FFmpeg/libavcodec/mpeg12dec.c

/*
 * MPEG-1/2 decoder
 * Copyright (c) 2000, 2001 Fabrice Bellard
 * Copyright (c) 2002-2004 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
 * MPEG-1/2 decoder
 */

#include <inttypes.h>

#include "libavutil/attributes.h"
#include "libavutil/internal.h"
#include "libavutil/stereo3d.h"

#include "avcodec.h"
#include "bytestream.h"
#include "error_resilience.h"
#include "idctdsp.h"
#include "internal.h"
#include "mpeg_er.h"
#include "mpeg12.h"
#include "mpeg12data.h"
#include "mpegutils.h"
#include "mpegvideo.h"
#include "mpegvideodata.h"
#include "profiles.h"
#include "thread.h"
#include "version.h"
#include "xvmc_internal.h"

typedef struct Mpeg1Context {
    MpegEncContext mpeg_enc_ctx;
    int mpeg_enc_ctx_allocated; /* true if decoding context allocated */
    int repeat_field;           /* true if we must repeat the field */
    AVPanScan pan_scan;         /* some temporary storage for the panscan */
    AVStereo3D stereo3d;
    int has_stereo3d;
    uint8_t *a53_caption;
    int a53_caption_size;
    uint8_t afd;
    int has_afd;
    int slice_count;
    int save_aspect_info;
    int save_width, save_height, save_progressive_seq;
    AVRational frame_rate_ext;  /* MPEG-2 specific framerate modificator */
    int sync;                   /* Did we reach a sync point like a GOP/SEQ/KEYFrame? */
    int closed_gop;             /* GOP is closed */
    int first_slice;
    int extradata_decoded;
} Mpeg1Context;

#define MB_TYPE_ZERO_MV   0x20000000

static const uint32_t ptype2mb_type[7] = {
                    MB_TYPE_INTRA,
                    MB_TYPE_L0 | MB_TYPE_CBP | MB_TYPE_ZERO_MV | MB_TYPE_16x16,
                    MB_TYPE_L0,
                    MB_TYPE_L0 | MB_TYPE_CBP,
    MB_TYPE_QUANT | MB_TYPE_INTRA,
    MB_TYPE_QUANT | MB_TYPE_L0 | MB_TYPE_CBP | MB_TYPE_ZERO_MV | MB_TYPE_16x16,
    MB_TYPE_QUANT | MB_TYPE_L0 | MB_TYPE_CBP,
};

static const uint32_t btype2mb_type[11] = {
                    MB_TYPE_INTRA,
                    MB_TYPE_L1,
                    MB_TYPE_L1   | MB_TYPE_CBP,
                    MB_TYPE_L0,
                    MB_TYPE_L0   | MB_TYPE_CBP,
                    MB_TYPE_L0L1,
                    MB_TYPE_L0L1 | MB_TYPE_CBP,
    MB_TYPE_QUANT | MB_TYPE_INTRA,
    MB_TYPE_QUANT | MB_TYPE_L1   | MB_TYPE_CBP,
    MB_TYPE_QUANT | MB_TYPE_L0   | MB_TYPE_CBP,
    MB_TYPE_QUANT | MB_TYPE_L0L1 | MB_TYPE_CBP,
};

static const uint8_t non_linear_qscale[32] = {
     0,  1,  2,  3,  4,  5,   6,   7,
     8, 10, 12, 14, 16, 18,  20,  22,
    24, 28, 32, 36, 40, 44,  48,  52,
    56, 64, 72, 80, 88, 96, 104, 112,
};

/* as H.263, but only 17 codes */
static int mpeg_decode_motion(MpegEncContext *s, int fcode, int pred)
{
    int code, sign, val, shift;

    code = get_vlc2(&s->gb, ff_mv_vlc.table, MV_VLC_BITS, 2);
    if (code == 0)
        return pred;
    if (code < 0)
        return 0xffff;

    sign  = get_bits1(&s->gb);
    shift = fcode - 1;
    val   = code;
    if (shift) {
        val  = (val - 1) << shift;
        val |= get_bits(&s->gb, shift);
        val++;
    }
    if (sign)
        val = -val;
    val += pred;

    /* modulo decoding */
    return sign_extend(val, 5 + shift);
}

#define MAX_INDEX (64 - 1)
#define check_scantable_index(ctx, x)                                         \
    do {                                                                      \
        if ((x) > MAX_INDEX) {                                                \
            av_log(ctx->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n",     \
                   ctx->mb_x, ctx->mb_y);                                     \
            return AVERROR_INVALIDDATA;                                       \
        }                                                                     \
    } while (0)

static inline int mpeg1_decode_block_inter(MpegEncContext *s,
                                           int16_t *block, int n)
{
    int level, i, j, run;
    RLTable *rl                  = &ff_rl_mpeg1;
    uint8_t *const scantable     = s->intra_scantable.permutated;
    const uint16_t *quant_matrix = s->inter_matrix;
    const int qscale             = s->qscale;

    {
        OPEN_READER(re, &s->gb);
        i = -1;
        // special case for first coefficient, no need to add second VLC table
        UPDATE_CACHE(re, &s->gb);
        if (((int32_t) GET_CACHE(re, &s->gb)) < 0) {
            level = (3 * qscale * quant_matrix[0]) >> 5;
            level = (level - 1) | 1;
            if (GET_CACHE(re, &s->gb) & 0x40000000)
                level = -level;
            block[0] = level;
            i++;
            SKIP_BITS(re, &s->gb, 2);
            if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
                goto end;
        }
        /* now quantify & encode AC coefficients */
        for (;;) {
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0],
                       TEX_VLC_BITS, 2, 0);

            if (level != 0) {
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                level = (level - 1) | 1;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) -
                        SHOW_SBITS(re, &s->gb, 1);
                SKIP_BITS(re, &s->gb, 1);
            } else {
                /* escape */
                run = SHOW_UBITS(re, &s->gb, 6) + 1;
                LAST_SKIP_BITS(re, &s->gb, 6);
                UPDATE_CACHE(re, &s->gb);
                level = SHOW_SBITS(re, &s->gb, 8);
                SKIP_BITS(re, &s->gb, 8);
                if (level == -128) {
                    level = SHOW_UBITS(re, &s->gb, 8) - 256;
                    SKIP_BITS(re, &s->gb, 8);
                } else if (level == 0) {
                    level = SHOW_UBITS(re, &s->gb, 8);
                    SKIP_BITS(re, &s->gb, 8);
                }
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                if (level < 0) {
                    level = -level;
                    level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                    level = (level - 1) | 1;
                    level = -level;
                } else {
                    level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                    level = (level - 1) | 1;
                }
            }

            block[j] = level;
            if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
                break;
            UPDATE_CACHE(re, &s->gb);
        }
end:
        LAST_SKIP_BITS(re, &s->gb, 2);
        CLOSE_READER(re, &s->gb);
    }

    check_scantable_index(s, i);

    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s,
                                                int16_t *block, int n)
{
    int level, i, j, run;
    RLTable *rl              = &ff_rl_mpeg1;
    uint8_t *const scantable = s->intra_scantable.permutated;
    const int qscale         = s->qscale;

    {
        OPEN_READER(re, &s->gb);
        i = -1;
        // Special case for first coefficient, no need to add second VLC table.
        UPDATE_CACHE(re, &s->gb);
        if (((int32_t) GET_CACHE(re, &s->gb)) < 0) {
            level = (3 * qscale) >> 1;
            level = (level - 1) | 1;
            if (GET_CACHE(re, &s->gb) & 0x40000000)
                level = -level;
            block[0] = level;
            i++;
            SKIP_BITS(re, &s->gb, 2);
            if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
                goto end;
        }

        /* now quantify & encode AC coefficients */
        for (;;) {
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0],
                       TEX_VLC_BITS, 2, 0);

            if (level != 0) {
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                level = ((level * 2 + 1) * qscale) >> 1;
                level = (level - 1) | 1;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) -
                        SHOW_SBITS(re, &s->gb, 1);
                SKIP_BITS(re, &s->gb, 1);
            } else {
                /* escape */
                run = SHOW_UBITS(re, &s->gb, 6) + 1;
                LAST_SKIP_BITS(re, &s->gb, 6);
                UPDATE_CACHE(re, &s->gb);
                level = SHOW_SBITS(re, &s->gb, 8);
                SKIP_BITS(re, &s->gb, 8);
                if (level == -128) {
                    level = SHOW_UBITS(re, &s->gb, 8) - 256;
                    SKIP_BITS(re, &s->gb, 8);
                } else if (level == 0) {
                    level = SHOW_UBITS(re, &s->gb, 8);
                    SKIP_BITS(re, &s->gb, 8);
                }
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                if (level < 0) {
                    level = -level;
                    level = ((level * 2 + 1) * qscale) >> 1;
                    level = (level - 1) | 1;
                    level = -level;
                } else {
                    level = ((level * 2 + 1) * qscale) >> 1;
                    level = (level - 1) | 1;
                }
            }

            block[j] = level;
            if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
                break;
            UPDATE_CACHE(re, &s->gb);
        }
end:
        LAST_SKIP_BITS(re, &s->gb, 2);
        CLOSE_READER(re, &s->gb);
    }

    check_scantable_index(s, i);

    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg2_decode_block_non_intra(MpegEncContext *s,
                                               int16_t *block, int n)
{
    int level, i, j, run;
    RLTable *rl = &ff_rl_mpeg1;
    uint8_t *const scantable = s->intra_scantable.permutated;
    const uint16_t *quant_matrix;
    const int qscale = s->qscale;
    int mismatch;

    mismatch = 1;

    {
        OPEN_READER(re, &s->gb);
        i = -1;
        if (n < 4)
            quant_matrix = s->inter_matrix;
        else
            quant_matrix = s->chroma_inter_matrix;

        // Special case for first coefficient, no need to add second VLC table.
        UPDATE_CACHE(re, &s->gb);
        if (((int32_t) GET_CACHE(re, &s->gb)) < 0) {
            level = (3 * qscale * quant_matrix[0]) >> 5;
            if (GET_CACHE(re, &s->gb) & 0x40000000)
                level = -level;
            block[0]  = level;
            mismatch ^= level;
            i++;
            SKIP_BITS(re, &s->gb, 2);
            if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
                goto end;
        }

        /* now quantify & encode AC coefficients */
        for (;;) {
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0],
                       TEX_VLC_BITS, 2, 0);

            if (level != 0) {
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) -
                        SHOW_SBITS(re, &s->gb, 1);
                SKIP_BITS(re, &s->gb, 1);
            } else {
                /* escape */
                run = SHOW_UBITS(re, &s->gb, 6) + 1;
                LAST_SKIP_BITS(re, &s->gb, 6);
                UPDATE_CACHE(re, &s->gb);
                level = SHOW_SBITS(re, &s->gb, 12);
                SKIP_BITS(re, &s->gb, 12);

                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                if (level < 0) {
                    level = ((-level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                    level = -level;
                } else {
                    level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                }
            }

            mismatch ^= level;
            block[j]  = level;
            if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
                break;
            UPDATE_CACHE(re, &s->gb);
        }
end:
        LAST_SKIP_BITS(re, &s->gb, 2);
        CLOSE_READER(re, &s->gb);
    }
    block[63] ^= (mismatch & 1);

    check_scantable_index(s, i);

    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
                                                    int16_t *block, int n)
{
    int level, i, j, run;
    RLTable *rl              = &ff_rl_mpeg1;
    uint8_t *const scantable = s->intra_scantable.permutated;
    const int qscale         = s->qscale;
    OPEN_READER(re, &s->gb);
    i = -1;

    // special case for first coefficient, no need to add second VLC table
    UPDATE_CACHE(re, &s->gb);
    if (((int32_t) GET_CACHE(re, &s->gb)) < 0) {
        level = (3 * qscale) >> 1;
        if (GET_CACHE(re, &s->gb) & 0x40000000)
            level = -level;
        block[0] = level;
        i++;
        SKIP_BITS(re, &s->gb, 2);
        if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
            goto end;
    }

    /* now quantify & encode AC coefficients */
    for (;;) {
        GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);

        if (level != 0) {
            i += run;
            if (i > MAX_INDEX)
                break;
            j = scantable[i];
            level = ((level * 2 + 1) * qscale) >> 1;
            level = (level ^ SHOW_SBITS(re, &s->gb, 1)) -
                    SHOW_SBITS(re, &s->gb, 1);
            SKIP_BITS(re, &s->gb, 1);
        } else {
            /* escape */
            run = SHOW_UBITS(re, &s->gb, 6) + 1;
            LAST_SKIP_BITS(re, &s->gb, 6);
            UPDATE_CACHE(re, &s->gb);
            level = SHOW_SBITS(re, &s->gb, 12);
            SKIP_BITS(re, &s->gb, 12);

            i += run;
            if (i > MAX_INDEX)
                break;
            j = scantable[i];
            if (level < 0) {
                level = ((-level * 2 + 1) * qscale) >> 1;
                level = -level;
            } else {
                level = ((level * 2 + 1) * qscale) >> 1;
            }
        }

        block[j] = level;
        if (((int32_t) GET_CACHE(re, &s->gb)) <= (int32_t) 0xBFFFFFFF)
            break;
        UPDATE_CACHE(re, &s->gb);
    }
end:
    LAST_SKIP_BITS(re, &s->gb, 2);
    CLOSE_READER(re, &s->gb);

    check_scantable_index(s, i);

    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg2_decode_block_intra(MpegEncContext *s,
                                           int16_t *block, int n)
{
    int level, dc, diff, i, j, run;
    int component;
    RLTable *rl;
    uint8_t *const scantable = s->intra_scantable.permutated;
    const uint16_t *quant_matrix;
    const int qscale = s->qscale;
    int mismatch;

    /* DC coefficient */
    if (n < 4) {
        quant_matrix = s->intra_matrix;
        component    = 0;
    } else {
        quant_matrix = s->chroma_intra_matrix;
        component    = (n & 1) + 1;
    }
    diff = decode_dc(&s->gb, component);
    if (diff >= 0xffff)
        return AVERROR_INVALIDDATA;
    dc  = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc << (3 - s->intra_dc_precision);
    ff_dlog(s->avctx, "dc=%d\n", block[0]);
    mismatch = block[0] ^ 1;
    i = 0;
    if (s->intra_vlc_format)
        rl = &ff_rl_mpeg2;
    else
        rl = &ff_rl_mpeg1;

    {
        OPEN_READER(re, &s->gb);
        /* now quantify & encode AC coefficients */
        for (;;) {
            UPDATE_CACHE(re, &s->gb);
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0],
                       TEX_VLC_BITS, 2, 0);

            if (level == 127) {
                break;
            } else if (level != 0) {
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                level = (level * qscale * quant_matrix[j]) >> 4;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) -
                        SHOW_SBITS(re, &s->gb, 1);
                LAST_SKIP_BITS(re, &s->gb, 1);
            } else {
                /* escape */
                run = SHOW_UBITS(re, &s->gb, 6) + 1;
                LAST_SKIP_BITS(re, &s->gb, 6);
                UPDATE_CACHE(re, &s->gb);
                level = SHOW_SBITS(re, &s->gb, 12);
                SKIP_BITS(re, &s->gb, 12);
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                if (level < 0) {
                    level = (-level * qscale * quant_matrix[j]) >> 4;
                    level = -level;
                } else {
                    level = (level * qscale * quant_matrix[j]) >> 4;
                }
            }

            mismatch ^= level;
            block[j]  = level;
        }
        CLOSE_READER(re, &s->gb);
    }
    block[63] ^= mismatch & 1;

    check_scantable_index(s, i);

    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s,
                                                int16_t *block, int n)
{
    int level, dc, diff, i, j, run;
    int component;
    RLTable *rl;
    uint8_t *const scantable = s->intra_scantable.permutated;
    const uint16_t *quant_matrix;
    const int qscale = s->qscale;

    /* DC coefficient */
    if (n < 4) {
        quant_matrix = s->intra_matrix;
        component    = 0;
    } else {
        quant_matrix = s->chroma_intra_matrix;
        component    = (n & 1) + 1;
    }
    diff = decode_dc(&s->gb, component);
    if (diff >= 0xffff)
        return AVERROR_INVALIDDATA;
    dc = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc << (3 - s->intra_dc_precision);
    i = 0;
    if (s->intra_vlc_format)
        rl = &ff_rl_mpeg2;
    else
        rl = &ff_rl_mpeg1;

    {
        OPEN_READER(re, &s->gb);
        /* now quantify & encode AC coefficients */
        for (;;) {
            UPDATE_CACHE(re, &s->gb);
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0],
                       TEX_VLC_BITS, 2, 0);

            if (level == 127) {
                break;
            } else if (level != 0) {
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                level = (level * qscale * quant_matrix[j]) >> 4;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) -
                        SHOW_SBITS(re, &s->gb, 1);
                LAST_SKIP_BITS(re, &s->gb, 1);
            } else {
                /* escape */
                run = SHOW_UBITS(re, &s->gb, 6) + 1;
                LAST_SKIP_BITS(re, &s->gb, 6);
                UPDATE_CACHE(re, &s->gb);
                level = SHOW_SBITS(re, &s->gb, 12);
                SKIP_BITS(re, &s->gb, 12);
                i += run;
                if (i > MAX_INDEX)
                    break;
                j = scantable[i];
                if (level < 0) {
                    level = (-level * qscale * quant_matrix[j]) >> 4;
                    level = -level;
                } else {
                    level = (level * qscale * quant_matrix[j]) >> 4;
                }
            }

            block[j] = level;
        }
        CLOSE_READER(re, &s->gb);
    }

    check_scantable_index(s, i);

    s->block_last_index[n] = i;
    return 0;
}

/******************************************/
/* decoding */

static inline int get_dmv(MpegEncContext *s)
{
    if (get_bits1(&s->gb))
        return 1 - (get_bits1(&s->gb) << 1);
    else
        return 0;
}

static inline int get_qscale(MpegEncContext *s)
{
    int qscale = get_bits(&s->gb, 5);
    if (s->q_scale_type)
        return non_linear_qscale[qscale];
    else
        return qscale << 1;
}

/* motion type (for MPEG-2) */
#define MT_FIELD 1
#define MT_FRAME 2
#define MT_16X8  2
#define MT_DMV   3

static int mpeg_decode_mb(MpegEncContext *s, int16_t block[12][64])
{
    int i, j, k, cbp, val, mb_type, motion_type;
    const int mb_block_count = 4 + (1 << s->chroma_format);
    int ret;

    ff_dlog(s->avctx, "decode_mb: x=%d y=%d\n", s->mb_x, s->mb_y);

    assert(s->mb_skipped == 0);

    if (s->mb_skip_run-- != 0) {
        if (s->pict_type == AV_PICTURE_TYPE_P) {
            s->mb_skipped = 1;
            s->current_picture.mb_type[s->mb_x + s->mb_y * s->mb_stride] =
                MB_TYPE_SKIP | MB_TYPE_L0 | MB_TYPE_16x16;
        } else {
            int mb_type;

            if (s->mb_x)
                mb_type = s->current_picture.mb_type[s->mb_x + s->mb_y * s->mb_stride - 1];
            else
                // FIXME not sure if this is allowed in MPEG at all
                mb_type = s->current_picture.mb_type[s->mb_width + (s->mb_y - 1) * s->mb_stride - 1];
            if (IS_INTRA(mb_type))
                return AVERROR_INVALIDDATA;
            s->current_picture.mb_type[s->mb_x + s->mb_y * s->mb_stride] =
                mb_type | MB_TYPE_SKIP;
//            assert(s->current_picture.mb_type[s->mb_x + s->mb_y * s->mb_stride - 1] & (MB_TYPE_16x16 | MB_TYPE_16x8));

            if ((s->mv[0][0][0] | s->mv[0][0][1] | s->mv[1][0][0] | s->mv[1][0][1]) == 0)
                s->mb_skipped = 1;
        }

        return 0;
    }

    switch (s->pict_type) {
    default:
    case AV_PICTURE_TYPE_I:
        if (get_bits1(&s->gb) == 0) {
            if (get_bits1(&s->gb) == 0) {
                av_log(s->avctx, AV_LOG_ERROR,
                       "Invalid mb type in I-frame at %d %d\n",
                       s->mb_x, s->mb_y);
                return AVERROR_INVALIDDATA;
            }
            mb_type = MB_TYPE_QUANT | MB_TYPE_INTRA;
        } else {
            mb_type = MB_TYPE_INTRA;
        }
        break;
    case AV_PICTURE_TYPE_P:
        mb_type = get_vlc2(&s->gb, ff_mb_ptype_vlc.table, MB_PTYPE_VLC_BITS, 1);
        if (mb_type < 0) {
            av_log(s->avctx, AV_LOG_ERROR,
                   "Invalid mb type in P-frame at %d %d\n", s->mb_x, s->mb_y);
            return AVERROR_INVALIDDATA;
        }
        mb_type = ptype2mb_type[mb_type];
        break;
    case AV_PICTURE_TYPE_B:
        mb_type = get_vlc2(&s->gb, ff_mb_btype_vlc.table, MB_BTYPE_VLC_BITS, 1);
        if (mb_type < 0) {
            av_log(s->avctx, AV_LOG_ERROR,
                   "Invalid mb type in B-frame at %d %d\n", s->mb_x, s->mb_y);
            return AVERROR_INVALIDDATA;
        }
        mb_type = btype2mb_type[mb_type];
        break;
    }
    ff_dlog(s->avctx, "mb_type=%x\n", mb_type);
//    motion_type = 0; /* avoid warning */
    if (IS_INTRA(mb_type)) {
        s->bdsp.clear_blocks(s->block[0]);

        if (!s->chroma_y_shift)
            s->bdsp.clear_blocks(s->block[6]);

        /* compute DCT type */
        // FIXME: add an interlaced_dct coded var?
        if (s->picture_structure == PICT_FRAME &&
            !s->frame_pred_frame_dct)
            s->interlaced_dct = get_bits1(&s->gb);

        if (IS_QUANT(mb_type))
            s->qscale = get_qscale(s);

        if (s->concealment_motion_vectors) {
            /* just parse them */
            if (s->picture_structure != PICT_FRAME)
                skip_bits1(&s->gb);  /* field select */

            s->mv[0][0][0]      =
            s->last_mv[0][0][0] =
            s->last_mv[0][1][0] = mpeg_decode_motion(s, s->mpeg_f_code[0][0],
                                                     s->last_mv[0][0][0]);
            s->mv[0][0][1]      =
            s->last_mv[0][0][1] =
            s->last_mv[0][1][1] = mpeg_decode_motion(s, s->mpeg_f_code[0][1],
                                                     s->last_mv[0][0][1]);

            skip_bits1(&s->gb); /* marker */
        } else {
            /* reset mv prediction */
            memset(s->last_mv, 0, sizeof(s->last_mv));
        }
        s->mb_intra = 1;
#if FF_API_XVMC
FF_DISABLE_DEPRECATION_WARNINGS
        // if 1, we memcpy blocks in xvmcvideo
        if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration > 1)
            ff_xvmc_pack_pblocks(s, -1); // inter are always full blocks
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_XVMC */

        if (s->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
            if (s->avctx->flags2 & AV_CODEC_FLAG2_FAST) {
                for (i = 0; i < 6; i++)
                    mpeg2_fast_decode_block_intra(s, *s->pblocks[i], i);
            } else {
                for (i = 0; i < mb_block_count; i++)
                    if ((ret = mpeg2_decode_block_intra(s, *s->pblocks[i], i)) < 0)
                        return ret;
            }
        } else {
            for (i = 0; i < 6; i++) {
                ret = ff_mpeg1_decode_block_intra(&s->gb,
                                                  s->intra_matrix,
                                                  s->intra_scantable.permutated,
                                                  s->last_dc, *s->pblocks[i],
                                                  i, s->qscale);
                if (ret < 0) {
                    av_log(s->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n",
                           s->mb_x, s->mb_y);
                    return ret;
                }

                s->block_last_index[i] = ret;
            }
        }
    } else {
        if (mb_type & MB_TYPE_ZERO_MV) {
            assert(mb_type & MB_TYPE_CBP);

            s->mv_dir = MV_DIR_FORWARD;
            if (s->picture_structure == PICT_FRAME) {
                if (!s->frame_pred_frame_dct)
                    s->interlaced_dct = get_bits1(&s->gb);
                s->mv_type = MV_TYPE_16X16;
            } else {
                s->mv_type            = MV_TYPE_FIELD;
                mb_type              |= MB_TYPE_INTERLACED;
                s->field_select[0][0] = s->picture_structure - 1;
            }

            if (IS_QUANT(mb_type))
                s->qscale = get_qscale(s);

            s->last_mv[0][0][0] = 0;
            s->last_mv[0][0][1] = 0;
            s->last_mv[0][1][0] = 0;
            s->last_mv[0][1][1] = 0;
            s->mv[0][0][0]      = 0;
            s->mv[0][0][1]      = 0;
        } else {
            assert(mb_type & MB_TYPE_L0L1);
            // FIXME decide if MBs in field pictures are MB_TYPE_INTERLACED
            /* get additional motion vector type */
            if (s->frame_pred_frame_dct) {
                motion_type = MT_FRAME;
            } else {
                motion_type = get_bits(&s->gb, 2);
                if (s->picture_structure == PICT_FRAME && HAS_CBP(mb_type))
                    s->interlaced_dct = get_bits1(&s->gb);
            }

            if (IS_QUANT(mb_type))
                s->qscale = get_qscale(s);

            /* motion vectors */
            s->mv_dir = (mb_type >> 13) & 3;
            ff_dlog(s->avctx, "motion_type=%d\n", motion_type);
            switch (motion_type) {
            case MT_FRAME: /* or MT_16X8 */
                if (s->picture_structure == PICT_FRAME) {
                    mb_type   |= MB_TYPE_16x16;
                    s->mv_type = MV_TYPE_16X16;
                    for (i = 0; i < 2; i++) {
                        if (USES_LIST(mb_type, i)) {
                            /* MT_FRAME */
                            s->mv[i][0][0]      =
                            s->last_mv[i][0][0] =
                            s->last_mv[i][1][0] =
                                mpeg_decode_motion(s, s->mpeg_f_code[i][0],
                                                   s->last_mv[i][0][0]);
                            s->mv[i][0][1]      =
                            s->last_mv[i][0][1] =
                            s->last_mv[i][1][1] =
                                mpeg_decode_motion(s, s->mpeg_f_code[i][1],
                                                   s->last_mv[i][0][1]);
                            /* full_pel: only for MPEG-1 */
                            if (s->full_pel[i]) {
                                s->mv[i][0][0] <<= 1;
                                s->mv[i][0][1] <<= 1;
                            }
                        }
                    }
                } else {
                    mb_type   |= MB_TYPE_16x8 | MB_TYPE_INTERLACED;
                    s->mv_type = MV_TYPE_16X8;
                    for (i = 0; i < 2; i++) {
                        if (USES_LIST(mb_type, i)) {
                            /* MT_16X8 */
                            for (j = 0; j < 2; j++) {
                                s->field_select[i][j] = get_bits1(&s->gb);
                                for (k = 0; k < 2; k++) {
                                    val = mpeg_decode_motion(s, s->mpeg_f_code[i][k],
                                                             s->last_mv[i][j][k]);
                                    s->last_mv[i][j][k] = val;
                                    s->mv[i][j][k]      = val;
                                }
                            }
                        }
                    }
                }
                break;
            case MT_FIELD:
                s->mv_type = MV_TYPE_FIELD;
                if (s->picture_structure == PICT_FRAME) {
                    mb_type |= MB_TYPE_16x8 | MB_TYPE_INTERLACED;
                    for (i = 0; i < 2; i++) {
                        if (USES_LIST(mb_type, i)) {
                            for (j = 0; j < 2; j++) {
                                s->field_select[i][j] = get_bits1(&s->gb);
                                val = mpeg_decode_motion(s, s->mpeg_f_code[i][0],
                                                         s->last_mv[i][j][0]);
                                s->last_mv[i][j][0] = val;
                                s->mv[i][j][0]      = val;
                                ff_dlog(s->avctx, "fmx=%d\n", val);
                                val = mpeg_decode_motion(s, s->mpeg_f_code[i][1],
                                                         s->last_mv[i][j][1] >> 1);
                                s->last_mv[i][j][1] = val << 1;
                                s->mv[i][j][1]      = val;
                                ff_dlog(s->avctx, "fmy=%d\n", val);
                            }
                        }
                    }
                } else {
                    mb_type |= MB_TYPE_16x16 | MB_TYPE_INTERLACED;
                    for (i = 0; i < 2; i++) {
                        if (USES_LIST(mb_type, i)) {
                            s->field_select[i][0] = get_bits1(&s->gb);
                            for (k = 0; k < 2; k++) {
                                val = mpeg_decode_motion(s, s->mpeg_f_code[i][k],
                                                         s->last_mv[i][0][k]);
                                s->last_mv[i][0][k] = val;
                                s->last_mv[i][1][k] = val;
                                s->mv[i][0][k]      = val;
                            }
                        }
                    }
                }
                break;
            case MT_DMV:
                s->mv_type = MV_TYPE_DMV;
                for (i = 0; i < 2; i++) {
                    if (USES_LIST(mb_type, i)) {
                        int dmx, dmy, mx, my, m;
                        const int my_shift = s->picture_structure == PICT_FRAME;

                        mx = mpeg_decode_motion(s, s->mpeg_f_code[i][0],
                                                s->last_mv[i][0][0]);
                        s->last_mv[i][0][0] = mx;
                        s->last_mv[i][1][0] = mx;
                        dmx = get_dmv(s);
                        my  = mpeg_decode_motion(s, s->mpeg_f_code[i][1],
                                                 s->last_mv[i][0][1] >> my_shift);
                        dmy = get_dmv(s);


                        s->last_mv[i][0][1] = my << my_shift;
                        s->last_mv[i][1][1] = my << my_shift;

                        s->mv[i][0][0] = mx;
                        s->mv[i][0][1] = my;
                        s->mv[i][1][0] = mx; // not used
                        s->mv[i][1][1] = my; // not used

                        if (s->picture_structure == PICT_FRAME) {
                            mb_type |= MB_TYPE_16x16 | MB_TYPE_INTERLACED;

                            // m = 1 + 2 * s->top_field_first;
                            m = s->top_field_first ? 1 : 3;

                            /* top -> top pred */
                            s->mv[i][2][0] = ((mx * m + (mx > 0)) >> 1) + dmx;
                            s->mv[i][2][1] = ((my * m + (my > 0)) >> 1) + dmy - 1;
                            m = 4 - m;
                            s->mv[i][3][0] = ((mx * m + (mx > 0)) >> 1) + dmx;
                            s->mv[i][3][1] = ((my * m + (my > 0)) >> 1) + dmy + 1;
                        } else {
                            mb_type |= MB_TYPE_16x16;

                            s->mv[i][2][0] = ((mx + (mx > 0)) >> 1) + dmx;
                            s->mv[i][2][1] = ((my + (my > 0)) >> 1) + dmy;
                            if (s->picture_structure == PICT_TOP_FIELD)
                                s->mv[i][2][1]--;
                            else
                                s->mv[i][2][1]++;
                        }
                    }
                }
                break;
            default:
                av_log(s->avctx, AV_LOG_ERROR,
                       "00 motion_type at %d %d\n", s->mb_x, s->mb_y);
                return AVERROR_INVALIDDATA;
            }
        }

        s->mb_intra = 0;
        if (HAS_CBP(mb_type)) {
            s->bdsp.clear_blocks(s->block[0]);

            cbp = get_vlc2(&s->gb, ff_mb_pat_vlc.table, MB_PAT_VLC_BITS, 1);
            if (mb_block_count > 6) {
                cbp <<= mb_block_count - 6;
                cbp  |= get_bits(&s->gb, mb_block_count - 6);
                s->bdsp.clear_blocks(s->block[6]);
            }
            if (cbp <= 0) {
                av_log(s->avctx, AV_LOG_ERROR,
                       "invalid cbp at %d %d\n", s->mb_x, s->mb_y);
                return AVERROR_INVALIDDATA;
            }

#if FF_API_XVMC
FF_DISABLE_DEPRECATION_WARNINGS
            // if 1, we memcpy blocks in xvmcvideo
            if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration > 1)
                ff_xvmc_pack_pblocks(s, cbp);
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_XVMC */

            if (s->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
                if (s->avctx->flags2 & AV_CODEC_FLAG2_FAST) {
                    for (i = 0; i < 6; i++) {
                        if (cbp & 32)
                            mpeg2_fast_decode_block_non_intra(s, *s->pblocks[i], i);
                        else
                            s->block_last_index[i] = -1;
                        cbp += cbp;
                    }
                } else {
                    cbp <<= 12 - mb_block_count;

                    for (i = 0; i < mb_block_count; i++) {
                        if (cbp & (1 << 11)) {
                            if ((ret = mpeg2_decode_block_non_intra(s, *s->pblocks[i], i)) < 0)
                                return ret;
                        } else {
                            s->block_last_index[i] = -1;
                        }
                        cbp += cbp;
                    }
                }
            } else {
                if (s->avctx->flags2 & AV_CODEC_FLAG2_FAST) {
                    for (i = 0; i < 6; i++) {
                        if (cbp & 32)
                            mpeg1_fast_decode_block_inter(s, *s->pblocks[i], i);
                        else
                            s->block_last_index[i] = -1;
                        cbp += cbp;
                    }
                } else {
                    for (i = 0; i < 6; i++) {
                        if (cbp & 32) {
                            if ((ret = mpeg1_decode_block_inter(s, *s->pblocks[i], i)) < 0)
                                return ret;
                        } else {
                            s->block_last_index[i] = -1;
                        }
                        cbp += cbp;
                    }
                }
            }
        } else {
            for (i = 0; i < 12; i++)
                s->block_last_index[i] = -1;
        }
    }

    s->current_picture.mb_type[s->mb_x + s->mb_y * s->mb_stride] = mb_type;

    return 0;
}

static av_cold int mpeg_decode_init(AVCodecContext *avctx)
{
    Mpeg1Context *s    = avctx->priv_data;
    MpegEncContext *s2 = &s->mpeg_enc_ctx;

    ff_mpv_decode_defaults(s2);

    s->mpeg_enc_ctx.avctx  = avctx;

    /* we need some permutation to store matrices,
     * until the decoder sets the real permutation. */
    ff_mpv_idct_init(s2);
    ff_mpeg12_common_init(&s->mpeg_enc_ctx);
    ff_mpeg12_init_vlcs();

    s->mpeg_enc_ctx_allocated      = 0;
    s->mpeg_enc_ctx.picture_number = 0;
    s->repeat_field                = 0;
    s->mpeg_enc_ctx.codec_id       = avctx->codec->id;
    avctx->color_range             = AVCOL_RANGE_MPEG;
    if (avctx->codec->id == AV_CODEC_ID_MPEG1VIDEO)
        avctx->chroma_sample_location = AVCHROMA_LOC_CENTER;
    else
        avctx->chroma_sample_location = AVCHROMA_LOC_LEFT;
    return 0;
}

static int mpeg_decode_update_thread_context(AVCodecContext *avctx,
                                             const AVCodecContext *avctx_from)
{
    Mpeg1Context *ctx = avctx->priv_data, *ctx_from = avctx_from->priv_data;
    MpegEncContext *s = &ctx->mpeg_enc_ctx, *s1 = &ctx_from->mpeg_enc_ctx;
    int err;

    if (avctx == avctx_from               ||
        !ctx_from->mpeg_enc_ctx_allocated ||
        !s1->context_initialized)
        return 0;

    err = ff_mpeg_update_thread_context(avctx, avctx_from);
    if (err)
        return err;

    if (!ctx->mpeg_enc_ctx_allocated) {
        // copy the whole context after the initial MpegEncContext structure
        memcpy(ctx, ctx_from, sizeof(*ctx));
        memset(&ctx->mpeg_enc_ctx, 0, sizeof(ctx->mpeg_enc_ctx));
    }

    if (!(s->pict_type == AV_PICTURE_TYPE_B || s->low_delay))
        s->picture_number++;

    return 0;
}

static void quant_matrix_rebuild(uint16_t *matrix, const uint8_t *old_perm,
                                 const uint8_t *new_perm)
{
    uint16_t temp_matrix[64];
    int i;

    memcpy(temp_matrix, matrix, 64 * sizeof(uint16_t));

    for (i = 0; i < 64; i++)
        matrix[new_perm[i]] = temp_matrix[old_perm[i]];
}

#if FF_API_XVMC
static const enum AVPixelFormat pixfmt_xvmc_mpg2_420[] = {
    AV_PIX_FMT_XVMC_MPEG2_IDCT,
    AV_PIX_FMT_XVMC_MPEG2_MC,
    AV_PIX_FMT_NONE
};
#endif /* FF_API_XVMC */

static const enum AVPixelFormat mpeg12_hwaccel_pixfmt_list_420[] = {
#if CONFIG_MPEG2_DXVA2_HWACCEL
    AV_PIX_FMT_DXVA2_VLD,
#endif
#if CONFIG_MPEG2_D3D11VA_HWACCEL
    AV_PIX_FMT_D3D11VA_VLD,
#endif
#if CONFIG_MPEG2_VAAPI_HWACCEL
    AV_PIX_FMT_VAAPI,
#endif
#if CONFIG_MPEG1_VDPAU_HWACCEL | CONFIG_MPEG2_VDPAU_HWACCEL
    AV_PIX_FMT_VDPAU,
#endif
    AV_PIX_FMT_YUV420P,
    AV_PIX_FMT_NONE
};

static const enum AVPixelFormat mpeg12_pixfmt_list_422[] = {
    AV_PIX_FMT_YUV422P,
    AV_PIX_FMT_NONE
};

static const enum AVPixelFormat mpeg12_pixfmt_list_444[] = {
    AV_PIX_FMT_YUV444P,
    AV_PIX_FMT_NONE
};

static enum AVPixelFormat mpeg_get_pixelformat(AVCodecContext *avctx)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    const enum AVPixelFormat *pix_fmts;

#if FF_API_XVMC
FF_DISABLE_DEPRECATION_WARNINGS
    if (avctx->xvmc_acceleration)
        return ff_get_format(avctx, pixfmt_xvmc_mpg2_420);
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_XVMC */

    if (s->chroma_format < 2)
        pix_fmts = mpeg12_hwaccel_pixfmt_list_420;
    else if (s->chroma_format == 2)
        pix_fmts = mpeg12_pixfmt_list_422;
    else
        pix_fmts = mpeg12_pixfmt_list_444;

    return ff_get_format(avctx, pix_fmts);
}

/* Call this function when we know all parameters.
 * It may be called in different places for MPEG-1 and MPEG-2. */
static int mpeg_decode_postinit(AVCodecContext *avctx)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    uint8_t old_permutation[64];
    int ret;

    if ((s1->mpeg_enc_ctx_allocated == 0)                   ||
        avctx->coded_width       != s->width                ||
        avctx->coded_height      != s->height               ||
        s1->save_width           != s->width                ||
        s1->save_height          != s->height               ||
        s1->save_aspect_info     != s->aspect_ratio_info    ||
        s1->save_progressive_seq != s->progressive_sequence ||
        0) {
        if (s1->mpeg_enc_ctx_allocated) {
            ParseContext pc = s->parse_context;
            s->parse_context.buffer = 0;
            ff_mpv_common_end(s);
            s->parse_context = pc;
        }

        ret = ff_set_dimensions(avctx, s->width, s->height);
        if (ret < 0)
            return ret;

        avctx->bit_rate          = s->bit_rate;
        s1->save_aspect_info     = s->aspect_ratio_info;
        s1->save_width           = s->width;
        s1->save_height          = s->height;
        s1->save_progressive_seq = s->progressive_sequence;

        /* low_delay may be forced, in this case we will have B-frames
         * that behave like P-frames. */
        avctx->has_b_frames = !s->low_delay;

        if (avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
            // MPEG-1 fps
            avctx->framerate = ff_mpeg12_frame_rate_tab[s->frame_rate_index];
            // MPEG-1 aspect
            avctx->sample_aspect_ratio = av_d2q(1.0 / ff_mpeg1_aspect[s->aspect_ratio_info], 255);
            avctx->ticks_per_frame     = 1;
        } else { // MPEG-2
            // MPEG-2 fps
            av_reduce(&s->avctx->framerate.num,
                      &s->avctx->framerate.den,
                      ff_mpeg12_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num * 2,
                      ff_mpeg12_frame_rate_tab[s->frame_rate_index].den * s1->frame_rate_ext.den,
                      1 << 30);
            avctx->ticks_per_frame = 2;
            // MPEG-2 aspect
            if (s->aspect_ratio_info > 1) {
                AVRational dar =
                    av_mul_q(av_div_q(ff_mpeg2_aspect[s->aspect_ratio_info],
                                      (AVRational) { s1->pan_scan.width,
                                                     s1->pan_scan.height }),
                             (AVRational) { s->width, s->height });

                /* We ignore the spec here and guess a bit as reality does not
                 * match the spec, see for example res_change_ffmpeg_aspect.ts
                 * and sequence-display-aspect.mpg.
                 * issue1613, 621, 562 */
                if ((s1->pan_scan.width == 0) || (s1->pan_scan.height == 0) ||
                    (av_cmp_q(dar, (AVRational) { 4, 3 }) &&
                     av_cmp_q(dar, (AVRational) { 16, 9 }))) {
                    s->avctx->sample_aspect_ratio =
                        av_div_q(ff_mpeg2_aspect[s->aspect_ratio_info],
                                 (AVRational) { s->width, s->height });
                } else {
                    s->avctx->sample_aspect_ratio =
                        av_div_q(ff_mpeg2_aspect[s->aspect_ratio_info],
                                 (AVRational) { s1->pan_scan.width, s1->pan_scan.height });
// issue1613 4/3 16/9 -> 16/9
// res_change_ffmpeg_aspect.ts 4/3 225/44 ->4/3
// widescreen-issue562.mpg 4/3 16/9 -> 16/9
//                    s->avctx->sample_aspect_ratio = av_mul_q(s->avctx->sample_aspect_ratio, (AVRational) {s->width, s->height});
                    ff_dlog(avctx, "A %d/%d\n",
                            ff_mpeg2_aspect[s->aspect_ratio_info].num,
                            ff_mpeg2_aspect[s->aspect_ratio_info].den);
                    ff_dlog(avctx, "B %d/%d\n", s->avctx->sample_aspect_ratio.num,
                            s->avctx->sample_aspect_ratio.den);
                }
            } else {
                s->avctx->sample_aspect_ratio =
                    ff_mpeg2_aspect[s->aspect_ratio_info];
            }
        } // MPEG-2

        ff_set_sar(s->avctx, s->avctx->sample_aspect_ratio);

        avctx->pix_fmt = mpeg_get_pixelformat(avctx);
        // until then pix_fmt may be changed right after codec init
#if FF_API_XVMC
        if ((avctx->pix_fmt == AV_PIX_FMT_XVMC_MPEG2_IDCT ||
             avctx->hwaccel) && avctx->idct_algo == FF_IDCT_AUTO)
#else
        if (avctx->hwaccel && avctx->idct_algo == FF_IDCT_AUTO)
#endif /* FF_API_XVMC */
            avctx->idct_algo = FF_IDCT_SIMPLE;

        /* Quantization matrices may need reordering
         * if DCT permutation is changed. */
        memcpy(old_permutation, s->idsp.idct_permutation, 64 * sizeof(uint8_t));

        ff_mpv_idct_init(s);
        if ((ret = ff_mpv_common_init(s)) < 0)
            return ret;

        quant_matrix_rebuild(s->intra_matrix,        old_permutation, s->idsp.idct_permutation);
        quant_matrix_rebuild(s->inter_matrix,        old_permutation, s->idsp.idct_permutation);
        quant_matrix_rebuild(s->chroma_intra_matrix, old_permutation, s->idsp.idct_permutation);
        quant_matrix_rebuild(s->chroma_inter_matrix, old_permutation, s->idsp.idct_permutation);

        s1->mpeg_enc_ctx_allocated = 1;
    }
    return 0;
}

static int mpeg1_decode_picture(AVCodecContext *avctx, const uint8_t *buf,
                                int buf_size)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int ref, f_code, vbv_delay;

    init_get_bits(&s->gb, buf, buf_size * 8);

    ref = get_bits(&s->gb, 10); /* temporal ref */
    s->pict_type = get_bits(&s->gb, 3);
    if (s->pict_type == 0 || s->pict_type > 3)
        return AVERROR_INVALIDDATA;

    vbv_delay = get_bits(&s->gb, 16);
    if (s->pict_type == AV_PICTURE_TYPE_P ||
        s->pict_type == AV_PICTURE_TYPE_B) {
        s->full_pel[0] = get_bits1(&s->gb);
        f_code = get_bits(&s->gb, 3);
        if (f_code == 0 && (avctx->err_recognition & AV_EF_BITSTREAM))
            return AVERROR_INVALIDDATA;
        s->mpeg_f_code[0][0] = f_code;
        s->mpeg_f_code[0][1] = f_code;
    }
    if (s->pict_type == AV_PICTURE_TYPE_B) {
        s->full_pel[1] = get_bits1(&s->gb);
        f_code = get_bits(&s->gb, 3);
        if (f_code == 0 && (avctx->err_recognition & AV_EF_BITSTREAM))
            return AVERROR_INVALIDDATA;
        s->mpeg_f_code[1][0] = f_code;
        s->mpeg_f_code[1][1] = f_code;
    }
    s->current_picture.f->pict_type = s->pict_type;
    s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;

    if (avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(avctx, AV_LOG_DEBUG,
               "vbv_delay %d, ref %d type:%d\n", vbv_delay, ref, s->pict_type);

    s->y_dc_scale = 8;
    s->c_dc_scale = 8;
    return 0;
}

static void mpeg_decode_sequence_extension(Mpeg1Context *s1)
{
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int horiz_size_ext, vert_size_ext;
    int bit_rate_ext;

    skip_bits(&s->gb, 1); /* profile and level esc*/
    s->avctx->profile       = get_bits(&s->gb, 3);
    s->avctx->level         = get_bits(&s->gb, 4);
    s->progressive_sequence = get_bits1(&s->gb);   /* progressive_sequence */
    s->chroma_format        = get_bits(&s->gb, 2); /* chroma_format 1=420, 2=422, 3=444 */
    horiz_size_ext          = get_bits(&s->gb, 2);
    vert_size_ext           = get_bits(&s->gb, 2);
    s->width  |= (horiz_size_ext << 12);
    s->height |= (vert_size_ext  << 12);
    bit_rate_ext = get_bits(&s->gb, 12);  /* XXX: handle it */
    s->bit_rate += (bit_rate_ext << 18) * 400;
    skip_bits1(&s->gb); /* marker */
    s->avctx->rc_buffer_size += get_bits(&s->gb, 8) * 1024 * 16 << 10;

    s->low_delay = get_bits1(&s->gb);
    if (s->avctx->flags & AV_CODEC_FLAG_LOW_DELAY)
        s->low_delay = 1;

    s1->frame_rate_ext.num = get_bits(&s->gb, 2) + 1;
    s1->frame_rate_ext.den = get_bits(&s->gb, 5) + 1;

    ff_dlog(s->avctx, "sequence extension\n");
    s->codec_id = s->avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;

    if (s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG,
               "profile: %d, level: %d vbv buffer: %d, bitrate:%d\n",
               s->avctx->profile, s->avctx->level,
               s->avctx->rc_buffer_size, s->bit_rate);
}

static void mpeg_decode_sequence_display_extension(Mpeg1Context *s1)
{
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int color_description, w, h;

    skip_bits(&s->gb, 3); /* video format */
    color_description = get_bits1(&s->gb);
    if (color_description) {
        s->avctx->color_primaries = get_bits(&s->gb, 8);
        s->avctx->color_trc       = get_bits(&s->gb, 8);
        s->avctx->colorspace      = get_bits(&s->gb, 8);
    }
    w = get_bits(&s->gb, 14);
    skip_bits(&s->gb, 1); // marker
    h = get_bits(&s->gb, 14);
    // remaining 3 bits are zero padding

    s1->pan_scan.width  = 16 * w;
    s1->pan_scan.height = 16 * h;

    if (s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG, "sde w:%d, h:%d\n", w, h);
}

static void mpeg_decode_picture_display_extension(Mpeg1Context *s1)
{
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int i, nofco;

    nofco = 1;
    if (s->progressive_sequence) {
        if (s->repeat_first_field) {
            nofco++;
            if (s->top_field_first)
                nofco++;
        }
    } else {
        if (s->picture_structure == PICT_FRAME) {
            nofco++;
            if (s->repeat_first_field)
                nofco++;
        }
    }
    for (i = 0; i < nofco; i++) {
        s1->pan_scan.position[i][0] = get_sbits(&s->gb, 16);
        skip_bits(&s->gb, 1); // marker
        s1->pan_scan.position[i][1] = get_sbits(&s->gb, 16);
        skip_bits(&s->gb, 1); // marker
    }

    if (s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG,
               "pde (%"PRId16",%"PRId16") (%"PRId16",%"PRId16") (%"PRId16",%"PRId16")\n",
               s1->pan_scan.position[0][0], s1->pan_scan.position[0][1],
               s1->pan_scan.position[1][0], s1->pan_scan.position[1][1],
               s1->pan_scan.position[2][0], s1->pan_scan.position[2][1]);
}

static int load_matrix(MpegEncContext *s, uint16_t matrix0[64],
                       uint16_t matrix1[64], int intra)
{
    int i;

    for (i = 0; i < 64; i++) {
        int j = s->idsp.idct_permutation[ff_zigzag_direct[i]];
        int v = get_bits(&s->gb, 8);
        if (v == 0) {
            av_log(s->avctx, AV_LOG_ERROR, "matrix damaged\n");
            return AVERROR_INVALIDDATA;
        }
        if (intra && i == 0 && v != 8) {
            av_log(s->avctx, AV_LOG_ERROR, "intra matrix invalid, ignoring\n");
            v = 8; // needed by pink.mpg / issue1046
        }
        matrix0[j] = v;
        if (matrix1)
            matrix1[j] = v;
    }
    return 0;
}

static void mpeg_decode_quant_matrix_extension(MpegEncContext *s)
{
    ff_dlog(s->avctx, "matrix extension\n");

    if (get_bits1(&s->gb))
        load_matrix(s, s->chroma_intra_matrix, s->intra_matrix, 1);
    if (get_bits1(&s->gb))
        load_matrix(s, s->chroma_inter_matrix, s->inter_matrix, 0);
    if (get_bits1(&s->gb))
        load_matrix(s, s->chroma_intra_matrix, NULL, 1);
    if (get_bits1(&s->gb))
        load_matrix(s, s->chroma_inter_matrix, NULL, 0);
}

static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
{
    MpegEncContext *s = &s1->mpeg_enc_ctx;

    s->full_pel[0]       = s->full_pel[1] = 0;
    s->mpeg_f_code[0][0] = get_bits(&s->gb, 4);
    s->mpeg_f_code[0][1] = get_bits(&s->gb, 4);
    s->mpeg_f_code[1][0] = get_bits(&s->gb, 4);
    s->mpeg_f_code[1][1] = get_bits(&s->gb, 4);
    if (!s->pict_type && s1->mpeg_enc_ctx_allocated) {
        av_log(s->avctx, AV_LOG_ERROR,
               "Missing picture start code, guessing missing values\n");
        if (s->mpeg_f_code[1][0] == 15 && s->mpeg_f_code[1][1] == 15) {
            if (s->mpeg_f_code[0][0] == 15 && s->mpeg_f_code[0][1] == 15)
                s->pict_type = AV_PICTURE_TYPE_I;
            else
                s->pict_type = AV_PICTURE_TYPE_P;
        } else
            s->pict_type = AV_PICTURE_TYPE_B;
        s->current_picture.f->pict_type = s->pict_type;
        s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
    }
    s->intra_dc_precision         = get_bits(&s->gb, 2);
    s->picture_structure          = get_bits(&s->gb, 2);
    s->top_field_first            = get_bits1(&s->gb);
    s->frame_pred_frame_dct       = get_bits1(&s->gb);
    s->concealment_motion_vectors = get_bits1(&s->gb);
    s->q_scale_type               = get_bits1(&s->gb);
    s->intra_vlc_format           = get_bits1(&s->gb);
    s->alternate_scan             = get_bits1(&s->gb);
    s->repeat_first_field         = get_bits1(&s->gb);
    s->chroma_420_type            = get_bits1(&s->gb);
    s->progressive_frame          = get_bits1(&s->gb);

    if (s->progressive_sequence && !s->progressive_frame) {
        s->progressive_frame = 1;
        av_log(s->avctx, AV_LOG_ERROR,
               "interlaced frame in progressive sequence, ignoring\n");
    }

    if (s->picture_structure == 0 ||
        (s->progressive_frame && s->picture_structure != PICT_FRAME)) {
        av_log(s->avctx, AV_LOG_ERROR,
               "picture_structure %d invalid, ignoring\n",
               s->picture_structure);
        s->picture_structure = PICT_FRAME;
    }

    if (s->progressive_sequence && !s->frame_pred_frame_dct)
        av_log(s->avctx, AV_LOG_WARNING, "invalid frame_pred_frame_dct\n");

    if (s->picture_structure == PICT_FRAME) {
        s->first_field = 0;
        s->v_edge_pos  = 16 * s->mb_height;
    } else {
        s->first_field ^= 1;
        s->v_edge_pos   = 8 * s->mb_height;
        memset(s->mbskip_table, 0, s->mb_stride * s->mb_height);
    }

    if (s->alternate_scan) {
        ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable, ff_alternate_vertical_scan);
        ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable, ff_alternate_vertical_scan);
    } else {
        ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable, ff_zigzag_direct);
        ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable, ff_zigzag_direct);
    }

    /* composite display not parsed */
    ff_dlog(s->avctx, "intra_dc_precision=%d\n", s->intra_dc_precision);
    ff_dlog(s->avctx, "picture_structure=%d\n", s->picture_structure);
    ff_dlog(s->avctx, "top field first=%d\n", s->top_field_first);
    ff_dlog(s->avctx, "repeat first field=%d\n", s->repeat_first_field);
    ff_dlog(s->avctx, "conceal=%d\n", s->concealment_motion_vectors);
    ff_dlog(s->avctx, "intra_vlc_format=%d\n", s->intra_vlc_format);
    ff_dlog(s->avctx, "alternate_scan=%d\n", s->alternate_scan);
    ff_dlog(s->avctx, "frame_pred_frame_dct=%d\n", s->frame_pred_frame_dct);
    ff_dlog(s->avctx, "progressive_frame=%d\n", s->progressive_frame);
}

static int mpeg_field_start(MpegEncContext *s, const uint8_t *buf, int buf_size)
{
    AVCodecContext *avctx = s->avctx;
    Mpeg1Context *s1      = (Mpeg1Context *) s;
    int ret;

    /* start frame decoding */
    if (s->first_field || s->picture_structure == PICT_FRAME) {
        AVFrameSideData *pan_scan;

        if ((ret = ff_mpv_frame_start(s, avctx)) < 0)
            return ret;

        ff_mpeg_er_frame_start(s);

        /* first check if we must repeat the frame */
        s->current_picture_ptr->f->repeat_pict = 0;
        if (s->repeat_first_field) {
            if (s->progressive_sequence) {
                if (s->top_field_first)
                    s->current_picture_ptr->f->repeat_pict = 4;
                else
                    s->current_picture_ptr->f->repeat_pict = 2;
            } else if (s->progressive_frame) {
                s->current_picture_ptr->f->repeat_pict = 1;
            }
        }

        pan_scan = av_frame_new_side_data(s->current_picture_ptr->f,
                                          AV_FRAME_DATA_PANSCAN,
                                          sizeof(s1->pan_scan));
        if (!pan_scan)
            return AVERROR(ENOMEM);
        memcpy(pan_scan->data, &s1->pan_scan, sizeof(s1->pan_scan));

        if (s1->a53_caption) {
            AVFrameSideData *sd = av_frame_new_side_data(
                s->current_picture_ptr->f, AV_FRAME_DATA_A53_CC,
                s1->a53_caption_size);
            if (sd)
                memcpy(sd->data, s1->a53_caption, s1->a53_caption_size);
            av_freep(&s1->a53_caption);
        }

        if (s1->has_stereo3d) {
            AVStereo3D *stereo = av_stereo3d_create_side_data(s->current_picture_ptr->f);
            if (!stereo)
                return AVERROR(ENOMEM);

            *stereo = s1->stereo3d;
            s1->has_stereo3d = 0;
        }

        if (s1->has_afd) {
            AVFrameSideData *sd =
                av_frame_new_side_data(s->current_picture_ptr->f,
                                       AV_FRAME_DATA_AFD, 1);
            if (!sd)
                return AVERROR(ENOMEM);

            *sd->data   = s1->afd;
            s1->has_afd = 0;
        }

        if (HAVE_THREADS && (avctx->active_thread_type & FF_THREAD_FRAME))
            ff_thread_finish_setup(avctx);
    } else { // second field
        int i;

        if (!s->current_picture_ptr) {
            av_log(s->avctx, AV_LOG_ERROR, "first field missing\n");
            return AVERROR_INVALIDDATA;
        }

        if (s->avctx->hwaccel &&
            (s->avctx->slice_flags & SLICE_FLAG_ALLOW_FIELD)) {
            if (s->avctx->hwaccel->end_frame(s->avctx) < 0)
                av_log(avctx, AV_LOG_ERROR,
                       "hardware accelerator failed to decode first field\n");
        }

        for (i = 0; i < 4; i++) {
            s->current_picture.f->data[i] = s->current_picture_ptr->f->data[i];
            if (s->picture_structure == PICT_BOTTOM_FIELD)
                s->current_picture.f->data[i] +=
                    s->current_picture_ptr->f->linesize[i];
        }
    }

    if (avctx->hwaccel) {
        if ((ret = avctx->hwaccel->start_frame(avctx, buf, buf_size)) < 0)
            return ret;
    }

#if FF_API_XVMC
FF_DISABLE_DEPRECATION_WARNINGS
// ff_mpv_frame_start will call this function too,
// but we need to call it on every field
    if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration)
        if (ff_xvmc_field_start(s, avctx) < 0)
            return -1;
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_XVMC */

    return 0;
}

#define DECODE_SLICE_ERROR -1
#define DECODE_SLICE_OK     0

/**
 * Decode a slice.
 * MpegEncContext.mb_y must be set to the MB row from the startcode.
 * @return DECODE_SLICE_ERROR if the slice is damaged,
 *         DECODE_SLICE_OK if this slice is OK
 */
static int mpeg_decode_slice(MpegEncContext *s, int mb_y,
                             const uint8_t **buf, int buf_size)
{
    AVCodecContext *avctx = s->avctx;
    const int field_pic   = s->picture_structure != PICT_FRAME;
    int ret;

    s->resync_mb_x =
    s->resync_mb_y = -1;

    assert(mb_y < s->mb_height);

    init_get_bits(&s->gb, *buf, buf_size * 8);

    ff_mpeg1_clean_buffers(s);
    s->interlaced_dct = 0;

    s->qscale = get_qscale(s);

    if (s->qscale == 0) {
        av_log(s->avctx, AV_LOG_ERROR, "qscale == 0\n");
        return AVERROR_INVALIDDATA;
    }

    /* extra slice info */
    while (get_bits1(&s->gb) != 0)
        skip_bits(&s->gb, 8);

    s->mb_x = 0;

    if (mb_y == 0 && s->codec_tag == AV_RL32("SLIF")) {
        skip_bits1(&s->gb);
    } else {
        while (get_bits_left(&s->gb) > 0) {
            int code = get_vlc2(&s->gb, ff_mbincr_vlc.table,
                                MBINCR_VLC_BITS, 2);
            if (code < 0) {
                av_log(s->avctx, AV_LOG_ERROR, "first mb_incr damaged\n");
                return AVERROR_INVALIDDATA;
            }
            if (code >= 33) {
                if (code == 33)
                    s->mb_x += 33;
                /* otherwise, stuffing, nothing to do */
            } else {
                s->mb_x += code;
                break;
            }
        }
    }

    if (s->mb_x >= (unsigned) s->mb_width) {
        av_log(s->avctx, AV_LOG_ERROR, "initial skip overflow\n");
        return AVERROR_INVALIDDATA;
    }

    if (avctx->hwaccel) {
        const uint8_t *buf_end, *buf_start = *buf - 4; /* include start_code */
        int start_code = -1;
        buf_end = avpriv_find_start_code(buf_start + 2, *buf + buf_size, &start_code);
        if (buf_end < *buf + buf_size)
            buf_end -= 4;
        s->mb_y = mb_y;
        if (avctx->hwaccel->decode_slice(avctx, buf_start, buf_end - buf_start) < 0)
            return DECODE_SLICE_ERROR;
        *buf = buf_end;
        return DECODE_SLICE_OK;
    }

    s->resync_mb_x = s->mb_x;
    s->resync_mb_y = s->mb_y = mb_y;
    s->mb_skip_run = 0;
    ff_init_block_index(s);

    if (s->mb_y == 0 && s->mb_x == 0 && (s->first_field || s->picture_structure == PICT_FRAME)) {
        if (s->avctx->debug & FF_DEBUG_PICT_INFO) {
            av_log(s->avctx, AV_LOG_DEBUG,
                   "qp:%d fc:%2d%2d%2d%2d %s %s %s %s %s dc:%d pstruct:%d fdct:%d cmv:%d qtype:%d ivlc:%d rff:%d %s\n",
                   s->qscale,
                   s->mpeg_f_code[0][0], s->mpeg_f_code[0][1],
                   s->mpeg_f_code[1][0], s->mpeg_f_code[1][1],
                   s->pict_type  == AV_PICTURE_TYPE_I ? "I" :
                   (s->pict_type == AV_PICTURE_TYPE_P ? "P" :
                   (s->pict_type == AV_PICTURE_TYPE_B ? "B" : "S")),
                   s->progressive_sequence ? "ps"  : "",
                   s->progressive_frame    ? "pf"  : "",
                   s->alternate_scan       ? "alt" : "",
                   s->top_field_first      ? "top" : "",
                   s->intra_dc_precision, s->picture_structure,
                   s->frame_pred_frame_dct, s->concealment_motion_vectors,
                   s->q_scale_type, s->intra_vlc_format,
                   s->repeat_first_field, s->chroma_420_type ? "420" : "");
        }
    }

    for (;;) {
#if FF_API_XVMC
FF_DISABLE_DEPRECATION_WARNINGS
        // If 1, we memcpy blocks in xvmcvideo.
        if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration > 1)
            ff_xvmc_init_block(s); // set s->block
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_XVMC */

        if ((ret = mpeg_decode_mb(s, s->block)) < 0)
            return ret;

        // Note motion_val is normally NULL unless we want to extract the MVs.
        if (s->current_picture.motion_val[0] && !s->encoding) {
            const int wrap = s->b8_stride;
            int xy         = s->mb_x * 2 + s->mb_y * 2 * wrap;
            int b8_xy      = 4 * (s->mb_x + s->mb_y * s->mb_stride);
            int motion_x, motion_y, dir, i;

            for (i = 0; i < 2; i++) {
                for (dir = 0; dir < 2; dir++) {
                    if (s->mb_intra ||
                        (dir == 1 && s->pict_type != AV_PICTURE_TYPE_B)) {
                        motion_x = motion_y = 0;
                    } else if (s->mv_type == MV_TYPE_16X16 ||
                               (s->mv_type == MV_TYPE_FIELD && field_pic)) {
                        motion_x = s->mv[dir][0][0];
                        motion_y = s->mv[dir][0][1];
                    } else { /* if ((s->mv_type == MV_TYPE_FIELD) || (s->mv_type == MV_TYPE_16X8)) */
                        motion_x = s->mv[dir][i][0];
                        motion_y = s->mv[dir][i][1];
                    }

                    s->current_picture.motion_val[dir][xy][0]     = motion_x;
                    s->current_picture.motion_val[dir][xy][1]     = motion_y;
                    s->current_picture.motion_val[dir][xy + 1][0] = motion_x;
                    s->current_picture.motion_val[dir][xy + 1][1] = motion_y;
                    s->current_picture.ref_index [dir][b8_xy]     =
                    s->current_picture.ref_index [dir][b8_xy + 1] = s->field_select[dir][i];
                    assert(s->field_select[dir][i] == 0 ||
                           s->field_select[dir][i] == 1);
                }
                xy    += wrap;
                b8_xy += 2;
            }
        }

        s->dest[0] += 16;
        s->dest[1] += 16 >> s->chroma_x_shift;
        s->dest[2] += 16 >> s->chroma_x_shift;

        ff_mpv_decode_mb(s, s->block);

        if (++s->mb_x >= s->mb_width) {
            const int mb_size = 16;

            ff_mpeg_draw_horiz_band(s, mb_size * (s->mb_y >> field_pic), mb_size);
            ff_mpv_report_decode_progress(s);

            s->mb_x  = 0;
            s->mb_y += 1 << field_pic;

            if (s->mb_y >= s->mb_height) {
                int left   = get_bits_left(&s->gb);
                int is_d10 = s->chroma_format == 2 &&
                             s->pict_type == AV_PICTURE_TYPE_I &&
                             avctx->profile == 0 && avctx->level == 5 &&
                             s->intra_dc_precision == 2 &&
                             s->q_scale_type == 1 && s->alternate_scan == 0 &&
                             s->progressive_frame == 0
                             /* vbv_delay == 0xBBB || 0xE10 */;

                if (left < 0 ||
                    (left && show_bits(&s->gb, FFMIN(left, 23)) && !is_d10) ||
                    ((avctx->err_recognition & AV_EF_BUFFER) && left > 8)) {
                    av_log(avctx, AV_LOG_ERROR, "end mismatch left=%d %0X\n",
                           left, show_bits(&s->gb, FFMIN(left, 23)));
                    return AVERROR_INVALIDDATA;
                } else
                    goto eos;
            }

            ff_init_block_index(s);
        }

        /* skip mb handling */
        if (s->mb_skip_run == -1) {
            /* read increment again */
            s->mb_skip_run = 0;
            for (;;) {
                int code = get_vlc2(&s->gb, ff_mbincr_vlc.table,
                                    MBINCR_VLC_BITS, 2);
                if (code < 0) {
                    av_log(s->avctx, AV_LOG_ERROR, "mb incr damaged\n");
                    return AVERROR_INVALIDDATA;
                }
                if (code >= 33) {
                    if (code == 33) {
                        s->mb_skip_run += 33;
                    } else if (code == 35) {
                        if (s->mb_skip_run != 0 || show_bits(&s->gb, 15) != 0) {
                            av_log(s->avctx, AV_LOG_ERROR, "slice mismatch\n");
                            return AVERROR_INVALIDDATA;
                        }
                        goto eos; /* end of slice */
                    }
                    /* otherwise, stuffing, nothing to do */
                } else {
                    s->mb_skip_run += code;
                    break;
                }
            }
            if (s->mb_skip_run) {
                int i;
                if (s->pict_type == AV_PICTURE_TYPE_I) {
                    av_log(s->avctx, AV_LOG_ERROR,
                           "skipped MB in I-frame at %d %d\n", s->mb_x, s->mb_y);
                    return AVERROR_INVALIDDATA;
                }

                /* skip mb */
                s->mb_intra = 0;
                for (i = 0; i < 12; i++)
                    s->block_last_index[i] = -1;
                if (s->picture_structure == PICT_FRAME)
                    s->mv_type = MV_TYPE_16X16;
                else
                    s->mv_type = MV_TYPE_FIELD;
                if (s->pict_type == AV_PICTURE_TYPE_P) {
                    /* if P type, zero motion vector is implied */
                    s->mv_dir             = MV_DIR_FORWARD;
                    s->mv[0][0][0]        = s->mv[0][0][1]      = 0;
                    s->last_mv[0][0][0]   = s->last_mv[0][0][1] = 0;
                    s->last_mv[0][1][0]   = s->last_mv[0][1][1] = 0;
                    s->field_select[0][0] = (s->picture_structure - 1) & 1;
                } else {
                    /* if B type, reuse previous vectors and directions */
                    s->mv[0][0][0] = s->last_mv[0][0][0];
                    s->mv[0][0][1] = s->last_mv[0][0][1];
                    s->mv[1][0][0] = s->last_mv[1][0][0];
                    s->mv[1][0][1] = s->last_mv[1][0][1];
                }
            }
        }
    }
eos: // end of slice
    *buf += (get_bits_count(&s->gb) - 1) / 8;
    ff_dlog(s, "y %d %d %d %d\n", s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y);
    return 0;
}

static int slice_decode_thread(AVCodecContext *c, void *arg)
{
    MpegEncContext *s   = *(void **) arg;
    const uint8_t *buf  = s->gb.buffer;
    int mb_y            = s->start_mb_y;
    const int field_pic = s->picture_structure != PICT_FRAME;

    s->er.error_count = (3 * (s->end_mb_y - s->start_mb_y) * s->mb_width) >> field_pic;

    for (;;) {
        uint32_t start_code;
        int ret;

        ret = mpeg_decode_slice(s, mb_y, &buf, s->gb.buffer_end - buf);
        emms_c();
        ff_dlog(c, "ret:%d resync:%d/%d mb:%d/%d ts:%d/%d ec:%d\n",
                ret, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y,
                s->start_mb_y, s->end_mb_y, s->er.error_count);
        if (ret < 0) {
            if (c->err_recognition & AV_EF_EXPLODE)
                return ret;
            if (s->resync_mb_x >= 0 && s->resync_mb_y >= 0)
                ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                                s->mb_x, s->mb_y,
                                ER_AC_ERROR | ER_DC_ERROR | ER_MV_ERROR);
        } else {
            ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                            s->mb_x - 1, s->mb_y,
                            ER_AC_END | ER_DC_END | ER_MV_END);
        }

        if (s->mb_y == s->end_mb_y)
            return 0;

        start_code = -1;
        buf        = avpriv_find_start_code(buf, s->gb.buffer_end, &start_code);
        mb_y       = (start_code - SLICE_MIN_START_CODE) << field_pic;
        if (s->picture_structure == PICT_BOTTOM_FIELD)
            mb_y++;
        if (mb_y < 0 || mb_y >= s->end_mb_y)
            return AVERROR_INVALIDDATA;
    }
}

/**
 * Handle slice ends.
 * @return 1 if it seems to be the last slice
 */
static int slice_end(AVCodecContext *avctx, AVFrame *pict)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;

    if (!s1->mpeg_enc_ctx_allocated || !s->current_picture_ptr)
        return 0;

    if (s->avctx->hwaccel) {
        if (s->avctx->hwaccel->end_frame(s->avctx) < 0)
            av_log(avctx, AV_LOG_ERROR,
                   "hardware accelerator failed to decode picture\n");
    }

#if FF_API_XVMC
FF_DISABLE_DEPRECATION_WARNINGS
    if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration)
        ff_xvmc_field_end(s);
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_XVMC */

    /* end of slice reached */
    if (/* s->mb_y << field_pic == s->mb_height && */ !s->first_field) {
        /* end of image */

        ff_er_frame_end(&s->er);

        ff_mpv_frame_end(s);

        if (s->pict_type == AV_PICTURE_TYPE_B || s->low_delay) {
            int ret = av_frame_ref(pict, s->current_picture_ptr->f);
            if (ret < 0)
                return ret;
            ff_print_debug_info(s, s->current_picture_ptr);
        } else {
            if (avctx->active_thread_type & FF_THREAD_FRAME)
                s->picture_number++;
            /* latency of 1 frame for I- and P-frames */
            /* XXX: use another variable than picture_number */
            if (s->last_picture_ptr) {
                int ret = av_frame_ref(pict, s->last_picture_ptr->f);
                if (ret < 0)
                    return ret;
                ff_print_debug_info(s, s->last_picture_ptr);
            }
        }

        return 1;
    } else {
        return 0;
    }
}

static int mpeg1_decode_sequence(AVCodecContext *avctx,
                                 const uint8_t *buf, int buf_size)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int width, height;
    int i, v, j;

    init_get_bits(&s->gb, buf, buf_size * 8);

    width  = get_bits(&s->gb, 12);
    height = get_bits(&s->gb, 12);
    if (width == 0 || height == 0) {
        av_log(avctx, AV_LOG_WARNING,
               "Invalid horizontal or vertical size value.\n");
        if (avctx->err_recognition & AV_EF_BITSTREAM)
            return AVERROR_INVALIDDATA;
    }
    s->aspect_ratio_info = get_bits(&s->gb, 4);
    if (s->aspect_ratio_info == 0) {
        av_log(avctx, AV_LOG_ERROR, "aspect ratio has forbidden 0 value\n");
        if (avctx->err_recognition & AV_EF_BITSTREAM)
            return AVERROR_INVALIDDATA;
    }
    s->frame_rate_index = get_bits(&s->gb, 4);
    if (s->frame_rate_index == 0 || s->frame_rate_index > 13) {
        av_log(avctx, AV_LOG_WARNING,
               "frame_rate_index %d is invalid\n", s->frame_rate_index);
        return AVERROR_INVALIDDATA;
    }
    s->bit_rate = get_bits(&s->gb, 18) * 400;
    if (get_bits1(&s->gb) == 0) { /* marker */
        av_log(avctx, AV_LOG_ERROR, "Marker in sequence header missing\n");
        return AVERROR_INVALIDDATA;
    }
    s->width  = width;
    s->height = height;

    s->avctx->rc_buffer_size = get_bits(&s->gb, 10) * 1024 * 16;
    skip_bits(&s->gb, 1);

    /* get matrix */
    if (get_bits1(&s->gb)) {
        load_matrix(s, s->chroma_intra_matrix, s->intra_matrix, 1);
    } else {
        for (i = 0; i < 64; i++) {
            j = s->idsp.idct_permutation[i];
            v = ff_mpeg1_default_intra_matrix[i];
            s->intra_matrix[j]        = v;
            s->chroma_intra_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        load_matrix(s, s->chroma_inter_matrix, s->inter_matrix, 0);
    } else {
        for (i = 0; i < 64; i++) {
            int j = s->idsp.idct_permutation[i];
            v = ff_mpeg1_default_non_intra_matrix[i];
            s->inter_matrix[j]        = v;
            s->chroma_inter_matrix[j] = v;
        }
    }

    if (show_bits(&s->gb, 23) != 0) {
        av_log(s->avctx, AV_LOG_ERROR, "sequence header damaged\n");
        return AVERROR_INVALIDDATA;
    }

    /* We set MPEG-2 parameters so that it emulates MPEG-1. */
    s->progressive_sequence = 1;
    s->progressive_frame    = 1;
    s->picture_structure    = PICT_FRAME;
    s->frame_pred_frame_dct = 1;
    s->chroma_format        = 1;
    s->codec_id             =
    s->avctx->codec_id      = AV_CODEC_ID_MPEG1VIDEO;
    s->out_format           = FMT_MPEG1;
    if (s->avctx->flags & AV_CODEC_FLAG_LOW_DELAY)
        s->low_delay = 1;

    if (s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG, "vbv buffer: %d, bitrate:%d\n",
               s->avctx->rc_buffer_size, s->bit_rate);

    return 0;
}

static int vcr2_init_sequence(AVCodecContext *avctx)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int i, v, ret;

    /* start new MPEG-1 context decoding */
    s->out_format = FMT_MPEG1;
    if (s1->mpeg_enc_ctx_allocated) {
        ff_mpv_common_end(s);
    }
    s->width            = avctx->coded_width;
    s->height           = avctx->coded_height;
    avctx->has_b_frames = 0; // true?
    s->low_delay        = 1;

    avctx->pix_fmt = mpeg_get_pixelformat(avctx);

#if FF_API_XVMC
    if ((avctx->pix_fmt == AV_PIX_FMT_XVMC_MPEG2_IDCT || avctx->hwaccel) &&
        avctx->idct_algo == FF_IDCT_AUTO)
#else
    if (avctx->hwaccel && avctx->idct_algo == FF_IDCT_AUTO)
#endif /* FF_API_XVMC */
        avctx->idct_algo = FF_IDCT_SIMPLE;

    ff_mpv_idct_init(s);
    if ((ret = ff_mpv_common_init(s)) < 0)
        return ret;
    s1->mpeg_enc_ctx_allocated = 1;

    for (i = 0; i < 64; i++) {
        int j = s->idsp.idct_permutation[i];
        v = ff_mpeg1_default_intra_matrix[i];
        s->intra_matrix[j]        = v;
        s->chroma_intra_matrix[j] = v;

        v = ff_mpeg1_default_non_intra_matrix[i];
        s->inter_matrix[j]        = v;
        s->chroma_inter_matrix[j] = v;
    }

    s->progressive_sequence  = 1;
    s->progressive_frame     = 1;
    s->picture_structure     = PICT_FRAME;
    s->frame_pred_frame_dct  = 1;
    s->chroma_format         = 1;
    s->codec_id              = s->avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
    s1->save_width           = s->width;
    s1->save_height          = s->height;
    s1->save_progressive_seq = s->progressive_sequence;
    return 0;
}

static int mpeg_decode_a53_cc(AVCodecContext *avctx,
                              const uint8_t *p, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;

    if (buf_size >= 6 &&
        p[0] == 'G' && p[1] == 'A' && p[2] == '9' && p[3] == '4' &&
        p[4] == 3 && (p[5] & 0x40)) {
        /* extract A53 Part 4 CC data */
        int cc_count = p[5] & 0x1f;
        if (cc_count > 0 && buf_size >= 7 + cc_count * 3) {
            av_freep(&s1->a53_caption);
            s1->a53_caption_size = cc_count * 3;
            s1->a53_caption      = av_malloc(s1->a53_caption_size);
            if (s1->a53_caption)
                memcpy(s1->a53_caption, p + 7, s1->a53_caption_size);
        }
        return 1;
    } else if (buf_size >= 11 &&
               p[0] == 'C' && p[1] == 'C' && p[2] == 0x01 && p[3] == 0xf8) {
        /* extract DVD CC data */
        int cc_count = 0;
        int i;
        // There is a caption count field in the data, but it is often
        // incorrect.  So count the number of captions present.
        for (i = 5; i + 6 <= buf_size && ((p[i] & 0xfe) == 0xfe); i += 6)
            cc_count++;
        // Transform the DVD format into A53 Part 4 format
        if (cc_count > 0) {
            av_freep(&s1->a53_caption);
            s1->a53_caption_size = cc_count * 6;
            s1->a53_caption      = av_malloc(s1->a53_caption_size);
            if (s1->a53_caption) {
                uint8_t field1 = !!(p[4] & 0x80);
                uint8_t *cap = s1->a53_caption;
                p += 5;
                for (i = 0; i < cc_count; i++) {
                    cap[0] = (p[0] == 0xff && field1) ? 0xfc : 0xfd;
                    cap[1] = p[1];
                    cap[2] = p[2];
                    cap[3] = (p[3] == 0xff && !field1) ? 0xfc : 0xfd;
                    cap[4] = p[4];
                    cap[5] = p[5];
                    cap += 6;
                    p += 6;
                }
            }
        }
        return 1;
    }
    return 0;
}

static void mpeg_decode_user_data(AVCodecContext *avctx,
                                  const uint8_t *p, int buf_size)
{
    const uint8_t *buf_end = p + buf_size;
    Mpeg1Context *s1 = avctx->priv_data;

    /* we parse the DTG active format information */
    if (buf_end - p >= 5 &&
        p[0] == 'D' && p[1] == 'T' && p[2] == 'G' && p[3] == '1') {
        int flags = p[4];
        p += 5;
        if (flags & 0x80) {
            /* skip event id */
            p += 2;
        }
        if (flags & 0x40) {
            if (buf_end - p < 1)
                return;
#if FF_API_AFD
FF_DISABLE_DEPRECATION_WARNINGS
            avctx->dtg_active_format = p[0] & 0x0f;
FF_ENABLE_DEPRECATION_WARNINGS
#endif /* FF_API_AFD */
            s1->has_afd = 1;
            s1->afd     = p[0] & 0x0f;
        }
    } else if (buf_end - p >= 6 &&
               p[0] == 'J' && p[1] == 'P' && p[2] == '3' && p[3] == 'D' &&
               p[4] == 0x03) { // S3D_video_format_length
        // the 0x7F mask ignores the reserved_bit value
        const uint8_t S3D_video_format_type = p[5] & 0x7F;

        if (S3D_video_format_type == 0x03 ||
            S3D_video_format_type == 0x04 ||
            S3D_video_format_type == 0x08 ||
            S3D_video_format_type == 0x23) {

            s1->has_stereo3d = 1;

            switch (S3D_video_format_type) {
            case 0x03:
                s1->stereo3d.type = AV_STEREO3D_SIDEBYSIDE;
                break;
            case 0x04:
                s1->stereo3d.type = AV_STEREO3D_TOPBOTTOM;
                break;
            case 0x08:
                s1->stereo3d.type = AV_STEREO3D_2D;
                break;
            case 0x23:
                s1->stereo3d.type = AV_STEREO3D_SIDEBYSIDE_QUINCUNX;
                break;
            }
        }
    } else if (mpeg_decode_a53_cc(avctx, p, buf_size)) {
        return;
    }
}

static void mpeg_decode_gop(AVCodecContext *avctx,
                            const uint8_t *buf, int buf_size)
{
    Mpeg1Context *s1  = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;

    int time_code_hours, time_code_minutes;
    int time_code_seconds, time_code_pictures;
    int broken_link;

    init_get_bits(&s->gb, buf, buf_size * 8);

    skip_bits1(&s->gb); /* drop_frame_flag */

    time_code_hours   = get_bits(&s->gb, 5);
    time_code_minutes = get_bits(&s->gb, 6);
    skip_bits1(&s->gb); // marker bit
    time_code_seconds  = get_bits(&s->gb, 6);
    time_code_pictures = get_bits(&s->gb, 6);

    s1->closed_gop = get_bits1(&s->gb);
    /* broken_link indicate that after editing the
     * reference frames of the first B-Frames after GOP I-Frame
     * are missing (open gop) */
    broken_link = get_bits1(&s->gb);

    if (s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG,
               "GOP (%2d:%02d:%02d.[%02d]) closed_gop=%d broken_link=%d\n",
               time_code_hours, time_code_minutes, time_code_seconds,
               time_code_pictures, s1->closed_gop, broken_link);
}

static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
                         int *got_output, const uint8_t *buf, int buf_size)
{
    Mpeg1Context *s = avctx->priv_data;
    MpegEncContext *s2 = &s->mpeg_enc_ctx;
    const uint8_t *buf_ptr = buf;
    const uint8_t *buf_end = buf + buf_size;
    int ret, input_size;
    int last_code = 0, skip_frame = 0;

    for (;;) {
        /* find next start code */
        uint32_t start_code = -1;
        buf_ptr = avpriv_find_start_code(buf_ptr, buf_end, &start_code);
        if (start_code > 0x1ff) {
            if (!skip_frame) {
                if (HAVE_THREADS &&
                    (avctx->active_thread_type & FF_THREAD_SLICE) &&
                    !avctx->hwaccel) {
                    int i;

                    avctx->execute(avctx, slice_decode_thread,
                                   &s2->thread_context[0], NULL,
                                   s->slice_count, sizeof(void *));
                    for (i = 0; i < s->slice_count; i++)
                        s2->er.error_count += s2->thread_context[i]->er.error_count;
                }

                ret = slice_end(avctx, picture);
                if (ret < 0)
                    return ret;
                else if (ret) {
                    // FIXME: merge with the stuff in mpeg_decode_slice
                    if (s2->last_picture_ptr || s2->low_delay)
                        *got_output = 1;
                }
            }
            s2->pict_type = 0;
            return FFMAX(0, buf_ptr - buf - s2->parse_context.last_index);
        }

        input_size = buf_end - buf_ptr;

        if (avctx->debug & FF_DEBUG_STARTCODE)
            av_log(avctx, AV_LOG_DEBUG, "%3"PRIX32" at %td left %d\n",
                   start_code, buf_ptr - buf, input_size);

        /* prepare data for next start code */
        switch (start_code) {
        case SEQ_START_CODE:
            if (last_code == 0) {
                mpeg1_decode_sequence(avctx, buf_ptr, input_size);
                s->sync = 1;
            } else {
                av_log(avctx, AV_LOG_ERROR,
                       "ignoring SEQ_START_CODE after %X\n", last_code);
                if (avctx->err_recognition & AV_EF_EXPLODE)
                    return AVERROR_INVALIDDATA;
            }
            break;

        case PICTURE_START_CODE:
            if (s2->width <= 0 || s2->height <= 0) {
                av_log(avctx, AV_LOG_ERROR, "Invalid frame dimensions %dx%d.\n",
                       s2->width, s2->height);
                return AVERROR_INVALIDDATA;
            }

            if (HAVE_THREADS && (avctx->active_thread_type & FF_THREAD_SLICE) &&
                !avctx->hwaccel && s->slice_count) {
                int i;

                avctx->execute(avctx, slice_decode_thread,
                               s2->thread_context, NULL,
                               s->slice_count, sizeof(void *));
                for (i = 0; i < s->slice_count; i++)
                    s2->er.error_count += s2->thread_context[i]->er.error_count;
                s->slice_count = 0;
            }
            if (last_code == 0 || last_code == SLICE_MIN_START_CODE) {
                ret = mpeg_decode_postinit(avctx);
                if (ret < 0) {
                    av_log(avctx, AV_LOG_ERROR,
                           "mpeg_decode_postinit() failure\n");
                    return ret;
                }

                /* We have a complete image: we try to decompress it. */
                if (mpeg1_decode_picture(avctx, buf_ptr, input_size) < 0)
                    s2->pict_type = 0;
                s->first_slice = 1;
                last_code      = PICTURE_START_CODE;
            } else {
                av_log(avctx, AV_LOG_ERROR,
                       "ignoring pic after %X\n", last_code);
                if (avctx->err_recognition & AV_EF_EXPLODE)
                    return AVERROR_INVALIDDATA;
            }
            break;
        case EXT_START_CODE:
            init_get_bits(&s2->gb, buf_ptr, input_size * 8);

            switch (get_bits(&s2->gb, 4)) {
            case 0x1:
                if (last_code == 0) {
                    mpeg_decode_sequence_extension(s);
                } else {
                    av_log(avctx, AV_LOG_ERROR,
                           "ignoring seq ext after %X\n", last_code);
                    if (avctx->err_recognition & AV_EF_EXPLODE)
                        return AVERROR_INVALIDDATA;
                }
                break;
            case 0x2:
                mpeg_decode_sequence_display_extension(s);
                break;
            case 0x3:
                mpeg_decode_quant_matrix_extension(s2);
                break;
            case 0x7:
                mpeg_decode_picture_display_extension(s);
                break;
            case 0x8:
                if (last_code == PICTURE_START_CODE) {
                    mpeg_decode_picture_coding_extension(s);
                } else {
                    av_log(avctx, AV_LOG_ERROR,
                           "ignoring pic cod ext after %X\n", last_code);
                    if (avctx->err_recognition & AV_EF_EXPLODE)
                        return AVERROR_INVALIDDATA;
                }
                break;
            }
            break;
        case USER_START_CODE:
            mpeg_decode_user_data(avctx, buf_ptr, input_size);
            break;
        case GOP_START_CODE:
            if (last_code == 0) {
                s2->first_field = 0;
                mpeg_decode_gop(avctx, buf_ptr, input_size);
                s->sync = 1;
            } else {
                av_log(avctx, AV_LOG_ERROR,
                       "ignoring GOP_START_CODE after %X\n", last_code);
                if (avctx->err_recognition & AV_EF_EXPLODE)
                    return AVERROR_INVALIDDATA;
            }
            break;
        default:
            if (start_code >= SLICE_MIN_START_CODE &&
                start_code <= SLICE_MAX_START_CODE && last_code != 0) {
                const int field_pic = s2->picture_structure != PICT_FRAME;
                int mb_y = (start_code - SLICE_MIN_START_CODE) << field_pic;
                last_code = SLICE_MIN_START_CODE;

                if (s2->picture_structure == PICT_BOTTOM_FIELD)
                    mb_y++;

                if (mb_y >= s2->mb_height) {
                    av_log(s2->avctx, AV_LOG_ERROR,
                           "slice below image (%d >= %d)\n", mb_y, s2->mb_height);
                    return AVERROR_INVALIDDATA;
                }

                if (!s2->last_picture_ptr) {
                    /* Skip B-frames if we do not have reference frames and
                     * GOP is not closed. */
                    if (s2->pict_type == AV_PICTURE_TYPE_B) {
                        if (!s->closed_gop) {
                            skip_frame = 1;
                            break;
                        }
                    }
                }
                if (s2->pict_type == AV_PICTURE_TYPE_I)
                    s->sync = 1;
                if (!s2->next_picture_ptr) {
                    /* Skip P-frames if we do not have a reference frame or
                     * we have an invalid header. */
                    if (s2->pict_type == AV_PICTURE_TYPE_P && !s->sync) {
                        skip_frame = 1;
                        break;
                    }
                }
                if ((avctx->skip_frame >= AVDISCARD_NONREF &&
                     s2->pict_type == AV_PICTURE_TYPE_B) ||
                    (avctx->skip_frame >= AVDISCARD_NONKEY &&
                     s2->pict_type != AV_PICTURE_TYPE_I) ||
                    avctx->skip_frame >= AVDISCARD_ALL) {
                    skip_frame = 1;
                    break;
                }

                if (!s->mpeg_enc_ctx_allocated)
                    break;

                if (s2->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
                    if (mb_y < avctx->skip_top ||
                        mb_y >= s2->mb_height - avctx->skip_bottom)
                        break;
                }

                if (!s2->pict_type) {
                    av_log(avctx, AV_LOG_ERROR, "Missing picture start code\n");
                    if (avctx->err_recognition & AV_EF_EXPLODE)
                        return AVERROR_INVALIDDATA;
                    break;
                }

                if (s->first_slice) {
                    skip_frame     = 0;
                    s->first_slice = 0;
                    if ((ret = mpeg_field_start(s2, buf, buf_size)) < 0)
                        return ret;
                }
                if (!s2->current_picture_ptr) {
                    av_log(avctx, AV_LOG_ERROR,
                           "current_picture not initialized\n");
                    return AVERROR_INVALIDDATA;
                }

                if (HAVE_THREADS &&
                    (avctx->active_thread_type & FF_THREAD_SLICE) &&
                    !avctx->hwaccel) {
                    int threshold = (s2->mb_height * s->slice_count +
                                     s2->slice_context_count / 2) /
                                    s2->slice_context_count;
                    if (threshold <= mb_y) {
                        MpegEncContext *thread_context = s2->thread_context[s->slice_count];

                        thread_context->start_mb_y = mb_y;
                        thread_context->end_mb_y   = s2->mb_height;
                        if (s->slice_count) {
                            s2->thread_context[s->slice_count - 1]->end_mb_y = mb_y;
                            ret = ff_update_duplicate_context(thread_context, s2);
                            if (ret < 0)
                                return ret;
                        }
                        init_get_bits(&thread_context->gb, buf_ptr, input_size * 8);
                        s->slice_count++;
                    }
                    buf_ptr += 2; // FIXME add minimum number of bytes per slice
                } else {
                    ret = mpeg_decode_slice(s2, mb_y, &buf_ptr, input_size);
                    emms_c();

                    if (ret < 0) {
                        if (avctx->err_recognition & AV_EF_EXPLODE)
                            return ret;
                        if (s2->resync_mb_x >= 0 && s2->resync_mb_y >= 0)
                            ff_er_add_slice(&s2->er, s2->resync_mb_x,
                                            s2->resync_mb_y, s2->mb_x, s2->mb_y,
                                            ER_AC_ERROR | ER_DC_ERROR | ER_MV_ERROR);
                    } else {
                        ff_er_add_slice(&s2->er, s2->resync_mb_x,
                                        s2->resync_mb_y, s2->mb_x - 1, s2->mb_y,
                                        ER_AC_END | ER_DC_END | ER_MV_END);
                    }
                }
            }
            break;
        }
    }
}

static int mpeg_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_output, AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    Mpeg1Context *s = avctx->priv_data;
    AVFrame *picture = data;
    MpegEncContext *s2 = &s->mpeg_enc_ctx;
    ff_dlog(avctx, "fill_buffer\n");

    if (buf_size == 0 || (buf_size == 4 && AV_RB32(buf) == SEQ_END_CODE)) {
        /* special case for last picture */
        if (s2->low_delay == 0 && s2->next_picture_ptr) {
            int ret = av_frame_ref(picture, s2->next_picture_ptr->f);
            if (ret < 0)
                return ret;

            s2->next_picture_ptr = NULL;

            *got_output = 1;
        }
        return buf_size;
    }

    if (s2->avctx->flags & AV_CODEC_FLAG_TRUNCATED) {
        int next = ff_mpeg1_find_frame_end(&s2->parse_context, buf,
                                           buf_size, NULL);

        if (ff_combine_frame(&s2->parse_context, next,
                             (const uint8_t **) &buf, &buf_size) < 0)
            return buf_size;
    }

    if (s->mpeg_enc_ctx_allocated == 0 && avctx->codec_tag == AV_RL32("VCR2"))
        vcr2_init_sequence(avctx);

    s->slice_count = 0;

    if (avctx->extradata && !s->extradata_decoded) {
        int ret = decode_chunks(avctx, picture, got_output,
                                avctx->extradata, avctx->extradata_size);
        s->extradata_decoded = 1;
        if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE))
            return ret;
    }

    return decode_chunks(avctx, picture, got_output, buf, buf_size);
}

static void flush(AVCodecContext *avctx)
{
    Mpeg1Context *s = avctx->priv_data;

    s->sync       = 0;
    s->closed_gop = 0;

    ff_mpeg_flush(avctx);
}

static av_cold int mpeg_decode_end(AVCodecContext *avctx)
{
    Mpeg1Context *s = avctx->priv_data;

    if (s->mpeg_enc_ctx_allocated)
        ff_mpv_common_end(&s->mpeg_enc_ctx);
    av_freep(&s->a53_caption);
    return 0;
}

AVCodec ff_mpeg1video_decoder = {
    .name                  = "mpeg1video",
    .long_name             = NULL_IF_CONFIG_SMALL("MPEG-1 video"),
    .type                  = AVMEDIA_TYPE_VIDEO,
    .id                    = AV_CODEC_ID_MPEG1VIDEO,
    .priv_data_size        = sizeof(Mpeg1Context),
    .init                  = mpeg_decode_init,
    .close                 = mpeg_decode_end,
    .decode                = mpeg_decode_frame,
    .capabilities          = AV_CODEC_CAP_DRAW_HORIZ_BAND | AV_CODEC_CAP_DR1 |
                             AV_CODEC_CAP_TRUNCATED | AV_CODEC_CAP_DELAY |
                             AV_CODEC_CAP_SLICE_THREADS,
    .flush                 = flush,
    .update_thread_context = ONLY_IF_THREADS_ENABLED(mpeg_decode_update_thread_context)
};

AVCodec ff_mpeg2video_decoder = {
    .name           = "mpeg2video",
    .long_name      = NULL_IF_CONFIG_SMALL("MPEG-2 video"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_MPEG2VIDEO,
    .priv_data_size = sizeof(Mpeg1Context),
    .init           = mpeg_decode_init,
    .close          = mpeg_decode_end,
    .decode         = mpeg_decode_frame,
    .capabilities   = AV_CODEC_CAP_DRAW_HORIZ_BAND | AV_CODEC_CAP_DR1 |
                      AV_CODEC_CAP_TRUNCATED | AV_CODEC_CAP_DELAY |
                      AV_CODEC_CAP_SLICE_THREADS,
    .flush          = flush,
    .profiles       = NULL_IF_CONFIG_SMALL(ff_mpeg2_video_profiles),
};

#if FF_API_XVMC
#if CONFIG_MPEG_XVMC_DECODER
static av_cold int mpeg_mc_decode_init(AVCodecContext *avctx)
{
    if (avctx->active_thread_type & FF_THREAD_SLICE)
        return -1;
    if (!(avctx->slice_flags & SLICE_FLAG_CODED_ORDER))
        return -1;
    if (!(avctx->slice_flags & SLICE_FLAG_ALLOW_FIELD)) {
        ff_dlog(avctx, "mpeg12.c: XvMC decoder will work better if SLICE_FLAG_ALLOW_FIELD is set\n");
    }
    mpeg_decode_init(avctx);

    avctx->pix_fmt           = AV_PIX_FMT_XVMC_MPEG2_IDCT;
    avctx->xvmc_acceleration = 2; // 2 - the blocks are packed!

    return 0;
}

AVCodec ff_mpeg_xvmc_decoder = {
    .name           = "mpegvideo_xvmc",
    .long_name      = NULL_IF_CONFIG_SMALL("MPEG-1/2 video XvMC (X-Video Motion Compensation)"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_MPEG2VIDEO_XVMC,
    .priv_data_size = sizeof(Mpeg1Context),
    .init           = mpeg_mc_decode_init,
    .close          = mpeg_decode_end,
    .decode         = mpeg_decode_frame,
    .capabilities   = AV_CODEC_CAP_DRAW_HORIZ_BAND | AV_CODEC_CAP_DR1 |
                      AV_CODEC_CAP_TRUNCATED | CODEC_CAP_HWACCEL |
                      AV_CODEC_CAP_DELAY,
    .flush          = flush,
};

#endif
#endif /* FF_API_XVMC */