summaryrefslogtreecommitdiff
path: root/libavcodec/h264_refs.c
blob: 855248781af7fc1c4f43cefaff02b46e840dcb80 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
/*
 * H.26L/H.264/AVC/JVT/14496-10/... reference picture handling
 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * H.264 / AVC / MPEG4 part10  reference picture handling.
 * @author Michael Niedermayer <michaelni@gmx.at>
 */

#include <inttypes.h>

#include "internal.h"
#include "avcodec.h"
#include "h264.h"
#include "golomb.h"
#include "mpegutils.h"

#include <assert.h>

static void pic_as_field(H264Ref *pic, const int parity)
{
    int i;
    for (i = 0; i < FF_ARRAY_ELEMS(pic->data); ++i) {
        if (parity == PICT_BOTTOM_FIELD)
            pic->data[i]   += pic->linesize[i];
        pic->reference      = parity;
        pic->linesize[i] *= 2;
    }
    pic->poc = pic->parent->field_poc[parity == PICT_BOTTOM_FIELD];
}

static void ref_from_h264pic(H264Ref *dst, H264Picture *src)
{
    memcpy(dst->data,     src->f->data,     sizeof(dst->data));
    memcpy(dst->linesize, src->f->linesize, sizeof(dst->linesize));
    dst->reference = src->reference;
    dst->poc       = src->poc;
    dst->pic_id    = src->pic_id;
    dst->parent = src;
}

static int split_field_copy(H264Ref *dest, H264Picture *src, int parity, int id_add)
{
    int match = !!(src->reference & parity);

    if (match) {
        ref_from_h264pic(dest, src);
        if (parity != PICT_FRAME) {
            pic_as_field(dest, parity);
            dest->pic_id *= 2;
            dest->pic_id += id_add;
        }
    }

    return match;
}

static int build_def_list(H264Ref *def, int def_len,
                          H264Picture * const *in, int len, int is_long, int sel)
{
    int  i[2] = { 0 };
    int index = 0;

    while ((i[0] < len || i[1] < len) && index < def_len) {
        while (i[0] < len && !(in[i[0]] && (in[i[0]]->reference & sel)))
            i[0]++;
        while (i[1] < len && !(in[i[1]] && (in[i[1]]->reference & (sel ^ 3))))
            i[1]++;
        if (i[0] < len && index < def_len) {
            in[i[0]]->pic_id = is_long ? i[0] : in[i[0]]->frame_num;
            split_field_copy(&def[index++], in[i[0]++], sel, 1);
        }
        if (i[1] < len && index < def_len) {
            in[i[1]]->pic_id = is_long ? i[1] : in[i[1]]->frame_num;
            split_field_copy(&def[index++], in[i[1]++], sel ^ 3, 0);
        }
    }

    return index;
}

static int add_sorted(H264Picture **sorted, H264Picture * const *src,
                      int len, int limit, int dir)
{
    int i, best_poc;
    int out_i = 0;

    for (;;) {
        best_poc = dir ? INT_MIN : INT_MAX;

        for (i = 0; i < len; i++) {
            const int poc = src[i]->poc;
            if (((poc > limit) ^ dir) && ((poc < best_poc) ^ dir)) {
                best_poc      = poc;
                sorted[out_i] = src[i];
            }
        }
        if (best_poc == (dir ? INT_MIN : INT_MAX))
            break;
        limit = sorted[out_i++]->poc - dir;
    }
    return out_i;
}

static void h264_initialise_ref_list(const H264Context *h, H264SliceContext *sl)
{
    int i, len;

    if (sl->slice_type_nos == AV_PICTURE_TYPE_B) {
        H264Picture *sorted[32];
        int cur_poc, list;
        int lens[2];

        if (FIELD_PICTURE(h))
            cur_poc = h->cur_pic_ptr->field_poc[h->picture_structure == PICT_BOTTOM_FIELD];
        else
            cur_poc = h->cur_pic_ptr->poc;

        for (list = 0; list < 2; list++) {
            len  = add_sorted(sorted,       h->short_ref, h->short_ref_count, cur_poc, 1 ^ list);
            len += add_sorted(sorted + len, h->short_ref, h->short_ref_count, cur_poc, 0 ^ list);
            assert(len <= 32);

            len  = build_def_list(sl->ref_list[list], FF_ARRAY_ELEMS(sl->ref_list[0]),
                                  sorted, len, 0, h->picture_structure);
            len += build_def_list(sl->ref_list[list] + len,
                                  FF_ARRAY_ELEMS(sl->ref_list[0]) - len,
                                  h->long_ref, 16, 1, h->picture_structure);

            if (len < sl->ref_count[list])
                memset(&sl->ref_list[list][len], 0, sizeof(H264Ref) * (sl->ref_count[list] - len));
            lens[list] = len;
        }

        if (lens[0] == lens[1] && lens[1] > 1) {
            for (i = 0; i < lens[0] &&
                        sl->ref_list[0][i].parent->f->buf[0]->buffer ==
                        sl->ref_list[1][i].parent->f->buf[0]->buffer; i++);
            if (i == lens[0]) {
                FFSWAP(H264Ref, sl->ref_list[1][0], sl->ref_list[1][1]);
            }
        }
    } else {
        len  = build_def_list(sl->ref_list[0], FF_ARRAY_ELEMS(sl->ref_list[0]),
                              h->short_ref, h->short_ref_count, 0, h->picture_structure);
        len += build_def_list(sl->ref_list[0] + len,
                              FF_ARRAY_ELEMS(sl->ref_list[0]) - len,
                              h-> long_ref, 16, 1, h->picture_structure);

        if (len < sl->ref_count[0])
            memset(&sl->ref_list[0][len], 0, sizeof(H264Ref) * (sl->ref_count[0] - len));
    }
}

/**
 * print short term list
 */
static void print_short_term(const H264Context *h)
{
    uint32_t i;
    if (h->avctx->debug & FF_DEBUG_MMCO) {
        av_log(h->avctx, AV_LOG_DEBUG, "short term list:\n");
        for (i = 0; i < h->short_ref_count; i++) {
            H264Picture *pic = h->short_ref[i];
            av_log(h->avctx, AV_LOG_DEBUG, "%"PRIu32" fn:%d poc:%d %p\n",
                   i, pic->frame_num, pic->poc, pic->f->data[0]);
        }
    }
}

/**
 * print long term list
 */
static void print_long_term(const H264Context *h)
{
    uint32_t i;
    if (h->avctx->debug & FF_DEBUG_MMCO) {
        av_log(h->avctx, AV_LOG_DEBUG, "long term list:\n");
        for (i = 0; i < 16; i++) {
            H264Picture *pic = h->long_ref[i];
            if (pic) {
                av_log(h->avctx, AV_LOG_DEBUG, "%"PRIu32" fn:%d poc:%d %p\n",
                       i, pic->frame_num, pic->poc, pic->f->data[0]);
            }
        }
    }
}

/**
 * Extract structure information about the picture described by pic_num in
 * the current decoding context (frame or field). Note that pic_num is
 * picture number without wrapping (so, 0<=pic_num<max_pic_num).
 * @param pic_num picture number for which to extract structure information
 * @param structure one of PICT_XXX describing structure of picture
 *                      with pic_num
 * @return frame number (short term) or long term index of picture
 *         described by pic_num
 */
static int pic_num_extract(const H264Context *h, int pic_num, int *structure)
{
    *structure = h->picture_structure;
    if (FIELD_PICTURE(h)) {
        if (!(pic_num & 1))
            /* opposite field */
            *structure ^= PICT_FRAME;
        pic_num >>= 1;
    }

    return pic_num;
}

int ff_h264_decode_ref_pic_list_reordering(const H264Context *h, H264SliceContext *sl)
{
    int list, index, pic_structure;

    print_short_term(h);
    print_long_term(h);

    h264_initialise_ref_list(h, sl);

    for (list = 0; list < sl->list_count; list++) {
        if (get_bits1(&sl->gb)) {    // ref_pic_list_modification_flag_l[01]
            int pred = h->curr_pic_num;

            for (index = 0; ; index++) {
                unsigned int modification_of_pic_nums_idc = get_ue_golomb_31(&sl->gb);
                unsigned int pic_id;
                int i;
                H264Picture *ref = NULL;

                if (modification_of_pic_nums_idc == 3)
                    break;

                if (index >= sl->ref_count[list]) {
                    av_log(h->avctx, AV_LOG_ERROR, "reference count overflow\n");
                    return -1;
                }

                switch (modification_of_pic_nums_idc) {
                case 0:
                case 1: {
                    const unsigned int abs_diff_pic_num = get_ue_golomb(&sl->gb) + 1;
                    int frame_num;

                    if (abs_diff_pic_num > h->max_pic_num) {
                        av_log(h->avctx, AV_LOG_ERROR,
                               "abs_diff_pic_num overflow\n");
                        return AVERROR_INVALIDDATA;
                    }

                    if (modification_of_pic_nums_idc == 0)
                        pred -= abs_diff_pic_num;
                    else
                        pred += abs_diff_pic_num;
                    pred &= h->max_pic_num - 1;

                    frame_num = pic_num_extract(h, pred, &pic_structure);

                    for (i = h->short_ref_count - 1; i >= 0; i--) {
                        ref = h->short_ref[i];
                        assert(ref->reference);
                        assert(!ref->long_ref);
                        if (ref->frame_num == frame_num &&
                            (ref->reference & pic_structure))
                            break;
                    }
                    if (i >= 0)
                        ref->pic_id = pred;
                    break;
                }
                case 2: {
                    int long_idx;
                    pic_id = get_ue_golomb(&sl->gb); // long_term_pic_idx

                    long_idx = pic_num_extract(h, pic_id, &pic_structure);

                    if (long_idx > 31) {
                        av_log(h->avctx, AV_LOG_ERROR,
                               "long_term_pic_idx overflow\n");
                        return AVERROR_INVALIDDATA;
                    }
                    ref = h->long_ref[long_idx];
                    assert(!(ref && !ref->reference));
                    if (ref && (ref->reference & pic_structure)) {
                        ref->pic_id = pic_id;
                        assert(ref->long_ref);
                        i = 0;
                    } else {
                        i = -1;
                    }
                    break;
                }
                default:
                    av_log(h->avctx, AV_LOG_ERROR,
                           "illegal modification_of_pic_nums_idc %u\n",
                           modification_of_pic_nums_idc);
                    return AVERROR_INVALIDDATA;
                }

                if (i < 0) {
                    av_log(h->avctx, AV_LOG_ERROR,
                           "reference picture missing during reorder\n");
                    memset(&sl->ref_list[list][index], 0, sizeof(sl->ref_list[0][0])); // FIXME
                } else {
                    for (i = index; i + 1 < sl->ref_count[list]; i++) {
                        if (sl->ref_list[list][i].parent &&
                            ref->long_ref == sl->ref_list[list][i].parent->long_ref &&
                            ref->pic_id   == sl->ref_list[list][i].pic_id)
                            break;
                    }
                    for (; i > index; i--) {
                        sl->ref_list[list][i] = sl->ref_list[list][i - 1];
                    }
                    ref_from_h264pic(&sl->ref_list[list][index], ref);
                    if (FIELD_PICTURE(h)) {
                        pic_as_field(&sl->ref_list[list][index], pic_structure);
                    }
                }
            }
        }
    }
    for (list = 0; list < sl->list_count; list++) {
        for (index = 0; index < sl->ref_count[list]; index++) {
            if (!sl->ref_list[list][index].parent) {
                av_log(h->avctx, AV_LOG_ERROR, "Missing reference picture\n");
                if (index == 0 || h->avctx->err_recognition & AV_EF_EXPLODE)
                    return AVERROR_INVALIDDATA;
                else
                    sl->ref_list[list][index] = sl->ref_list[list][index - 1];
            }
        }
    }

    return 0;
}

void ff_h264_fill_mbaff_ref_list(H264SliceContext *sl)
{
    int list, i, j;
    for (list = 0; list < sl->list_count; list++) { //FIXME try list_count
        for (i = 0; i < sl->ref_count[list]; i++) {
            H264Ref *frame = &sl->ref_list[list][i];
            H264Ref *field = &sl->ref_list[list][16 + 2 * i];

            field[0] = *frame;

            for (j = 0; j < 3; j++)
                field[0].linesize[j] <<= 1;
            field[0].reference = PICT_TOP_FIELD;
            field[0].poc       = field[0].parent->field_poc[0];

            field[1] = field[0];

            for (j = 0; j < 3; j++)
                field[1].data[j] += frame->parent->f->linesize[j];
            field[1].reference = PICT_BOTTOM_FIELD;
            field[1].poc       = field[1].parent->field_poc[1];

            sl->pwt.luma_weight[16 + 2 * i][list][0] = sl->pwt.luma_weight[16 + 2 * i + 1][list][0] = sl->pwt.luma_weight[i][list][0];
            sl->pwt.luma_weight[16 + 2 * i][list][1] = sl->pwt.luma_weight[16 + 2 * i + 1][list][1] = sl->pwt.luma_weight[i][list][1];
            for (j = 0; j < 2; j++) {
                sl->pwt.chroma_weight[16 + 2 * i][list][j][0] = sl->pwt.chroma_weight[16 + 2 * i + 1][list][j][0] = sl->pwt.chroma_weight[i][list][j][0];
                sl->pwt.chroma_weight[16 + 2 * i][list][j][1] = sl->pwt.chroma_weight[16 + 2 * i + 1][list][j][1] = sl->pwt.chroma_weight[i][list][j][1];
            }
        }
    }
}

/**
 * Mark a picture as no longer needed for reference. The refmask
 * argument allows unreferencing of individual fields or the whole frame.
 * If the picture becomes entirely unreferenced, but is being held for
 * display purposes, it is marked as such.
 * @param refmask mask of fields to unreference; the mask is bitwise
 *                anded with the reference marking of pic
 * @return non-zero if pic becomes entirely unreferenced (except possibly
 *         for display purposes) zero if one of the fields remains in
 *         reference
 */
static inline int unreference_pic(H264Context *h, H264Picture *pic, int refmask)
{
    int i;
    if (pic->reference &= refmask) {
        return 0;
    } else {
        for(i = 0; h->delayed_pic[i]; i++)
            if(pic == h->delayed_pic[i]){
                pic->reference = DELAYED_PIC_REF;
                break;
            }
        return 1;
    }
}

/**
 * Find a H264Picture in the short term reference list by frame number.
 * @param frame_num frame number to search for
 * @param idx the index into h->short_ref where returned picture is found
 *            undefined if no picture found.
 * @return pointer to the found picture, or NULL if no pic with the provided
 *                 frame number is found
 */
static H264Picture *find_short(H264Context *h, int frame_num, int *idx)
{
    int i;

    for (i = 0; i < h->short_ref_count; i++) {
        H264Picture *pic = h->short_ref[i];
        if (h->avctx->debug & FF_DEBUG_MMCO)
            av_log(h->avctx, AV_LOG_DEBUG, "%d %d %p\n", i, pic->frame_num, pic);
        if (pic->frame_num == frame_num) {
            *idx = i;
            return pic;
        }
    }
    return NULL;
}

/**
 * Remove a picture from the short term reference list by its index in
 * that list.  This does no checking on the provided index; it is assumed
 * to be valid. Other list entries are shifted down.
 * @param i index into h->short_ref of picture to remove.
 */
static void remove_short_at_index(H264Context *h, int i)
{
    assert(i >= 0 && i < h->short_ref_count);
    h->short_ref[i] = NULL;
    if (--h->short_ref_count)
        memmove(&h->short_ref[i], &h->short_ref[i + 1],
                (h->short_ref_count - i) * sizeof(H264Picture*));
}

/**
 * @return the removed picture or NULL if an error occurs
 */
static H264Picture *remove_short(H264Context *h, int frame_num, int ref_mask)
{
    H264Picture *pic;
    int i;

    if (h->avctx->debug & FF_DEBUG_MMCO)
        av_log(h->avctx, AV_LOG_DEBUG, "remove short %d count %d\n", frame_num, h->short_ref_count);

    pic = find_short(h, frame_num, &i);
    if (pic) {
        if (unreference_pic(h, pic, ref_mask))
            remove_short_at_index(h, i);
    }

    return pic;
}

/**
 * Remove a picture from the long term reference list by its index in
 * that list.
 * @return the removed picture or NULL if an error occurs
 */
static H264Picture *remove_long(H264Context *h, int i, int ref_mask)
{
    H264Picture *pic;

    pic = h->long_ref[i];
    if (pic) {
        if (unreference_pic(h, pic, ref_mask)) {
            assert(h->long_ref[i]->long_ref == 1);
            h->long_ref[i]->long_ref = 0;
            h->long_ref[i]           = NULL;
            h->long_ref_count--;
        }
    }

    return pic;
}

void ff_h264_remove_all_refs(H264Context *h)
{
    int i;

    for (i = 0; i < 16; i++) {
        remove_long(h, i, 0);
    }
    assert(h->long_ref_count == 0);

    for (i = 0; i < h->short_ref_count; i++) {
        unreference_pic(h, h->short_ref[i], 0);
        h->short_ref[i] = NULL;
    }
    h->short_ref_count = 0;
}

static int check_opcodes(MMCO *mmco1, MMCO *mmco2, int n_mmcos)
{
    int i;

    for (i = 0; i < n_mmcos; i++) {
        if (mmco1[i].opcode != mmco2[i].opcode)
            return -1;
    }

    return 0;
}

int ff_generate_sliding_window_mmcos(H264Context *h, int first_slice)
{
    MMCO mmco_temp[MAX_MMCO_COUNT], *mmco = first_slice ? h->mmco : mmco_temp;
    int mmco_index = 0, i = 0;

    assert(h->long_ref_count + h->short_ref_count <= h->ps.sps->ref_frame_count);

    if (h->short_ref_count &&
        h->long_ref_count + h->short_ref_count == h->ps.sps->ref_frame_count &&
        !(FIELD_PICTURE(h) && !h->first_field && h->cur_pic_ptr->reference)) {
        mmco[0].opcode        = MMCO_SHORT2UNUSED;
        mmco[0].short_pic_num = h->short_ref[h->short_ref_count - 1]->frame_num;
        mmco_index            = 1;
        if (FIELD_PICTURE(h)) {
            mmco[0].short_pic_num *= 2;
            mmco[1].opcode         = MMCO_SHORT2UNUSED;
            mmco[1].short_pic_num  = mmco[0].short_pic_num + 1;
            mmco_index             = 2;
        }
    }

    if (first_slice) {
        h->mmco_index = mmco_index;
    } else if (!first_slice && mmco_index >= 0 &&
               (mmco_index != h->mmco_index ||
                (i = check_opcodes(h->mmco, mmco_temp, mmco_index)))) {
        av_log(h->avctx, AV_LOG_ERROR,
               "Inconsistent MMCO state between slices [%d, %d, %d]\n",
               mmco_index, h->mmco_index, i);
        return AVERROR_INVALIDDATA;
    }
    return 0;
}

int ff_h264_execute_ref_pic_marking(H264Context *h, MMCO *mmco, int mmco_count)
{
    int i, av_uninit(j);
    int current_ref_assigned = 0, err = 0;
    H264Picture *av_uninit(pic);

    if ((h->avctx->debug & FF_DEBUG_MMCO) && mmco_count == 0)
        av_log(h->avctx, AV_LOG_DEBUG, "no mmco here\n");

    for (i = 0; i < mmco_count; i++) {
        int av_uninit(structure), av_uninit(frame_num);
        if (h->avctx->debug & FF_DEBUG_MMCO)
            av_log(h->avctx, AV_LOG_DEBUG, "mmco:%d %d %d\n", h->mmco[i].opcode,
                   h->mmco[i].short_pic_num, h->mmco[i].long_arg);

        if (mmco[i].opcode == MMCO_SHORT2UNUSED ||
            mmco[i].opcode == MMCO_SHORT2LONG) {
            frame_num = pic_num_extract(h, mmco[i].short_pic_num, &structure);
            pic       = find_short(h, frame_num, &j);
            if (!pic) {
                if (mmco[i].opcode != MMCO_SHORT2LONG ||
                    !h->long_ref[mmco[i].long_arg]    ||
                    h->long_ref[mmco[i].long_arg]->frame_num != frame_num) {
                    av_log(h->avctx, AV_LOG_ERROR, "mmco: unref short failure\n");
                    err = AVERROR_INVALIDDATA;
                }
                continue;
            }
        }

        switch (mmco[i].opcode) {
        case MMCO_SHORT2UNUSED:
            if (h->avctx->debug & FF_DEBUG_MMCO)
                av_log(h->avctx, AV_LOG_DEBUG, "mmco: unref short %d count %d\n",
                       h->mmco[i].short_pic_num, h->short_ref_count);
            remove_short(h, frame_num, structure ^ PICT_FRAME);
            break;
        case MMCO_SHORT2LONG:
                if (h->long_ref[mmco[i].long_arg] != pic)
                    remove_long(h, mmco[i].long_arg, 0);

                remove_short_at_index(h, j);
                h->long_ref[ mmco[i].long_arg ] = pic;
                if (h->long_ref[mmco[i].long_arg]) {
                    h->long_ref[mmco[i].long_arg]->long_ref = 1;
                    h->long_ref_count++;
                }
            break;
        case MMCO_LONG2UNUSED:
            j   = pic_num_extract(h, mmco[i].long_arg, &structure);
            pic = h->long_ref[j];
            if (pic) {
                remove_long(h, j, structure ^ PICT_FRAME);
            } else if (h->avctx->debug & FF_DEBUG_MMCO)
                av_log(h->avctx, AV_LOG_DEBUG, "mmco: unref long failure\n");
            break;
        case MMCO_LONG:
                    // Comment below left from previous code as it is an interresting note.
                    /* First field in pair is in short term list or
                     * at a different long term index.
                     * This is not allowed; see 7.4.3.3, notes 2 and 3.
                     * Report the problem and keep the pair where it is,
                     * and mark this field valid.
                     */
            if (h->short_ref[0] == h->cur_pic_ptr)
                remove_short_at_index(h, 0);

            /* make sure the current picture is not already assigned as a long ref */
            if (h->cur_pic_ptr->long_ref) {
                for (j = 0; j < FF_ARRAY_ELEMS(h->long_ref); j++) {
                    if (h->long_ref[j] == h->cur_pic_ptr)
                        remove_long(h, j, 0);
                }
            }


            if (h->long_ref[mmco[i].long_arg] != h->cur_pic_ptr) {
                remove_long(h, mmco[i].long_arg, 0);

                h->long_ref[mmco[i].long_arg]           = h->cur_pic_ptr;
                h->long_ref[mmco[i].long_arg]->long_ref = 1;
                h->long_ref_count++;
            }

            h->cur_pic_ptr->reference |= h->picture_structure;
            current_ref_assigned = 1;
            break;
        case MMCO_SET_MAX_LONG:
            assert(mmco[i].long_arg <= 16);
            // just remove the long term which index is greater than new max
            for (j = mmco[i].long_arg; j < 16; j++) {
                remove_long(h, j, 0);
            }
            break;
        case MMCO_RESET:
            while (h->short_ref_count) {
                remove_short(h, h->short_ref[0]->frame_num, 0);
            }
            for (j = 0; j < 16; j++) {
                remove_long(h, j, 0);
            }
            h->poc.frame_num = h->cur_pic_ptr->frame_num = 0;
            h->mmco_reset = 1;
            h->cur_pic_ptr->mmco_reset = 1;
            break;
        default: assert(0);
        }
    }

    if (!current_ref_assigned) {
        /* Second field of complementary field pair; the first field of
         * which is already referenced. If short referenced, it
         * should be first entry in short_ref. If not, it must exist
         * in long_ref; trying to put it on the short list here is an
         * error in the encoded bit stream (ref: 7.4.3.3, NOTE 2 and 3).
         */
        if (h->short_ref_count && h->short_ref[0] == h->cur_pic_ptr) {
            /* Just mark the second field valid */
            h->cur_pic_ptr->reference = PICT_FRAME;
        } else if (h->cur_pic_ptr->long_ref) {
            av_log(h->avctx, AV_LOG_ERROR, "illegal short term reference "
                                           "assignment for second field "
                                           "in complementary field pair "
                                           "(first field is long term)\n");
            err = AVERROR_INVALIDDATA;
        } else {
            pic = remove_short(h, h->cur_pic_ptr->frame_num, 0);
            if (pic) {
                av_log(h->avctx, AV_LOG_ERROR, "illegal short term buffer state detected\n");
                err = AVERROR_INVALIDDATA;
            }

            if (h->short_ref_count)
                memmove(&h->short_ref[1], &h->short_ref[0],
                        h->short_ref_count * sizeof(H264Picture*));

            h->short_ref[0] = h->cur_pic_ptr;
            h->short_ref_count++;
            h->cur_pic_ptr->reference |= h->picture_structure;
        }
    }

    if (h->long_ref_count + h->short_ref_count -
        (h->short_ref[0] == h->cur_pic_ptr) > h->ps.sps->ref_frame_count) {

        /* We have too many reference frames, probably due to corrupted
         * stream. Need to discard one frame. Prevents overrun of the
         * short_ref and long_ref buffers.
         */
        av_log(h->avctx, AV_LOG_ERROR,
               "number of reference frames (%d+%d) exceeds max (%d; probably "
               "corrupt input), discarding one\n",
               h->long_ref_count, h->short_ref_count, h->ps.sps->ref_frame_count);
        err = AVERROR_INVALIDDATA;

        if (h->long_ref_count && !h->short_ref_count) {
            for (i = 0; i < 16; ++i)
                if (h->long_ref[i])
                    break;

            assert(i < 16);
            remove_long(h, i, 0);
        } else {
            pic = h->short_ref[h->short_ref_count - 1];
            remove_short(h, pic->frame_num, 0);
        }
    }

    print_short_term(h);
    print_long_term(h);
    return (h->avctx->err_recognition & AV_EF_EXPLODE) ? err : 0;
}

int ff_h264_decode_ref_pic_marking(H264Context *h, GetBitContext *gb,
                                   int first_slice)
{
    int i, ret;
    MMCO mmco_temp[MAX_MMCO_COUNT], *mmco = first_slice ? h->mmco : mmco_temp;
    int mmco_index = 0;

    if (h->nal_unit_type == NAL_IDR_SLICE) { // FIXME fields
        skip_bits1(gb); // broken_link
        if (get_bits1(gb)) {
            mmco[0].opcode   = MMCO_LONG;
            mmco[0].long_arg = 0;
            mmco_index       = 1;
        }
    } else {
        if (get_bits1(gb)) { // adaptive_ref_pic_marking_mode_flag
            for (i = 0; i < MAX_MMCO_COUNT; i++) {
                MMCOOpcode opcode = get_ue_golomb_31(gb);

                mmco[i].opcode = opcode;
                if (opcode == MMCO_SHORT2UNUSED || opcode == MMCO_SHORT2LONG) {
                    mmco[i].short_pic_num =
                        (h->curr_pic_num - get_ue_golomb(gb) - 1) &
                            (h->max_pic_num - 1);
#if 0
                    if (mmco[i].short_pic_num >= h->short_ref_count ||
                        !h->short_ref[mmco[i].short_pic_num]) {
                        av_log(s->avctx, AV_LOG_ERROR,
                               "illegal short ref in memory management control "
                               "operation %d\n", mmco);
                        return -1;
                    }
#endif
                }
                if (opcode == MMCO_SHORT2LONG || opcode == MMCO_LONG2UNUSED ||
                    opcode == MMCO_LONG || opcode == MMCO_SET_MAX_LONG) {
                    unsigned int long_arg = get_ue_golomb_31(gb);
                    if (long_arg >= 32 ||
                        (long_arg >= 16 && !(opcode == MMCO_SET_MAX_LONG &&
                                             long_arg == 16) &&
                         !(opcode == MMCO_LONG2UNUSED && FIELD_PICTURE(h)))) {
                        av_log(h->avctx, AV_LOG_ERROR,
                               "illegal long ref in memory management control "
                               "operation %d\n", opcode);
                        return -1;
                    }
                    mmco[i].long_arg = long_arg;
                }

                if (opcode > (unsigned) MMCO_LONG) {
                    av_log(h->avctx, AV_LOG_ERROR,
                           "illegal memory management control operation %d\n",
                           opcode);
                    return -1;
                }
                if (opcode == MMCO_END)
                    break;
            }
            mmco_index = i;
        } else {
            if (first_slice) {
                ret = ff_generate_sliding_window_mmcos(h, first_slice);
                if (ret < 0 && h->avctx->err_recognition & AV_EF_EXPLODE)
                    return ret;
            }
            mmco_index = -1;
        }
    }

    if (first_slice && mmco_index != -1) {
        h->mmco_index = mmco_index;
    } else if (!first_slice && mmco_index >= 0 &&
               (mmco_index != h->mmco_index ||
                check_opcodes(h->mmco, mmco_temp, mmco_index))) {
        av_log(h->avctx, AV_LOG_ERROR,
               "Inconsistent MMCO state between slices [%d, %d]\n",
               mmco_index, h->mmco_index);
        return AVERROR_INVALIDDATA;
    }

    return 0;
}