FFmpeg/libavcodec/msmpeg4.c

/*
 * MSMPEG4 backend for ffmpeg encoder and decoder
 * Copyright (c) 2001 Gerard Lantau.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <stdlib.h>
#include <stdio.h>
#include "common.h"
#include "dsputil.h"
#include "mpegvideo.h"
#include "avcodec.h"

/*
 * You can also call this codec : MPEG4 with a twist ! 
 *
 * TODO: 
 *        - (encoding) select best mv table (two choices)
 *        - (encoding) select best vlc/dc table 
 */
//#define DEBUG

/* motion vector table */
typedef struct MVTable {
    int n;
    const UINT16 *table_mv_code;
    const UINT8 *table_mv_bits;
    const UINT8 *table_mvx;
    const UINT8 *table_mvy;
    UINT16 *table_mv_index; /* encoding: convert mv to index in table_mv */
    VLC vlc;                /* decoding: vlc */
} MVTable;

static UINT32 v2_dc_lum_table[512][2];
static UINT32 v2_dc_chroma_table[512][2];

static void msmpeg4_encode_block(MpegEncContext * s, DCTELEM * block, int n);
static int msmpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
                                int n, int coded);
static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr);
static int msmpeg4_decode_motion(MpegEncContext * s, 
                                 int *mx_ptr, int *my_ptr);

extern UINT32 inverse[256];

#ifdef DEBUG
int intra_count = 0;
int frame_count = 0;
#endif
/* XXX: move it to mpegvideo.h */

static int init_done = 0;

#include "msmpeg4data.h"

#ifdef STATS

const char *st_names[ST_NB] = {
    "unknown",
    "dc",
    "intra_ac",
    "inter_ac",
    "intra_mb",
    "inter_mb",
    "mv",
};

int st_current_index = 0;
unsigned int st_bit_counts[ST_NB];
unsigned int st_out_bit_counts[ST_NB];

#define set_stat(var) st_current_index = var;

void print_stats(void)
{
    unsigned int total;
    int i;

    printf("Input:\n");
    total = 0;
    for(i=0;i<ST_NB;i++)
        total += st_bit_counts[i];
    if (total == 0)
        total = 1;
    for(i=0;i<ST_NB;i++) {
        printf("%-10s : %10.1f %5.1f%%\n", 
               st_names[i], 
               (double)st_bit_counts[i] / 8.0, 
               (double)st_bit_counts[i] * 100.0 / total);
    }
    printf("%-10s : %10.1f %5.1f%%\n",
           "total", 
           (double)total / 8.0, 
           100.0);

    printf("Output:\n");
    total = 0;
    for(i=0;i<ST_NB;i++)
        total += st_out_bit_counts[i];
    if (total == 0)
        total = 1;
    for(i=0;i<ST_NB;i++) {
        printf("%-10s : %10.1f %5.1f%%\n", 
               st_names[i], 
               (double)st_out_bit_counts[i] / 8.0, 
               (double)st_out_bit_counts[i] * 100.0 / total);
    }
    printf("%-10s : %10.1f %5.1f%%\n",
           "total", 
           (double)total / 8.0, 
           100.0);
}

#else

#define set_stat(var)

#endif

/* build the table which associate a (x,y) motion vector to a vlc */
static void init_mv_table(MVTable *tab)
{
    int i, x, y;

    tab->table_mv_index = malloc(sizeof(UINT16) * 4096);
    /* mark all entries as not used */
    for(i=0;i<4096;i++)
        tab->table_mv_index[i] = tab->n;
    
    for(i=0;i<tab->n;i++) {
        x = tab->table_mvx[i];
        y = tab->table_mvy[i];
        tab->table_mv_index[(x << 6) | y] = i;
    }
}

static void code012(PutBitContext *pb, int n)
{
    if (n == 0) {
        put_bits(pb, 1, 0);
    } else {
        put_bits(pb, 1, 1);
        put_bits(pb, 1, (n >= 2));
    }
}

/* write MSMPEG4 V3 compatible frame header */
void msmpeg4_encode_picture_header(MpegEncContext * s, int picture_number)
{
    int i;

    align_put_bits(&s->pb);

    put_bits(&s->pb, 2, s->pict_type - 1);

    put_bits(&s->pb, 5, s->qscale);

    s->rl_table_index = 2;
    s->rl_chroma_table_index = 1; /* only for I frame */
    s->dc_table_index = 1;
    s->mv_table_index = 1; /* only if P frame */
    s->use_skip_mb_code = 1; /* only if P frame */
    
    if (s->pict_type == I_TYPE) {
        put_bits(&s->pb, 5, 0x17); /* indicate only one "slice" */

        code012(&s->pb, s->rl_chroma_table_index);
        code012(&s->pb, s->rl_table_index);

        put_bits(&s->pb, 1, s->dc_table_index);
        s->no_rounding = 1;
    } else {
        put_bits(&s->pb, 1, s->use_skip_mb_code);
        
        s->rl_chroma_table_index = s->rl_table_index;
        code012(&s->pb, s->rl_table_index);

        put_bits(&s->pb, 1, s->dc_table_index);

        put_bits(&s->pb, 1, s->mv_table_index);
	
	if(s->flipflop_rounding){
	    s->no_rounding ^= 1;
	}else{
	    s->no_rounding = 0;
	}
    }

    if (!init_done) {
        /* init various encoding tables */
        init_done = 1;
        init_mv_table(&mv_tables[0]);
        init_mv_table(&mv_tables[1]);
        for(i=0;i<NB_RL_TABLES;i++)
            init_rl(&rl_table[i]);
    }

#ifdef DEBUG
    intra_count = 0;
    printf("*****frame %d:\n", frame_count++);
#endif
}

void msmpeg4_encode_ext_header(MpegEncContext * s)
{
        s->flipflop_rounding=1;
        s->bitrate= 910; // FIXME

        put_bits(&s->pb, 5, s->frame_rate / FRAME_RATE_BASE); //yes 29.97 -> 29

	put_bits(&s->pb, 11, s->bitrate);

	put_bits(&s->pb, 1, s->flipflop_rounding);
}

/* predict coded block */
static inline int coded_block_pred(MpegEncContext * s, int n, UINT8 **coded_block_ptr)
{
    int xy, wrap, pred, a, b, c;

    xy = s->block_index[n];
    wrap = s->block_wrap[0];

    /* B C
     * A X 
     */
    a = s->coded_block[xy - 1       ];
    b = s->coded_block[xy - 1 - wrap];
    c = s->coded_block[xy     - wrap];
    
    if (b == c) {
        pred = a;
    } else {
        pred = c;
    }
    
    /* store value */
    *coded_block_ptr = &s->coded_block[xy];

    return pred;
}

static void msmpeg4_encode_motion(MpegEncContext * s, 
                                  int mx, int my)
{
    int code;
    MVTable *mv;

    /* modulo encoding */
    /* WARNING : you cannot reach all the MVs even with the modulo
       encoding. This is a somewhat strange compromise they took !!!  */
    if (mx <= -64)
        mx += 64;
    else if (mx >= 64)
        mx -= 64;
    if (my <= -64)
        my += 64;
    else if (my >= 64)
        my -= 64;
    
    mx += 32;
    my += 32;
#if 0
    if ((unsigned)mx >= 64 ||
        (unsigned)my >= 64) 
        fprintf(stderr, "error mx=%d my=%d\n", mx, my);
#endif
    mv = &mv_tables[s->mv_table_index];

    code = mv->table_mv_index[(mx << 6) | my];
    set_stat(ST_MV);
    put_bits(&s->pb, 
             mv->table_mv_bits[code], 
             mv->table_mv_code[code]);
    if (code == mv->n) {
        /* escape : code litterally */
        put_bits(&s->pb, 6, mx);
        put_bits(&s->pb, 6, my);
    }
}

void msmpeg4_encode_mb(MpegEncContext * s, 
                       DCTELEM block[6][64],
                       int motion_x, int motion_y)
{
    int cbp, coded_cbp, i;
    int pred_x, pred_y;
    UINT8 *coded_block;

    if (!s->mb_intra) {
	/* compute cbp */
        set_stat(ST_INTER_MB);
	cbp = 0;
	for (i = 0; i < 6; i++) {
	    if (s->block_last_index[i] >= 0)
		cbp |= 1 << (5 - i);
	}
	if (s->use_skip_mb_code && (cbp | motion_x | motion_y) == 0) {
	    /* skip macroblock */
	    put_bits(&s->pb, 1, 1);
	    return;
	}
        if (s->use_skip_mb_code)
            put_bits(&s->pb, 1, 0);	/* mb coded */
        
        put_bits(&s->pb, 
                 table_mb_non_intra[cbp + 64][1], 
                 table_mb_non_intra[cbp + 64][0]);

        /* motion vector */
        h263_pred_motion(s, 0, &pred_x, &pred_y);
        msmpeg4_encode_motion(s, motion_x - pred_x, 
                              motion_y - pred_y);
    } else {
	/* compute cbp */
	cbp = 0;
        coded_cbp = 0;
	for (i = 0; i < 6; i++) {
            int val, pred;
            val = (s->block_last_index[i] >= 1);
            cbp |= val << (5 - i);
            if (i < 4) {
                /* predict value for close blocks only for luma */
                pred = coded_block_pred(s, i, &coded_block);
                *coded_block = val;
                val = val ^ pred;
            }
            coded_cbp |= val << (5 - i);
	}
#if 0
        if (coded_cbp)
            printf("cbp=%x %x\n", cbp, coded_cbp);
#endif

	if (s->pict_type == I_TYPE) {
            set_stat(ST_INTRA_MB);
            put_bits(&s->pb, 
                     table_mb_intra[coded_cbp][1], table_mb_intra[coded_cbp][0]);
        } else {
            if (s->use_skip_mb_code)
                put_bits(&s->pb, 1, 0);	/* mb coded */
            put_bits(&s->pb, 
                     table_mb_non_intra[cbp][1], 
                     table_mb_non_intra[cbp][0]);
        }
        set_stat(ST_INTRA_MB);
        put_bits(&s->pb, 1, 0);	/* no AC prediction yet */
    }

    for (i = 0; i < 6; i++) {
        msmpeg4_encode_block(s, block[i], i);
    }
}


/* strongly inspirated from MPEG4, but not exactly the same ! */
void msmpeg4_dc_scale(MpegEncContext * s)
{
    if (s->qscale < 5 || s->msmpeg4_version==2){
        s->y_dc_scale = 8;
        s->c_dc_scale = 8;
    }else if (s->qscale < 9){
        s->y_dc_scale = 2 * s->qscale;
        s->c_dc_scale = (s->qscale + 13)>>1;
    }else{
        s->y_dc_scale = s->qscale + 8;
        s->c_dc_scale = (s->qscale + 13)>>1;
    }
}

/* dir = 0: left, dir = 1: top prediction */
static int msmpeg4_pred_dc(MpegEncContext * s, int n, 
                           INT16 **dc_val_ptr, int *dir_ptr)
{
    int a, b, c, wrap, pred, scale;
    INT16 *dc_val;

    /* find prediction */
    if (n < 4) {
	scale = s->y_dc_scale;
    } else {
	scale = s->c_dc_scale;
    }
    wrap = s->block_wrap[n];
    dc_val= s->dc_val[0] + s->block_index[n];

    /* B C
     * A X 
     */
    a = dc_val[ - 1];
    b = dc_val[ - 1 - wrap];
    c = dc_val[ - wrap];

    /* XXX: the following solution consumes divisions, but it does not
       necessitate to modify mpegvideo.c. The problem comes from the
       fact they decided to store the quantized DC (which would lead
       to problems if Q could vary !) */
#if defined ARCH_X86 && !defined PIC
    asm volatile(
        "movl %3, %%eax		\n\t"
	"shrl $1, %%eax		\n\t"
	"addl %%eax, %2		\n\t"
	"addl %%eax, %1		\n\t"
	"addl %0, %%eax		\n\t"
	"mull %4		\n\t"
	"movl %%edx, %0		\n\t"
	"movl %1, %%eax		\n\t"
	"mull %4		\n\t"
	"movl %%edx, %1		\n\t"
	"movl %2, %%eax		\n\t"
	"mull %4		\n\t"
	"movl %%edx, %2		\n\t"
	: "+b" (a), "+c" (b), "+D" (c)
	: "g" (scale), "S" (inverse[scale])
	: "%eax", "%edx"
    );
#else
    /* #elif defined (ARCH_ALPHA) */
    /* Divisions are extremely costly on Alpha; optimize the most
       common case. But they are costly everywhere...
     */
    if (scale == 8) {
	a = (a + (8 >> 1)) / 8;
	b = (b + (8 >> 1)) / 8;
	c = (c + (8 >> 1)) / 8;
    } else {
	a = (a + (scale >> 1)) / scale;
	b = (b + (scale >> 1)) / scale;
	c = (c + (scale >> 1)) / scale;
    }
#endif
    /* XXX: WARNING: they did not choose the same test as MPEG4. This
       is very important ! */
    if (abs(a - b) <= abs(b - c)) {
	pred = c;
        *dir_ptr = 1;
    } else {
	pred = a;
        *dir_ptr = 0;
    }

    /* update predictor */
    *dc_val_ptr = &dc_val[0];
    return pred;
}

#define DC_MAX 119

static void msmpeg4_encode_dc(MpegEncContext * s, int level, int n, int *dir_ptr)
{
    int sign, code;
    int pred;
    INT16 *dc_val;

    pred = msmpeg4_pred_dc(s, n, &dc_val, dir_ptr);

    /* update predictor */
    if (n < 4) {
        *dc_val = level * s->y_dc_scale;
    } else {
        *dc_val = level * s->c_dc_scale;
    }

    /* do the prediction */
    level -= pred;

    sign = 0;
    if (level < 0) {
        level = -level;
        sign = 1;
    }
    
    code = level;
    if (code > DC_MAX) 
        code = DC_MAX;

    if (s->dc_table_index == 0) {
        if (n < 4) {
            put_bits(&s->pb, table0_dc_lum[code][1], table0_dc_lum[code][0]);
        } else {
            put_bits(&s->pb, table0_dc_chroma[code][1], table0_dc_chroma[code][0]);
        }
    } else {
        if (n < 4) {
            put_bits(&s->pb, table1_dc_lum[code][1], table1_dc_lum[code][0]);
        } else {
            put_bits(&s->pb, table1_dc_chroma[code][1], table1_dc_chroma[code][0]);
        }
    }
        
    if (code == DC_MAX)
        put_bits(&s->pb, 8, level);
        
    if (level != 0) {
        put_bits(&s->pb, 1, sign);
    }
}

/* Encoding of a block. Very similar to MPEG4 except for a different
   escape coding (same as H263) and more vlc tables.
 */
static void msmpeg4_encode_block(MpegEncContext * s, DCTELEM * block, int n)
{
    int level, run, last, i, j, last_index;
    int last_non_zero, sign, slevel;
    int code, run_diff, dc_pred_dir;
    const RLTable *rl;

    if (s->mb_intra) {
        set_stat(ST_DC);
        msmpeg4_encode_dc(s, block[0], n, &dc_pred_dir);
        i = 1;
        if (n < 4) {
            rl = &rl_table[s->rl_table_index];
        } else {
            rl = &rl_table[3 + s->rl_chroma_table_index];
        }
        run_diff = 0;
        set_stat(ST_INTRA_AC);
    } else {
        i = 0;
        rl = &rl_table[3 + s->rl_table_index];
        run_diff = 1;
        set_stat(ST_INTER_AC);
    }

    /* AC coefs */
    last_index = s->block_last_index[n];
    last_non_zero = i - 1;
    for (; i <= last_index; i++) {
	j = zigzag_direct[i];
	level = block[j];
	if (level) {
	    run = i - last_non_zero - 1;
	    last = (i == last_index);
	    sign = 0;
	    slevel = level;
	    if (level < 0) {
		sign = 1;
		level = -level;
	    }
            code = get_rl_index(rl, last, run, level);
            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
            if (code == rl->n) {
                int level1, run1;

                level1 = level - rl->max_level[last][run];
                if (level1 < 1) 
                    goto esc2;
                code = get_rl_index(rl, last, run, level1);
                if (code == rl->n) {
                esc2:
                    put_bits(&s->pb, 1, 0);
                    if (level > MAX_LEVEL)
                        goto esc3;
                    run1 = run - rl->max_run[last][level] - run_diff;
                    if (run1 < 0)
                        goto esc3;
                    code = get_rl_index(rl, last, run1, level);
                    if (code == rl->n) {
                    esc3:
                        /* third escape */
                        put_bits(&s->pb, 1, 0);
                        put_bits(&s->pb, 1, last);
                        put_bits(&s->pb, 6, run);
                        put_bits(&s->pb, 8, slevel & 0xff);
                    } else {
                        /* second escape */
                        put_bits(&s->pb, 1, 1);
                        put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
                        put_bits(&s->pb, 1, sign);
                    }
                } else {
                    /* first escape */
                    put_bits(&s->pb, 1, 1);
                    put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
                    put_bits(&s->pb, 1, sign);
                }
            } else {
                put_bits(&s->pb, 1, sign);
            }
	    last_non_zero = i;
	}
    }
}

/****************************************/
/* decoding stuff */

static VLC mb_non_intra_vlc;
static VLC mb_intra_vlc;
static VLC dc_lum_vlc[2];
static VLC dc_chroma_vlc[2];
static VLC v2_dc_lum_vlc;
static VLC v2_dc_chroma_vlc;
static VLC cbpy_vlc;
static VLC v2_intra_cbpc_vlc;
static VLC v2_mb_type_vlc;
static VLC v2_mv_vlc;

/* this table is practically identical to the one from h263 except that its inverted */
static void init_h263_dc_for_msmpeg4()
{
    static int inited=0;
    
    if(!inited){
        int level, uni_code, uni_len;
        inited=1;

        for(level=-256; level<256; level++){
            int size, v, l;
            /* find number of bits */
            size = 0;
            v = abs(level);
            while (v) {
                v >>= 1;
		    size++;
            }

            if (level < 0)
                l= (-level) ^ ((1 << size) - 1);
            else
                l= level;

            /* luminance h263 */
            uni_code= DCtab_lum[size][0];
            uni_len = DCtab_lum[size][1];
            uni_code ^= (1<<uni_len)-1; //M$ doesnt like compatibility

            if (size > 0) {
                uni_code<<=size; uni_code|=l;
                uni_len+=size;
                if (size > 8){
                    uni_code<<=1; uni_code|=1;
                    uni_len++;
                }
            }
            v2_dc_lum_table[level+256][0]= uni_code;
            v2_dc_lum_table[level+256][1]= uni_len;

            /* chrominance h263 */
            uni_code= DCtab_chrom[size][0];
            uni_len = DCtab_chrom[size][1];
            uni_code ^= (1<<uni_len)-1; //M$ doesnt like compatibility
            
            if (size > 0) {
                uni_code<<=size; uni_code|=l;
                uni_len+=size;
                if (size > 8){
                    uni_code<<=1; uni_code|=1;
                    uni_len++;
                }
            }
            v2_dc_chroma_table[level+256][0]= uni_code;
            v2_dc_chroma_table[level+256][1]= uni_len;

        }
    }
}

/* init all vlc decoding tables */
int msmpeg4_decode_init_vlc(MpegEncContext *s)
{
    int i;
    MVTable *mv;

    for(i=0;i<NB_RL_TABLES;i++) {
        init_rl(&rl_table[i]);
        init_vlc_rl(&rl_table[i]);
    }
    for(i=0;i<2;i++) {
        mv = &mv_tables[i];
        init_vlc(&mv->vlc, 9, mv->n + 1, 
                 mv->table_mv_bits, 1, 1,
                 mv->table_mv_code, 2, 2);
    }

    init_vlc(&dc_lum_vlc[0], 9, 120, 
             &table0_dc_lum[0][1], 8, 4,
             &table0_dc_lum[0][0], 8, 4);
    init_vlc(&dc_chroma_vlc[0], 9, 120, 
             &table0_dc_chroma[0][1], 8, 4,
             &table0_dc_chroma[0][0], 8, 4);
    init_vlc(&dc_lum_vlc[1], 9, 120, 
             &table1_dc_lum[0][1], 8, 4,
             &table1_dc_lum[0][0], 8, 4);
    init_vlc(&dc_chroma_vlc[1], 9, 120, 
             &table1_dc_chroma[0][1], 8, 4,
             &table1_dc_chroma[0][0], 8, 4);
    
    init_h263_dc_for_msmpeg4();
    init_vlc(&v2_dc_lum_vlc, 9, 512, 
             &v2_dc_lum_table[0][1], 8, 4,
             &v2_dc_lum_table[0][0], 8, 4);
    init_vlc(&v2_dc_chroma_vlc, 9, 512, 
             &v2_dc_chroma_table[0][1], 8, 4,
             &v2_dc_chroma_table[0][0], 8, 4);
    
    init_vlc(&cbpy_vlc, 6, 16,
             &cbpy_tab[0][1], 2, 1,
             &cbpy_tab[0][0], 2, 1);
    init_vlc(&v2_intra_cbpc_vlc, 3, 4,
             &v2_intra_cbpc[0][1], 2, 1,
             &v2_intra_cbpc[0][0], 2, 1);
    init_vlc(&v2_mb_type_vlc, 5, 8,
             &v2_mb_type[0][1], 2, 1,
             &v2_mb_type[0][0], 2, 1);
    init_vlc(&v2_mv_vlc, 9, 33,
             &mvtab[0][1], 2, 1,
             &mvtab[0][0], 2, 1);

    init_vlc(&mb_non_intra_vlc, 9, 128, 
             &table_mb_non_intra[0][1], 8, 4,
             &table_mb_non_intra[0][0], 8, 4);
    init_vlc(&mb_intra_vlc, 9, 64, 
             &table_mb_intra[0][1], 4, 2,
             &table_mb_intra[0][0], 4, 2);
    return 0;
}

static int decode012(GetBitContext *gb)
{
    int n;
    n = get_bits1(gb);
    if (n == 0)
        return 0;
    else
        return get_bits1(gb) + 1;
}

int msmpeg4_decode_picture_header(MpegEncContext * s)
{
    int code;

    s->pict_type = get_bits(&s->gb, 2) + 1;
    if (s->pict_type != I_TYPE &&
        s->pict_type != P_TYPE)
        return -1;

    s->qscale = get_bits(&s->gb, 5);

    if (s->pict_type == I_TYPE) {
        code = get_bits(&s->gb, 5); 
        /* 0x17: one slice, 0x18: two slices */
        if (code < 0x17)
            return -1;
        s->slice_height = s->mb_height / (code - 0x16);
        if(s->msmpeg4_version==2){
            s->rl_chroma_table_index = 2;
            s->rl_table_index = 2;

            s->dc_table_index = 0; //not used
        }else{
            s->rl_chroma_table_index = decode012(&s->gb);
            s->rl_table_index = decode012(&s->gb);

            s->dc_table_index = get_bits1(&s->gb);
        }
        s->no_rounding = 1;
/*	printf(" %d %d %d %d     \n", 
		s->qscale,
		s->rl_chroma_table_index,
		s->rl_table_index, 
		s->dc_table_index);*/
    } else {
        s->use_skip_mb_code = get_bits1(&s->gb);
        
        if(s->msmpeg4_version==2){
            s->rl_table_index = 2;
            s->rl_chroma_table_index = s->rl_table_index;

            s->dc_table_index = 0; //not used

            s->mv_table_index = 0;
        }else{
            s->rl_table_index = decode012(&s->gb);
            s->rl_chroma_table_index = s->rl_table_index;

            s->dc_table_index = get_bits1(&s->gb);

            s->mv_table_index = get_bits1(&s->gb);
        }
/*	printf(" %d %d %d %d %d     \n", 
		s->use_skip_mb_code, 
		s->rl_table_index, 
		s->rl_chroma_table_index, 
		s->dc_table_index,
		s->mv_table_index);*/
	if(s->flipflop_rounding){
	    s->no_rounding ^= 1;
	}else{
	    s->no_rounding = 0;
	}
//	printf("%d", s->no_rounding);
    }
    
#if 0
if(s->msmpeg4_version==2)
{
int i;
for(i=0; i<s->gb.size*8; i++)
//    printf("%d", get_bits1(&s->gb));
    get_bits1(&s->gb);
printf("END\n");
return -1;
}
#endif

#ifdef DEBUG
    printf("*****frame %d:\n", frame_count++);
#endif
    return 0;
}

int msmpeg4_decode_ext_header(MpegEncContext * s, int buf_size)
{
    /* the alt_bitstream reader could read over the end so we need to check it */
    if(get_bits_count(&s->gb) + 16 < buf_size*8)
    {
        int fps;

        fps= get_bits(&s->gb, 5);
        s->bitrate= get_bits(&s->gb, 11);
        s->flipflop_rounding= get_bits1(&s->gb);

//        printf("fps:%2d bps:%2d roundingType:%1d\n", fps, s->bitrate, s->flipflop_rounding);
    }
    else
    {
        s->flipflop_rounding= 0;
        s->bitrate= 0;
    }

    return 0;
}

static inline void memsetw(short *tab, int val, int n)
{
    int i;
    for(i=0;i<n;i++)
        tab[i] = val;
}

/* this is identical to h263 except that its range is multiplied by 2 */
static int msmpeg4v2_decode_motion(MpegEncContext * s, int pred, int f_code)
{
    int code, val, sign, shift;

    code = get_vlc(&s->gb, &v2_mv_vlc);
    if (code < 0)
        return 0xffff;

    if (code == 0)
        return pred;
    sign = get_bits1(&s->gb);
    shift = f_code - 1;
    val = (code - 1) << shift;
    if (shift > 0)
        val |= get_bits(&s->gb, shift);
    val++;
    if (sign)
        val = -val;
    val += pred;

    if (val <= -64)
        val += 64;
    else if (val >= 64)
        val -= 64;

    return val;
}


int msmpeg4v2_decode_mb(MpegEncContext *s, 
                      DCTELEM block[6][64])
{
    int cbp, code, i;
    if (s->pict_type == P_TYPE) {
        if (s->use_skip_mb_code) {
            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;
                s->mv[0][0][0] = 0;
                s->mv[0][0][1] = 0;
                s->mb_skiped = 1;
                return 0;
            }
        }

        code = get_vlc(&s->gb, &v2_mb_type_vlc);
        s->mb_intra = code >>2;
    
        cbp = code & 0x3;
    } else {
        s->mb_intra = 1;
        cbp= get_vlc(&s->gb, &v2_intra_cbpc_vlc);
    }

    if (!s->mb_intra) {
        int mx, my;

        cbp|= get_vlc(&s->gb, &cbpy_vlc)<<2;
        if((cbp&3) != 3) cbp^= 0x3C;
        
        h263_pred_motion(s, 0, &mx, &my);
        mx= msmpeg4v2_decode_motion(s, mx, 1);
        my= msmpeg4v2_decode_motion(s, my, 1);
        
        s->mv_dir = MV_DIR_FORWARD;
        s->mv_type = MV_TYPE_16X16;
        s->mv[0][0][0] = mx;
        s->mv[0][0][1] = my;
    } else {
        s->ac_pred = get_bits1(&s->gb);
        cbp|= get_vlc(&s->gb, &cbpy_vlc)<<2;
    }

    for (i = 0; i < 6; i++) {
        if (msmpeg4_decode_block(s, block[i], i, (cbp >> (5 - i)) & 1) < 0)
	{
             fprintf(stderr,"\nIgnoring error while decoding block: %d x %d (%d)\n", s->mb_x, s->mb_y, i);
             return -1;
	}
    }
    return 0;
}

int msmpeg4_decode_mb(MpegEncContext *s, 
                      DCTELEM block[6][64])
{
    int cbp, code, i;
    UINT8 *coded_val;

    /* special slice handling */
    if (s->mb_x == 0) {
        if (s->slice_height && (s->mb_y % s->slice_height) == 0) {
            int wrap;
            /* reset DC pred (set previous line to 1024) */
            wrap = 2 * s->mb_width + 2;
            memsetw(&s->dc_val[0][(1) + (2 * s->mb_y) * wrap], 
                    1024, 2 * s->mb_width);
            wrap = s->mb_width + 2;
            memsetw(&s->dc_val[1][(1) + (s->mb_y) * wrap], 
                    1024, s->mb_width);
            memsetw(&s->dc_val[2][(1) + (s->mb_y) * wrap], 
                    1024, s->mb_width);
            
            /* reset AC pred (set previous line to 0) */
            wrap = s->mb_width * 2 + 2;
            memsetw(s->ac_val[0][0] + (1 + (2 * s->mb_y) * wrap)*16,
                    0, 2 * s->mb_width*16);
            wrap = s->mb_width + 2;
            memsetw(s->ac_val[1][0] + (1 + (s->mb_y) * wrap)*16,
                    0, s->mb_width*16);
            memsetw(s->ac_val[2][0] + (1 + (s->mb_y) * wrap)*16,
                    0, s->mb_width*16);

            s->first_slice_line = 1;
        } else {
            s->first_slice_line = 0; 
        }
    }

    if(s->msmpeg4_version==2) return msmpeg4v2_decode_mb(s, block); //FIXME merge if possible
    
    if (s->pict_type == P_TYPE) {
        set_stat(ST_INTER_MB);
        if (s->use_skip_mb_code) {
            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;
                s->mv[0][0][0] = 0;
                s->mv[0][0][1] = 0;
                s->mb_skiped = 1;
                return 0;
            }
        }
        
        code = get_vlc(&s->gb, &mb_non_intra_vlc);
        if (code < 0)
            return -1;
	//s->mb_intra = (code & 0x40) ? 0 : 1;
	s->mb_intra = (~code & 0x40) >> 6;
            
        cbp = code & 0x3f;
    } else {
        set_stat(ST_INTRA_MB);
        s->mb_intra = 1;
        code = get_vlc(&s->gb, &mb_intra_vlc);
        if (code < 0)
            return -1;
        /* predict coded block pattern */
        cbp = 0;
        for(i=0;i<6;i++) {
            int val = ((code >> (5 - i)) & 1);
            if (i < 4) {
                int pred = coded_block_pred(s, i, &coded_val);
                val = val ^ pred;
                *coded_val = val;
            }
            cbp |= val << (5 - i);
        }
    }

    if (!s->mb_intra) {
        int mx, my;
        set_stat(ST_MV);
        h263_pred_motion(s, 0, &mx, &my);
        if (msmpeg4_decode_motion(s, &mx, &my) < 0)
            return -1;
        s->mv_dir = MV_DIR_FORWARD;
        s->mv_type = MV_TYPE_16X16;
        s->mv[0][0][0] = mx;
        s->mv[0][0][1] = my;
    } else {
        set_stat(ST_INTRA_MB);
        s->ac_pred = get_bits1(&s->gb);
    }

    for (i = 0; i < 6; i++) {
        if (msmpeg4_decode_block(s, block[i], i, (cbp >> (5 - i)) & 1) < 0)
	{
	    fprintf(stderr,"\nIgnoring error while decoding block: %d x %d (%d)\n", s->mb_x, s->mb_y, i);
	    // return -1;
	}
    }
    return 0;
}

static int msmpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
                              int n, int coded)
{
    int code, level, i, j, last, run, run_diff;
    int dc_pred_dir;
    RLTable *rl;
    const UINT8 *scan_table;
    int qmul, qadd;

    if (s->mb_intra) {
        qmul=1;
        qadd=0;

	/* DC coef */
        set_stat(ST_DC);
        level = msmpeg4_decode_dc(s, n, &dc_pred_dir);
        if (level < 0)
            return -1;
        block[0] = level;
        if (n < 4) {
            rl = &rl_table[s->rl_table_index];
        } else {
            rl = &rl_table[3 + s->rl_chroma_table_index];
        }

        run_diff = 0;
	i = 1;
        if (!coded) {
            goto not_coded;
        }
        if (s->ac_pred) {
            if (dc_pred_dir == 0) 
                scan_table = ff_alternate_vertical_scan; /* left */
            else
                scan_table = ff_alternate_horizontal_scan; /* top */
        } else {
            scan_table = zigzag_direct;
        }
        set_stat(ST_INTRA_AC);
    } else {
        qmul = s->qscale << 1;
        qadd = (s->qscale - 1) | 1;
	i = 0;
        rl = &rl_table[3 + s->rl_table_index];

        if(s->msmpeg4_version==2)
            run_diff = 0;
        else
            run_diff = 1;

        if (!coded) {
            s->block_last_index[n] = i - 1;
            return 0;
        }
        scan_table = zigzag_direct;
        set_stat(ST_INTER_AC);
    }

    for(;;) {
        code = get_vlc(&s->gb, &rl->vlc);
        if (code < 0)
            return -1;
        if (code == rl->n) {
            /* escape */
            if (get_bits1(&s->gb) == 0) {
                if (get_bits1(&s->gb) == 0) {
                    /* third escape */
                    last = get_bits1(&s->gb);
                    run = get_bits(&s->gb, 6);
                    level = get_bits(&s->gb, 8);
                    level = (level << 24) >> 24; /* sign extend */
		    //level = level * qmul + (level>0) * qadd - (level<=0) * qadd ;
		    if (level>0) level= level * qmul + qadd;
                    else        level= level * qmul - qadd;
                } else {
                    /* second escape */
                    code = get_vlc(&s->gb, &rl->vlc);
                    if (code < 0 || code >= rl->n)
                        return -1;
                    run = rl->table_run[code];
                    level = rl->table_level[code];
                    last = code >= rl->last;
                    run += rl->max_run[last][level] + run_diff;
                    level= level * qmul + qadd;
                    if (get_bits1(&s->gb))
                        level = -level;
                }
            } else {
                /* first escape */
                code = get_vlc(&s->gb, &rl->vlc);
                if (code < 0 || code >= rl->n)
                    return -1;
                run = rl->table_run[code];
                level = rl->table_level[code];
                last = code >= rl->last;
                level += rl->max_level[last][run];
                level= level * qmul + qadd;
                if (get_bits1(&s->gb))
                    level = -level;
            }
        } else {
            run = rl->table_run[code];
            level = rl->table_level[code] * qmul + qadd;
            last = code >= rl->last;
            if (get_bits1(&s->gb))
                level = -level;
        }
        i += run;
        if (i >= 64)
            return -1;
	j = scan_table[i];
        block[j] = level;
        i++;
        if (last)
            break;
    }
 not_coded:
    if (s->mb_intra) {
        mpeg4_pred_ac(s, block, n, dc_pred_dir);
        if (s->ac_pred) {
            i = 64; /* XXX: not optimal */
        }
    }
    s->block_last_index[n] = i - 1;

    return 0;
}

static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr)
{
    int level, pred;
    INT16 *dc_val;

    if(s->msmpeg4_version==2){
        if (n < 4) {
            level = get_vlc(&s->gb, &v2_dc_lum_vlc);
        } else {
            level = get_vlc(&s->gb, &v2_dc_chroma_vlc);
        }
        if (level < 0) 
            return -1;
        level-=256;
    }else{  //FIXME optimize use unified tables & index
        if (n < 4) {
            level = get_vlc(&s->gb, &dc_lum_vlc[s->dc_table_index]);
        } else {
            level = get_vlc(&s->gb, &dc_chroma_vlc[s->dc_table_index]);
        }
        if (level < 0)
            return -1;

        if (level == DC_MAX) {
            level = get_bits(&s->gb, 8);
            if (get_bits1(&s->gb))
                level = -level;
        } else if (level != 0) {
            if (get_bits1(&s->gb))
                level = -level;
        }
    }

    pred = msmpeg4_pred_dc(s, n, &dc_val, dir_ptr);
    level += pred;

    /* update predictor */
    if (n < 4) {
        *dc_val = level * s->y_dc_scale;
    } else {
        *dc_val = level * s->c_dc_scale;
    }

    return level;
}

static int msmpeg4_decode_motion(MpegEncContext * s, 
                                 int *mx_ptr, int *my_ptr)
{
    MVTable *mv;
    int code, mx, my;

    mv = &mv_tables[s->mv_table_index];

    code = get_vlc(&s->gb, &mv->vlc);
    if (code < 0)
        return -1;
    if (code == mv->n) {
        mx = get_bits(&s->gb, 6);
        my = get_bits(&s->gb, 6);
    } else {
        mx = mv->table_mvx[code];
        my = mv->table_mvy[code];
    }

    mx += *mx_ptr - 32;
    my += *my_ptr - 32;
    /* WARNING : they do not do exactly modulo encoding */
    if (mx <= -64)
        mx += 64;
    else if (mx >= 64)
        mx -= 64;

    if (my <= -64)
        my += 64;
    else if (my >= 64)
        my -= 64;
    *mx_ptr = mx;
    *my_ptr = my;
    return 0;
}