mmco[i].long_arg, &structure);
 610             pic = h->long_ref[j];
 611             if (pic) {
 612                 remove_long(h, j, structure ^ PICT_FRAME);
 613             } else if (h->avctx->debug & FF_DEBUG_MMCO)
 614                 av_log(h->avctx, AV_LOG_DEBUG, "mmco: unref long failure\n");
 615             break;
 616         case MMCO_LONG:
 617                     // Comment below left from previous code as it is an interresting note.
 618                     /* First field in pair is in short term list or
 619                      * at a different long term index.
 620                      * This is not allowed; see 7.4.3.3, notes 2 and 3.
 621                      * Report the problem and keep the pair where it is,
 622                      * and mark this field valid.
 623                      */
 624             if (h->short_ref[0] == h->cur_pic_ptr)
 625                 remove_short_at_index(h, 0);
 626
 627             if (h->long_ref[mmco[i].long_arg] != h->cur_pic_ptr) {
 628                 remove_long(h, mmco[i].long_arg, 0);
 629
 630                 h->long_ref[mmco[i].long_arg]           = h->cur_pic_ptr;
 631                 h->long_ref[mmco[i].long_arg]->long_ref = 1;
 632                 h->long_ref_count++;
 633             }
 634
 635             h->cur_pic_ptr->reference |= h->picture_structure;
 636             current_ref_assigned = 1;
 637             break;
 638         case MMCO_SET_MAX_LONG:
 639             assert(mmco[i].long_arg <= 16);
 640             // just remove the long term which index is greater than new max
 641             for (j = mmco[i].long_arg; j < 16; j++) {
 642                 remove_long(h, j, 0);
 643             }
 644             break;
 645         case MMCO_RESET:
 646             while (h->short_ref_count) {
 647                 remove_short(h, h->short_ref[0]->frame_num, 0);
 648             }
 649             for (j = 0; j < 16; j++) {
 650                 remove_long(h, j, 0);
 651             }
 652             h->frame_num  = h->cur_pic_ptr->frame_num = 0;
 653             h->mmco_reset = 1;
 654             h->cur_pic_ptr->mmco_reset = 1;
 655             break;
 656         default: assert(0);
 657         }
 658     }
 659
 660     if (!current_ref_assigned) {
 661         /* Second field of complementary field pair; the first field of
 662          * which is already referenced. If short referenced, it
 663          * should be first entry in short_ref. If not, it must exist
 664          * in long_ref; trying to put it on the short list here is an
 665          * error in the encoded bit stream (ref: 7.4.3.3, NOTE 2 and 3).
 666          */
 667         if (h->short_ref_count && h->short_ref[0] == h->cur_pic_ptr) {
 668             /* Just mark the second field valid */
 669             h->cur_pic_ptr->reference = PICT_FRAME;
 670         } else if (h->cur_pic_ptr->long_ref) {
 671             av_log(h->avctx, AV_LOG_ERROR, "illegal short term reference "
 672                                            "assignment for second field "
 673                                            "in complementary field pair "
 674                                            "(first field is long term)\n");
 675             err = AVERROR_INVALIDDATA;
 676         } else {
 677             pic = remove_short(h, h->cur_pic_ptr->frame_num, 0);
 678             if (pic) {
 679                 av_log(h->avctx, AV_LOG_ERROR, "illegal short term buffer state detected\n");
 680                 err = AVERROR_INVALIDDATA;
 681             }
 682
 683             if (h->short_ref_count)
 684                 memmove(&h->short_ref[1], &h->short_ref[0],
 685                         h->short_ref_count * sizeof(Picture*));
 686
 687             h->short_ref[0] = h->cur_pic_ptr;
 688             h->short_ref_count++;
 689             h->cur_pic_ptr->reference |= h->picture_structure;
 690         }
 691     }
 692
 693     if (h->long_ref_count + h->short_ref_count -
 694         (h->short_ref[0] == h->cur_pic_ptr) > h->sps.ref_frame_count) {
 695
 696         /* We have too many reference frames, probably due to corrupted
 697          * stream. Need to discard one frame. Prevents overrun of the
 698          * short_ref and long_ref buffers.
 699          */
 700         av_log(h->avctx, AV_LOG_ERROR,
 701                "number of reference frames (%d+%d) exceeds max (%d; probably "
 702                "corrupt input), discarding one\n",
 703                h->long_ref_count, h->short_ref_count, h->sps.ref_frame_count);
 704         err = AVERROR_INVALIDDATA;
 705
 706         if (h->long_ref_count && !h->short_ref_count) {
 707             for (i = 0; i < 16; ++i)
 708                 if (h->long_ref[i])
 709                     break;
 710
 711             assert(i < 16);
 712             remove_long(h, i, 0);
 713         } else {
 714             pic = h->short_ref[h->short_ref_count - 1];
 715             remove_short(h, pic->frame_num, 0);
 716         }
 717     }
 718
 719     print_short_term(h);
 720     print_long_term(h);
 721     return (h->avctx->err_recognition & AV_EF_EXPLODE) ? err : 0;
 722 }
 723
 724 int ff_h264_decode_ref_pic_marking(H264Context *h, GetBitContext *gb,
 725                                    int first_slice)
 726 {
 727     int i, ret;
 728     MMCO mmco_temp[MAX_MMCO_COUNT], *mmco = first_slice ? h->mmco : mmco_temp;
 729     int mmco_index = 0;
 730
 731     if (h->nal_unit_type == NAL_IDR_SLICE) { // FIXME fields
 732         skip_bits1(gb); // broken_link
 733         if (get_bits1(gb)) {
 734             mmco[0].opcode   = MMCO_LONG;
 735             mmco[0].long_arg = 0;
 736             mmco_index       = 1;
 737         }
 738     } else {
 739         if (get_bits1(gb)) { // adaptive_ref_pic_marking_mode_flag
 740             for (i = 0; i < MAX_MMCO_COUNT; i++) {
 741                 MMCOOpcode opcode = get_ue_golomb_31(gb);
 742
 743                 mmco[i].opcode = opcode;
 744                 if (opcode == MMCO_SHORT2UNUSED || opcode == MMCO_SHORT2LONG) {
 745                     mmco[i].short_pic_num =
 746                         (h->curr_pic_num - get_ue_golomb(gb) - 1) &
 747                             (h->max_pic_num - 1);
 748 #if 0
 749                     if (mmco[i].short_pic_num >= h->short_ref_count ||
 750                         h->short_ref[ mmco[i].short_pic_num ] == NULL){
 751                         av_log(s->avctx, AV_LOG_ERROR,
 752                                "illegal short ref in memory management control "
 753                                "operation %d\n", mmco);
 754                         return -1;
 755                     }
 756 #endif
 757                 }
 758                 if (opcode == MMCO_SHORT2LONG || opcode == MMCO_LONG2UNUSED ||
 759                     opcode == MMCO_LONG || opcode == MMCO_SET_MAX_LONG) {
 760                     unsigned int long_arg = get_ue_golomb_31(gb);
 761                     if (long_arg >= 32 ||
 762                         (long_arg >= 16 && !(opcode == MMCO_SET_MAX_LONG &&
 763                                              long_arg == 16) &&
 764                          !(opcode == MMCO_LONG2UNUSED && FIELD_PICTURE(h)))) {
 765                         av_log(h->avctx, AV_LOG_ERROR,
 766                                "illegal long ref in memory management control "
 767                                "operation %d\n", opcode);
 768                         return -1;
 769                     }
 770                     mmco[i].long_arg = long_arg;
 771                 }
 772
 773                 if (opcode > (unsigned) MMCO_LONG) {
 774                     av_log(h->avctx, AV_LOG_ERROR,
 775                            "illegal memory management control operation %d\n",
 776                            opcode);
 777                     return -1;
 778                 }
 779                 if (opcode == MMCO_END)
 780                     break;
 781             }
 782             mmco_index = i;
 783         } else {
 784             if (first_slice) {
 785                 ret = ff_generate_sliding_window_mmcos(h, first_slice);
 786                 if (ret < 0 && h->avctx->err_recognition & AV_EF_EXPLODE)
 787                     return ret;
 788             }
 789             mmco_index = -1;
 790         }
 791     }
 792
 793     if (first_slice && mmco_index != -1) {
 794         h->mmco_index = mmco_index;
 795     } else if (!first_slice && mmco_index >= 0 &&
 796                (mmco_index != h->mmco_index ||
 797                 check_opcodes(h->mmco, mmco_temp, mmco_index))) {
 798         av_log(h->avctx, AV_LOG_ERROR,
 799                "Inconsistent MMCO state between slices [%d, %d]\n",
 800                mmco_index, h->mmco_index);
 801         return AVERROR_INVALIDDATA;
 802     }
 803
 804     return 0;
 805 }