ffmpeg/libavcodec/mpeg4videodec.c

/*
 * MPEG4 decoder.
 * Copyright (c) 2000,2001 Fabrice Bellard
 * Copyright (c) 2002-2010 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
 */

#include "mpegvideo.h"
#include "mpeg4video.h"
#include "h263.h"
#include "thread.h"

// The defines below define the number of bits that are read at once for
// reading vlc values. Changing these may improve speed and data cache needs
// be aware though that decreasing them may need the number of stages that is
// passed to get_vlc* to be increased.
#define SPRITE_TRAJ_VLC_BITS 6
#define DC_VLC_BITS 9
#define MB_TYPE_B_VLC_BITS 4


static VLC dc_lum, dc_chrom;
static VLC sprite_trajectory;
static VLC mb_type_b_vlc;

static const int mb_type_b_map[4]= {
    MB_TYPE_DIRECT2 | MB_TYPE_L0L1,
    MB_TYPE_L0L1 | MB_TYPE_16x16,
    MB_TYPE_L1 | MB_TYPE_16x16,
    MB_TYPE_L0 | MB_TYPE_16x16,
};

/**
 * predicts the ac.
 * @param n block index (0-3 are luma, 4-5 are chroma)
 * @param dir the ac prediction direction
 */
void mpeg4_pred_ac(MpegEncContext * s, DCTELEM *block, int n,
                   int dir)
{
    int i;
    int16_t *ac_val, *ac_val1;
    int8_t * const qscale_table= s->current_picture.qscale_table;

    /* find prediction */
    ac_val = s->ac_val[0][0] + s->block_index[n] * 16;
    ac_val1 = ac_val;
    if (s->ac_pred) {
        if (dir == 0) {
            const int xy= s->mb_x-1 + s->mb_y*s->mb_stride;
            /* left prediction */
            ac_val -= 16;

            if(s->mb_x==0 || s->qscale == qscale_table[xy] || n==1 || n==3){
                /* same qscale */
                for(i=1;i<8;i++) {
                    block[s->dsp.idct_permutation[i<<3]] += ac_val[i];
                }
            }else{
                /* different qscale, we must rescale */
                for(i=1;i<8;i++) {
                    block[s->dsp.idct_permutation[i<<3]] += ROUNDED_DIV(ac_val[i]*qscale_table[xy], s->qscale);
                }
            }
        } else {
            const int xy= s->mb_x + s->mb_y*s->mb_stride - s->mb_stride;
            /* top prediction */
            ac_val -= 16 * s->block_wrap[n];

            if(s->mb_y==0 || s->qscale == qscale_table[xy] || n==2 || n==3){
                /* same qscale */
                for(i=1;i<8;i++) {
                    block[s->dsp.idct_permutation[i]] += ac_val[i + 8];
                }
            }else{
                /* different qscale, we must rescale */
                for(i=1;i<8;i++) {
                    block[s->dsp.idct_permutation[i]] += ROUNDED_DIV(ac_val[i + 8]*qscale_table[xy], s->qscale);
                }
            }
        }
    }
    /* left copy */
    for(i=1;i<8;i++)
        ac_val1[i    ] = block[s->dsp.idct_permutation[i<<3]];

    /* top copy */
    for(i=1;i<8;i++)
        ac_val1[8 + i] = block[s->dsp.idct_permutation[i   ]];

}

/**
 * check if the next stuff is a resync marker or the end.
 * @return 0 if not
 */
static inline int mpeg4_is_resync(MpegEncContext *s){
    int bits_count= get_bits_count(&s->gb);
    int v= show_bits(&s->gb, 16);

    if(s->workaround_bugs&FF_BUG_NO_PADDING){
        return 0;
    }

    while(v<=0xFF){
        if(s->pict_type==FF_B_TYPE || (v>>(8-s->pict_type)!=1) || s->partitioned_frame)
            break;
        skip_bits(&s->gb, 8+s->pict_type);
        bits_count+= 8+s->pict_type;
        v= show_bits(&s->gb, 16);
    }

    if(bits_count + 8 >= s->gb.size_in_bits){
        v>>=8;
        v|= 0x7F >> (7-(bits_count&7));

        if(v==0x7F)
            return 1;
    }else{
        if(v == ff_mpeg4_resync_prefix[bits_count&7]){
            int len;
            GetBitContext gb= s->gb;

            skip_bits(&s->gb, 1);
            align_get_bits(&s->gb);

            for(len=0; len<32; len++){
                if(get_bits1(&s->gb)) break;
            }

            s->gb= gb;

            if(len>=ff_mpeg4_get_video_packet_prefix_length(s))
                return 1;
        }
    }
    return 0;
}

static void mpeg4_decode_sprite_trajectory(MpegEncContext * s, GetBitContext *gb)
{
    int i;
    int a= 2<<s->sprite_warping_accuracy;
    int rho= 3-s->sprite_warping_accuracy;
    int r=16/a;
    const int vop_ref[4][2]= {{0,0}, {s->width,0}, {0, s->height}, {s->width, s->height}}; // only true for rectangle shapes
    int d[4][2]={{0,0}, {0,0}, {0,0}, {0,0}};
    int sprite_ref[4][2];
    int virtual_ref[2][2];
    int w2, h2, w3, h3;
    int alpha=0, beta=0;
    int w= s->width;
    int h= s->height;
    int min_ab;

    for(i=0; i<s->num_sprite_warping_points; i++){
        int length;
        int x=0, y=0;

        length= get_vlc2(gb, sprite_trajectory.table, SPRITE_TRAJ_VLC_BITS, 3);
        if(length){
            x= get_xbits(gb, length);
        }
        if(!(s->divx_version==500 && s->divx_build==413)) skip_bits1(gb); /* marker bit */

        length= get_vlc2(gb, sprite_trajectory.table, SPRITE_TRAJ_VLC_BITS, 3);
        if(length){
            y=get_xbits(gb, length);
        }
        skip_bits1(gb); /* marker bit */
        s->sprite_traj[i][0]= d[i][0]= x;
        s->sprite_traj[i][1]= d[i][1]= y;
    }
    for(; i<4; i++)
        s->sprite_traj[i][0]= s->sprite_traj[i][1]= 0;

    while((1<<alpha)<w) alpha++;
    while((1<<beta )<h) beta++; // there seems to be a typo in the mpeg4 std for the definition of w' and h'
    w2= 1<<alpha;
    h2= 1<<beta;

// Note, the 4th point isn't used for GMC
    if(s->divx_version==500 && s->divx_build==413){
        sprite_ref[0][0]= a*vop_ref[0][0] + d[0][0];
        sprite_ref[0][1]= a*vop_ref[0][1] + d[0][1];
        sprite_ref[1][0]= a*vop_ref[1][0] + d[0][0] + d[1][0];
        sprite_ref[1][1]= a*vop_ref[1][1] + d[0][1] + d[1][1];
        sprite_ref[2][0]= a*vop_ref[2][0] + d[0][0] + d[2][0];
        sprite_ref[2][1]= a*vop_ref[2][1] + d[0][1] + d[2][1];
    } else {
        sprite_ref[0][0]= (a>>1)*(2*vop_ref[0][0] + d[0][0]);
        sprite_ref[0][1]= (a>>1)*(2*vop_ref[0][1] + d[0][1]);
        sprite_ref[1][0]= (a>>1)*(2*vop_ref[1][0] + d[0][0] + d[1][0]);
        sprite_ref[1][1]= (a>>1)*(2*vop_ref[1][1] + d[0][1] + d[1][1]);
        sprite_ref[2][0]= (a>>1)*(2*vop_ref[2][0] + d[0][0] + d[2][0]);
        sprite_ref[2][1]= (a>>1)*(2*vop_ref[2][1] + d[0][1] + d[2][1]);
    }
/*    sprite_ref[3][0]= (a>>1)*(2*vop_ref[3][0] + d[0][0] + d[1][0] + d[2][0] + d[3][0]);
    sprite_ref[3][1]= (a>>1)*(2*vop_ref[3][1] + d[0][1] + d[1][1] + d[2][1] + d[3][1]); */

// this is mostly identical to the mpeg4 std (and is totally unreadable because of that ...)
// perhaps it should be reordered to be more readable ...
// the idea behind this virtual_ref mess is to be able to use shifts later per pixel instead of divides
// so the distance between points is converted from w&h based to w2&h2 based which are of the 2^x form
    virtual_ref[0][0]= 16*(vop_ref[0][0] + w2)
        + ROUNDED_DIV(((w - w2)*(r*sprite_ref[0][0] - 16*vop_ref[0][0]) + w2*(r*sprite_ref[1][0] - 16*vop_ref[1][0])),w);
    virtual_ref[0][1]= 16*vop_ref[0][1]
        + ROUNDED_DIV(((w - w2)*(r*sprite_ref[0][1] - 16*vop_ref[0][1]) + w2*(r*sprite_ref[1][1] - 16*vop_ref[1][1])),w);
    virtual_ref[1][0]= 16*vop_ref[0][0]
        + ROUNDED_DIV(((h - h2)*(r*sprite_ref[0][0] - 16*vop_ref[0][0]) + h2*(r*sprite_ref[2][0] - 16*vop_ref[2][0])),h);
    virtual_ref[1][1]= 16*(vop_ref[0][1] + h2)
        + ROUNDED_DIV(((h - h2)*(r*sprite_ref[0][1] - 16*vop_ref[0][1]) + h2*(r*sprite_ref[2][1] - 16*vop_ref[2][1])),h);

    switch(s->num_sprite_warping_points)
    {
        case 0:
            s->sprite_offset[0][0]= 0;
            s->sprite_offset[0][1]= 0;
            s->sprite_offset[1][0]= 0;
            s->sprite_offset[1][1]= 0;
            s->sprite_delta[0][0]= a;
            s->sprite_delta[0][1]= 0;
            s->sprite_delta[1][0]= 0;
            s->sprite_delta[1][1]= a;
            s->sprite_shift[0]= 0;
            s->sprite_shift[1]= 0;
            break;
        case 1: //GMC only
            s->sprite_offset[0][0]= sprite_ref[0][0] - a*vop_ref[0][0];
            s->sprite_offset[0][1]= sprite_ref[0][1] - a*vop_ref[0][1];
            s->sprite_offset[1][0]= ((sprite_ref[0][0]>>1)|(sprite_ref[0][0]&1)) - a*(vop_ref[0][0]/2);
            s->sprite_offset[1][1]= ((sprite_ref[0][1]>>1)|(sprite_ref[0][1]&1)) - a*(vop_ref[0][1]/2);
            s->sprite_delta[0][0]= a;
            s->sprite_delta[0][1]= 0;
            s->sprite_delta[1][0]= 0;
            s->sprite_delta[1][1]= a;
            s->sprite_shift[0]= 0;
            s->sprite_shift[1]= 0;
            break;
        case 2:
            s->sprite_offset[0][0]= (sprite_ref[0][0]<<(alpha+rho))
                                                  + (-r*sprite_ref[0][0] + virtual_ref[0][0])*(-vop_ref[0][0])
                                                  + ( r*sprite_ref[0][1] - virtual_ref[0][1])*(-vop_ref[0][1])
                                                  + (1<<(alpha+rho-1));
            s->sprite_offset[0][1]= (sprite_ref[0][1]<<(alpha+rho))
                                                  + (-r*sprite_ref[0][1] + virtual_ref[0][1])*(-vop_ref[0][0])
                                                  + (-r*sprite_ref[0][0] + virtual_ref[0][0])*(-vop_ref[0][1])
                                                  + (1<<(alpha+rho-1));
            s->sprite_offset[1][0]= ( (-r*sprite_ref[0][0] + virtual_ref[0][0])*(-2*vop_ref[0][0] + 1)
                                     +( r*sprite_ref[0][1] - virtual_ref[0][1])*(-2*vop_ref[0][1] + 1)
                                     +2*w2*r*sprite_ref[0][0]
                                     - 16*w2
                                     + (1<<(alpha+rho+1)));
            s->sprite_offset[1][1]= ( (-r*sprite_ref[0][1] + virtual_ref[0][1])*(-2*vop_ref[0][0] + 1)
                                     +(-r*sprite_ref[0][0] + virtual_ref[0][0])*(-2*vop_ref[0][1] + 1)
                                     +2*w2*r*sprite_ref[0][1]
                                     - 16*w2
                                     + (1<<(alpha+rho+1)));
            s->sprite_delta[0][0]=   (-r*sprite_ref[0][0] + virtual_ref[0][0]);
            s->sprite_delta[0][1]=   (+r*sprite_ref[0][1] - virtual_ref[0][1]);
            s->sprite_delta[1][0]=   (-r*sprite_ref[0][1] + virtual_ref[0][1]);
            s->sprite_delta[1][1]=   (-r*sprite_ref[0][0] + virtual_ref[0][0]);

            s->sprite_shift[0]= alpha+rho;
            s->sprite_shift[1]= alpha+rho+2;
            break;
        case 3:
            min_ab= FFMIN(alpha, beta);
            w3= w2>>min_ab;
            h3= h2>>min_ab;
            s->sprite_offset[0][0]=  (sprite_ref[0][0]<<(alpha+beta+rho-min_ab))
                                   + (-r*sprite_ref[0][0] + virtual_ref[0][0])*h3*(-vop_ref[0][0])
                                   + (-r*sprite_ref[0][0] + virtual_ref[1][0])*w3*(-vop_ref[0][1])
                                   + (1<<(alpha+beta+rho-min_ab-1));
            s->sprite_offset[0][1]=  (sprite_ref[0][1]<<(alpha+beta+rho-min_ab))
                                   + (-r*sprite_ref[0][1] + virtual_ref[0][1])*h3*(-vop_ref[0][0])
                                   + (-r*sprite_ref[0][1] + virtual_ref[1][1])*w3*(-vop_ref[0][1])
                                   + (1<<(alpha+beta+rho-min_ab-1));
            s->sprite_offset[1][0]=  (-r*sprite_ref[0][0] + virtual_ref[0][0])*h3*(-2*vop_ref[0][0] + 1)
                                   + (-r*sprite_ref[0][0] + virtual_ref[1][0])*w3*(-2*vop_ref[0][1] + 1)
                                   + 2*w2*h3*r*sprite_ref[0][0]
                                   - 16*w2*h3
                                   + (1<<(alpha+beta+rho-min_ab+1));
            s->sprite_offset[1][1]=  (-r*sprite_ref[0][1] + virtual_ref[0][1])*h3*(-2*vop_ref[0][0] + 1)
                                   + (-r*sprite_ref[0][1] + virtual_ref[1][1])*w3*(-2*vop_ref[0][1] + 1)
                                   + 2*w2*h3*r*sprite_ref[0][1]
                                   - 16*w2*h3
                                   + (1<<(alpha+beta+rho-min_ab+1));
            s->sprite_delta[0][0]=   (-r*sprite_ref[0][0] + virtual_ref[0][0])*h3;
            s->sprite_delta[0][1]=   (-r*sprite_ref[0][0] + virtual_ref[1][0])*w3;
            s->sprite_delta[1][0]=   (-r*sprite_ref[0][1] + virtual_ref[0][1])*h3;
            s->sprite_delta[1][1]=   (-r*sprite_ref[0][1] + virtual_ref[1][1])*w3;

            s->sprite_shift[0]= alpha + beta + rho - min_ab;
            s->sprite_shift[1]= alpha + beta + rho - min_ab + 2;
            break;
    }
    /* try to simplify the situation */
    if(   s->sprite_delta[0][0] == a<<s->sprite_shift[0]
       && s->sprite_delta[0][1] == 0
       && s->sprite_delta[1][0] == 0
       && s->sprite_delta[1][1] == a<<s->sprite_shift[0])
    {
        s->sprite_offset[0][0]>>=s->sprite_shift[0];
        s->sprite_offset[0][1]>>=s->sprite_shift[0];
        s->sprite_offset[1][0]>>=s->sprite_shift[1];
        s->sprite_offset[1][1]>>=s->sprite_shift[1];
        s->sprite_delta[0][0]= a;
        s->sprite_delta[0][1]= 0;
        s->sprite_delta[1][0]= 0;
        s->sprite_delta[1][1]= a;
        s->sprite_shift[0]= 0;
        s->sprite_shift[1]= 0;
        s->real_sprite_warping_points=1;
    }
    else{
        int shift_y= 16 - s->sprite_shift[0];
        int shift_c= 16 - s->sprite_shift[1];
        for(i=0; i<2; i++){
            s->sprite_offset[0][i]<<= shift_y;
            s->sprite_offset[1][i]<<= shift_c;
            s->sprite_delta[0][i]<<= shift_y;
            s->sprite_delta[1][i]<<= shift_y;
            s->sprite_shift[i]= 16;
        }
        s->real_sprite_warping_points= s->num_sprite_warping_points;
    }
}

/**
 * decodes the next video packet.
 * @return <0 if something went wrong
 */
int mpeg4_decode_video_packet_header(MpegEncContext *s)
{
    int mb_num_bits= av_log2(s->mb_num - 1) + 1;
    int header_extension=0, mb_num, len;

    /* is there enough space left for a video packet + header */
    if( get_bits_count(&s->gb) > s->gb.size_in_bits-20) return -1;

    for(len=0; len<32; len++){
        if(get_bits1(&s->gb)) break;
    }

    if(len!=ff_mpeg4_get_video_packet_prefix_length(s)){
        av_log(s->avctx, AV_LOG_ERROR, "marker does not match f_code\n");
        return -1;
    }

    if(s->shape != RECT_SHAPE){
        header_extension= get_bits1(&s->gb);
        //FIXME more stuff here
    }

    mb_num= get_bits(&s->gb, mb_num_bits);
    if(mb_num>=s->mb_num){
        av_log(s->avctx, AV_LOG_ERROR, "illegal mb_num in video packet (%d %d) \n", mb_num, s->mb_num);
        return -1;
    }
    if(s->pict_type == FF_B_TYPE){
        int mb_x = 0, mb_y = 0;

        while(s->next_picture.mbskip_table[ s->mb_index2xy[ mb_num ] ]) {
            if (!mb_x) ff_thread_await_progress((AVFrame*)s->next_picture_ptr, mb_y++, 0);
            mb_num++;
            if (++mb_x == s->mb_width) mb_x = 0;
        }
        if(mb_num >= s->mb_num) return -1; // slice contains just skipped MBs which where already decoded
    }

    s->mb_x= mb_num % s->mb_width;
    s->mb_y= mb_num / s->mb_width;

    if(s->shape != BIN_ONLY_SHAPE){
        int qscale= get_bits(&s->gb, s->quant_precision);
        if(qscale)
            s->chroma_qscale=s->qscale= qscale;
    }

    if(s->shape == RECT_SHAPE){
        header_extension= get_bits1(&s->gb);
    }
    if(header_extension){
        int time_increment;
        int time_incr=0;

        while (get_bits1(&s->gb) != 0)
            time_incr++;

        check_marker(&s->gb, "before time_increment in video packed header");
        time_increment= get_bits(&s->gb, s->time_increment_bits);
        check_marker(&s->gb, "before vop_coding_type in video packed header");

        skip_bits(&s->gb, 2); /* vop coding type */
        //FIXME not rect stuff here

        if(s->shape != BIN_ONLY_SHAPE){
            skip_bits(&s->gb, 3); /* intra dc vlc threshold */
//FIXME don't just ignore everything
            if(s->pict_type == FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE){
                mpeg4_decode_sprite_trajectory(s, &s->gb);
                av_log(s->avctx, AV_LOG_ERROR, "untested\n");
            }

            //FIXME reduced res stuff here

            if (s->pict_type != FF_I_TYPE) {
                int f_code = get_bits(&s->gb, 3);       /* fcode_for */
                if(f_code==0){
                    av_log(s->avctx, AV_LOG_ERROR, "Error, video packet header damaged (f_code=0)\n");
                }
            }
            if (s->pict_type == FF_B_TYPE) {
                int b_code = get_bits(&s->gb, 3);
                if(b_code==0){
                    av_log(s->avctx, AV_LOG_ERROR, "Error, video packet header damaged (b_code=0)\n");
                }
            }
        }
    }
    //FIXME new-pred stuff

    return 0;
}

/**
 * gets the average motion vector for a GMC MB.
 * @param n either 0 for the x component or 1 for y
 * @return the average MV for a GMC MB
 */
static inline int get_amv(MpegEncContext *s, int n){
    int x, y, mb_v, sum, dx, dy, shift;
    int len = 1 << (s->f_code + 4);
    const int a= s->sprite_warping_accuracy;

    if(s->workaround_bugs & FF_BUG_AMV)
        len >>= s->quarter_sample;

    if(s->real_sprite_warping_points==1){
        if(s->divx_version==500 && s->divx_build==413)
            sum= s->sprite_offset[0][n] / (1<<(a - s->quarter_sample));
        else
            sum= RSHIFT(s->sprite_offset[0][n]<<s->quarter_sample, a);
    }else{
        dx= s->sprite_delta[n][0];
        dy= s->sprite_delta[n][1];
        shift= s->sprite_shift[0];
        if(n) dy -= 1<<(shift + a + 1);
        else  dx -= 1<<(shift + a + 1);
        mb_v= s->sprite_offset[0][n] + dx*s->mb_x*16 + dy*s->mb_y*16;

        sum=0;
        for(y=0; y<16; y++){
            int v;

            v= mb_v + dy*y;
            //XXX FIXME optimize
            for(x=0; x<16; x++){
                sum+= v>>shift;
                v+= dx;
            }
        }
        sum= RSHIFT(sum, a+8-s->quarter_sample);
    }

    if      (sum < -len) sum= -len;
    else if (sum >= len) sum= len-1;

    return sum;
}

/**
 * decodes the dc value.
 * @param n block index (0-3 are luma, 4-5 are chroma)
 * @param dir_ptr the prediction direction will be stored here
 * @return the quantized dc
 */
static inline int mpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr)
{
    int level, code;

    if (n < 4)
        code = get_vlc2(&s->gb, dc_lum.table, DC_VLC_BITS, 1);
    else
        code = get_vlc2(&s->gb, dc_chrom.table, DC_VLC_BITS, 1);
    if (code < 0 || code > 9 /* && s->nbit<9 */){
        av_log(s->avctx, AV_LOG_ERROR, "illegal dc vlc\n");
        return -1;
    }
    if (code == 0) {
        level = 0;
    } else {
        if(IS_3IV1){
            if(code==1)
                level= 2*get_bits1(&s->gb)-1;
            else{
                if(get_bits1(&s->gb))
                    level = get_bits(&s->gb, code-1) + (1<<(code-1));
                else
                    level = -get_bits(&s->gb, code-1) - (1<<(code-1));
            }
        }else{
            level = get_xbits(&s->gb, code);
        }

        if (code > 8){
            if(get_bits1(&s->gb)==0){ /* marker */
                if(s->error_recognition>=2){
                    av_log(s->avctx, AV_LOG_ERROR, "dc marker bit missing\n");
                    return -1;
                }
            }
        }
    }

    return ff_mpeg4_pred_dc(s, n, level, dir_ptr, 0);
}

/**
 * decodes first partition.
 * @return number of MBs decoded or <0 if an error occurred
 */
static int mpeg4_decode_partition_a(MpegEncContext *s){
    int mb_num;
    static const int8_t quant_tab[4] = { -1, -2, 1, 2 };

    /* decode first partition */
    mb_num=0;
    s->first_slice_line=1;
    for(; s->mb_y<s->mb_height; s->mb_y++){
        ff_init_block_index(s);
        for(; s->mb_x<s->mb_width; s->mb_x++){
            const int xy= s->mb_x + s->mb_y*s->mb_stride;
            int cbpc;
            int dir=0;

            mb_num++;
            ff_update_block_index(s);
            if(s->mb_x == s->resync_mb_x && s->mb_y == s->resync_mb_y+1)
                s->first_slice_line=0;

            if(s->pict_type==FF_I_TYPE){
                int i;

                do{
                    if(show_bits_long(&s->gb, 19)==DC_MARKER){
                        return mb_num-1;
                    }

                    cbpc = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc.table, INTRA_MCBPC_VLC_BITS, 2);
                    if (cbpc < 0){
                        av_log(s->avctx, AV_LOG_ERROR, "cbpc corrupted at %d %d\n", s->mb_x, s->mb_y);
                        return -1;
                    }
                }while(cbpc == 8);

                s->cbp_table[xy]= cbpc & 3;
                s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
                s->mb_intra = 1;

                if(cbpc & 4) {
                    ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
                }
                s->current_picture.qscale_table[xy]= s->qscale;

                s->mbintra_table[xy]= 1;
                for(i=0; i<6; i++){
                    int dc_pred_dir;
                    int dc= mpeg4_decode_dc(s, i, &dc_pred_dir);
                    if(dc < 0){
                        av_log(s->avctx, AV_LOG_ERROR, "DC corrupted at %d %d\n", s->mb_x, s->mb_y);
                        return -1;
                    }
                    dir<<=1;
                    if(dc_pred_dir) dir|=1;
                }
                s->pred_dir_table[xy]= dir;
            }else{ /* P/S_TYPE */
                int mx, my, pred_x, pred_y, bits;
                int16_t * const mot_val= s->current_picture.motion_val[0][s->block_index[0]];
                const int stride= s->b8_stride*2;

try_again:
                bits= show_bits(&s->gb, 17);
                if(bits==MOTION_MARKER){
                    return mb_num-1;
                }
                skip_bits1(&s->gb);
                if(bits&0x10000){
                    /* skip mb */
                    if(s->pict_type==FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE){
                        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_GMC | MB_TYPE_L0;
                        mx= get_amv(s, 0);
                        my= get_amv(s, 1);
                    }else{
                        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
                        mx=my=0;
                    }
                    mot_val[0       ]= mot_val[2       ]=
                    mot_val[0+stride]= mot_val[2+stride]= mx;
                    mot_val[1       ]= mot_val[3       ]=
                    mot_val[1+stride]= mot_val[3+stride]= my;

                    if(s->mbintra_table[xy])
                        ff_clean_intra_table_entries(s);
                    continue;
                }

                cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
                if (cbpc < 0){
                    av_log(s->avctx, AV_LOG_ERROR, "cbpc corrupted at %d %d\n", s->mb_x, s->mb_y);
                    return -1;
                }
                if(cbpc == 20)
                    goto try_again;

                s->cbp_table[xy]= cbpc&(8+3); //8 is dquant

                s->mb_intra = ((cbpc & 4) != 0);

                if(s->mb_intra){
                    s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
                    s->mbintra_table[xy]= 1;
                    mot_val[0       ]= mot_val[2       ]=
                    mot_val[0+stride]= mot_val[2+stride]= 0;
                    mot_val[1       ]= mot_val[3       ]=
                    mot_val[1+stride]= mot_val[3+stride]= 0;
                }else{
                    if(s->mbintra_table[xy])
                        ff_clean_intra_table_entries(s);

                    if(s->pict_type==FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE && (cbpc & 16) == 0)
                        s->mcsel= get_bits1(&s->gb);
                    else s->mcsel= 0;

                    if ((cbpc & 16) == 0) {
                        /* 16x16 motion prediction */

                        h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
                        if(!s->mcsel){
                            mx = h263_decode_motion(s, pred_x, s->f_code);
                            if (mx >= 0xffff)
                                return -1;

                            my = h263_decode_motion(s, pred_y, s->f_code);
                            if (my >= 0xffff)
                                return -1;
                            s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
                        } else {
                            mx = get_amv(s, 0);
                            my = get_amv(s, 1);
                            s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_GMC | MB_TYPE_L0;
                        }

                        mot_val[0       ]= mot_val[2       ] =
                        mot_val[0+stride]= mot_val[2+stride]= mx;
                        mot_val[1       ]= mot_val[3       ]=
                        mot_val[1+stride]= mot_val[3+stride]= my;
                    } else {
                        int i;
                        s->current_picture.mb_type[xy]= MB_TYPE_8x8 | MB_TYPE_L0;
                        for(i=0;i<4;i++) {
                            int16_t *mot_val= h263_pred_motion(s, i, 0, &pred_x, &pred_y);
                            mx = h263_decode_motion(s, pred_x, s->f_code);
                            if (mx >= 0xffff)
                                return -1;

                            my = h263_decode_motion(s, pred_y, s->f_code);
                            if (my >= 0xffff)
                                return -1;
                            mot_val[0] = mx;
                            mot_val[1] = my;
                        }
                    }
                }
            }
        }
        s->mb_x= 0;
    }

    return mb_num;
}

/**
 * decode second partition.
 * @return <0 if an error occurred
 */
static int mpeg4_decode_partition_b(MpegEncContext *s, int mb_count){
    int mb_num=0;
    static const int8_t quant_tab[4] = { -1, -2, 1, 2 };

    s->mb_x= s->resync_mb_x;
    s->first_slice_line=1;
    for(s->mb_y= s->resync_mb_y; mb_num < mb_count; s->mb_y++){
        ff_init_block_index(s);
        for(; mb_num < mb_count && s->mb_x<s->mb_width; s->mb_x++){
            const int xy= s->mb_x + s->mb_y*s->mb_stride;

            mb_num++;
            ff_update_block_index(s);
            if(s->mb_x == s->resync_mb_x && s->mb_y == s->resync_mb_y+1)
                s->first_slice_line=0;

            if(s->pict_type==FF_I_TYPE){
                int ac_pred= get_bits1(&s->gb);
                int cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
                if(cbpy<0){
                    av_log(s->avctx, AV_LOG_ERROR, "cbpy corrupted at %d %d\n", s->mb_x, s->mb_y);
                    return -1;
                }

                s->cbp_table[xy]|= cbpy<<2;
                s->current_picture.mb_type[xy] |= ac_pred*MB_TYPE_ACPRED;
            }else{ /* P || S_TYPE */
                if(IS_INTRA(s->current_picture.mb_type[xy])){
                    int dir=0,i;
                    int ac_pred = get_bits1(&s->gb);
                    int cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

                    if(cbpy<0){
                        av_log(s->avctx, AV_LOG_ERROR, "I cbpy corrupted at %d %d\n", s->mb_x, s->mb_y);
                        return -1;
                    }

                    if(s->cbp_table[xy] & 8) {
                        ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
                    }
                    s->current_picture.qscale_table[xy]= s->qscale;

                    for(i=0; i<6; i++){
                        int dc_pred_dir;
                        int dc= mpeg4_decode_dc(s, i, &dc_pred_dir);
                        if(dc < 0){
                            av_log(s->avctx, AV_LOG_ERROR, "DC corrupted at %d %d\n", s->mb_x, s->mb_y);
                            return -1;
                        }
                        dir<<=1;
                        if(dc_pred_dir) dir|=1;
                    }
                    s->cbp_table[xy]&= 3; //remove dquant
                    s->cbp_table[xy]|= cbpy<<2;
                    s->current_picture.mb_type[xy] |= ac_pred*MB_TYPE_ACPRED;
                    s->pred_dir_table[xy]= dir;
                }else if(IS_SKIP(s->current_picture.mb_type[xy])){
                    s->current_picture.qscale_table[xy]= s->qscale;
                    s->cbp_table[xy]= 0;
                }else{
                    int cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

                    if(cbpy<0){
                        av_log(s->avctx, AV_LOG_ERROR, "P cbpy corrupted at %d %d\n", s->mb_x, s->mb_y);
                        return -1;
                    }

                    if(s->cbp_table[xy] & 8) {
                        ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
                    }
                    s->current_picture.qscale_table[xy]= s->qscale;

                    s->cbp_table[xy]&= 3; //remove dquant
                    s->cbp_table[xy]|= (cbpy^0xf)<<2;
                }
            }
        }
        if(mb_num >= mb_count) return 0;
        s->mb_x= 0;
    }
    return 0;
}

/**
 * decodes the first & second partition
 * @return <0 if error (and sets error type in the error_status_table)
 */
int ff_mpeg4_decode_partitions(MpegEncContext *s)
{
    int mb_num;
    const int part_a_error= s->pict_type==FF_I_TYPE ? (DC_ERROR|MV_ERROR) : MV_ERROR;
    const int part_a_end  = s->pict_type==FF_I_TYPE ? (DC_END  |MV_END)   : MV_END;

    mb_num= mpeg4_decode_partition_a(s);
    if(mb_num<0){
        ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, part_a_error);
        return -1;
    }

    if(s->resync_mb_x + s->resync_mb_y*s->mb_width + mb_num > s->mb_num){
        av_log(s->avctx, AV_LOG_ERROR, "slice below monitor ...\n");
        ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, part_a_error);
        return -1;
    }

    s->mb_num_left= mb_num;

    if(s->pict_type==FF_I_TYPE){
        while(show_bits(&s->gb, 9) == 1)
            skip_bits(&s->gb, 9);
        if(get_bits_long(&s->gb, 19)!=DC_MARKER){
            av_log(s->avctx, AV_LOG_ERROR, "marker missing after first I partition at %d %d\n", s->mb_x, s->mb_y);
            return -1;
        }
    }else{
        while(show_bits(&s->gb, 10) == 1)
            skip_bits(&s->gb, 10);
        if(get_bits(&s->gb, 17)!=MOTION_MARKER){
            av_log(s->avctx, AV_LOG_ERROR, "marker missing after first P partition at %d %d\n", s->mb_x, s->mb_y);
            return -1;
        }
    }
    ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x-1, s->mb_y, part_a_end);

    if( mpeg4_decode_partition_b(s, mb_num) < 0){
        if(s->pict_type==FF_P_TYPE)
            ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, DC_ERROR);
        return -1;
    }else{
        if(s->pict_type==FF_P_TYPE)
            ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x-1, s->mb_y, DC_END);
    }

    return 0;
}

/**
 * decodes a block.
 * @return <0 if an error occurred
 */
static inline int mpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
                              int n, int coded, int intra, int rvlc)
{
    int level, i, last, run;
    int dc_pred_dir;
    RLTable * rl;
    RL_VLC_ELEM * rl_vlc;
    const uint8_t * scan_table;
    int qmul, qadd;

    //Note intra & rvlc should be optimized away if this is inlined

    if(intra) {
      if(s->use_intra_dc_vlc){
        /* DC coef */
        if(s->partitioned_frame){
            level = s->dc_val[0][ s->block_index[n] ];
            if(n<4) level= FASTDIV((level + (s->y_dc_scale>>1)), s->y_dc_scale);
            else    level= FASTDIV((level + (s->c_dc_scale>>1)), s->c_dc_scale);
            dc_pred_dir= (s->pred_dir_table[s->mb_x + s->mb_y*s->mb_stride]<<n)&32;
        }else{
            level = mpeg4_decode_dc(s, n, &dc_pred_dir);
            if (level < 0)
                return -1;
        }
        block[0] = level;
        i = 0;
      }else{
            i = -1;
            ff_mpeg4_pred_dc(s, n, 0, &dc_pred_dir, 0);
      }
      if (!coded)
          goto not_coded;

      if(rvlc){
          rl = &rvlc_rl_intra;
          rl_vlc = rvlc_rl_intra.rl_vlc[0];
      }else{
          rl = &ff_mpeg4_rl_intra;
          rl_vlc = ff_mpeg4_rl_intra.rl_vlc[0];
      }
      if (s->ac_pred) {
          if (dc_pred_dir == 0)
              scan_table = s->intra_v_scantable.permutated; /* left */
          else
              scan_table = s->intra_h_scantable.permutated; /* top */
      } else {
            scan_table = s->intra_scantable.permutated;
      }
      qmul=1;
      qadd=0;
    } else {
        i = -1;
        if (!coded) {
            s->block_last_index[n] = i;
            return 0;
        }
        if(rvlc) rl = &rvlc_rl_inter;
        else     rl = &ff_h263_rl_inter;

        scan_table = s->intra_scantable.permutated;

        if(s->mpeg_quant){
            qmul=1;
            qadd=0;
            if(rvlc){
                rl_vlc = rvlc_rl_inter.rl_vlc[0];
            }else{
                rl_vlc = ff_h263_rl_inter.rl_vlc[0];
            }
        }else{
            qmul = s->qscale << 1;
            qadd = (s->qscale - 1) | 1;
            if(rvlc){
                rl_vlc = rvlc_rl_inter.rl_vlc[s->qscale];
            }else{
                rl_vlc = ff_h263_rl_inter.rl_vlc[s->qscale];
            }
        }
    }
  {
    OPEN_READER(re, &s->gb);
    for(;;) {
        UPDATE_CACHE(re, &s->gb);
        GET_RL_VLC(level, run, re, &s->gb, rl_vlc, TEX_VLC_BITS, 2, 0);
        if (level==0) {
          /* escape */
          if(rvlc){
                if(SHOW_UBITS(re, &s->gb, 1)==0){
                    av_log(s->avctx, AV_LOG_ERROR, "1. marker bit missing in rvlc esc\n");
                    return -1;
                }; SKIP_CACHE(re, &s->gb, 1);

                last=  SHOW_UBITS(re, &s->gb, 1); SKIP_CACHE(re, &s->gb, 1);
                run=   SHOW_UBITS(re, &s->gb, 6); LAST_SKIP_CACHE(re, &s->gb, 6);
                SKIP_COUNTER(re, &s->gb, 1+1+6);
                UPDATE_CACHE(re, &s->gb);

                if(SHOW_UBITS(re, &s->gb, 1)==0){
                    av_log(s->avctx, AV_LOG_ERROR, "2. marker bit missing in rvlc esc\n");
                    return -1;
                }; SKIP_CACHE(re, &s->gb, 1);

                level= SHOW_UBITS(re, &s->gb, 11); SKIP_CACHE(re, &s->gb, 11);

                if(SHOW_UBITS(re, &s->gb, 5)!=0x10){
                    av_log(s->avctx, AV_LOG_ERROR, "reverse esc missing\n");
                    return -1;
                }; SKIP_CACHE(re, &s->gb, 5);

                level=  level * qmul + qadd;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1); LAST_SKIP_CACHE(re, &s->gb, 1);
                SKIP_COUNTER(re, &s->gb, 1+11+5+1);

                i+= run + 1;
                if(last) i+=192;
          }else{
            int cache;
            cache= GET_CACHE(re, &s->gb);

            if(IS_3IV1)
                cache ^= 0xC0000000;

            if (cache&0x80000000) {
                if (cache&0x40000000) {
                    /* third escape */
                    SKIP_CACHE(re, &s->gb, 2);
                    last=  SHOW_UBITS(re, &s->gb, 1); SKIP_CACHE(re, &s->gb, 1);
                    run=   SHOW_UBITS(re, &s->gb, 6); LAST_SKIP_CACHE(re, &s->gb, 6);
                    SKIP_COUNTER(re, &s->gb, 2+1+6);
                    UPDATE_CACHE(re, &s->gb);

                    if(IS_3IV1){
                        level= SHOW_SBITS(re, &s->gb, 12); LAST_SKIP_BITS(re, &s->gb, 12);
                    }else{
                        if(SHOW_UBITS(re, &s->gb, 1)==0){
                            av_log(s->avctx, AV_LOG_ERROR, "1. marker bit missing in 3. esc\n");
                            return -1;
                        }; SKIP_CACHE(re, &s->gb, 1);

                        level= SHOW_SBITS(re, &s->gb, 12); SKIP_CACHE(re, &s->gb, 12);

                        if(SHOW_UBITS(re, &s->gb, 1)==0){
                            av_log(s->avctx, AV_LOG_ERROR, "2. marker bit missing in 3. esc\n");
                            return -1;
                        }; LAST_SKIP_CACHE(re, &s->gb, 1);

                        SKIP_COUNTER(re, &s->gb, 1+12+1);
                    }

#if 0
                    if(s->error_recognition >= FF_ER_COMPLIANT){
                        const int abs_level= FFABS(level);
                        if(abs_level<=MAX_LEVEL && run<=MAX_RUN){
                            const int run1= run - rl->max_run[last][abs_level] - 1;
                            if(abs_level <= rl->max_level[last][run]){
                                av_log(s->avctx, AV_LOG_ERROR, "illegal 3. esc, vlc encoding possible\n");
                                return -1;
                            }
                            if(s->error_recognition > FF_ER_COMPLIANT){
                                if(abs_level <= rl->max_level[last][run]*2){
                                    av_log(s->avctx, AV_LOG_ERROR, "illegal 3. esc, esc 1 encoding possible\n");
                                    return -1;
                                }
                                if(run1 >= 0 && abs_level <= rl->max_level[last][run1]){
                                    av_log(s->avctx, AV_LOG_ERROR, "illegal 3. esc, esc 2 encoding possible\n");
                                    return -1;
                                }
                            }
                        }
                    }
#endif
                    if (level>0) level= level * qmul + qadd;
                    else         level= level * qmul - qadd;

                    if((unsigned)(level + 2048) > 4095){
                        if(s->error_recognition > FF_ER_COMPLIANT){
                            if(level > 2560 || level<-2560){
                                av_log(s->avctx, AV_LOG_ERROR, "|level| overflow in 3. esc, qp=%d\n", s->qscale);
                                return -1;
                            }
                        }
                        level= level<0 ? -2048 : 2047;
                    }

                    i+= run + 1;
                    if(last) i+=192;
                } else {
                    /* second escape */
                    SKIP_BITS(re, &s->gb, 2);
                    GET_RL_VLC(level, run, re, &s->gb, rl_vlc, TEX_VLC_BITS, 2, 1);
                    i+= run + rl->max_run[run>>7][level/qmul] +1; //FIXME opt indexing
                    level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                    LAST_SKIP_BITS(re, &s->gb, 1);
                }
            } else {
                /* first escape */
                SKIP_BITS(re, &s->gb, 1);
                GET_RL_VLC(level, run, re, &s->gb, rl_vlc, TEX_VLC_BITS, 2, 1);
                i+= run;
                level = level + rl->max_level[run>>7][(run-1)&63] * qmul;//FIXME opt indexing
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                LAST_SKIP_BITS(re, &s->gb, 1);
            }
          }
        } else {
            i+= run;
            level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
            LAST_SKIP_BITS(re, &s->gb, 1);
        }
        if (i > 62){
            i-= 192;
            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[scan_table[i]] = level;
            break;
        }

        block[scan_table[i]] = level;
    }
    CLOSE_READER(re, &s->gb);
  }
 not_coded:
    if (intra) {
        if(!s->use_intra_dc_vlc){
            block[0] = ff_mpeg4_pred_dc(s, n, block[0], &dc_pred_dir, 0);

            i -= i>>31; //if(i == -1) i=0;
        }

        mpeg4_pred_ac(s, block, n, dc_pred_dir);
        if (s->ac_pred) {
            i = 63; /* XXX: not optimal */
        }
    }
    s->block_last_index[n] = i;
    return 0;
}

/**
 * decode partition C of one MB.
 * @return <0 if an error occurred
 */
static int mpeg4_decode_partitioned_mb(MpegEncContext *s, DCTELEM block[6][64])
{
    int cbp, mb_type;
    const int xy= s->mb_x + s->mb_y*s->mb_stride;

    mb_type= s->current_picture.mb_type[xy];
    cbp = s->cbp_table[xy];

    s->use_intra_dc_vlc= s->qscale < s->intra_dc_threshold;

    if(s->current_picture.qscale_table[xy] != s->qscale){
        ff_set_qscale(s, s->current_picture.qscale_table[xy] );
    }

    if (s->pict_type == FF_P_TYPE || s->pict_type==FF_S_TYPE) {
        int i;
        for(i=0; i<4; i++){
            s->mv[0][i][0] = s->current_picture.motion_val[0][ s->block_index[i] ][0];
            s->mv[0][i][1] = s->current_picture.motion_val[0][ s->block_index[i] ][1];
        }
        s->mb_intra = IS_INTRA(mb_type);

        if (IS_SKIP(mb_type)) {
            /* skip mb */
            for(i=0;i<6;i++)
                s->block_last_index[i] = -1;
            s->mv_dir = MV_DIR_FORWARD;
            s->mv_type = MV_TYPE_16X16;
            if(s->pict_type==FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE){
                s->mcsel=1;
                s->mb_skipped = 0;
            }else{
                s->mcsel=0;
                s->mb_skipped = 1;
            }
        }else if(s->mb_intra){
            s->ac_pred = IS_ACPRED(s->current_picture.mb_type[xy]);
        }else if(!s->mb_intra){
//            s->mcsel= 0; //FIXME do we need to init that

            s->mv_dir = MV_DIR_FORWARD;
            if (IS_8X8(mb_type)) {
                s->mv_type = MV_TYPE_8X8;
            } else {
                s->mv_type = MV_TYPE_16X16;
            }
        }
    } else { /* I-Frame */
        s->mb_intra = 1;
        s->ac_pred = IS_ACPRED(s->current_picture.mb_type[xy]);
    }

    if (!IS_SKIP(mb_type)) {
        int i;
        s->dsp.clear_blocks(s->block[0]);
        /* decode each block */
        for (i = 0; i < 6; i++) {
            if(mpeg4_decode_block(s, block[i], i, cbp&32, s->mb_intra, s->rvlc) < 0){
                av_log(s->avctx, AV_LOG_ERROR, "texture corrupted at %d %d %d\n", s->mb_x, s->mb_y, s->mb_intra);
                return -1;
            }
            cbp+=cbp;
        }
    }

    /* per-MB end of slice check */

    if(--s->mb_num_left <= 0){
        if(mpeg4_is_resync(s))
            return SLICE_END;
        else
            return SLICE_NOEND;
    }else{
        if(mpeg4_is_resync(s)){
            const int delta= s->mb_x + 1 == s->mb_width ? 2 : 1;
            if(s->cbp_table[xy+delta])
                return SLICE_END;
        }
        return SLICE_OK;
    }
}

static int mpeg4_decode_mb(MpegEncContext *s,
                      DCTELEM block[6][64])
{
    int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
    int16_t *mot_val;
    static int8_t quant_tab[4] = { -1, -2, 1, 2 };
    const int xy= s->mb_x + s->mb_y * s->mb_stride;

    assert(s->h263_pred);

    if (s->pict_type == FF_P_TYPE || s->pict_type==FF_S_TYPE) {
        do{
            if (get_bits1(&s->gb)) {
                /* skip mb */
                s->mb_intra = 0;
                for(i=0;i<6;i++)
                    s->block_last_index[i] = -1;
                s->mv_dir = MV_DIR_FORWARD;
                s->mv_type = MV_TYPE_16X16;
                if(s->pict_type==FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE){
                    s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_GMC | MB_TYPE_16x16 | MB_TYPE_L0;
                    s->mcsel=1;
                    s->mv[0][0][0]= get_amv(s, 0);
                    s->mv[0][0][1]= get_amv(s, 1);

                    s->mb_skipped = 0;
                }else{
                    s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
                    s->mcsel=0;
                    s->mv[0][0][0] = 0;
                    s->mv[0][0][1] = 0;
                    s->mb_skipped = 1;
                }
                goto end;
            }
            cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
            if (cbpc < 0){
                av_log(s->avctx, AV_LOG_ERROR, "cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
        }while(cbpc == 20);

        s->dsp.clear_blocks(s->block[0]);
        dquant = cbpc & 8;
        s->mb_intra = ((cbpc & 4) != 0);
        if (s->mb_intra) goto intra;

        if(s->pict_type==FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE && (cbpc & 16) == 0)
            s->mcsel= get_bits1(&s->gb);
        else s->mcsel= 0;
        cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1) ^ 0x0F;

        cbp = (cbpc & 3) | (cbpy << 2);
        if (dquant) {
            ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
        }
        if((!s->progressive_sequence) && (cbp || (s->workaround_bugs&FF_BUG_XVID_ILACE)))
            s->interlaced_dct= get_bits1(&s->gb);

        s->mv_dir = MV_DIR_FORWARD;
        if ((cbpc & 16) == 0) {
            if(s->mcsel){
                s->current_picture.mb_type[xy]= MB_TYPE_GMC | MB_TYPE_16x16 | MB_TYPE_L0;
                /* 16x16 global motion prediction */
                s->mv_type = MV_TYPE_16X16;
                mx= get_amv(s, 0);
                my= get_amv(s, 1);
                s->mv[0][0][0] = mx;
                s->mv[0][0][1] = my;
            }else if((!s->progressive_sequence) && get_bits1(&s->gb)){
                s->current_picture.mb_type[xy]= MB_TYPE_16x8 | MB_TYPE_L0 | MB_TYPE_INTERLACED;
                /* 16x8 field motion prediction */
                s->mv_type= MV_TYPE_FIELD;

                s->field_select[0][0]= get_bits1(&s->gb);
                s->field_select[0][1]= get_bits1(&s->gb);

                h263_pred_motion(s, 0, 0, &pred_x, &pred_y);

                for(i=0; i<2; i++){
                    mx = h263_decode_motion(s, pred_x, s->f_code);
                    if (mx >= 0xffff)
                        return -1;

                    my = h263_decode_motion(s, pred_y/2, s->f_code);
                    if (my >= 0xffff)
                        return -1;

                    s->mv[0][i][0] = mx;
                    s->mv[0][i][1] = my;
                }
            }else{
                s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
                /* 16x16 motion prediction */
                s->mv_type = MV_TYPE_16X16;
                h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
                mx = h263_decode_motion(s, pred_x, s->f_code);

                if (mx >= 0xffff)
                    return -1;

                my = h263_decode_motion(s, pred_y, s->f_code);

                if (my >= 0xffff)
                    return -1;
                s->mv[0][0][0] = mx;
                s->mv[0][0][1] = my;
            }
        } else {
            s->current_picture.mb_type[xy]= MB_TYPE_8x8 | MB_TYPE_L0;
            s->mv_type = MV_TYPE_8X8;
            for(i=0;i<4;i++) {
                mot_val = h263_pred_motion(s, i, 0, &pred_x, &pred_y);
                mx = h263_decode_motion(s, pred_x, s->f_code);
                if (mx >= 0xffff)
                    return -1;

                my = h263_decode_motion(s, pred_y, s->f_code);
                if (my >= 0xffff)
                    return -1;
                s->mv[0][i][0] = mx;
                s->mv[0][i][1] = my;
                mot_val[0] = mx;
                mot_val[1] = my;
            }
        }
    } else if(s->pict_type==FF_B_TYPE) {
        int modb1; // first bit of modb
        int modb2; // second bit of modb
        int mb_type;

        s->mb_intra = 0; //B-frames never contain intra blocks
        s->mcsel=0;      //     ...               true gmc blocks

        if(s->mb_x==0){
            for(i=0; i<2; i++){
                s->last_mv[i][0][0]=
                s->last_mv[i][0][1]=
                s->last_mv[i][1][0]=
                s->last_mv[i][1][1]= 0;
            }

            ff_thread_await_progress((AVFrame*)s->next_picture_ptr, s->mb_y, 0);
        }

        /* if we skipped it in the future P Frame than skip it now too */
        s->mb_skipped= s->next_picture.mbskip_table[s->mb_y * s->mb_stride + s->mb_x]; // Note, skiptab=0 if last was GMC

        if(s->mb_skipped){
                /* skip mb */
            for(i=0;i<6;i++)
                s->block_last_index[i] = -1;

            s->mv_dir = MV_DIR_FORWARD;
            s->mv_type = MV_TYPE_16X16;
            s->mv[0][0][0] = 0;
            s->mv[0][0][1] = 0;
            s->mv[1][0][0] = 0;
            s->mv[1][0][1] = 0;
            s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
            goto end;
        }

        modb1= get_bits1(&s->gb);
        if(modb1){
            mb_type= MB_TYPE_DIRECT2 | MB_TYPE_SKIP | MB_TYPE_L0L1; //like MB_TYPE_B_DIRECT but no vectors coded
            cbp=0;
        }else{
            modb2= get_bits1(&s->gb);
            mb_type= get_vlc2(&s->gb, mb_type_b_vlc.table, MB_TYPE_B_VLC_BITS, 1);
            if(mb_type<0){
                av_log(s->avctx, AV_LOG_ERROR, "illegal MB_type\n");
                return -1;
            }
            mb_type= mb_type_b_map[ mb_type ];
            if(modb2) cbp= 0;
            else{
                s->dsp.clear_blocks(s->block[0]);
                cbp= get_bits(&s->gb, 6);
            }

            if ((!IS_DIRECT(mb_type)) && cbp) {
                if(get_bits1(&s->gb)){
                    ff_set_qscale(s, s->qscale + get_bits1(&s->gb)*4 - 2);
                }
            }

            if(!s->progressive_sequence){
                if(cbp)
                    s->interlaced_dct= get_bits1(&s->gb);

                if(!IS_DIRECT(mb_type) && get_bits1(&s->gb)){
                    mb_type |= MB_TYPE_16x8 | MB_TYPE_INTERLACED;
                    mb_type &= ~MB_TYPE_16x16;

                    if(USES_LIST(mb_type, 0)){
                        s->field_select[0][0]= get_bits1(&s->gb);
                        s->field_select[0][1]= get_bits1(&s->gb);
                    }
                    if(USES_LIST(mb_type, 1)){
                        s->field_select[1][0]= get_bits1(&s->gb);
                        s->field_select[1][1]= get_bits1(&s->gb);
                    }
                }
            }

            s->mv_dir = 0;
            if((mb_type & (MB_TYPE_DIRECT2|MB_TYPE_INTERLACED)) == 0){
                s->mv_type= MV_TYPE_16X16;

                if(USES_LIST(mb_type, 0)){
                    s->mv_dir = MV_DIR_FORWARD;

                    mx = h263_decode_motion(s, s->last_mv[0][0][0], s->f_code);
                    my = h263_decode_motion(s, s->last_mv[0][0][1], s->f_code);
                    s->last_mv[0][1][0]= s->last_mv[0][0][0]= s->mv[0][0][0] = mx;
                    s->last_mv[0][1][1]= s->last_mv[0][0][1]= s->mv[0][0][1] = my;
                }

                if(USES_LIST(mb_type, 1)){
                    s->mv_dir |= MV_DIR_BACKWARD;

                    mx = h263_decode_motion(s, s->last_mv[1][0][0], s->b_code);
                    my = h263_decode_motion(s, s->last_mv[1][0][1], s->b_code);
                    s->last_mv[1][1][0]= s->last_mv[1][0][0]= s->mv[1][0][0] = mx;
                    s->last_mv[1][1][1]= s->last_mv[1][0][1]= s->mv[1][0][1] = my;
                }
            }else if(!IS_DIRECT(mb_type)){
                s->mv_type= MV_TYPE_FIELD;

                if(USES_LIST(mb_type, 0)){
                    s->mv_dir = MV_DIR_FORWARD;

                    for(i=0; i<2; i++){
                        mx = h263_decode_motion(s, s->last_mv[0][i][0]  , s->f_code);
                        my = h263_decode_motion(s, s->last_mv[0][i][1]/2, s->f_code);
                        s->last_mv[0][i][0]=  s->mv[0][i][0] = mx;
                        s->last_mv[0][i][1]= (s->mv[0][i][1] = my)*2;
                    }
                }

                if(USES_LIST(mb_type, 1)){
                    s->mv_dir |= MV_DIR_BACKWARD;

                    for(i=0; i<2; i++){
                        mx = h263_decode_motion(s, s->last_mv[1][i][0]  , s->b_code);
                        my = h263_decode_motion(s, s->last_mv[1][i][1]/2, s->b_code);
                        s->last_mv[1][i][0]=  s->mv[1][i][0] = mx;
                        s->last_mv[1][i][1]= (s->mv[1][i][1] = my)*2;
                    }
                }
            }
        }

        if(IS_DIRECT(mb_type)){
            if(IS_SKIP(mb_type))
                mx=my=0;
            else{
                mx = h263_decode_motion(s, 0, 1);
                my = h263_decode_motion(s, 0, 1);
            }

            s->mv_dir = MV_DIR_FORWARD | MV_DIR_BACKWARD | MV_DIRECT;
            mb_type |= ff_mpeg4_set_direct_mv(s, mx, my);
        }
        s->current_picture.mb_type[xy]= mb_type;
    } else { /* I-Frame */
        do{
            cbpc = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc.table, INTRA_MCBPC_VLC_BITS, 2);
            if (cbpc < 0){
                av_log(s->avctx, AV_LOG_ERROR, "I cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
        }while(cbpc == 8);

        dquant = cbpc & 4;
        s->mb_intra = 1;
intra:
        s->ac_pred = get_bits1(&s->gb);
        if(s->ac_pred)
            s->current_picture.mb_type[xy]= MB_TYPE_INTRA | MB_TYPE_ACPRED;
        else
            s->current_picture.mb_type[xy]= MB_TYPE_INTRA;

        cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
        if(cbpy<0){
            av_log(s->avctx, AV_LOG_ERROR, "I cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
            return -1;
        }
        cbp = (cbpc & 3) | (cbpy << 2);

        s->use_intra_dc_vlc= s->qscale < s->intra_dc_threshold;

        if (dquant) {
            ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
        }

        if(!s->progressive_sequence)
            s->interlaced_dct= get_bits1(&s->gb);

        s->dsp.clear_blocks(s->block[0]);
        /* decode each block */
        for (i = 0; i < 6; i++) {
            if (mpeg4_decode_block(s, block[i], i, cbp&32, 1, 0) < 0)
                return -1;
            cbp+=cbp;
        }
        goto end;
    }

    /* decode each block */
    for (i = 0; i < 6; i++) {
        if (mpeg4_decode_block(s, block[i], i, cbp&32, 0, 0) < 0)
            return -1;
        cbp+=cbp;
    }
end:

        /* per-MB end of slice check */
    if(s->codec_id==CODEC_ID_MPEG4){
        if(mpeg4_is_resync(s)){
            const int delta= s->mb_x + 1 == s->mb_width ? 2 : 1;

            if(s->pict_type==FF_B_TYPE){
                ff_thread_await_progress((AVFrame*)s->next_picture_ptr,
                                        (s->mb_x + delta >= s->mb_width) ? FFMIN(s->mb_y+1, s->mb_height-1) : s->mb_y, 0);
            }

            if(s->pict_type==FF_B_TYPE && s->next_picture.mbskip_table[xy + delta])
                return SLICE_OK;
            return SLICE_END;
        }
    }

    return SLICE_OK;
}


static int mpeg4_decode_gop_header(MpegEncContext * s, GetBitContext *gb){
    int hours, minutes, seconds;

    if(!show_bits(gb, 23)){
        av_log(s->avctx, AV_LOG_WARNING, "GOP header invalid\n");
        return -1;
    }

    hours= get_bits(gb, 5);
    minutes= get_bits(gb, 6);
    skip_bits1(gb);
    seconds= get_bits(gb, 6);

    s->time_base= seconds + 60*(minutes + 60*hours);

    skip_bits1(gb);
    skip_bits1(gb);

    return 0;
}

static int decode_vol_header(MpegEncContext *s, GetBitContext *gb){
    int width, height, vo_ver_id;

    /* vol header */
    skip_bits(gb, 1); /* random access */
    s->vo_type= get_bits(gb, 8);
    if (get_bits1(gb) != 0) { /* is_ol_id */
        vo_ver_id = get_bits(gb, 4); /* vo_ver_id */
        skip_bits(gb, 3); /* vo_priority */
    } else {
        vo_ver_id = 1;
    }
    s->aspect_ratio_info= get_bits(gb, 4);
    if(s->aspect_ratio_info == FF_ASPECT_EXTENDED){
        s->avctx->sample_aspect_ratio.num= get_bits(gb, 8); // par_width
        s->avctx->sample_aspect_ratio.den= get_bits(gb, 8); // par_height
    }else{
        s->avctx->sample_aspect_ratio= ff_h263_pixel_aspect[s->aspect_ratio_info];
    }

    if ((s->vol_control_parameters=get_bits1(gb))) { /* vol control parameter */
        int chroma_format= get_bits(gb, 2);
        if(chroma_format!=CHROMA_420){
            av_log(s->avctx, AV_LOG_ERROR, "illegal chroma format\n");
        }
        s->low_delay= get_bits1(gb);
        if(get_bits1(gb)){ /* vbv parameters */
            get_bits(gb, 15);   /* first_half_bitrate */
            skip_bits1(gb);     /* marker */
            get_bits(gb, 15);   /* latter_half_bitrate */
            skip_bits1(gb);     /* marker */
            get_bits(gb, 15);   /* first_half_vbv_buffer_size */
            skip_bits1(gb);     /* marker */
            get_bits(gb, 3);    /* latter_half_vbv_buffer_size */
            get_bits(gb, 11);   /* first_half_vbv_occupancy */
            skip_bits1(gb);     /* marker */
            get_bits(gb, 15);   /* latter_half_vbv_occupancy */
            skip_bits1(gb);     /* marker */
        }
    }else{
        // set low delay flag only once the smartest? low delay detection won't be overriden
        if(s->picture_number==0)
            s->low_delay=0;
    }

    s->shape = get_bits(gb, 2); /* vol shape */
    if(s->shape != RECT_SHAPE) av_log(s->avctx, AV_LOG_ERROR, "only rectangular vol supported\n");
    if(s->shape == GRAY_SHAPE && vo_ver_id != 1){
        av_log(s->avctx, AV_LOG_ERROR, "Gray shape not supported\n");
        skip_bits(gb, 4);  //video_object_layer_shape_extension
    }

    check_marker(gb, "before time_increment_resolution");

    s->avctx->time_base.den = get_bits(gb, 16);
    if(!s->avctx->time_base.den){
        av_log(s->avctx, AV_LOG_ERROR, "time_base.den==0\n");
        s->avctx->time_base.num = 0;
        return -1;
    }

    s->time_increment_bits = av_log2(s->avctx->time_base.den - 1) + 1;
    if (s->time_increment_bits < 1)
        s->time_increment_bits = 1;

    check_marker(gb, "before fixed_vop_rate");

    if (get_bits1(gb) != 0) {   /* fixed_vop_rate  */
        s->avctx->time_base.num = get_bits(gb, s->time_increment_bits);
    }else
        s->avctx->time_base.num = 1;

    s->t_frame=0;

    if (s->shape != BIN_ONLY_SHAPE) {
        if (s->shape == RECT_SHAPE) {
            skip_bits1(gb);   /* marker */
            width = get_bits(gb, 13);
            skip_bits1(gb);   /* marker */
            height = get_bits(gb, 13);
            skip_bits1(gb);   /* marker */
            if(width && height && !(s->width && s->codec_tag == AV_RL32("MP4S"))){ /* they should be non zero but who knows ... */
                s->width = width;
                s->height = height;
            }
        }

        s->progressive_sequence=
        s->progressive_frame= get_bits1(gb)^1;
        s->interlaced_dct=0;
        if(!get_bits1(gb) && (s->avctx->debug & FF_DEBUG_PICT_INFO))
            av_log(s->avctx, AV_LOG_INFO, "MPEG4 OBMC not supported (very likely buggy encoder)\n");   /* OBMC Disable */
        if (vo_ver_id == 1) {
            s->vol_sprite_usage = get_bits1(gb); /* vol_sprite_usage */
        } else {
            s->vol_sprite_usage = get_bits(gb, 2); /* vol_sprite_usage */
        }
        if(s->vol_sprite_usage==STATIC_SPRITE) av_log(s->avctx, AV_LOG_ERROR, "Static Sprites not supported\n");
        if(s->vol_sprite_usage==STATIC_SPRITE || s->vol_sprite_usage==GMC_SPRITE){
            if(s->vol_sprite_usage==STATIC_SPRITE){
                s->sprite_width = get_bits(gb, 13);
                skip_bits1(gb); /* marker */
                s->sprite_height= get_bits(gb, 13);
                skip_bits1(gb); /* marker */
                s->sprite_left  = get_bits(gb, 13);
                skip_bits1(gb); /* marker */
                s->sprite_top   = get_bits(gb, 13);
                skip_bits1(gb); /* marker */
            }
            s->num_sprite_warping_points= get_bits(gb, 6);
            if(s->num_sprite_warping_points > 3){
                av_log(s->avctx, AV_LOG_ERROR, "%d sprite_warping_points\n", s->num_sprite_warping_points);
                s->num_sprite_warping_points= 0;
                return -1;
            }
            s->sprite_warping_accuracy = get_bits(gb, 2);
            s->sprite_brightness_change= get_bits1(gb);
            if(s->vol_sprite_usage==STATIC_SPRITE)
                s->low_latency_sprite= get_bits1(gb);
        }
        // FIXME sadct disable bit if verid!=1 && shape not rect

        if (get_bits1(gb) == 1) {   /* not_8_bit */
            s->quant_precision = get_bits(gb, 4); /* quant_precision */
            if(get_bits(gb, 4)!=8) av_log(s->avctx, AV_LOG_ERROR, "N-bit not supported\n"); /* bits_per_pixel */
            if(s->quant_precision!=5) av_log(s->avctx, AV_LOG_ERROR, "quant precision %d\n", s->quant_precision);
        } else {
            s->quant_precision = 5;
        }

        // FIXME a bunch of grayscale shape things

        if((s->mpeg_quant=get_bits1(gb))){ /* vol_quant_type */
            int i, v;

            /* load default matrixes */
            for(i=0; i<64; i++){
                int j= s->dsp.idct_permutation[i];
                v= ff_mpeg4_default_intra_matrix[i];
                s->intra_matrix[j]= v;
                s->chroma_intra_matrix[j]= v;

                v= ff_mpeg4_default_non_intra_matrix[i];
                s->inter_matrix[j]= v;
                s->chroma_inter_matrix[j]= v;
            }

            /* load custom intra matrix */
            if(get_bits1(gb)){
                int last=0;
                for(i=0; i<64; i++){
                    int j;
                    v= get_bits(gb, 8);
                    if(v==0) break;

                    last= v;
                    j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
                    s->intra_matrix[j]= v;
                    s->chroma_intra_matrix[j]= v;
                }

                /* replicate last value */
                for(; i<64; i++){
                    int j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
                    s->intra_matrix[j]= last;
                    s->chroma_intra_matrix[j]= last;
                }
            }

            /* load custom non intra matrix */
            if(get_bits1(gb)){
                int last=0;
                for(i=0; i<64; i++){
                    int j;
                    v= get_bits(gb, 8);
                    if(v==0) break;

                    last= v;
                    j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
                    s->inter_matrix[j]= v;
                    s->chroma_inter_matrix[j]= v;
                }

                /* replicate last value */
                for(; i<64; i++){
                    int j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
                    s->inter_matrix[j]= last;
                    s->chroma_inter_matrix[j]= last;
                }
            }

            // FIXME a bunch of grayscale shape things
        }

        if(vo_ver_id != 1)
             s->quarter_sample= get_bits1(gb);
        else s->quarter_sample=0;

        if(!get_bits1(gb)){
            int pos= get_bits_count(gb);
            int estimation_method= get_bits(gb, 2);
            if(estimation_method<2){
                if(!get_bits1(gb)){
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //opaque
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //transparent
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //intra_cae
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //inter_cae
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //no_update
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //upampling
                }
                if(!get_bits1(gb)){
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //intra_blocks
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //inter_blocks
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //inter4v_blocks
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //not coded blocks
                }
                if(!check_marker(gb, "in complexity estimation part 1")){
                    skip_bits_long(gb, pos - get_bits_count(gb));
                    goto no_cplx_est;
                }
                if(!get_bits1(gb)){
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //dct_coeffs
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //dct_lines
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //vlc_syms
                    s->cplx_estimation_trash_i += 4*get_bits1(gb); //vlc_bits
                }
                if(!get_bits1(gb)){
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //apm
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //npm
                    s->cplx_estimation_trash_b += 8*get_bits1(gb); //interpolate_mc_q
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //forwback_mc_q
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //halfpel2
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //halfpel4
                }
                if(!check_marker(gb, "in complexity estimation part 2")){
                    skip_bits_long(gb, pos - get_bits_count(gb));
                    goto no_cplx_est;
                }
                if(estimation_method==1){
                    s->cplx_estimation_trash_i += 8*get_bits1(gb); //sadct
                    s->cplx_estimation_trash_p += 8*get_bits1(gb); //qpel
                }
            }else
                av_log(s->avctx, AV_LOG_ERROR, "Invalid Complexity estimation method %d\n", estimation_method);
        }else{
no_cplx_est:
            s->cplx_estimation_trash_i=
            s->cplx_estimation_trash_p=
            s->cplx_estimation_trash_b= 0;
        }

        s->resync_marker= !get_bits1(gb); /* resync_marker_disabled */

        s->data_partitioning= get_bits1(gb);
        if(s->data_partitioning){
            s->rvlc= get_bits1(gb);
        }

        if(vo_ver_id != 1) {
            s->new_pred= get_bits1(gb);
            if(s->new_pred){
                av_log(s->avctx, AV_LOG_ERROR, "new pred not supported\n");
                skip_bits(gb, 2); /* requested upstream message type */
                skip_bits1(gb); /* newpred segment type */
            }
            s->reduced_res_vop= get_bits1(gb);
            if(s->reduced_res_vop) av_log(s->avctx, AV_LOG_ERROR, "reduced resolution VOP not supported\n");
        }
        else{
            s->new_pred=0;
            s->reduced_res_vop= 0;
        }

        s->scalability= get_bits1(gb);

        if (s->scalability) {
            GetBitContext bak= *gb;
            int ref_layer_id;
            int ref_layer_sampling_dir;
            int h_sampling_factor_n;
            int h_sampling_factor_m;
            int v_sampling_factor_n;
            int v_sampling_factor_m;

            s->hierachy_type= get_bits1(gb);
            ref_layer_id= get_bits(gb, 4);
            ref_layer_sampling_dir= get_bits1(gb);
            h_sampling_factor_n= get_bits(gb, 5);
            h_sampling_factor_m= get_bits(gb, 5);
            v_sampling_factor_n= get_bits(gb, 5);
            v_sampling_factor_m= get_bits(gb, 5);
            s->enhancement_type= get_bits1(gb);

            if(   h_sampling_factor_n==0 || h_sampling_factor_m==0
               || v_sampling_factor_n==0 || v_sampling_factor_m==0){
                /* illegal scalability header (VERY broken encoder),
                 * trying to workaround */
                s->scalability=0;
                *gb= bak;
            }else
                av_log(s->avctx, AV_LOG_ERROR, "scalability not supported\n");

            // bin shape stuff FIXME
        }
    }
    return 0;
}

/**
 * decodes the user data stuff in the header.
 * Also initializes divx/xvid/lavc_version/build.
 */
static int decode_user_data(MpegEncContext *s, GetBitContext *gb){
    char buf[256];
    int i;
    int e;
    int ver = 0, build = 0, ver2 = 0, ver3 = 0;
    char last;

    for(i=0; i<255 && get_bits_count(gb) < gb->size_in_bits; i++){
        if(show_bits(gb, 23) == 0) break;
        buf[i]= get_bits(gb, 8);
    }
    buf[i]=0;

    /* divx detection */
    e=sscanf(buf, "DivX%dBuild%d%c", &ver, &build, &last);
    if(e<2)
        e=sscanf(buf, "DivX%db%d%c", &ver, &build, &last);
    if(e>=2){
        s->divx_version= ver;
        s->divx_build= build;
        s->divx_packed= e==3 && last=='p';
        if(s->divx_packed && !s->showed_packed_warning) {
            av_log(s->avctx, AV_LOG_WARNING, "Invalid and inefficient vfw-avi packed B frames detected\n");
            s->showed_packed_warning=1;
        }
    }

    /* ffmpeg detection */
    e=sscanf(buf, "FFmpe%*[^b]b%d", &build)+3;
    if(e!=4)
        e=sscanf(buf, "FFmpeg v%d.%d.%d / libavcodec build: %d", &ver, &ver2, &ver3, &build);
    if(e!=4){
        e=sscanf(buf, "Lavc%d.%d.%d", &ver, &ver2, &ver3)+1;
        if (e>1)
            build= (ver<<16) + (ver2<<8) + ver3;
    }
    if(e!=4){
        if(strcmp(buf, "ffmpeg")==0){
            s->lavc_build= 4600;
        }
    }
    if(e==4){
        s->lavc_build= build;
    }

    /* Xvid detection */
    e=sscanf(buf, "XviD%d", &build);
    if(e==1){
        s->xvid_build= build;
    }

    return 0;
}

static int decode_vop_header(MpegEncContext *s, GetBitContext *gb){
    int time_incr, time_increment;

    s->pict_type = get_bits(gb, 2) + FF_I_TYPE;        /* pict type: I = 0 , P = 1 */
    if(s->pict_type==FF_B_TYPE && s->low_delay && s->vol_control_parameters==0 && !(s->flags & CODEC_FLAG_LOW_DELAY)){
        av_log(s->avctx, AV_LOG_ERROR, "low_delay flag incorrectly, clearing it\n");
        s->low_delay=0;
    }

    s->partitioned_frame= s->data_partitioning && s->pict_type!=FF_B_TYPE;
    if(s->partitioned_frame)
        s->decode_mb= mpeg4_decode_partitioned_mb;
    else
        s->decode_mb= mpeg4_decode_mb;

    time_incr=0;
    while (get_bits1(gb) != 0)
        time_incr++;

    check_marker(gb, "before time_increment");

    if(s->time_increment_bits==0 || !(show_bits(gb, s->time_increment_bits+1)&1)){
        av_log(s->avctx, AV_LOG_ERROR, "hmm, seems the headers are not complete, trying to guess time_increment_bits\n");

        for(s->time_increment_bits=1 ;s->time_increment_bits<16; s->time_increment_bits++){
            if (    s->pict_type == FF_P_TYPE
                || (s->pict_type == FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE)) {
                if((show_bits(gb, s->time_increment_bits+6)&0x37) == 0x30) break;
            }else
                if((show_bits(gb, s->time_increment_bits+5)&0x1F) == 0x18) break;
        }

        av_log(s->avctx, AV_LOG_ERROR, "my guess is %d bits ;)\n",s->time_increment_bits);
    }

    if(IS_3IV1) time_increment= get_bits1(gb); //FIXME investigate further
    else time_increment= get_bits(gb, s->time_increment_bits);

    if(s->pict_type!=FF_B_TYPE){
        s->last_time_base= s->time_base;
        s->time_base+= time_incr;
        s->time= s->time_base*s->avctx->time_base.den + time_increment;
        if(s->workaround_bugs&FF_BUG_UMP4){
            if(s->time < s->last_non_b_time){
                /* header is not mpeg-4-compatible, broken encoder,
                 * trying to workaround */
                s->time_base++;
                s->time+= s->avctx->time_base.den;
            }
        }
        s->pp_time= s->time - s->last_non_b_time;
        s->last_non_b_time= s->time;
    }else{
        s->time= (s->last_time_base + time_incr)*s->avctx->time_base.den + time_increment;
        s->pb_time= s->pp_time - (s->last_non_b_time - s->time);
        if(s->pp_time <=s->pb_time || s->pp_time <= s->pp_time - s->pb_time || s->pp_time<=0){
            /* messed up order, maybe after seeking? skipping current b-frame */
            return FRAME_SKIPPED;
        }
        ff_mpeg4_init_direct_mv(s);

        if(s->t_frame==0) s->t_frame= s->pb_time;
        if(s->t_frame==0) s->t_frame=1; // 1/0 protection
        s->pp_field_time= (  ROUNDED_DIV(s->last_non_b_time, s->t_frame)
                           - ROUNDED_DIV(s->last_non_b_time - s->pp_time, s->t_frame))*2;
        s->pb_field_time= (  ROUNDED_DIV(s->time, s->t_frame)
                           - ROUNDED_DIV(s->last_non_b_time - s->pp_time, s->t_frame))*2;
        if(!s->progressive_sequence){
            if(s->pp_field_time <= s->pb_field_time || s->pb_field_time <= 1)
                return FRAME_SKIPPED;
        }
    }

    if(s->avctx->time_base.num)
        s->current_picture_ptr->pts= (s->time + s->avctx->time_base.num/2) / s->avctx->time_base.num;
    else
        s->current_picture_ptr->pts= AV_NOPTS_VALUE;
    if(s->avctx->debug&FF_DEBUG_PTS)
        av_log(s->avctx, AV_LOG_DEBUG, "MPEG4 PTS: %"PRId64"\n", s->current_picture_ptr->pts);

    check_marker(gb, "before vop_coded");

    /* vop coded */
    if (get_bits1(gb) != 1){
        if(s->avctx->debug&FF_DEBUG_PICT_INFO)
            av_log(s->avctx, AV_LOG_ERROR, "vop not coded\n");
        return FRAME_SKIPPED;
    }
    if (s->shape != BIN_ONLY_SHAPE && ( s->pict_type == FF_P_TYPE
                          || (s->pict_type == FF_S_TYPE && s->vol_sprite_usage==GMC_SPRITE))) {
        /* rounding type for motion estimation */
        s->no_rounding = get_bits1(gb);
    } else {
        s->no_rounding = 0;
    }
//FIXME reduced res stuff

     if (s->shape != RECT_SHAPE) {
         if (s->vol_sprite_usage != 1 || s->pict_type != FF_I_TYPE) {
             int width, height, hor_spat_ref, ver_spat_ref;

             width = get_bits(gb, 13);
             skip_bits1(gb);   /* marker */
             height = get_bits(gb, 13);
             skip_bits1(gb);   /* marker */
             hor_spat_ref = get_bits(gb, 13); /* hor_spat_ref */
             skip_bits1(gb);   /* marker */
             ver_spat_ref = get_bits(gb, 13); /* ver_spat_ref */
         }
         skip_bits1(gb); /* change_CR_disable */

         if (get_bits1(gb) != 0) {
             skip_bits(gb, 8); /* constant_alpha_value */
         }
     }
//FIXME complexity estimation stuff

     if (s->shape != BIN_ONLY_SHAPE) {
         skip_bits_long(gb, s->cplx_estimation_trash_i);
         if(s->pict_type != FF_I_TYPE)
            skip_bits_long(gb, s->cplx_estimation_trash_p);
         if(s->pict_type == FF_B_TYPE)
            skip_bits_long(gb, s->cplx_estimation_trash_b);

         s->intra_dc_threshold= mpeg4_dc_threshold[ get_bits(gb, 3) ];
         if(!s->progressive_sequence){
             s->top_field_first= get_bits1(gb);
             s->alternate_scan= get_bits1(gb);
         }else
             s->alternate_scan= 0;
     }

     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);
         ff_init_scantable(s->dsp.idct_permutation, &s->intra_h_scantable, ff_alternate_vertical_scan);
         ff_init_scantable(s->dsp.idct_permutation, &s->intra_v_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);
         ff_init_scantable(s->dsp.idct_permutation, &s->intra_h_scantable, ff_alternate_horizontal_scan);
         ff_init_scantable(s->dsp.idct_permutation, &s->intra_v_scantable, ff_alternate_vertical_scan);
     }

     if(s->pict_type == FF_S_TYPE && (s->vol_sprite_usage==STATIC_SPRITE || s->vol_sprite_usage==GMC_SPRITE)){
         mpeg4_decode_sprite_trajectory(s, gb);
         if(s->sprite_brightness_change) av_log(s->avctx, AV_LOG_ERROR, "sprite_brightness_change not supported\n");
         if(s->vol_sprite_usage==STATIC_SPRITE) av_log(s->avctx, AV_LOG_ERROR, "static sprite not supported\n");
     }

     if (s->shape != BIN_ONLY_SHAPE) {
         s->chroma_qscale= s->qscale = get_bits(gb, s->quant_precision);
         if(s->qscale==0){
             av_log(s->avctx, AV_LOG_ERROR, "Error, header damaged or not MPEG4 header (qscale=0)\n");
             return -1; // makes no sense to continue, as there is nothing left from the image then
         }

         if (s->pict_type != FF_I_TYPE) {
             s->f_code = get_bits(gb, 3);       /* fcode_for */
             if(s->f_code==0){
                 av_log(s->avctx, AV_LOG_ERROR, "Error, header damaged or not MPEG4 header (f_code=0)\n");
                 return -1; // makes no sense to continue, as the MV decoding will break very quickly
             }
         }else
             s->f_code=1;

         if (s->pict_type == FF_B_TYPE) {
             s->b_code = get_bits(gb, 3);
         }else
             s->b_code=1;

         if(s->avctx->debug&FF_DEBUG_PICT_INFO){
             av_log(s->avctx, AV_LOG_DEBUG, "qp:%d fc:%d,%d %s size:%d pro:%d alt:%d top:%d %spel part:%d resync:%d w:%d a:%d rnd:%d vot:%d%s dc:%d ce:%d/%d/%d\n",
                 s->qscale, s->f_code, s->b_code,
                 s->pict_type == FF_I_TYPE ? "I" : (s->pict_type == FF_P_TYPE ? "P" : (s->pict_type == FF_B_TYPE ? "B" : "S")),
                 gb->size_in_bits,s->progressive_sequence, s->alternate_scan, s->top_field_first,
                 s->quarter_sample ? "q" : "h", s->data_partitioning, s->resync_marker, s->num_sprite_warping_points,
                 s->sprite_warping_accuracy, 1-s->no_rounding, s->vo_type, s->vol_control_parameters ? " VOLC" : " ", s->intra_dc_threshold, s->cplx_estimation_trash_i, s->cplx_estimation_trash_p, s->cplx_estimation_trash_b);
         }

         if(!s->scalability){
             if (s->shape!=RECT_SHAPE && s->pict_type!=FF_I_TYPE) {
                 skip_bits1(gb); // vop shape coding type
             }
         }else{
             if(s->enhancement_type){
                 int load_backward_shape= get_bits1(gb);
                 if(load_backward_shape){
                     av_log(s->avctx, AV_LOG_ERROR, "load backward shape isn't supported\n");
                 }
             }
             skip_bits(gb, 2); //ref_select_code
         }
     }
     /* detect buggy encoders which don't set the low_delay flag (divx4/xvid/opendivx)*/
     // note we cannot detect divx5 without b-frames easily (although it's buggy too)
     if(s->vo_type==0 && s->vol_control_parameters==0 && s->divx_version==-1 && s->picture_number==0){
         av_log(s->avctx, AV_LOG_WARNING, "looks like this file was encoded with (divx4/(old)xvid/opendivx) -> forcing low_delay flag\n");
         s->low_delay=1;
     }

     s->picture_number++; // better than pic number==0 always ;)

     s->y_dc_scale_table= ff_mpeg4_y_dc_scale_table; //FIXME add short header support
     s->c_dc_scale_table= ff_mpeg4_c_dc_scale_table;

     if(s->workaround_bugs&FF_BUG_EDGE){
         s->h_edge_pos= s->width;
         s->v_edge_pos= s->height;
     }
     return 0;
}

/**
 * decode mpeg4 headers
 * @return <0 if no VOP found (or a damaged one)
 *         FRAME_SKIPPED if a not coded VOP is found
 *         0 if a VOP is found
 */
int ff_mpeg4_decode_picture_header(MpegEncContext * s, GetBitContext *gb)
{
    int startcode, v;

    /* search next start code */
    align_get_bits(gb);

    if(s->codec_tag == AV_RL32("WV1F") && show_bits(gb, 24) == 0x575630){
        skip_bits(gb, 24);
        if(get_bits(gb, 8) == 0xF0)
            goto end;
    }

    startcode = 0xff;
    for(;;) {
        if(get_bits_count(gb) >= gb->size_in_bits){
            if(gb->size_in_bits==8 && (s->divx_version>=0 || s->xvid_build>=0)){
                av_log(s->avctx, AV_LOG_WARNING, "frame skip %d\n", gb->size_in_bits);
                return FRAME_SKIPPED; //divx bug
            }else
                return -1; //end of stream
        }

        /* use the bits after the test */
        v = get_bits(gb, 8);
        startcode = ((startcode << 8) | v) & 0xffffffff;

        if((startcode&0xFFFFFF00) != 0x100)
            continue; //no startcode

        if(s->avctx->debug&FF_DEBUG_STARTCODE){
            av_log(s->avctx, AV_LOG_DEBUG, "startcode: %3X ", startcode);
            if     (startcode<=0x11F) av_log(s->avctx, AV_LOG_DEBUG, "Video Object Start");
            else if(startcode<=0x12F) av_log(s->avctx, AV_LOG_DEBUG, "Video Object Layer Start");
            else if(startcode<=0x13F) av_log(s->avctx, AV_LOG_DEBUG, "Reserved");
            else if(startcode<=0x15F) av_log(s->avctx, AV_LOG_DEBUG, "FGS bp start");
            else if(startcode<=0x1AF) av_log(s->avctx, AV_LOG_DEBUG, "Reserved");
            else if(startcode==0x1B0) av_log(s->avctx, AV_LOG_DEBUG, "Visual Object Seq Start");
            else if(startcode==0x1B1) av_log(s->avctx, AV_LOG_DEBUG, "Visual Object Seq End");
            else if(startcode==0x1B2) av_log(s->avctx, AV_LOG_DEBUG, "User Data");
            else if(startcode==0x1B3) av_log(s->avctx, AV_LOG_DEBUG, "Group of VOP start");
            else if(startcode==0x1B4) av_log(s->avctx, AV_LOG_DEBUG, "Video Session Error");
            else if(startcode==0x1B5) av_log(s->avctx, AV_LOG_DEBUG, "Visual Object Start");
            else if(startcode==0x1B6) av_log(s->avctx, AV_LOG_DEBUG, "Video Object Plane start");
            else if(startcode==0x1B7) av_log(s->avctx, AV_LOG_DEBUG, "slice start");
            else if(startcode==0x1B8) av_log(s->avctx, AV_LOG_DEBUG, "extension start");
            else if(startcode==0x1B9) av_log(s->avctx, AV_LOG_DEBUG, "fgs start");
            else if(startcode==0x1BA) av_log(s->avctx, AV_LOG_DEBUG, "FBA Object start");
            else if(startcode==0x1BB) av_log(s->avctx, AV_LOG_DEBUG, "FBA Object Plane start");
            else if(startcode==0x1BC) av_log(s->avctx, AV_LOG_DEBUG, "Mesh Object start");
            else if(startcode==0x1BD) av_log(s->avctx, AV_LOG_DEBUG, "Mesh Object Plane start");
            else if(startcode==0x1BE) av_log(s->avctx, AV_LOG_DEBUG, "Still Texture Object start");
            else if(startcode==0x1BF) av_log(s->avctx, AV_LOG_DEBUG, "Texture Spatial Layer start");
            else if(startcode==0x1C0) av_log(s->avctx, AV_LOG_DEBUG, "Texture SNR Layer start");
            else if(startcode==0x1C1) av_log(s->avctx, AV_LOG_DEBUG, "Texture Tile start");
            else if(startcode==0x1C2) av_log(s->avctx, AV_LOG_DEBUG, "Texture Shape Layer start");
            else if(startcode==0x1C3) av_log(s->avctx, AV_LOG_DEBUG, "stuffing start");
            else if(startcode<=0x1C5) av_log(s->avctx, AV_LOG_DEBUG, "reserved");
            else if(startcode<=0x1FF) av_log(s->avctx, AV_LOG_DEBUG, "System start");
            av_log(s->avctx, AV_LOG_DEBUG, " at %d\n", get_bits_count(gb));
        }

        if(startcode >= 0x120 && startcode <= 0x12F){
            if(decode_vol_header(s, gb) < 0)
                return -1;
        }
        else if(startcode == USER_DATA_STARTCODE){
            decode_user_data(s, gb);
        }
        else if(startcode == GOP_STARTCODE){
            mpeg4_decode_gop_header(s, gb);
        }
        else if(startcode == VOP_STARTCODE){
            break;
        }

        align_get_bits(gb);
        startcode = 0xff;
    }
end:
    if(s->flags& CODEC_FLAG_LOW_DELAY)
        s->low_delay=1;
    s->avctx->has_b_frames= !s->low_delay;
    return decode_vop_header(s, gb);
}

static av_cold int decode_init(AVCodecContext *avctx)
{
    MpegEncContext *s = avctx->priv_data;
    int ret;
    static int done = 0;

    s->divx_version=
    s->divx_build=
    s->xvid_build=
    s->lavc_build= -1;

    if((ret=ff_h263_decode_init(avctx)) < 0)
        return ret;

    if (!done) {
        done = 1;

        init_rl(&ff_mpeg4_rl_intra, ff_mpeg4_static_rl_table_store[0]);
        init_rl(&rvlc_rl_inter, ff_mpeg4_static_rl_table_store[1]);
        init_rl(&rvlc_rl_intra, ff_mpeg4_static_rl_table_store[2]);
        INIT_VLC_RL(ff_mpeg4_rl_intra, 554);
        INIT_VLC_RL(rvlc_rl_inter, 1072);
        INIT_VLC_RL(rvlc_rl_intra, 1072);
        INIT_VLC_STATIC(&dc_lum, DC_VLC_BITS, 10 /* 13 */,
                 &ff_mpeg4_DCtab_lum[0][1], 2, 1,
                 &ff_mpeg4_DCtab_lum[0][0], 2, 1, 512);
        INIT_VLC_STATIC(&dc_chrom, DC_VLC_BITS, 10 /* 13 */,
                 &ff_mpeg4_DCtab_chrom[0][1], 2, 1,
                 &ff_mpeg4_DCtab_chrom[0][0], 2, 1, 512);
        INIT_VLC_STATIC(&sprite_trajectory, SPRITE_TRAJ_VLC_BITS, 15,
                 &sprite_trajectory_tab[0][1], 4, 2,
                 &sprite_trajectory_tab[0][0], 4, 2, 128);
        INIT_VLC_STATIC(&mb_type_b_vlc, MB_TYPE_B_VLC_BITS, 4,
                 &mb_type_b_tab[0][1], 2, 1,
                 &mb_type_b_tab[0][0], 2, 1, 16);
    }

    s->h263_pred = 1;
    s->low_delay = 0; //default, might be overriden in the vol header during header parsing
    s->decode_mb= mpeg4_decode_mb;
    s->time_increment_bits = 4; /* default value for broken headers */
    avctx->chroma_sample_location = AVCHROMA_LOC_LEFT;

    return 0;
}

AVCodec ff_mpeg4_decoder = {
    "mpeg4",
    AVMEDIA_TYPE_VIDEO,
    CODEC_ID_MPEG4,
    sizeof(MpegEncContext),
    decode_init,
    NULL,
    ff_h263_decode_end,
    ff_h263_decode_frame,
    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY | CODEC_CAP_FRAME_THREADS,
    .flush= ff_mpeg_flush,
    .max_lowres= 3,
    .long_name= NULL_IF_CONFIG_SMALL("MPEG-4 part 2"),
    .pix_fmts= ff_hwaccel_pixfmt_list_420,
    .update_thread_context= ONLY_IF_THREADS_ENABLED(ff_mpeg_update_thread_context)
};


#if CONFIG_MPEG4_VDPAU_DECODER
AVCodec ff_mpeg4_vdpau_decoder = {
    "mpeg4_vdpau",
    AVMEDIA_TYPE_VIDEO,
    CODEC_ID_MPEG4,
    sizeof(MpegEncContext),
    decode_init,
    NULL,
    ff_h263_decode_end,
    ff_h263_decode_frame,
    CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY | CODEC_CAP_HWACCEL_VDPAU,
    .long_name= NULL_IF_CONFIG_SMALL("MPEG-4 part 2 (VDPAU)"),
    .pix_fmts= (const enum PixelFormat[]){PIX_FMT_VDPAU_MPEG4, PIX_FMT_NONE},
};
#endif