mpeg12.c 63.8 KB
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/*
 * MPEG1 encoder / MPEG2 decoder
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 * Copyright (c) 2000,2001 Fabrice Bellard.
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 *
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 * This library 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 of the License, or (at your option) any later version.
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 *
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 * This library is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 */
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//#define DEBUG
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#include "avcodec.h"
#include "dsputil.h"
#include "mpegvideo.h"

#include "mpeg12data.h"

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#if 1
#define PRINT_QP(a, b) {}
#else
#define PRINT_QP(a, b) printf(a, b)
#endif

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/* Start codes. */
#define SEQ_END_CODE		0x000001b7
#define SEQ_START_CODE		0x000001b3
#define GOP_START_CODE		0x000001b8
#define PICTURE_START_CODE	0x00000100
#define SLICE_MIN_START_CODE	0x00000101
#define SLICE_MAX_START_CODE	0x000001af
#define EXT_START_CODE		0x000001b5
#define USER_START_CODE		0x000001b2

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#define DC_VLC_BITS 9
#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
#define TEX_VLC_BITS 9

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static void mpeg1_encode_block(MpegEncContext *s, 
                         DCTELEM *block, 
                         int component);
static void mpeg1_encode_motion(MpegEncContext *s, int val);
static void mpeg1_skip_picture(MpegEncContext *s, int pict_num);
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static inline int mpeg1_decode_block_inter(MpegEncContext *s, 
                              DCTELEM *block, 
                              int n);
static inline int mpeg1_decode_block_intra(MpegEncContext *s, 
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                              DCTELEM *block, 
                              int n);
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static inline int mpeg2_decode_block_non_intra(MpegEncContext *s, 
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                                        DCTELEM *block, 
                                        int n);
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static inline int mpeg2_decode_block_intra(MpegEncContext *s, 
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                                    DCTELEM *block, 
                                    int n);
static int mpeg_decode_motion(MpegEncContext *s, int fcode, int pred);

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static UINT16 mv_penalty[MAX_FCODE+1][MAX_MV*2+1];
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static UINT8 fcode_tab[MAX_MV*2+1];

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static inline int get_bits_diff(MpegEncContext *s){
    int bits,ret;
    
    bits= get_bit_count(&s->pb);
    ret= bits - s->last_bits;
    s->last_bits=bits;
    
    return ret;
}

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static void init_2d_vlc_rl(RLTable *rl)
{
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    int i;
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    init_vlc(&rl->vlc, TEX_VLC_BITS, rl->n + 2, 
             &rl->table_vlc[0][1], 4, 2,
             &rl->table_vlc[0][0], 4, 2);

    
    rl->rl_vlc[0]= av_malloc(rl->vlc.table_size*sizeof(RL_VLC_ELEM));
    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
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                run= 0;
                level= 127;
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            }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;
    }
}


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static void put_header(MpegEncContext *s, int header)
{
    align_put_bits(&s->pb);
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    put_bits(&s->pb, 16, header>>16);
    put_bits(&s->pb, 16, header&0xFFFF);
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}

/* put sequence header if needed */
static void mpeg1_encode_sequence_header(MpegEncContext *s)
{
        unsigned int vbv_buffer_size;
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        unsigned int fps, v;
        int n;
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        UINT64 time_code;
        
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        if (s->picture_in_gop_number == 0) {
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            /* mpeg1 header repeated every gop */
            put_header(s, SEQ_START_CODE);
            
            /* search closest frame rate */
            {
                int i, dmin, d;
                s->frame_rate_index = 0;
                dmin = 0x7fffffff;
                for(i=1;i<9;i++) {
                    d = abs(s->frame_rate - frame_rate_tab[i]);
                    if (d < dmin) {
                        dmin = d;
                        s->frame_rate_index = i;
                    }
                }
            }
 
            put_bits(&s->pb, 12, s->width);
            put_bits(&s->pb, 12, s->height);
            put_bits(&s->pb, 4, 1); /* 1/1 aspect ratio */
            put_bits(&s->pb, 4, s->frame_rate_index);
            v = s->bit_rate / 400;
            if (v > 0x3ffff)
                v = 0x3ffff;
            put_bits(&s->pb, 18, v);
            put_bits(&s->pb, 1, 1); /* marker */
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            if(s->avctx->rc_buffer_size)
                vbv_buffer_size = s->avctx->rc_buffer_size;
            else
                /* VBV calculation: Scaled so that a VCD has the proper VBV size of 40 kilobytes */
                vbv_buffer_size = (( 20 * s->bit_rate) / (1151929 / 2)) * 8 * 1024;	 
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            put_bits(&s->pb, 10, (vbv_buffer_size + 16383) / 16384); 
            put_bits(&s->pb, 1, 1); /* constrained parameter flag */
            put_bits(&s->pb, 1, 0); /* no custom intra matrix */
            put_bits(&s->pb, 1, 0); /* no custom non intra matrix */

            put_header(s, GOP_START_CODE);
            put_bits(&s->pb, 1, 0); /* do drop frame */
            /* time code : we must convert from the real frame rate to a
               fake mpeg frame rate in case of low frame rate */
            fps = frame_rate_tab[s->frame_rate_index];
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            time_code = (INT64)s->fake_picture_number * FRAME_RATE_BASE;
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            s->gop_picture_number = s->fake_picture_number;
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            put_bits(&s->pb, 5, (UINT32)((time_code / (fps * 3600)) % 24));
            put_bits(&s->pb, 6, (UINT32)((time_code / (fps * 60)) % 60));
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            put_bits(&s->pb, 1, 1);
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            put_bits(&s->pb, 6, (UINT32)((time_code / fps) % 60));
            put_bits(&s->pb, 6, (UINT32)((time_code % fps) / FRAME_RATE_BASE));
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            put_bits(&s->pb, 1, 1); /* closed gop */
            put_bits(&s->pb, 1, 0); /* broken link */
        }

        if (s->frame_rate < (24 * FRAME_RATE_BASE) && s->picture_number > 0) {
            /* insert empty P pictures to slow down to the desired
               frame rate. Each fake pictures takes about 20 bytes */
            fps = frame_rate_tab[s->frame_rate_index];
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            n = (((INT64)s->picture_number * fps) / s->frame_rate) - 1;
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            while (s->fake_picture_number < n) {
                mpeg1_skip_picture(s, s->fake_picture_number - 
                                   s->gop_picture_number); 
                s->fake_picture_number++;
            }

        }
}


/* insert a fake P picture */
static void mpeg1_skip_picture(MpegEncContext *s, int pict_num)
{
    unsigned int mb_incr;

    /* mpeg1 picture header */
    put_header(s, PICTURE_START_CODE);
    /* temporal reference */
    put_bits(&s->pb, 10, pict_num & 0x3ff); 
    
    put_bits(&s->pb, 3, P_TYPE);
    put_bits(&s->pb, 16, 0xffff); /* non constant bit rate */
    
    put_bits(&s->pb, 1, 1); /* integer coordinates */
    put_bits(&s->pb, 3, 1); /* forward_f_code */
    
    put_bits(&s->pb, 1, 0); /* extra bit picture */
    
    /* only one slice */
    put_header(s, SLICE_MIN_START_CODE);
    put_bits(&s->pb, 5, 1); /* quantizer scale */
    put_bits(&s->pb, 1, 0); /* slice extra information */
    
    mb_incr = 1;
    put_bits(&s->pb, mbAddrIncrTable[mb_incr - 1][1], 
             mbAddrIncrTable[mb_incr - 1][0]);
    
    /* empty macroblock */
    put_bits(&s->pb, 3, 1); /* motion only */
    
    /* zero motion x & y */
    put_bits(&s->pb, 1, 1); 
    put_bits(&s->pb, 1, 1); 

    /* output a number of empty slice */
    mb_incr = s->mb_width * s->mb_height - 1;
    while (mb_incr > 33) {
        put_bits(&s->pb, 11, 0x008);
        mb_incr -= 33;
    }
    put_bits(&s->pb, mbAddrIncrTable[mb_incr - 1][1], 
             mbAddrIncrTable[mb_incr - 1][0]);
    
    /* empty macroblock */
    put_bits(&s->pb, 3, 1); /* motion only */
    
    /* zero motion x & y */
    put_bits(&s->pb, 1, 1); 
    put_bits(&s->pb, 1, 1); 
}

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static void common_init(MpegEncContext *s)
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{
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    s->y_dc_scale_table=
    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
}
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void mpeg1_encode_picture_header(MpegEncContext *s, int picture_number)
{
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    mpeg1_encode_sequence_header(s);

    /* mpeg1 picture header */
    put_header(s, PICTURE_START_CODE);
    /* temporal reference */
    put_bits(&s->pb, 10, (s->fake_picture_number - 
                          s->gop_picture_number) & 0x3ff); 
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    s->fake_picture_number++;
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    put_bits(&s->pb, 3, s->pict_type);
    put_bits(&s->pb, 16, 0xffff); /* non constant bit rate */
    
    if (s->pict_type == P_TYPE) {
        put_bits(&s->pb, 1, 0); /* half pel coordinates */
        put_bits(&s->pb, 3, s->f_code); /* forward_f_code */
    }
    
    put_bits(&s->pb, 1, 0); /* extra bit picture */
    
    /* only one slice */
    put_header(s, SLICE_MIN_START_CODE);
    put_bits(&s->pb, 5, s->qscale); /* quantizer scale */
    put_bits(&s->pb, 1, 0); /* slice extra information */
}

void mpeg1_encode_mb(MpegEncContext *s,
                     DCTELEM block[6][64],
                     int motion_x, int motion_y)
{
    int mb_incr, i, cbp, mb_x, mb_y;

    mb_x = s->mb_x;
    mb_y = s->mb_y;

    /* compute cbp */
    cbp = 0;
    for(i=0;i<6;i++) {
        if (s->block_last_index[i] >= 0)
            cbp |= 1 << (5 - i);
    }

    /* skip macroblock, except if first or last macroblock of a slice */
    if ((cbp | motion_x | motion_y) == 0 &&
        (!((mb_x | mb_y) == 0 ||
           (mb_x == s->mb_width - 1 && mb_y == s->mb_height - 1)))) {
        s->mb_incr++;
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        s->qscale -= s->dquant;
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        s->skip_count++;
        s->misc_bits++;
        s->last_bits++;
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    } else {
        /* output mb incr */
        mb_incr = s->mb_incr;

        while (mb_incr > 33) {
            put_bits(&s->pb, 11, 0x008);
            mb_incr -= 33;
        }
        put_bits(&s->pb, mbAddrIncrTable[mb_incr - 1][1], 
                 mbAddrIncrTable[mb_incr - 1][0]);
        
        if (s->pict_type == I_TYPE) {
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            if(s->dquant && cbp){
                put_bits(&s->pb, 2, 1); /* macroblock_type : macroblock_quant = 1 */
                put_bits(&s->pb, 5, s->qscale);
            }else{
                put_bits(&s->pb, 1, 1); /* macroblock_type : macroblock_quant = 0 */
                s->qscale -= s->dquant;
            }
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            s->misc_bits+= get_bits_diff(s);
            s->i_count++;
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        } else {
            if (s->mb_intra) {
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                if(s->dquant && cbp){
                    put_bits(&s->pb, 6, 0x01);
                    put_bits(&s->pb, 5, s->qscale);
                }else{
                    put_bits(&s->pb, 5, 0x03);
                    s->qscale -= s->dquant;
                }
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                s->misc_bits+= get_bits_diff(s);
                s->i_count++;
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            } else {
                if (cbp != 0) {
                    if (motion_x == 0 && motion_y == 0) {
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                        if(s->dquant){
                            put_bits(&s->pb, 5, 1); /* macroblock_pattern & quant */
                            put_bits(&s->pb, 5, s->qscale);
                        }else{
                            put_bits(&s->pb, 2, 1); /* macroblock_pattern only */
                        }
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                        s->misc_bits+= get_bits_diff(s);
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                        put_bits(&s->pb, mbPatTable[cbp - 1][1], mbPatTable[cbp - 1][0]);
                    } else {
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                        if(s->dquant){
                            put_bits(&s->pb, 5, 2); /* motion + cbp */
                            put_bits(&s->pb, 5, s->qscale);
                        }else{
                            put_bits(&s->pb, 1, 1); /* motion + cbp */
                        }
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                        s->misc_bits+= get_bits_diff(s);
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                        mpeg1_encode_motion(s, motion_x - s->last_mv[0][0][0]); 
                        mpeg1_encode_motion(s, motion_y - s->last_mv[0][0][1]); 
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                        s->mv_bits+= get_bits_diff(s);
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                        put_bits(&s->pb, mbPatTable[cbp - 1][1], mbPatTable[cbp - 1][0]);
                    }
                } else {
                    put_bits(&s->pb, 3, 1); /* motion only */
                    mpeg1_encode_motion(s, motion_x - s->last_mv[0][0][0]); 
                    mpeg1_encode_motion(s, motion_y - s->last_mv[0][0][1]); 
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                    s->qscale -= s->dquant;
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                    s->mv_bits+= get_bits_diff(s);
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                }
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                s->f_count++;
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            }
        }
        for(i=0;i<6;i++) {
            if (cbp & (1 << (5 - i))) {
                mpeg1_encode_block(s, block[i], i);
            }
        }
        s->mb_incr = 1;
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        if(s->mb_intra)
            s->i_tex_bits+= get_bits_diff(s);
        else
            s->p_tex_bits+= get_bits_diff(s);
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    }
    s->last_mv[0][0][0] = motion_x;
    s->last_mv[0][0][1] = motion_y;
}

static void mpeg1_encode_motion(MpegEncContext *s, int val)
{
    int code, bit_size, l, m, bits, range, sign;

    if (val == 0) {
        /* zero vector */
        code = 0;
        put_bits(&s->pb,
                 mbMotionVectorTable[0][1], 
                 mbMotionVectorTable[0][0]); 
    } else {
        bit_size = s->f_code - 1;
        range = 1 << bit_size;
        /* modulo encoding */
        l = 16 * range;
        m = 2 * l;
        if (val < -l) {
            val += m;
        } else if (val >= l) {
            val -= m;
        }

        if (val >= 0) {
            val--;
            code = (val >> bit_size) + 1;
            bits = val & (range - 1);
            sign = 0;
        } else {
            val = -val;
            val--;
            code = (val >> bit_size) + 1;
            bits = val & (range - 1);
            sign = 1;
        }
        put_bits(&s->pb,
                 mbMotionVectorTable[code][1], 
                 mbMotionVectorTable[code][0]); 
        put_bits(&s->pb, 1, sign);
        if (bit_size > 0) {
            put_bits(&s->pb, bit_size, bits);
        }
    }
}

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void ff_mpeg1_encode_init(MpegEncContext *s)
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{
    static int done=0;
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    common_init(s);

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    if(!done){
        int f_code;
        int mv;
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	int i;
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        done=1;
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        init_rl(&rl_mpeg1);
	
	for(i=0; i<64; i++)
	{
		mpeg1_max_level[0][i]= rl_mpeg1.max_level[0][i];
		mpeg1_index_run[0][i]= rl_mpeg1.index_run[0][i];
	}

	/* build unified dc encoding tables */
	for(i=-255; i<256; i++)
	{
		int adiff, index;
		int bits, code;
		int diff=i;

		adiff = ABS(diff);
		if(diff<0) diff--;
		index = vlc_dc_table[adiff];

		bits= vlc_dc_lum_bits[index] + index;
		code= (vlc_dc_lum_code[index]<<index) + (diff & ((1 << index) - 1));
		mpeg1_lum_dc_uni[i+255]= bits + (code<<8);
		
		bits= vlc_dc_chroma_bits[index] + index;
		code= (vlc_dc_chroma_code[index]<<index) + (diff & ((1 << index) - 1));
		mpeg1_chr_dc_uni[i+255]= bits + (code<<8);
	}

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        for(f_code=1; f_code<=MAX_FCODE; f_code++){
            for(mv=-MAX_MV; mv<=MAX_MV; mv++){
                int len;

                if(mv==0) len= mbMotionVectorTable[0][1];
                else{
                    int val, bit_size, range, code;

                    bit_size = s->f_code - 1;
                    range = 1 << bit_size;

                    val=mv;
                    if (val < 0) 
                        val = -val;
                    val--;
                    code = (val >> bit_size) + 1;
                    if(code<17){
                        len= mbMotionVectorTable[code][1] + 1 + bit_size;
                    }else{
                        len= mbMotionVectorTable[16][1] + 2 + bit_size;
                    }
                }

                mv_penalty[f_code][mv+MAX_MV]= len;
            }
        }
        

        for(f_code=MAX_FCODE; f_code>0; f_code--){
            for(mv=-(8<<f_code); mv<(8<<f_code); mv++){
                fcode_tab[mv+MAX_MV]= f_code;
            }
        }
    }
    s->mv_penalty= mv_penalty;
    s->fcode_tab= fcode_tab;
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    s->min_qcoeff=-255;
    s->max_qcoeff= 255;
    s->intra_quant_bias= 3<<(QUANT_BIAS_SHIFT-3); //(a + x*3/8)/x
    s->inter_quant_bias= 0;
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}
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static inline void encode_dc(MpegEncContext *s, int diff, int component)
{
    if (component == 0) {
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        put_bits(
	    &s->pb, 
	    mpeg1_lum_dc_uni[diff+255]&0xFF,
	    mpeg1_lum_dc_uni[diff+255]>>8);
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    } else {
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        put_bits(
            &s->pb, 
	    mpeg1_chr_dc_uni[diff+255]&0xFF,
	    mpeg1_chr_dc_uni[diff+255]>>8);
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    }
}

static void mpeg1_encode_block(MpegEncContext *s, 
                               DCTELEM *block, 
                               int n)
{
    int alevel, level, last_non_zero, dc, diff, i, j, run, last_index, sign;
    int code, component;
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//    RLTable *rl = &rl_mpeg1;
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    last_index = s->block_last_index[n];

    /* DC coef */
    if (s->mb_intra) {
        component = (n <= 3 ? 0 : n - 4 + 1);
        dc = block[0]; /* overflow is impossible */
        diff = dc - s->last_dc[component];
        encode_dc(s, diff, component);
        s->last_dc[component] = dc;
        i = 1;
    } else {
        /* encode the first coefficient : needs to be done here because
           it is handled slightly differently */
        level = block[0];
        if (abs(level) == 1) {
                code = ((UINT32)level >> 31); /* the sign bit */
                put_bits(&s->pb, 2, code | 0x02);
                i = 1;
        } else {
            i = 0;
            last_non_zero = -1;
            goto next_coef;
        }
    }

    /* now quantify & encode AC coefs */
    last_non_zero = i - 1;
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    for(;i<=last_index;i++) {
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        j = s->intra_scantable.permutated[i];
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        level = block[j];
    next_coef:
#if 0
        if (level != 0)
            dprintf("level[%d]=%d\n", i, level);
#endif            
        /* encode using VLC */
        if (level != 0) {
            run = i - last_non_zero - 1;
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            alevel= level;
            MASK_ABS(sign, alevel)
            sign&=1;

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//            code = get_rl_index(rl, 0, run, alevel);
            if (alevel > mpeg1_max_level[0][run])
                code= 111; /*rl->n*/
            else
                code= mpeg1_index_run[0][run] + alevel - 1;

            if (code < 111 /* rl->n */) {
	    	/* store the vlc & sign at once */
                put_bits(&s->pb, mpeg1_vlc[code][1]+1, (mpeg1_vlc[code][0]<<1) + sign);
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            } else {
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		/* escape seems to be pretty rare <5% so i dont optimize it */
                put_bits(&s->pb, mpeg1_vlc[111/*rl->n*/][1], mpeg1_vlc[111/*rl->n*/][0]);
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                /* escape: only clip in this case */
                put_bits(&s->pb, 6, run);
                if (alevel < 128) {
                    put_bits(&s->pb, 8, level & 0xff);
                } else {
                    if (level < 0) {
                        put_bits(&s->pb, 16, 0x8001 + level + 255);
                    } else {
                        put_bits(&s->pb, 16, level & 0xffff);
                    }
                }
            }
            last_non_zero = i;
        }
    }
    /* end of block */
    put_bits(&s->pb, 2, 0x2);
}

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

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

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static void init_vlcs(MpegEncContext *s)
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{
    static int done = 0;

    if (!done) {
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        done = 1;
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        init_vlc(&dc_lum_vlc, DC_VLC_BITS, 12, 
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                 vlc_dc_lum_bits, 1, 1,
                 vlc_dc_lum_code, 2, 2);
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        init_vlc(&dc_chroma_vlc,  DC_VLC_BITS, 12, 
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                 vlc_dc_chroma_bits, 1, 1,
                 vlc_dc_chroma_code, 2, 2);
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        init_vlc(&mv_vlc, MV_VLC_BITS, 17, 
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                 &mbMotionVectorTable[0][1], 2, 1,
                 &mbMotionVectorTable[0][0], 2, 1);
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        init_vlc(&mbincr_vlc, MBINCR_VLC_BITS, 35, 
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                 &mbAddrIncrTable[0][1], 2, 1,
                 &mbAddrIncrTable[0][0], 2, 1);
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        init_vlc(&mb_pat_vlc, MB_PAT_VLC_BITS, 63, 
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                 &mbPatTable[0][1], 2, 1,
                 &mbPatTable[0][0], 2, 1);
        
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        init_vlc(&mb_ptype_vlc, MB_PTYPE_VLC_BITS, 32, 
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                 &table_mb_ptype[0][1], 2, 1,
                 &table_mb_ptype[0][0], 2, 1);
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        init_vlc(&mb_btype_vlc, MB_BTYPE_VLC_BITS, 32, 
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                 &table_mb_btype[0][1], 2, 1,
                 &table_mb_btype[0][0], 2, 1);
        init_rl(&rl_mpeg1);
        init_rl(&rl_mpeg2);
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        init_2d_vlc_rl(&rl_mpeg1);
        init_2d_vlc_rl(&rl_mpeg2);
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    }
}

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

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static inline int get_qscale(MpegEncContext *s)
{
    int qscale;
    if (s->mpeg2) {
        if (s->q_scale_type) {
            qscale = non_linear_qscale[get_bits(&s->gb, 5)];
        } else {
            qscale = get_bits(&s->gb, 5) << 1;
        }
    } else {
        /* for mpeg1, we use the generic unquant code */
        qscale = get_bits(&s->gb, 5);
    }
    return qscale;
}

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/* motion type (for mpeg2) */
#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[6][64])
{
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    int i, j, k, cbp, val, mb_type, motion_type;
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    dprintf("decode_mb: x=%d y=%d\n", s->mb_x, s->mb_y);

    if (--s->mb_incr != 0) {
        /* skip mb */
        s->mb_intra = 0;
        for(i=0;i<6;i++)
            s->block_last_index[i] = -1;
        s->mv_type = MV_TYPE_16X16;
        if (s->pict_type == 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;
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            s->last_mv[0][1][0] = s->last_mv[0][1][1] = 0;
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        } 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];
        }
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        s->mb_skiped = 1;
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        return 0;
    }

    switch(s->pict_type) {
    default:
    case I_TYPE:
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        if (get_bits1(&s->gb) == 0) {
            if (get_bits1(&s->gb) == 0)
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                return -1;
            mb_type = MB_QUANT | MB_INTRA;
        } else {
            mb_type = MB_INTRA;
        }
        break;
    case P_TYPE:
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        mb_type = get_vlc2(&s->gb, mb_ptype_vlc.table, MB_PTYPE_VLC_BITS, 1);
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        if (mb_type < 0){
            fprintf(stderr, "invalid mb type in P Frame at %d %d\n", s->mb_x, s->mb_y);
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            return -1;
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        }
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        break;
    case B_TYPE:
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        mb_type = get_vlc2(&s->gb, mb_btype_vlc.table, MB_BTYPE_VLC_BITS, 1);
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        if (mb_type < 0){
            fprintf(stderr, "invalid mb type in B Frame at %d %d\n", s->mb_x, s->mb_y);
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            return -1;
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        }
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        break;
    }
    dprintf("mb_type=%x\n", mb_type);
    motion_type = 0; /* avoid warning */
    if (mb_type & (MB_FOR|MB_BACK)) {
        /* get additionnal motion vector type */
        if (s->picture_structure == PICT_FRAME && s->frame_pred_frame_dct) 
            motion_type = MT_FRAME;
        else
            motion_type = get_bits(&s->gb, 2);
    }
    /* compute dct type */
    if (s->picture_structure == PICT_FRAME && 
        !s->frame_pred_frame_dct &&
        (mb_type & (MB_PAT | MB_INTRA))) {
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        s->interlaced_dct = get_bits1(&s->gb);
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#ifdef DEBUG
        if (s->interlaced_dct)
            printf("interlaced_dct\n");
#endif
    } else {
        s->interlaced_dct = 0; /* frame based */
    }

    if (mb_type & MB_QUANT) {
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        s->qscale = get_qscale(s);
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    }
    if (mb_type & MB_INTRA) {
        if (s->concealment_motion_vectors) {
            /* just parse them */
            if (s->picture_structure != PICT_FRAME) 
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                skip_bits1(&s->gb); /* field select */
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            mpeg_decode_motion(s, s->mpeg_f_code[0][0], 0);
            mpeg_decode_motion(s, s->mpeg_f_code[0][1], 0);
        }
        s->mb_intra = 1;
        cbp = 0x3f;
        memset(s->last_mv, 0, sizeof(s->last_mv)); /* reset mv prediction */
    } else {
        s->mb_intra = 0;
        cbp = 0;
    }
    /* special case of implicit zero motion vector */
    if (s->pict_type == P_TYPE && !(mb_type & MB_FOR)) {
        s->mv_dir = MV_DIR_FORWARD;
        s->mv_type = MV_TYPE_16X16;
        s->last_mv[0][0][0] = 0;
        s->last_mv[0][0][1] = 0;
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        s->last_mv[0][1][0] = 0;
        s->last_mv[0][1][1] = 0;
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        s->mv[0][0][0] = 0;
        s->mv[0][0][1] = 0;
    } else if (mb_type & (MB_FOR | MB_BACK)) {
        /* motion vectors */
        s->mv_dir = 0;
        for(i=0;i<2;i++) {
            if (mb_type & (MB_FOR >> i)) {
                s->mv_dir |= (MV_DIR_FORWARD >> i);
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                dprintf("motion_type=%d\n", motion_type);
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                switch(motion_type) {
                case MT_FRAME: /* or MT_16X8 */
                    if (s->picture_structure == PICT_FRAME) {
                        /* MT_FRAME */
                        s->mv_type = MV_TYPE_16X16;
                        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;
                            /* full_pel: only for mpeg1 */
                            if (s->full_pel[i])
                                val = val << 1;
                            s->mv[i][0][k] = val;
                            dprintf("mv%d: %d\n", k, val);
                        }
                    } else {
                        /* MT_16X8 */
                        s->mv_type = MV_TYPE_16X8;
                        for(j=0;j<2;j++) {
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                            s->field_select[i][j] = get_bits1(&s->gb);
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                            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:
                    if (s->picture_structure == PICT_FRAME) {
                        s->mv_type = MV_TYPE_FIELD;
                        for(j=0;j<2;j++) {
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                            s->field_select[i][j] = get_bits1(&s->gb);
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                            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("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("fmy=%d\n", val);
                        }
                    } else {
                        s->mv_type = MV_TYPE_16X16;
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                        s->field_select[i][0] = get_bits1(&s->gb);
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                        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:
                    {
                        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->mv_type = MV_TYPE_DMV;
                        /* XXX: totally broken */
                        if (s->picture_structure == PICT_FRAME) {
                            s->last_mv[i][0][1] = my << 1;
                            s->last_mv[i][1][1] = my << 1;

                            m = s->top_field_first ? 1 : 3;
                            /* top -> top pred */
                            s->mv[i][0][0] = mx; 
                            s->mv[i][0][1] = my << 1;
                            s->mv[i][1][0] = ((mx * m + (mx > 0)) >> 1) + dmx;
                            s->mv[i][1][1] = ((my * m + (my > 0)) >> 1) + dmy - 1;
                            m = 4 - m;
                            s->mv[i][2][0] = mx;
                            s->mv[i][2][1] = my << 1;
                            s->mv[i][3][0] = ((mx * m + (mx > 0)) >> 1) + dmx;
                            s->mv[i][3][1] = ((my * m + (my > 0)) >> 1) + dmy + 1;
                        } else {
                            s->last_mv[i][0][1] = my;
                            s->last_mv[i][1][1] = my;
                            s->mv[i][0][0] = mx;
                            s->mv[i][0][1] = my;
                            s->mv[i][1][0] = ((mx + (mx > 0)) >> 1) + dmx;
                            s->mv[i][1][1] = ((my + (my > 0)) >> 1) + dmy - 1 
                                /* + 2 * cur_field */;
                        }
                    }
                    break;
                }
            }
        }
    }

    if ((mb_type & MB_INTRA) && s->concealment_motion_vectors) {
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        skip_bits1(&s->gb); /* marker */
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    }
    
    if (mb_type & MB_PAT) {
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        cbp = get_vlc2(&s->gb, mb_pat_vlc.table, MB_PAT_VLC_BITS, 1);
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        if (cbp < 0){
            fprintf(stderr, "invalid cbp at %d %d\n", s->mb_x, s->mb_y);
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            return -1;
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        }
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        cbp++;
    }
    dprintf("cbp=%x\n", cbp);

    if (s->mpeg2) {
        if (s->mb_intra) {
            for(i=0;i<6;i++) {
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                if (mpeg2_decode_block_intra(s, block[i], i) < 0)
                    return -1;
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            }
        } else {
            for(i=0;i<6;i++) {
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                if (cbp & 32) {
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                    if (mpeg2_decode_block_non_intra(s, block[i], i) < 0)
                        return -1;
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                } else {
                    s->block_last_index[i] = -1;
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                }
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                cbp+=cbp;
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            }
        }
    } else {
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        if (s->mb_intra) {
            for(i=0;i<6;i++) {
                if (mpeg1_decode_block_intra(s, block[i], i) < 0)
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                    return -1;
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            }
        }else{
            for(i=0;i<6;i++) {
                if (cbp & 32) {
                    if (mpeg1_decode_block_inter(s, block[i], i) < 0)
                        return -1;
                } else {
                    s->block_last_index[i] = -1;
                }
                cbp+=cbp;
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            }
        }
    }
    return 0;
}

/* as h263, but only 17 codes */
static int mpeg_decode_motion(MpegEncContext *s, int fcode, int pred)
{
    int code, sign, val, m, l, shift;

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    code = get_vlc2(&s->gb, mv_vlc.table, MV_VLC_BITS, 2);
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    if (code < 0) {
        return 0xffff;
    }
    if (code == 0) {
        return pred;
    }
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    sign = get_bits1(&s->gb);
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    shift = fcode - 1;
    val = (code - 1) << shift;
    if (shift > 0)
        val |= get_bits(&s->gb, shift);
    val++;
    if (sign)
        val = -val;
    val += pred;
    
    /* modulo decoding */
    l = (1 << shift) * 16;
    m = 2 * l;
    if (val < -l) {
        val += m;
    } else if (val >= l) {
        val -= m;
    }
    return val;
}

static inline int decode_dc(MpegEncContext *s, int component)
{
    int code, diff;

    if (component == 0) {
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        code = get_vlc2(&s->gb, dc_lum_vlc.table, DC_VLC_BITS, 2);
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    } else {
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        code = get_vlc2(&s->gb, dc_chroma_vlc.table, DC_VLC_BITS, 2);
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    }
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    if (code < 0){
        fprintf(stderr, "invalid dc code at %d %d\n", s->mb_x, s->mb_y);
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        return 0xffff;
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    }
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    if (code == 0) {
        diff = 0;
    } else {
        diff = get_bits(&s->gb, code);
        if ((diff & (1 << (code - 1))) == 0) 
            diff = (-1 << code) | (diff + 1);
    }
    return diff;
}

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static inline int mpeg1_decode_block_intra(MpegEncContext *s, 
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                               DCTELEM *block, 
                               int n)
{
    int level, dc, diff, i, j, run;
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    int component;
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    RLTable *rl = &rl_mpeg1;
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    UINT8 * const scantable= s->intra_scantable.permutated;
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    const UINT16 *quant_matrix= s->intra_matrix;
    const int qscale= s->qscale;
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    /* DC coef */
    component = (n <= 3 ? 0 : n - 4 + 1);
    diff = decode_dc(s, component);
    if (diff >= 0xffff)
        return -1;
    dc = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc<<3;
    dprintf("dc=%d diff=%d\n", dc, diff);
    i = 0;
    {
        OPEN_READER(re, &s->gb);    
        /* now quantify & encode AC coefs */
        for(;;) {
            UPDATE_CACHE(re, &s->gb);
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2);
            
            if(level == 127){
                break;
            } else if(level != 0) {
                i += run;
                j = scantable[i];
                level= (level*qscale*quant_matrix[j])>>3;
                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])>>3;
                    level= (level-1)|1;
                    level= -level;
                }else{
                    level= (level*qscale*quant_matrix[j])>>3;
                    level= (level-1)|1;
                }
            }
            if (i > 63){
                fprintf(stderr, "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 = &rl_mpeg1;
    UINT8 * const scantable= s->intra_scantable.permutated;
    const UINT16 *quant_matrix= s->inter_matrix;
    const int qscale= s->qscale;

    {
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        int v;
        OPEN_READER(re, &s->gb);
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        i = -1;
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        /* special case for the first coef. no need to add a second vlc table */
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        UPDATE_CACHE(re, &s->gb);
        v= SHOW_UBITS(re, &s->gb, 2);
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        if (v & 2) {
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            LAST_SKIP_BITS(re, &s->gb, 2);
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            level= (3*qscale*quant_matrix[0])>>4;
            level= (level-1)|1;
            if(v&1)
                level= -level;
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            block[0] = level;
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            i++;
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        }
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        /* now quantify & encode AC coefs */
        for(;;) {
            UPDATE_CACHE(re, &s->gb);
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2);
            
            if(level == 127){
                break;
            } else if(level != 0) {
                i += run;
                j = scantable[i];
                level= ((level*2+1)*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*2+1)*qscale*quant_matrix[j])>>4;
                    level= (level-1)|1;
                    level= -level;
                }else{
                    level= ((level*2+1)*qscale*quant_matrix[j])>>4;
                    level= (level-1)|1;
                }
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            }
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            if (i > 63){
                fprintf(stderr, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

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

/* Also does unquantization here, since I will never support mpeg2
   encoding */
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static inline int mpeg2_decode_block_non_intra(MpegEncContext *s, 
                               DCTELEM *block, 
                               int n)
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{
    int level, i, j, run;
    RLTable *rl = &rl_mpeg1;
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    UINT8 * const scantable= s->intra_scantable.permutated;
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    const UINT16 *quant_matrix;
    const int qscale= s->qscale;
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    int mismatch;

    mismatch = 1;

    {
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        int v;
        OPEN_READER(re, &s->gb);
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        i = -1;
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        if (n < 4)
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            quant_matrix = s->inter_matrix;
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        else
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            quant_matrix = s->chroma_inter_matrix;
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        /* special case for the first coef. no need to add a second vlc table */
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        UPDATE_CACHE(re, &s->gb);
        v= SHOW_UBITS(re, &s->gb, 2);
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        if (v & 2) {
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            LAST_SKIP_BITS(re, &s->gb, 2);
            level= (3*qscale*quant_matrix[0])>>5;
            if(v&1)
                level= -level;
            block[0] = level;
            mismatch ^= level;
            i++;
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        }

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