/*

 * H.26L/H.264/AVC/JVT/14496-10/... reference picture handling

 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * H.264 / AVC / MPEG-4 part10  reference picture handling.

 * @author Michael Niedermayer <michaelni@gmx.at>

 */

#include <inttypes.h>

#include "libavutil/avassert.h"

#include "avcodec.h"

#include "h264.h"

#include "h264dec.h"

#include "golomb.h"

#include "mpegutils.h"

#include <assert.h>

static void pic_as_field(H264Ref *pic, const int parity)

{

    for (int 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, const 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, const 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) {

        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) {

            av_assert0(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) {

            av_assert0(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 out_i = 0;

    for (;;) {

        int best_poc = dir ? INT_MIN : INT_MAX;

        for (int 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 int mismatches_ref(const H264Context *h, const H264Picture *pic)

{

    const AVFrame *f = pic->f;

    return (h->cur_pic_ptr->f->width  != f->width ||

            h->cur_pic_ptr->f->height != f->height ||

            h->cur_pic_ptr->f->format != f->format);

}

static void h264_initialise_ref_list(H264Context *h, H264SliceContext *sl)

{

    int len;

    if (sl->slice_type_nos == AV_PICTURE_TYPE_B) {

        H264Picture *sorted[32];

        int cur_poc;

        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 (int 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);

            av_assert0(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);

            av_assert0(len <= 32);

            memset(&sl->ref_list[list][len], 0, sizeof(H264Ref) * (32 - len));

            lens[list] = len;

        }

        if (lens[0] == lens[1] && lens[1] > 1) {

            int i;

            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);

        av_assert0(len <= 32);

        memset(&sl->ref_list[0][len], 0, sizeof(H264Ref) * (32 - len));

    }

#ifdef TRACE

    for (int i = 0; i < sl->ref_count[0]; i++) {

        ff_tlog(h->avctx, "List0: %s fn:%d 0x%p\n",

                (sl->ref_list[0][i].parent ? (sl->ref_list[0][i].parent->long_ref ? "LT" : "ST") : "??"),

                sl->ref_list[0][i].pic_id,

                sl->ref_list[0][i].data[0]);

    }

    if (sl->slice_type_nos == AV_PICTURE_TYPE_B) {

        for (int i = 0; i < sl->ref_count[1]; i++) {

            ff_tlog(h->avctx, "List1: %s fn:%d 0x%p\n",

                    (sl->ref_list[1][i].parent ? (sl->ref_list[1][i].parent->long_ref ? "LT" : "ST") : "??"),

                    sl->ref_list[1][i].pic_id,

                    sl->ref_list[1][i].data[0]);

        }

    }

#endif

    for (int j = 0; j < 1 + (sl->slice_type_nos == AV_PICTURE_TYPE_B); j++) {

        for (int i = 0; i < sl->ref_count[j]; i++) {

            if (sl->ref_list[j][i].parent) {

                if (mismatches_ref(h, sl->ref_list[j][i].parent)) {

                    av_log(h->avctx, AV_LOG_ERROR, "Discarding mismatching reference\n");

                    memset(&sl->ref_list[j][i], 0, sizeof(sl->ref_list[j][i]));

                }

            }

        }

    }

    for (int i = 0; i < sl->list_count; i++)

        h->default_ref[i] = sl->ref_list[i][0];

}

/**

 * print short term list

 */

static void print_short_term(const H264Context *h)

{

    if (h->avctx->debug & FF_DEBUG_MMCO) {

        av_log(h->avctx, AV_LOG_DEBUG, "short term list:\n");

        for (uint32_t 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)

{

    if (h->avctx->debug & FF_DEBUG_MMCO) {

        av_log(h->avctx, AV_LOG_DEBUG, "long term list:\n");

        for (uint32_t 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;

}

static void h264_fill_mbaff_ref_list(H264SliceContext *sl)

{

    for (int list = 0; list < sl->list_count; list++) {

        for (int i = 0; i < sl->ref_count[list]; i++) {

            const H264Ref *frame = &sl->ref_list[list][i];

            H264Ref *field = &sl->ref_list[list][16 + 2 * i];

            field[0] = *frame;

            for (int 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 (int 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];

        }

    }

}

int ff_h264_build_ref_list(H264Context *h, H264SliceContext *sl)

{

    print_short_term(h);

    print_long_term(h);

    h264_initialise_ref_list(h, sl);

    for (int list = 0; list < sl->list_count; list++) {

        int pred = sl->curr_pic_num;

        for (int index = 0; index < sl->nb_ref_modifications[list]; index++) {

            unsigned int modification_of_pic_nums_idc = sl->ref_modifications[list][index].op;

            unsigned int                          val = sl->ref_modifications[list][index].val;

            unsigned int pic_id;

            int i, pic_structure;

            H264Picture *ref = NULL;

            switch (modification_of_pic_nums_idc) {

            case 0:

            case 1: {

                const unsigned int abs_diff_pic_num = val + 1;

                int frame_num;

                if (abs_diff_pic_num > sl->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 &= sl->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)

                    pic_id = pred;

                break;

            }

            case 2: {

                int long_idx;

                pic_id = val; // long_term_pic_idx

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

                if (long_idx > 31U) {

                    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)) {

                    assert(ref->long_ref);

                    i = 0;

                } else {

                    i = -1;

                }

                break;

            }

            default:

                av_assert0(0);

            }

            if (i < 0 || mismatches_ref(h, ref)) {

                av_log(h->avctx, AV_LOG_ERROR,

                       i < 0 ? "reference picture missing during reorder\n" :

                               "mismatching reference\n"

                      );

                if (h->avctx->err_recognition & AV_EF_EXPLODE) {

                    return AVERROR_INVALIDDATA;

                }

                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 &&

                        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 (int list = 0; list < sl->list_count; list++) {

        for (int index = 0; index < sl->ref_count[list]; index++) {

            if (   !sl->ref_list[list][index].parent

                || (!FIELD_PICTURE(h) && (sl->ref_list[list][index].reference&3) != 3)) {

                if (h->avctx->err_recognition & AV_EF_EXPLODE) {

                    av_log(h->avctx, AV_LOG_ERROR, "Missing reference picture\n");

                    return AVERROR_INVALIDDATA;

                }

                av_log(h->avctx, AV_LOG_ERROR, "Missing reference picture, default is %d\n", h->default_ref[list].poc);

                for (int i = 0; i < FF_ARRAY_ELEMS(h->last_pocs); i++)

                    h->last_pocs[i] = INT_MIN;

                if (h->default_ref[list].parent

                    && !(!FIELD_PICTURE(h) && (h->default_ref[list].reference&3) != 3))

                    sl->ref_list[list][index] = h->default_ref[list];

                else

                    return -1;

            }

            if (h->noref_gray>0 && sl->ref_list[list][index].parent->gray && h->non_gray) {

                for (int j=0; j<sl->list_count; j++) {

                    int list2 = (list+j)&1;

                    if (h->default_ref[list2].parent && !h->default_ref[list2].parent->gray

                        && !(!FIELD_PICTURE(h) && (h->default_ref[list2].reference&3) != 3)) {

                        sl->ref_list[list][index] = h->default_ref[list2];

                        av_log(h->avctx, AV_LOG_DEBUG, "replacement of gray gap frame\n");

                        break;

                    }

                }

            }

            av_assert0(av_buffer_get_ref_count(sl->ref_list[list][index].parent->f->buf[0]) > 0);

        }

    }

    if (FRAME_MBAFF(h))

        h264_fill_mbaff_ref_list(sl);

    return 0;

}

int ff_h264_decode_ref_pic_list_reordering(H264SliceContext *sl, void *logctx)

{

    sl->nb_ref_modifications[0] = 0;

    sl->nb_ref_modifications[1] = 0;

    for (int list = 0; list < sl->list_count; list++) {

        if (!get_bits1(&sl->gb))    // ref_pic_list_modification_flag_l[01]

            continue;

        for (int index = 0; ; index++) {

            unsigned int op = get_ue_golomb_31(&sl->gb);

            if (op == 3)

                break;

            if (index >= sl->ref_count[list]) {

                av_log(logctx, AV_LOG_ERROR, "reference count overflow\n");

                return AVERROR_INVALIDDATA;

            } else if (op > 2) {

                av_log(logctx, AV_LOG_ERROR,

                       "illegal modification_of_pic_nums_idc %u\n",

                       op);

                return AVERROR_INVALIDDATA;

            }

            sl->ref_modifications[list][index].val = get_ue_golomb_long(&sl->gb);

            sl->ref_modifications[list][index].op  = op;

            sl->nb_ref_modifications[list]++;

        }

    }

    return 0;

}

/**

 * 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)

{

    if (pic->reference &= refmask) {

        return 0;

    } else {

        for (int 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)

{

    for (int 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)

{

    for (int i = 0; i < 16; i++)

        remove_long(h, i, 0);

    assert(h->long_ref_count == 0);

    if (h->short_ref_count && !h->last_pic_for_ec.f->data[0]) {

        ff_h264_unref_picture(&h->last_pic_for_ec);

        ff_h264_ref_picture(&h->last_pic_for_ec, h->short_ref[0]);

    }

    for (int 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;

    memset(h->default_ref, 0, sizeof(h->default_ref));

}

static void generate_sliding_window_mmcos(H264Context *h)

{

    MMCO *mmco = h->mmco;

    int nb_mmco = 0;

    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;

        nb_mmco               = 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;

            nb_mmco                = 2;

        }

    }

    h->nb_mmco = nb_mmco;

}

int ff_h264_execute_ref_pic_marking(H264Context *h)

{

    MMCO *mmco = h->mmco;

    int mmco_count;

    int pps_ref_count[2] = {0};

    int current_ref_assigned = 0, err = 0;

    if (!h->ps.sps) {

        av_log(h->avctx, AV_LOG_ERROR, "SPS is unset\n");

        err = AVERROR_INVALIDDATA;

        goto out;

    }

    if (!h->explicit_ref_marking)

        generate_sliding_window_mmcos(h);

    mmco_count = h->nb_mmco;

    if ((h->avctx->debug & FF_DEBUG_MMCO) && mmco_count == 0)

        av_log(h->avctx, AV_LOG_DEBUG, "no mmco here\n");

    for (int i = 0; i < mmco_count; i++) {

        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);

        switch (mmco[i].opcode) {

        case MMCO_SHORT2UNUSED:

        case MMCO_SHORT2LONG: {

            int structure, j;

            int frame_num = pic_num_extract(h, mmco[i].short_pic_num, &structure);

            H264Picture *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, h->short_ref_count ? AV_LOG_ERROR : AV_LOG_DEBUG, "mmco: unref short failure\n");

                    err = AVERROR_INVALIDDATA;

                }

                continue;

            }

            if (mmco[i].opcode == 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);

            } else {

                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: {

            int structure, j = pic_num_extract(h, mmco[i].long_arg, &structure);

            H264Picture *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 interesting 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) {

                av_log(h->avctx, AV_LOG_ERROR, "mmco: cannot assign current picture to short and long at the same time\n");

                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 (int j = 0; j < FF_ARRAY_ELEMS(h->long_ref); j++) {

                    if (h->long_ref[j] == h->cur_pic_ptr) {

                        if (j != mmco[i].long_arg)

                            av_log(h->avctx, AV_LOG_ERROR, "mmco: cannot assign current picture to 2 long term references\n");

                        remove_long(h, j, 0);

                    }

                }

            }

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

                av_assert0(!h->cur_pic_ptr->long_ref);

                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 (int 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 (int 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;

            for (int j = 0; j < FF_ARRAY_ELEMS(h->last_pocs); j++)

                h->last_pocs[j] = INT_MIN;

            break;

        default: av_assert0(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 |= h->picture_structure;

        } 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 {

            H264Picture *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 > FFMAX(h->ps.sps->ref_frame_count, 1)) {

        /* 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) {

            int i;

            for (i = 0; i < 16; ++i)

                if (h->long_ref[i])

                    break;

            assert(i < 16);

            remove_long(h, i, 0);

        } else {

            H264Picture *pic = h->short_ref[h->short_ref_count - 1];

            remove_short(h, pic->frame_num, 0);

        }

    }

    for (int i = 0; i < h->short_ref_count; i++) {

        H264Picture *pic = h->short_ref[i];

        if (pic->invalid_gap) {

            int d = av_zero_extend(h->cur_pic_ptr->frame_num - pic->frame_num, h->ps.sps->log2_max_frame_num);

            if (d > h->ps.sps->ref_frame_count)

                remove_short(h, pic->frame_num, 0);

        }

    }

    print_short_term(h);

    print_long_term(h);

    for (int i = 0; i < FF_ARRAY_ELEMS(h->ps.pps_list); i++) {

        if (h->ps.pps_list[i]) {

            const PPS *pps = h->ps.pps_list[i];

            pps_ref_count[0] = FFMAX(pps_ref_count[0], pps->ref_count[0]);

            pps_ref_count[1] = FFMAX(pps_ref_count[1], pps->ref_count[1]);

        }

    }

    // Detect unmarked random access points

    if (   err >= 0

        && h->long_ref_count==0

        && (   h->short_ref_count<=2

            || pps_ref_count[0] <= 2 && pps_ref_count[1] <= 1 && h->avctx->has_b_frames

            || pps_ref_count[0] <= 1 + (h->picture_structure != PICT_FRAME) && pps_ref_count[1] <= 1)

        && pps_ref_count[0]<=2 + (h->picture_structure != PICT_FRAME) + (2*!h->has_recovery_point)

        && h->cur_pic_ptr->f->pict_type == AV_PICTURE_TYPE_I){

        h->cur_pic_ptr->recovered |= FRAME_RECOVERED_HEURISTIC;

        if(!h->avctx->has_b_frames)

            h->frame_recovered |= FRAME_RECOVERED_HEURISTIC;

    }

out:

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

}

int ff_h264_decode_ref_pic_marking(H264SliceContext *sl, GetBitContext *gb,

                                   const H2645NAL *nal, void *logctx)

{

    MMCO *mmco = sl->mmco;

    int nb_mmco = 0;

    if (nal->type == H264_NAL_IDR_SLICE) { // FIXME fields

        skip_bits1(gb); // broken_link

        if (get_bits1(gb)) {

            mmco[0].opcode   = MMCO_LONG;

            mmco[0].long_arg = 0;

            nb_mmco          = 1;

        }

        sl->explicit_ref_marking = 1;

    } else {

        sl->explicit_ref_marking = get_bits1(gb);

        if (sl->explicit_ref_marking) {

            int i;

            for (i = 0; i < FF_ARRAY_ELEMS(sl->mmco); i++) {

                MMCOOpcode opcode = get_ue_golomb_31(gb);

                mmco[i].opcode = opcode;

                if (opcode == MMCO_SHORT2UNUSED || opcode == MMCO_SHORT2LONG) {

                    mmco[i].short_pic_num =

                        (sl->curr_pic_num - get_ue_golomb_long(gb) - 1) &

                            (sl->max_pic_num - 1);

                }

                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(sl)))) {

                        av_log(logctx, AV_LOG_ERROR,

                               "illegal long ref in memory management control "

                               "operation %d\n", opcode);

                        sl->nb_mmco = i;

                        return -1;

                    }

                    mmco[i].long_arg = long_arg;

                }

                if (opcode > (unsigned) MMCO_LONG) {

                    av_log(logctx, AV_LOG_ERROR,

                           "illegal memory management control operation %d\n",

                           opcode);

                    sl->nb_mmco = i;

                    return -1;

                }

                if (opcode == MMCO_END)

                    break;

            }

            nb_mmco = i;

        }

    }

    sl->nb_mmco = nb_mmco;

    return 0;

}