FFmpeg/libavcodec/mpeg12.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 FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file mpeg12.c
 * MPEG-1/2 decoder
 */

//#define DEBUG
#include "avcodec.h"
#include "dsputil.h"
#include "mpegvideo.h"

#include "mpeg12.h"
#include "mpeg12data.h"
#include "mpeg12decdata.h"
#include "bytestream.h"

//#undef NDEBUG
//#include <assert.h>


#define MV_VLC_BITS 9
#define MBINCR_VLC_BITS 9
#define MB_PAT_VLC_BITS 9
#define MB_PTYPE_VLC_BITS 6
#define MB_BTYPE_VLC_BITS 6

static inline int mpeg1_decode_block_inter(MpegEncContext *s,
                              DCTELEM *block,
                              int n);
static inline int mpeg1_decode_block_intra(MpegEncContext *s,
                              DCTELEM *block,
                              int n);
static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s, DCTELEM *block, int n);
static inline int mpeg2_decode_block_non_intra(MpegEncContext *s,
                                        DCTELEM *block,
                                        int n);
static inline int mpeg2_decode_block_intra(MpegEncContext *s,
                                    DCTELEM *block,
                                    int n);
static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s, DCTELEM *block, int n);
static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, DCTELEM *block, int n);
static int mpeg_decode_motion(MpegEncContext *s, int fcode, int pred);
static void exchange_uv(MpegEncContext *s);

extern int XVMC_field_start(MpegEncContext *s, AVCodecContext *avctx);
extern int XVMC_field_end(MpegEncContext *s);
extern void XVMC_pack_pblocks(MpegEncContext *s,int cbp);
extern void XVMC_init_block(MpegEncContext *s);//set s->block

static const enum PixelFormat pixfmt_xvmc_mpg2_420[] = {
                                           PIX_FMT_XVMC_MPEG2_IDCT,
                                           PIX_FMT_XVMC_MPEG2_MC,
                                           PIX_FMT_NONE};

uint8_t ff_mpeg12_static_rl_table_store[2][2][2*MAX_RUN + MAX_LEVEL + 3];


#define INIT_2D_VLC_RL(rl, static_size)\
{\
    static RL_VLC_ELEM rl_vlc_table[static_size];\
    INIT_VLC_STATIC(&rl.vlc, TEX_VLC_BITS, rl.n + 2,\
             &rl.table_vlc[0][1], 4, 2,\
             &rl.table_vlc[0][0], 4, 2, static_size);\
\
    rl.rl_vlc[0]= rl_vlc_table;\
    init_2d_vlc_rl(&rl);\
}

static void init_2d_vlc_rl(RLTable *rl)
{
    int i;

    for(i=0; i<rl->vlc.table_size; i++){
        int code= rl->vlc.table[i][0];
        int len = rl->vlc.table[i][1];
        int level, run;

        if(len==0){ // illegal code
            run= 65;
            level= MAX_LEVEL;
        }else if(len<0){ //more bits needed
            run= 0;
            level= code;
        }else{
            if(code==rl->n){ //esc
                run= 65;
                level= 0;
            }else if(code==rl->n+1){ //eob
                run= 0;
                level= 127;
            }else{
                run=   rl->table_run  [code] + 1;
                level= rl->table_level[code];
            }
        }
        rl->rl_vlc[0][i].len= len;
        rl->rl_vlc[0][i].level= level;
        rl->rl_vlc[0][i].run= run;
    }
}

void ff_mpeg12_common_init(MpegEncContext *s)
{

    s->y_dc_scale_table=
    s->c_dc_scale_table= mpeg2_dc_scale_table[s->intra_dc_precision];

}

void ff_mpeg1_clean_buffers(MpegEncContext *s){
    s->last_dc[0] = 1 << (7 + s->intra_dc_precision);
    s->last_dc[1] = s->last_dc[0];
    s->last_dc[2] = s->last_dc[0];
    memset(s->last_mv, 0, sizeof(s->last_mv));
}


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

static VLC mv_vlc;
static VLC mbincr_vlc;
static VLC mb_ptype_vlc;
static VLC mb_btype_vlc;
static VLC mb_pat_vlc;

av_cold void ff_mpeg12_init_vlcs(void)
{
    static int done = 0;

    if (!done) {
        done = 1;

        INIT_VLC_STATIC(&dc_lum_vlc, DC_VLC_BITS, 12,
                 ff_mpeg12_vlc_dc_lum_bits, 1, 1,
                 ff_mpeg12_vlc_dc_lum_code, 2, 2, 512);
        INIT_VLC_STATIC(&dc_chroma_vlc,  DC_VLC_BITS, 12,
                 ff_mpeg12_vlc_dc_chroma_bits, 1, 1,
                 ff_mpeg12_vlc_dc_chroma_code, 2, 2, 514);
        INIT_VLC_STATIC(&mv_vlc, MV_VLC_BITS, 17,
                 &ff_mpeg12_mbMotionVectorTable[0][1], 2, 1,
                 &ff_mpeg12_mbMotionVectorTable[0][0], 2, 1, 518);
        INIT_VLC_STATIC(&mbincr_vlc, MBINCR_VLC_BITS, 36,
                 &ff_mpeg12_mbAddrIncrTable[0][1], 2, 1,
                 &ff_mpeg12_mbAddrIncrTable[0][0], 2, 1, 538);
        INIT_VLC_STATIC(&mb_pat_vlc, MB_PAT_VLC_BITS, 64,
                 &ff_mpeg12_mbPatTable[0][1], 2, 1,
                 &ff_mpeg12_mbPatTable[0][0], 2, 1, 512);

        INIT_VLC_STATIC(&mb_ptype_vlc, MB_PTYPE_VLC_BITS, 7,
                 &table_mb_ptype[0][1], 2, 1,
                 &table_mb_ptype[0][0], 2, 1, 64);
        INIT_VLC_STATIC(&mb_btype_vlc, MB_BTYPE_VLC_BITS, 11,
                 &table_mb_btype[0][1], 2, 1,
                 &table_mb_btype[0][0], 2, 1, 64);
        init_rl(&ff_rl_mpeg1, ff_mpeg12_static_rl_table_store[0]);
        init_rl(&ff_rl_mpeg2, ff_mpeg12_static_rl_table_store[1]);

        INIT_2D_VLC_RL(ff_rl_mpeg1, 680);
        INIT_2D_VLC_RL(ff_rl_mpeg2, 674);
    }
}

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

    dprintf(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 == FF_P_TYPE) {
            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
                mb_type= s->current_picture.mb_type[ s->mb_width + (s->mb_y-1)*s->mb_stride - 1]; // FIXME not sure if this is allowed in MPEG at all
            if(IS_INTRA(mb_type))
                return -1;

            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 FF_I_TYPE:
        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 -1;
            }
            mb_type = MB_TYPE_QUANT | MB_TYPE_INTRA;
        } else {
            mb_type = MB_TYPE_INTRA;
        }
        break;
    case FF_P_TYPE:
        mb_type = get_vlc2(&s->gb, 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 -1;
        }
        mb_type = ptype2mb_type[ mb_type ];
        break;
    case FF_B_TYPE:
        mb_type = get_vlc2(&s->gb, 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 -1;
        }
        mb_type = btype2mb_type[ mb_type ];
        break;
    }
    dprintf(s->avctx, "mb_type=%x\n", mb_type);
//    motion_type = 0; /* avoid warning */
    if (IS_INTRA(mb_type)) {
        s->dsp.clear_blocks(s->block[0]);

        if(!s->chroma_y_shift){
            s->dsp.clear_blocks(s->block[6]);
        }

        /* compute DCT type */
        if (s->picture_structure == PICT_FRAME && //FIXME add an interlaced_dct coded var?
            !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
            memset(s->last_mv, 0, sizeof(s->last_mv)); /* reset mv prediction */
        s->mb_intra = 1;
#ifdef HAVE_XVMC
        //if 1, we memcpy blocks in xvmcvideo
        if(s->avctx->xvmc_acceleration > 1){
            XVMC_pack_pblocks(s,-1);//inter are always full blocks
            if(s->swap_uv){
                exchange_uv(s);
            }
        }
#endif

        if (s->codec_id == CODEC_ID_MPEG2VIDEO) {
            if(s->flags2 & 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 (mpeg2_decode_block_intra(s, s->pblocks[i], i) < 0)
                        return -1;
                }
            }
        } else {
            for(i=0;i<6;i++) {
                if (mpeg1_decode_block_intra(s, s->pblocks[i], i) < 0)
                    return -1;
            }
        }
    } 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;
            dprintf(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;
                                dprintf(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;
                                dprintf(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;
                        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] >> 1);
                        dmy = get_dmv(s);


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

                        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 -1;
            }
        }

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

            cbp = get_vlc2(&s->gb, 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->dsp.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 -1;
            }

#ifdef HAVE_XVMC
            //if 1, we memcpy blocks in xvmcvideo
            if(s->avctx->xvmc_acceleration > 1){
                XVMC_pack_pblocks(s,cbp);
                if(s->swap_uv){
                    exchange_uv(s);
                }
            }
#endif

            if (s->codec_id == CODEC_ID_MPEG2VIDEO) {
                if(s->flags2 & 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 (mpeg2_decode_block_non_intra(s, s->pblocks[i], i) < 0)
                                return -1;
                        } else {
                            s->block_last_index[i] = -1;
                        }
                        cbp+=cbp;
                    }
                }
            } else {
                if(s->flags2 & 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 (mpeg1_decode_block_inter(s, s->pblocks[i], i) < 0)
                                return -1;
                        } 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;
}

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

    code = get_vlc2(&s->gb, 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 */
    l= INT_BIT - 5 - shift;
    val = (val<<l)>>l;
    return val;
}

static inline int mpeg1_decode_block_intra(MpegEncContext *s,
                               DCTELEM *block,
                               int n)
{
    int level, dc, diff, i, j, run;
    int component;
    RLTable *rl = &ff_rl_mpeg1;
    uint8_t * const scantable= s->intra_scantable.permutated;
    const uint16_t *quant_matrix= s->intra_matrix;
    const int qscale= s->qscale;

    /* DC coefficient */
    component = (n <= 3 ? 0 : n - 4 + 1);
    diff = decode_dc(&s->gb, component);
    if (diff >= 0xffff)
        return -1;
    dc = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc<<3;
    dprintf(s->avctx, "dc=%d diff=%d\n", dc, diff);
    i = 0;
    {
        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;
                j = scantable[i];
                level= (level*qscale*quant_matrix[j])>>4;
                level= (level-1)|1;
                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, 8); SKIP_BITS(re, &s->gb, 8);
                if (level == -128) {
                    level = SHOW_UBITS(re, &s->gb, 8) - 256; LAST_SKIP_BITS(re, &s->gb, 8);
                } else if (level == 0) {
                    level = SHOW_UBITS(re, &s->gb, 8)      ; LAST_SKIP_BITS(re, &s->gb, 8);
                }
                i += run;
                j = scantable[i];
                if(level<0){
                    level= -level;
                    level= (level*qscale*quant_matrix[j])>>4;
                    level= (level-1)|1;
                    level= -level;
                }else{
                    level= (level*qscale*quant_matrix[j])>>4;
                    level= (level-1)|1;
                }
            }
            if (i > 63){
                av_log(s->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

            block[j] = level;
        }
        CLOSE_READER(re, &s->gb);
    }
    s->block_last_index[n] = i;
   return 0;
}

static inline int mpeg1_decode_block_inter(MpegEncContext *s,
                               DCTELEM *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;
        }
#if MIN_CACHE_BITS < 19
        UPDATE_CACHE(re, &s->gb);
#endif
        /* 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;
                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;
                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;
                }
            }
            if (i > 63){
                av_log(s->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

            block[j] = level;
#if MIN_CACHE_BITS < 19
            UPDATE_CACHE(re, &s->gb);
#endif
            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
                break;
#if MIN_CACHE_BITS >= 19
            UPDATE_CACHE(re, &s->gb);
#endif
        }
end:
        LAST_SKIP_BITS(re, &s->gb, 2);
        CLOSE_READER(re, &s->gb);
    }
    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s, DCTELEM *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;
        }
#if MIN_CACHE_BITS < 19
        UPDATE_CACHE(re, &s->gb);
#endif

        /* 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;
                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;
                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 MIN_CACHE_BITS < 19
            UPDATE_CACHE(re, &s->gb);
#endif
            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
                break;
#if MIN_CACHE_BITS >= 19
            UPDATE_CACHE(re, &s->gb);
#endif
        }
end:
        LAST_SKIP_BITS(re, &s->gb, 2);
        CLOSE_READER(re, &s->gb);
    }
    s->block_last_index[n] = i;
    return 0;
}


static inline int mpeg2_decode_block_non_intra(MpegEncContext *s,
                               DCTELEM *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;
        }
#if MIN_CACHE_BITS < 19
        UPDATE_CACHE(re, &s->gb);
#endif

        /* 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;
                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;
                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;
                }
            }
            if (i > 63){
                av_log(s->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

            mismatch ^= level;
            block[j] = level;
#if MIN_CACHE_BITS < 19
            UPDATE_CACHE(re, &s->gb);
#endif
            if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
                break;
#if MIN_CACHE_BITS >= 19
            UPDATE_CACHE(re, &s->gb);
#endif
        }
end:
        LAST_SKIP_BITS(re, &s->gb, 2);
        CLOSE_READER(re, &s->gb);
    }
    block[63] ^= (mismatch & 1);

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

static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
                               DCTELEM *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;
    }
#if MIN_CACHE_BITS < 19
    UPDATE_CACHE(re, &s->gb);
#endif

    /* 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;
            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;
            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 MIN_CACHE_BITS < 19
        UPDATE_CACHE(re, &s->gb);
#endif
        if(((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
            break;
#if MIN_CACHE_BITS >=19
        UPDATE_CACHE(re, &s->gb);
#endif
    }
end:
    LAST_SKIP_BITS(re, &s->gb, 2);
    CLOSE_READER(re, &s->gb);
    s->block_last_index[n] = i;
    return 0;
}


static inline int mpeg2_decode_block_intra(MpegEncContext *s,
                               DCTELEM *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 -1;
    dc = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc << (3 - s->intra_dc_precision);
    dprintf(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;
                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;
                j = scantable[i];
                if(level<0){
                    level= (-level*qscale*quant_matrix[j])>>4;
                    level= -level;
                }else{
                    level= (level*qscale*quant_matrix[j])>>4;
                }
            }
            if (i > 63){
                av_log(s->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

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

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

static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s,
                               DCTELEM *block,
                               int n)
{
    int level, dc, diff, j, run;
    int component;
    RLTable *rl;
    uint8_t * 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 -1;
    dc = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc << (3 - s->intra_dc_precision);
    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) {
                scantable += run;
                j = *scantable;
                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);
                scantable += run;
                j = *scantable;
                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);
    }

    s->block_last_index[n] = scantable - s->intra_scantable.permutated;
    return 0;
}

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 */
    int slice_count;
    int swap_uv;//indicate VCR2
    int save_aspect_info;
    int save_width, save_height;
    AVRational frame_rate_ext;       ///< MPEG-2 specific framerate modificator

} Mpeg1Context;

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

    /* we need some permutation to store matrices,
     * until MPV_common_init() sets the real permutation. */
    for(i=0;i<64;i++)
       s2->dsp.idct_permutation[i]=i;

    MPV_decode_defaults(s2);

    s->mpeg_enc_ctx.avctx= avctx;
    s->mpeg_enc_ctx.flags= avctx->flags;
    s->mpeg_enc_ctx.flags2= avctx->flags2;
    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;
    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]];
    }
}

/* 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];

    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||
        0)
    {

        if (s1->mpeg_enc_ctx_allocated) {
            ParseContext pc= s->parse_context;
            s->parse_context.buffer=0;
            MPV_common_end(s);
            s->parse_context= pc;
        }

        if( (s->width == 0 )||(s->height == 0))
            return -2;

        avcodec_set_dimensions(avctx, s->width, s->height);
        avctx->bit_rate = s->bit_rate;
        s1->save_aspect_info = s->aspect_ratio_info;
        s1->save_width = s->width;
        s1->save_height = s->height;

        /* 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->sub_id==1){//s->codec_id==avctx->codec_id==CODEC_ID
            //MPEG-1 fps
            avctx->time_base.den= ff_frame_rate_tab[s->frame_rate_index].num;
            avctx->time_base.num= ff_frame_rate_tab[s->frame_rate_index].den;
            //MPEG-1 aspect
            avctx->sample_aspect_ratio= av_d2q(
                    1.0/ff_mpeg1_aspect[s->aspect_ratio_info], 255);

        }else{//MPEG-2
        //MPEG-2 fps
            av_reduce(
                &s->avctx->time_base.den,
                &s->avctx->time_base.num,
                ff_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num,
                ff_frame_rate_tab[s->frame_rate_index].den * s1->frame_rate_ext.den,
                1<<30);
        //MPEG-2 aspect
            if(s->aspect_ratio_info > 1){
                if( (s1->pan_scan.width == 0 )||(s1->pan_scan.height == 0) ){
                    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}
                        );
                }
            }else{
                s->avctx->sample_aspect_ratio=
                    ff_mpeg2_aspect[s->aspect_ratio_info];
            }
        }//MPEG-2

        if(avctx->xvmc_acceleration){
            avctx->pix_fmt = avctx->get_format(avctx,pixfmt_xvmc_mpg2_420);
        }else{
            if(s->chroma_format <  2){
                avctx->pix_fmt = PIX_FMT_YUV420P;
            }else
            if(s->chroma_format == 2){
                avctx->pix_fmt = PIX_FMT_YUV422P;
            }else
            if(s->chroma_format >  2){
                avctx->pix_fmt = PIX_FMT_YUV444P;
            }
        }
        //until then pix_fmt may be changed right after codec init
        if( avctx->pix_fmt == PIX_FMT_XVMC_MPEG2_IDCT )
            if( avctx->idct_algo == FF_IDCT_AUTO )
                avctx->idct_algo = FF_IDCT_SIMPLE;

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

        if (MPV_common_init(s) < 0)
            return -2;

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

    if(mpeg_decode_postinit(s->avctx) < 0)
       return -2;

    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 -1;

    vbv_delay= get_bits(&s->gb, 16);
    if (s->pict_type == FF_P_TYPE || s->pict_type == FF_B_TYPE) {
        s->full_pel[0] = get_bits1(&s->gb);
        f_code = get_bits(&s->gb, 3);
        if (f_code == 0 && avctx->error_resilience >= FF_ER_COMPLIANT)
            return -1;
        s->mpeg_f_code[0][0] = f_code;
        s->mpeg_f_code[0][1] = f_code;
    }
    if (s->pict_type == FF_B_TYPE) {
        s->full_pel[1] = get_bits1(&s->gb);
        f_code = get_bits(&s->gb, 3);
        if (f_code == 0 && avctx->error_resilience >= FF_ER_COMPLIANT)
            return -1;
        s->mpeg_f_code[1][0] = f_code;
        s->mpeg_f_code[1][1] = f_code;
    }
    s->current_picture.pict_type= s->pict_type;
    s->current_picture.key_frame= s->pict_type == FF_I_TYPE;

    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;
    s->first_slice = 1;
    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->flags & 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;

    dprintf(s->avctx, "sequence extension\n");
    s->codec_id= s->avctx->codec_id= CODEC_ID_MPEG2VIDEO;
    s->avctx->sub_id = 2; /* indicates MPEG-2 found */

    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){
        skip_bits(&s->gb, 8); /* color primaries */
        skip_bits(&s->gb, 8); /* transfer_characteristics */
        skip_bits(&s->gb, 8); /* matrix_coefficients */
    }
    w= get_bits(&s->gb, 14);
    skip_bits(&s->gb, 1); //marker
    h= get_bits(&s->gb, 14);
    skip_bits(&s->gb, 1); //marker

    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 (%d,%d) (%d,%d) (%d,%d)\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 void mpeg_decode_quant_matrix_extension(MpegEncContext *s)
{
    int i, v, j;

    dprintf(s->avctx, "matrix extension\n");

    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->intra_matrix[j] = v;
            s->chroma_intra_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->inter_matrix[j] = v;
            s->chroma_inter_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->chroma_intra_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->chroma_inter_matrix[j] = v;
        }
    }
}

static void mpeg_decode_picture_coding_extension(MpegEncContext *s)
{
    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);
    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->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->dsp.idct_permutation, &s->inter_scantable  , ff_alternate_vertical_scan);
        ff_init_scantable(s->dsp.idct_permutation, &s->intra_scantable  , ff_alternate_vertical_scan);
    }else{
        ff_init_scantable(s->dsp.idct_permutation, &s->inter_scantable  , ff_zigzag_direct);
        ff_init_scantable(s->dsp.idct_permutation, &s->intra_scantable  , ff_zigzag_direct);
    }

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

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

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

    ext_type = get_bits(&s->gb, 4);
    switch(ext_type) {
    case 0x1:
        mpeg_decode_sequence_extension(s1);
        break;
    case 0x2:
        mpeg_decode_sequence_display_extension(s1);
        break;
    case 0x3:
        mpeg_decode_quant_matrix_extension(s);
        break;
    case 0x7:
        mpeg_decode_picture_display_extension(s1);
        break;
    case 0x8:
        mpeg_decode_picture_coding_extension(s);
        break;
    }
}

static void exchange_uv(MpegEncContext *s){
    short * tmp = s->pblocks[4];
    s->pblocks[4] = s->pblocks[5];
    s->pblocks[5] = tmp;
}

static int mpeg_field_start(MpegEncContext *s){
    AVCodecContext *avctx= s->avctx;
    Mpeg1Context *s1 = (Mpeg1Context*)s;

    /* start frame decoding */
    if(s->first_field || s->picture_structure==PICT_FRAME){
        if(MPV_frame_start(s, avctx) < 0)
            return -1;

        ff_er_frame_start(s);

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

        *s->current_picture_ptr->pan_scan= s1->pan_scan;
    }else{ //second field
            int i;

            if(!s->current_picture_ptr){
                av_log(s->avctx, AV_LOG_ERROR, "first field missing\n");
                return -1;
            }

            for(i=0; i<4; i++){
                s->current_picture.data[i] = s->current_picture_ptr->data[i];
                if(s->picture_structure == PICT_BOTTOM_FIELD){
                    s->current_picture.data[i] += s->current_picture_ptr->linesize[i];
                }
            }
    }
#ifdef HAVE_XVMC
// MPV_frame_start will call this function too,
// but we need to call it on every field
    if(s->avctx->xvmc_acceleration)
         XVMC_field_start(s,avctx);
#endif

    return 0;
}

#define DECODE_SLICE_ERROR -1
#define DECODE_SLICE_OK 0

/**
 * decodes a slice. MpegEncContext.mb_y must be set to the MB row from the startcode
 * @return DECODE_SLICE_ERROR if the slice is damaged<br>
 *         DECODE_SLICE_OK if this slice is ok<br>
 */
static int mpeg_decode_slice(Mpeg1Context *s1, int mb_y,
                             const uint8_t **buf, int buf_size)
{
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    AVCodecContext *avctx= s->avctx;
    const int field_pic= s->picture_structure != PICT_FRAME;
    const int lowres= s->avctx->lowres;

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

    if (mb_y<<field_pic >= s->mb_height){
        av_log(s->avctx, AV_LOG_ERROR, "slice below image (%d >= %d)\n", mb_y, s->mb_height);
        return -1;
    }

    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 -1;
    }

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

    s->mb_x=0;

    for(;;) {
        int code = get_vlc2(&s->gb, mbincr_vlc.table, MBINCR_VLC_BITS, 2);
        if (code < 0){
            av_log(s->avctx, AV_LOG_ERROR, "first mb_incr damaged\n");
            return -1;
        }
        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 -1;
    }

    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 == FF_I_TYPE ? "I" : (s->pict_type == FF_P_TYPE ? "P" : (s->pict_type == FF_B_TYPE ? "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(;;) {
#ifdef HAVE_XVMC
        //If 1, we memcpy blocks in xvmcvideo.
        if(s->avctx->xvmc_acceleration > 1)
            XVMC_init_block(s);//set s->block
#endif

        if(mpeg_decode_mb(s, s->block) < 0)
            return -1;

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

            for(i=0; i<2; i++){
                for(dir=0; dir<2; dir++){
                    if (s->mb_intra || (dir==1 && s->pict_type != FF_B_TYPE)) {
                        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][xy    ]=
                    s->current_picture.ref_index [dir][xy + 1]= s->field_select[dir][i];
                    assert(s->field_select[dir][i]==0 || s->field_select[dir][i]==1);
                }
                xy += wrap;
            }
        }

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

        MPV_decode_mb(s, s->block);

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

            ff_draw_horiz_band(s, mb_size*s->mb_y, mb_size);

            s->mb_x = 0;
            s->mb_y++;

            if(s->mb_y<<field_pic >= s->mb_height){
                int left= s->gb.size_in_bits - get_bits_count(&s->gb);
                int is_d10= s->chroma_format==2 && s->pict_type==FF_I_TYPE && 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->error_resilience >= FF_ER_AGGRESSIVE && left>8)){
                    av_log(avctx, AV_LOG_ERROR, "end mismatch left=%d %0X\n", left, show_bits(&s->gb, FFMIN(left, 23)));
                    return -1;
                }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, mbincr_vlc.table, MBINCR_VLC_BITS, 2);
                if (code < 0){
                    av_log(s->avctx, AV_LOG_ERROR, "mb incr damaged\n");
                    return -1;
                }
                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 -1;
                        }
                        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 == FF_I_TYPE){
                    av_log(s->avctx, AV_LOG_ERROR, "skipped MB in I frame at %d %d\n", s->mb_x, s->mb_y);
                    return -1;
                }

                /* 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 == FF_P_TYPE) {
                    /* 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;
                } 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;
//printf("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= arg;
    const uint8_t *buf= s->gb.buffer;
    int mb_y= s->start_mb_y;

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

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

        ret= mpeg_decode_slice((Mpeg1Context*)s, mb_y, &buf, s->gb.buffer_end - buf);
        emms_c();
//av_log(c, AV_LOG_DEBUG, "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->error_count);
        if(ret < 0){
            if(s->resync_mb_x>=0 && s->resync_mb_y>=0)
                ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, AC_ERROR|DC_ERROR|MV_ERROR);
        }else{
            ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x-1, s->mb_y, AC_END|DC_END|MV_END);
        }

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

        start_code= -1;
        buf = ff_find_start_code(buf, s->gb.buffer_end, &start_code);
        mb_y= start_code - SLICE_MIN_START_CODE;
        if(mb_y < 0 || mb_y >= s->end_mb_y)
            return -1;
    }

    return 0; //not reached
}

/**
 * Handles 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;

#ifdef HAVE_XVMC
    if(s->avctx->xvmc_acceleration)
        XVMC_field_end(s);
#endif
    /* end of slice reached */
    if (/*s->mb_y<<field_pic == s->mb_height &&*/ !s->first_field) {
        /* end of image */

        s->current_picture_ptr->qscale_type= FF_QSCALE_TYPE_MPEG2;

        ff_er_frame_end(s);

        MPV_frame_end(s);

        if (s->pict_type == FF_B_TYPE || s->low_delay) {
            *pict= *(AVFrame*)s->current_picture_ptr;
            ff_print_debug_info(s, pict);
        } else {
            s->picture_number++;
            /* latency of 1 frame for I- and P-frames */
            /* XXX: use another variable than picture_number */
            if (s->last_picture_ptr != NULL) {
                *pict= *(AVFrame*)s->last_picture_ptr;
                 ff_print_debug_info(s, pict);
            }
        }

        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)
        return -1;
    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->error_resilience >= FF_ER_COMPLIANT)
            return -1;
    }
    s->frame_rate_index = get_bits(&s->gb, 4);
    if (s->frame_rate_index == 0 || s->frame_rate_index > 13)
        return -1;
    s->bit_rate = get_bits(&s->gb, 18) * 400;
    if (get_bits1(&s->gb) == 0) /* marker */
        return -1;
    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)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            if(v==0){
                av_log(s->avctx, AV_LOG_ERROR, "intra matrix damaged\n");
                return -1;
            }
            j = s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->intra_matrix[j] = v;
            s->chroma_intra_matrix[j] = v;
        }
#ifdef DEBUG
        dprintf(s->avctx, "intra matrix present\n");
        for(i=0;i<64;i++)
            dprintf(s->avctx, " %d", s->intra_matrix[s->dsp.idct_permutation[i]]);
        dprintf(s->avctx, "\n");
#endif
    } else {
        for(i=0;i<64;i++) {
            j = s->dsp.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)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            if(v==0){
                av_log(s->avctx, AV_LOG_ERROR, "inter matrix damaged\n");
                return -1;
            }
            j = s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->inter_matrix[j] = v;
            s->chroma_inter_matrix[j] = v;
        }
#ifdef DEBUG
        dprintf(s->avctx, "non-intra matrix present\n");
        for(i=0;i<64;i++)
            dprintf(s->avctx, " %d", s->inter_matrix[s->dsp.idct_permutation[i]]);
        dprintf(s->avctx, "\n");
#endif
    } else {
        for(i=0;i<64;i++) {
            int j= s->dsp.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 -1;
    }

    /* 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= CODEC_ID_MPEG1VIDEO;
    avctx->sub_id = 1; /* indicates MPEG-1 */
    s->out_format = FMT_MPEG1;
    s->swap_uv = 0;//AFAIK VCR2 does not have SEQ_HEADER
    if(s->flags & 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;

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

    if(avctx->xvmc_acceleration){
        avctx->pix_fmt = avctx->get_format(avctx,pixfmt_xvmc_mpg2_420);
    }else{
        avctx->pix_fmt = PIX_FMT_YUV420P;
    }

    if( avctx->pix_fmt == PIX_FMT_XVMC_MPEG2_IDCT )
        if( avctx->idct_algo == FF_IDCT_AUTO )
            avctx->idct_algo = FF_IDCT_SIMPLE;

    if (MPV_common_init(s) < 0)
        return -1;
    exchange_uv(s);//common init reset pblocks, so we swap them here
    s->swap_uv = 1;// in case of xvmc we need to swap uv for each MB
    s1->mpeg_enc_ctx_allocated = 1;

    for(i=0;i<64;i++) {
        int j= s->dsp.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= CODEC_ID_MPEG2VIDEO;
    avctx->sub_id = 2; /* indicates MPEG-2 */
    return 0;
}


static void mpeg_decode_user_data(AVCodecContext *avctx,
                                  const uint8_t *buf, int buf_size)
{
    const uint8_t *p;
    int len, flags;
    p = buf;
    len = buf_size;

    /* we parse the DTG active format information */
    if (len >= 5 &&
        p[0] == 'D' && p[1] == 'T' && p[2] == 'G' && p[3] == '1') {
        flags = p[4];
        p += 5;
        len -= 5;
        if (flags & 0x80) {
            /* skip event id */
            if (len < 2)
                return;
            p += 2;
            len -= 2;
        }
        if (flags & 0x40) {
            if (len < 1)
                return;
            avctx->dtg_active_format = p[0] & 0x0f;
        }
    }
}

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

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

    drop_frame_flag = get_bits1(&s->gb);

    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);

    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, closed_gop, broken_link);
}
/**
 * Finds the end of the current frame in the bitstream.
 * @return the position of the first byte of the next frame, or -1
 */
int ff_mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
{
    int i;
    uint32_t state= pc->state;

    /* EOF considered as end of frame */
    if (buf_size == 0)
        return 0;

/*
 0  frame start         -> 1/4
 1  first_SEQEXT        -> 0/2
 2  first field start   -> 3/0
 3  second_SEQEXT       -> 2/0
 4  searching end
*/

    for(i=0; i<buf_size; i++){
        assert(pc->frame_start_found>=0 && pc->frame_start_found<=4);
        if(pc->frame_start_found&1){
            if(state == EXT_START_CODE && (buf[i]&0xF0) != 0x80)
                pc->frame_start_found--;
            else if(state == EXT_START_CODE+2){
                if((buf[i]&3) == 3) pc->frame_start_found= 0;
                else                pc->frame_start_found= (pc->frame_start_found+1)&3;
            }
            state++;
        }else{
            i= ff_find_start_code(buf+i, buf+buf_size, &state) - buf - 1;
            if(pc->frame_start_found==0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE){
                i++;
                pc->frame_start_found=4;
            }
            if(state == SEQ_END_CODE){
                pc->state=-1;
                return i+1;
            }
            if(pc->frame_start_found==2 && state == SEQ_START_CODE)
                pc->frame_start_found= 0;
            if(pc->frame_start_found<4 && state == EXT_START_CODE)
                pc->frame_start_found++;
            if(pc->frame_start_found == 4 && (state&0xFFFFFF00) == 0x100){
                if(state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE){
                    pc->frame_start_found=0;
                    pc->state=-1;
                    return i-3;
                }
            }
        }
    }
    pc->state= state;
    return END_NOT_FOUND;
}

static int decode_chunks(AVCodecContext *avctx,
                             AVFrame *picture, int *data_size,
                             const uint8_t *buf, int buf_size);

/* handle buffering and image synchronisation */
static int mpeg_decode_frame(AVCodecContext *avctx,
                             void *data, int *data_size,
                             const uint8_t *buf, int buf_size)
{
    Mpeg1Context *s = avctx->priv_data;
    AVFrame *picture = data;
    MpegEncContext *s2 = &s->mpeg_enc_ctx;
    dprintf(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) {
            *picture= *(AVFrame*)s2->next_picture_ptr;
            s2->next_picture_ptr= NULL;

            *data_size = sizeof(AVFrame);
        }
        return buf_size;
    }

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

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

#if 0
    if (s->repeat_field % 2 == 1) {
        s->repeat_field++;
        //fprintf(stderr,"\nRepeating last frame: %d -> %d! pict: %d %d", avctx->frame_number-1, avctx->frame_number,
        //        s2->picture_number, s->repeat_field);
        if (avctx->flags & CODEC_FLAG_REPEAT_FIELD) {
            *data_size = sizeof(AVPicture);
            goto the_end;
        }
    }
#endif

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

    s->slice_count= 0;

    if(avctx->extradata && !avctx->frame_number)
        decode_chunks(avctx, picture, data_size, avctx->extradata, avctx->extradata_size);

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

static int decode_chunks(AVCodecContext *avctx,
                             AVFrame *picture, int *data_size,
                             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;

    for(;;) {
        /* find next start code */
        uint32_t start_code = -1;
        buf_ptr = ff_find_start_code(buf_ptr,buf_end, &start_code);
        if (start_code > 0x1ff){
            if(s2->pict_type != FF_B_TYPE || avctx->skip_frame <= AVDISCARD_DEFAULT){
                if(avctx->thread_count > 1){
                    int i;

                    avctx->execute(avctx, slice_decode_thread,  (void**)&(s2->thread_context[0]), NULL, s->slice_count);
                    for(i=0; i<s->slice_count; i++)
                        s2->error_count += s2->thread_context[i]->error_count;
                }
                if (slice_end(avctx, picture)) {
                    if(s2->last_picture_ptr || s2->low_delay) //FIXME merge with the stuff in mpeg_decode_slice
                        *data_size = sizeof(AVPicture);
                }
            }
            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, "%3X 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:
            mpeg1_decode_sequence(avctx, buf_ptr,
                                    input_size);
            break;

        case PICTURE_START_CODE:
            /* we have a complete image: we try to decompress it */
            mpeg1_decode_picture(avctx,
                                    buf_ptr, input_size);
            break;
        case EXT_START_CODE:
            mpeg_decode_extension(avctx,
                                    buf_ptr, input_size);
            break;
        case USER_START_CODE:
            mpeg_decode_user_data(avctx,
                                    buf_ptr, input_size);
            break;
        case GOP_START_CODE:
            s2->first_field=0;
            mpeg_decode_gop(avctx,
                                    buf_ptr, input_size);
            break;
        default:
            if (start_code >= SLICE_MIN_START_CODE &&
                start_code <= SLICE_MAX_START_CODE) {
                int mb_y= start_code - SLICE_MIN_START_CODE;

                if(s2->last_picture_ptr==NULL){
                /* Skip B-frames if we do not have reference frames. */
                    if(s2->pict_type==FF_B_TYPE) break;
                }
                if(s2->next_picture_ptr==NULL){
                /* Skip P-frames if we do not have a reference frame or we have an invalid header. */
                    if(s2->pict_type==FF_P_TYPE && (s2->first_field || s2->picture_structure==PICT_FRAME)) break;
                }
                /* Skip B-frames if we are in a hurry. */
                if(avctx->hurry_up && s2->pict_type==FF_B_TYPE) break;
                if(  (avctx->skip_frame >= AVDISCARD_NONREF && s2->pict_type==FF_B_TYPE)
                    ||(avctx->skip_frame >= AVDISCARD_NONKEY && s2->pict_type!=FF_I_TYPE)
                    || avctx->skip_frame >= AVDISCARD_ALL)
                    break;
                /* Skip everything if we are in a hurry>=5. */
                if(avctx->hurry_up>=5) break;

                if (!s->mpeg_enc_ctx_allocated) break;

                if(s2->codec_id == CODEC_ID_MPEG2VIDEO){
                    if(mb_y < avctx->skip_top || mb_y >= s2->mb_height - avctx->skip_bottom)
                        break;
                }

                if(s2->first_slice){
                    s2->first_slice=0;
                            if(mpeg_field_start(s2) < 0)
                        return -1;
                    }
                if(!s2->current_picture_ptr){
                    av_log(avctx, AV_LOG_ERROR, "current_picture not initialized\n");
                    return -1;
                }

                if(avctx->thread_count > 1){
                    int threshold= (s2->mb_height*s->slice_count + avctx->thread_count/2) / avctx->thread_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;
                            ff_update_duplicate_context(thread_context, s2);
                        }
                        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(s, mb_y, &buf_ptr, input_size);
                    emms_c();

                    if(ret < 0){
                        if(s2->resync_mb_x>=0 && s2->resync_mb_y>=0)
                            ff_er_add_slice(s2, s2->resync_mb_x, s2->resync_mb_y, s2->mb_x, s2->mb_y, AC_ERROR|DC_ERROR|MV_ERROR);
                    }else{
                        ff_er_add_slice(s2, s2->resync_mb_x, s2->resync_mb_y, s2->mb_x-1, s2->mb_y, AC_END|DC_END|MV_END);
                    }
                }
            }
            break;
        }
    }
}

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

    if (s->mpeg_enc_ctx_allocated)
        MPV_common_end(&s->mpeg_enc_ctx);
    return 0;
}

AVCodec mpeg1video_decoder = {
    "mpeg1video",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG1VIDEO,
    sizeof(Mpeg1Context),
    mpeg_decode_init,
    NULL,
    mpeg_decode_end,
    mpeg_decode_frame,
    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY,
    .flush= ff_mpeg_flush,
    .long_name= NULL_IF_CONFIG_SMALL("MPEG-1 video"),
};

AVCodec mpeg2video_decoder = {
    "mpeg2video",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG2VIDEO,
    sizeof(Mpeg1Context),
    mpeg_decode_init,
    NULL,
    mpeg_decode_end,
    mpeg_decode_frame,
    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY,
    .flush= ff_mpeg_flush,
    .long_name= NULL_IF_CONFIG_SMALL("MPEG-2 video"),
};

//legacy decoder
AVCodec mpegvideo_decoder = {
    "mpegvideo",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG2VIDEO,
    sizeof(Mpeg1Context),
    mpeg_decode_init,
    NULL,
    mpeg_decode_end,
    mpeg_decode_frame,
    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY,
    .flush= ff_mpeg_flush,
    .long_name= NULL_IF_CONFIG_SMALL("MPEG-1 video"),
};

#ifdef HAVE_XVMC
static av_cold int mpeg_mc_decode_init(AVCodecContext *avctx){
    Mpeg1Context *s;

    if( avctx->thread_count > 1)
        return -1;
    if( !(avctx->slice_flags & SLICE_FLAG_CODED_ORDER) )
        return -1;
    if( !(avctx->slice_flags & SLICE_FLAG_ALLOW_FIELD) ){
        dprintf(avctx, "mpeg12.c: XvMC decoder will work better if SLICE_FLAG_ALLOW_FIELD is set\n");
    }
    mpeg_decode_init(avctx);
    s = avctx->priv_data;

    avctx->pix_fmt = PIX_FMT_XVMC_MPEG2_IDCT;
    avctx->xvmc_acceleration = 2;//2 - the blocks are packed!

    return 0;
}

AVCodec mpeg_xvmc_decoder = {
    "mpegvideo_xvmc",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG2VIDEO_XVMC,
    sizeof(Mpeg1Context),
    mpeg_mc_decode_init,
    NULL,
    mpeg_decode_end,
    mpeg_decode_frame,
    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED| CODEC_CAP_HWACCEL | CODEC_CAP_DELAY,
    .flush= ff_mpeg_flush,
    .long_name = NULL_IF_CONFIG_SMALL("MPEG-1 video XvMC (X-Video Motion Compensation)"),
};

#endif