mpeg4videoenc.c

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/*
 * MPEG4 encoder.
 * 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 "libavutil/log.h"
#include "libavutil/opt.h"
#include "mpegvideo.h"
#include "h263.h"
#include "mpeg4video.h"

//The uni_DCtab_* tables below contain unified bits+length tables to encode DC
//differences in mpeg4. Unified in the sense that the specification specifies
//this encoding in several steps.
static uint8_t uni_DCtab_lum_len[512];
static uint8_t uni_DCtab_chrom_len[512];
static uint16_t uni_DCtab_lum_bits[512];
static uint16_t uni_DCtab_chrom_bits[512];

//unified encoding tables for run length encoding of coefficients
//unified in the sense that the specification specifies the encoding in several steps.
static uint32_t uni_mpeg4_intra_rl_bits[64*64*2*2];
static uint8_t  uni_mpeg4_intra_rl_len [64*64*2*2];
static uint32_t uni_mpeg4_inter_rl_bits[64*64*2*2];
static uint8_t  uni_mpeg4_inter_rl_len [64*64*2*2];
//#define UNI_MPEG4_ENC_INDEX(last,run,level) ((last)*128 + (run)*256 + (level))
//#define UNI_MPEG4_ENC_INDEX(last,run,level) ((last)*128*64 + (run) + (level)*64)
#define UNI_MPEG4_ENC_INDEX(last,run,level) ((last)*128*64 + (run)*128 + (level))

/* mpeg4
inter
max level: 24/6
max run: 53/63

intra
max level: 53/16
max run: 29/41
*/


/**
 * Return the number of bits that encoding the 8x8 block in block would need.
 * @param[in]  block_last_index last index in scantable order that refers to a non zero element in block.
 */
static inline int get_block_rate(MpegEncContext * s, DCTELEM block[64], int block_last_index, uint8_t scantable[64]){
    int last=0;
    int j;
    int rate=0;

    for(j=1; j<=block_last_index; j++){
        const int index= scantable[j];
        int level= block[index];
        if(level){
            level+= 64;
            if((level&(~127)) == 0){
                if(j<block_last_index) rate+= s->intra_ac_vlc_length     [UNI_AC_ENC_INDEX(j-last-1, level)];
                else                   rate+= s->intra_ac_vlc_last_length[UNI_AC_ENC_INDEX(j-last-1, level)];
            }else
                rate += s->ac_esc_length;

            last= j;
        }
    }

    return rate;
}


/**
 * Restore the ac coefficients in block that have been changed by decide_ac_pred().
 * This function also restores s->block_last_index.
 * @param[in,out] block MB coefficients, these will be restored
 * @param[in] dir ac prediction direction for each 8x8 block
 * @param[out] st scantable for each 8x8 block
 * @param[in] zigzag_last_index index referring to the last non zero coefficient in zigzag order
 */
static inline void restore_ac_coeffs(MpegEncContext * s, DCTELEM block[6][64], const int dir[6], uint8_t *st[6], const int zigzag_last_index[6])
{
    int i, n;
    memcpy(s->block_last_index, zigzag_last_index, sizeof(int)*6);

    for(n=0; n<6; n++){
        int16_t *ac_val = s->ac_val[0][0] + s->block_index[n] * 16;

        st[n]= s->intra_scantable.permutated;
        if(dir[n]){
            /* top prediction */
            for(i=1; i<8; i++){
                block[n][s->dsp.idct_permutation[i   ]] = ac_val[i+8];
            }
        }else{
            /* left prediction */
            for(i=1; i<8; i++){
                block[n][s->dsp.idct_permutation[i<<3]]= ac_val[i  ];
            }
        }
    }
}

/**
 * Return the optimal value (0 or 1) for the ac_pred element for the given MB in mpeg4.
 * This function will also update s->block_last_index and s->ac_val.
 * @param[in,out] block MB coefficients, these will be updated if 1 is returned
 * @param[in] dir ac prediction direction for each 8x8 block
 * @param[out] st scantable for each 8x8 block
 * @param[out] zigzag_last_index index referring to the last non zero coefficient in zigzag order
 */
static inline int decide_ac_pred(MpegEncContext * s, DCTELEM block[6][64], const int dir[6], uint8_t *st[6], int zigzag_last_index[6])
{
    int score= 0;
    int i, n;
    int8_t * const qscale_table = s->current_picture.f.qscale_table;

    memcpy(zigzag_last_index, s->block_last_index, sizeof(int)*6);

    for(n=0; n<6; n++){
        int16_t *ac_val, *ac_val1;

        score -= get_block_rate(s, block[n], s->block_last_index[n], s->intra_scantable.permutated);

        ac_val = s->ac_val[0][0] + s->block_index[n] * 16;
        ac_val1= ac_val;
        if(dir[n]){
            const int xy= s->mb_x + s->mb_y*s->mb_stride - s->mb_stride;
            /* top prediction */
            ac_val-= s->block_wrap[n]*16;
            if(s->mb_y==0 || s->qscale == qscale_table[xy] || n==2 || n==3){
                /* same qscale */
                for(i=1; i<8; i++){
                    const int level= block[n][s->dsp.idct_permutation[i   ]];
                    block[n][s->dsp.idct_permutation[i   ]] = level - ac_val[i+8];
                    ac_val1[i  ]=    block[n][s->dsp.idct_permutation[i<<3]];
                    ac_val1[i+8]= level;
                }
            }else{
                /* different qscale, we must rescale */
                for(i=1; i<8; i++){
                    const int level= block[n][s->dsp.idct_permutation[i   ]];
                    block[n][s->dsp.idct_permutation[i   ]] = level - ROUNDED_DIV(ac_val[i + 8]*qscale_table[xy], s->qscale);
                    ac_val1[i  ]=    block[n][s->dsp.idct_permutation[i<<3]];
                    ac_val1[i+8]= level;
                }
            }
            st[n]= s->intra_h_scantable.permutated;
        }else{
            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++){
                    const int level= block[n][s->dsp.idct_permutation[i<<3]];
                    block[n][s->dsp.idct_permutation[i<<3]]= level - ac_val[i];
                    ac_val1[i  ]= level;
                    ac_val1[i+8]=    block[n][s->dsp.idct_permutation[i   ]];
                }
            }else{
                /* different qscale, we must rescale */
                for(i=1; i<8; i++){
                    const int level= block[n][s->dsp.idct_permutation[i<<3]];
                    block[n][s->dsp.idct_permutation[i<<3]]= level - ROUNDED_DIV(ac_val[i]*qscale_table[xy], s->qscale);
                    ac_val1[i  ]= level;
                    ac_val1[i+8]=    block[n][s->dsp.idct_permutation[i   ]];
                }
            }
            st[n]= s->intra_v_scantable.permutated;
        }

        for(i=63; i>0; i--) //FIXME optimize
            if(block[n][ st[n][i] ]) break;
        s->block_last_index[n]= i;

        score += get_block_rate(s, block[n], s->block_last_index[n], st[n]);
    }

    if(score < 0){
        return 1;
    }else{
        restore_ac_coeffs(s, block, dir, st, zigzag_last_index);
        return 0;
    }
}

/**
 * modify mb_type & qscale so that encoding is actually possible in mpeg4
 */
void ff_clean_mpeg4_qscales(MpegEncContext *s){
    int i;
    int8_t * const qscale_table = s->current_picture.f.qscale_table;

    ff_clean_h263_qscales(s);

    if(s->pict_type== AV_PICTURE_TYPE_B){
        int odd=0;
        /* ok, come on, this isn't funny anymore, there's more code for handling this mpeg4 mess than for the actual adaptive quantization */

        for(i=0; i<s->mb_num; i++){
            int mb_xy= s->mb_index2xy[i];
            odd += qscale_table[mb_xy]&1;
        }

        if(2*odd > s->mb_num) odd=1;
        else                  odd=0;

        for(i=0; i<s->mb_num; i++){
            int mb_xy= s->mb_index2xy[i];
            if((qscale_table[mb_xy]&1) != odd)
                qscale_table[mb_xy]++;
            if(qscale_table[mb_xy] > 31)
                qscale_table[mb_xy]= 31;
        }

        for(i=1; i<s->mb_num; i++){
            int mb_xy= s->mb_index2xy[i];
            if(qscale_table[mb_xy] != qscale_table[s->mb_index2xy[i-1]] && (s->mb_type[mb_xy]&CANDIDATE_MB_TYPE_DIRECT)){
                s->mb_type[mb_xy]|= CANDIDATE_MB_TYPE_BIDIR;
            }
        }
    }
}


/**
 * Encode the dc value.
 * @param n block index (0-3 are luma, 4-5 are chroma)
 */
static inline void mpeg4_encode_dc(PutBitContext * s, int level, int n)
{
#if 1
    /* DC will overflow if level is outside the [-255,255] range. */
    level+=256;
    if (n < 4) {
        /* luminance */
        put_bits(s, uni_DCtab_lum_len[level], uni_DCtab_lum_bits[level]);
    } else {
        /* chrominance */
        put_bits(s, uni_DCtab_chrom_len[level], uni_DCtab_chrom_bits[level]);
    }
#else
    int size, v;
    /* find number of bits */
    size = 0;
    v = abs(level);
    while (v) {
        v >>= 1;
        size++;
    }

    if (n < 4) {
        /* luminance */
        put_bits(&s->pb, ff_mpeg4_DCtab_lum[size][1], ff_mpeg4_DCtab_lum[size][0]);
    } else {
        /* chrominance */
        put_bits(&s->pb, ff_mpeg4_DCtab_chrom[size][1], ff_mpeg4_DCtab_chrom[size][0]);
    }

    /* encode remaining bits */
    if (size > 0) {
        if (level < 0)
            level = (-level) ^ ((1 << size) - 1);
        put_bits(&s->pb, size, level);
        if (size > 8)
            put_bits(&s->pb, 1, 1);
    }
#endif
}

static inline int mpeg4_get_dc_length(int level, int n){
    if (n < 4) {
        return uni_DCtab_lum_len[level + 256];
    } else {
        return uni_DCtab_chrom_len[level + 256];
    }
}

/**
 * Encode an 8x8 block.
 * @param n block index (0-3 are luma, 4-5 are chroma)
 */
static inline void mpeg4_encode_block(MpegEncContext * s, DCTELEM * block, int n, int intra_dc,
                               uint8_t *scan_table, PutBitContext *dc_pb, PutBitContext *ac_pb)
{
    int i, last_non_zero;
    uint32_t *bits_tab;
    uint8_t *len_tab;
    const int last_index = s->block_last_index[n];

    if (s->mb_intra) { //Note gcc (3.2.1 at least) will optimize this away
        /* mpeg4 based DC predictor */
        mpeg4_encode_dc(dc_pb, intra_dc, n);
        if(last_index<1) return;
        i = 1;
        bits_tab= uni_mpeg4_intra_rl_bits;
        len_tab = uni_mpeg4_intra_rl_len;
    } else {
        if(last_index<0) return;
        i = 0;
        bits_tab= uni_mpeg4_inter_rl_bits;
        len_tab = uni_mpeg4_inter_rl_len;
    }

    /* AC coefs */
    last_non_zero = i - 1;
    for (; i < last_index; i++) {
        int level = block[ scan_table[i] ];
        if (level) {
            int run = i - last_non_zero - 1;
            level+=64;
            if((level&(~127)) == 0){
                const int index= UNI_MPEG4_ENC_INDEX(0, run, level);
                put_bits(ac_pb, len_tab[index], bits_tab[index]);
            }else{ //ESC3
                put_bits(ac_pb, 7+2+1+6+1+12+1, (3<<23)+(3<<21)+(0<<20)+(run<<14)+(1<<13)+(((level-64)&0xfff)<<1)+1);
            }
            last_non_zero = i;
        }
    }
    /*if(i<=last_index)*/{
        int level = block[ scan_table[i] ];
        int run = i - last_non_zero - 1;
        level+=64;
        if((level&(~127)) == 0){
            const int index= UNI_MPEG4_ENC_INDEX(1, run, level);
            put_bits(ac_pb, len_tab[index], bits_tab[index]);
        }else{ //ESC3
            put_bits(ac_pb, 7+2+1+6+1+12+1, (3<<23)+(3<<21)+(1<<20)+(run<<14)+(1<<13)+(((level-64)&0xfff)<<1)+1);
        }
    }
}

static int mpeg4_get_block_length(MpegEncContext * s, DCTELEM * block, int n, int intra_dc,
                               uint8_t *scan_table)
{
    int i, last_non_zero;
    uint8_t *len_tab;
    const int last_index = s->block_last_index[n];
    int len=0;

    if (s->mb_intra) { //Note gcc (3.2.1 at least) will optimize this away
        /* mpeg4 based DC predictor */
        len += mpeg4_get_dc_length(intra_dc, n);
        if(last_index<1) return len;
        i = 1;
        len_tab = uni_mpeg4_intra_rl_len;
    } else {
        if(last_index<0) return 0;
        i = 0;
        len_tab = uni_mpeg4_inter_rl_len;
    }

    /* AC coefs */
    last_non_zero = i - 1;
    for (; i < last_index; i++) {
        int level = block[ scan_table[i] ];
        if (level) {
            int run = i - last_non_zero - 1;
            level+=64;
            if((level&(~127)) == 0){
                const int index= UNI_MPEG4_ENC_INDEX(0, run, level);
                len += len_tab[index];
            }else{ //ESC3
                len += 7+2+1+6+1+12+1;
            }
            last_non_zero = i;
        }
    }
    /*if(i<=last_index)*/{
        int level = block[ scan_table[i] ];
        int run = i - last_non_zero - 1;
        level+=64;
        if((level&(~127)) == 0){
            const int index= UNI_MPEG4_ENC_INDEX(1, run, level);
            len += len_tab[index];
        }else{ //ESC3
            len += 7+2+1+6+1+12+1;
        }
    }

    return len;
}

static inline void mpeg4_encode_blocks(MpegEncContext * s, DCTELEM block[6][64], int intra_dc[6],
                               uint8_t **scan_table, PutBitContext *dc_pb, PutBitContext *ac_pb){
    int i;

    if(scan_table){
        if(s->flags2 & CODEC_FLAG2_NO_OUTPUT){
            for (i = 0; i < 6; i++) {
                skip_put_bits(&s->pb, mpeg4_get_block_length(s, block[i], i, intra_dc[i], scan_table[i]));
            }
        }else{
            /* encode each block */
            for (i = 0; i < 6; i++) {
                mpeg4_encode_block(s, block[i], i, intra_dc[i], scan_table[i], dc_pb, ac_pb);
            }
        }
    }else{
        if(s->flags2 & CODEC_FLAG2_NO_OUTPUT){
            for (i = 0; i < 6; i++) {
                skip_put_bits(&s->pb, mpeg4_get_block_length(s, block[i], i, 0, s->intra_scantable.permutated));
            }
        }else{
            /* encode each block */
            for (i = 0; i < 6; i++) {
                mpeg4_encode_block(s, block[i], i, 0, s->intra_scantable.permutated, dc_pb, ac_pb);
            }
        }
    }
}

static inline int get_b_cbp(MpegEncContext * s, DCTELEM block[6][64],
                            int motion_x, int motion_y, int mb_type)
{
    int cbp = 0, i;

    if (s->mpv_flags & FF_MPV_FLAG_CBP_RD) {
        int score = 0;
        const int lambda = s->lambda2 >> (FF_LAMBDA_SHIFT - 6);

        for (i = 0; i < 6; i++)
            if (s->coded_score[i] < 0) {
                score += s->coded_score[i];
                cbp   |= 1 << (5 - i);
            }

        if (cbp) {
            int zero_score = -6;
            if ((motion_x | motion_y | s->dquant | mb_type) == 0)
                zero_score -= 4; //2*MV + mb_type + cbp bit

            zero_score *= lambda;
            if (zero_score <= score)
                cbp = 0;
        }

        for (i = 0; i < 6; i++) {
            if (s->block_last_index[i] >= 0 && ((cbp >> (5 - i)) & 1) == 0) {
                s->block_last_index[i] = -1;
                s->dsp.clear_block(s->block[i]);
            }
        }
    } else {
        for (i = 0; i < 6; i++) {
            if (s->block_last_index[i] >= 0)
                cbp |= 1 << (5 - i);
        }
    }
    return cbp;
}

//FIXME this is duplicated to h263.c
static const int dquant_code[5]= {1,0,9,2,3};

void ff_mpeg4_encode_mb(MpegEncContext * s,
                        DCTELEM block[6][64],
                        int motion_x, int motion_y)
{
    int cbpc, cbpy, pred_x, pred_y;
    PutBitContext * const pb2    = s->data_partitioning                         ? &s->pb2    : &s->pb;
    PutBitContext * const tex_pb = s->data_partitioning && s->pict_type!=AV_PICTURE_TYPE_B ? &s->tex_pb : &s->pb;
    PutBitContext * const dc_pb  = s->data_partitioning && s->pict_type!=AV_PICTURE_TYPE_I ? &s->pb2    : &s->pb;
    const int interleaved_stats= (s->flags&CODEC_FLAG_PASS1) && !s->data_partitioning ? 1 : 0;

    if (!s->mb_intra) {
        int i, cbp;

        if(s->pict_type==AV_PICTURE_TYPE_B){
            static const int mb_type_table[8]= {-1, 3, 2, 1,-1,-1,-1, 0}; /* convert from mv_dir to type */
            int mb_type=  mb_type_table[s->mv_dir];

            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;
                }
            }

            av_assert2(s->dquant>=-2 && s->dquant<=2);
            av_assert2((s->dquant&1)==0);
            av_assert2(mb_type>=0);

            /* nothing to do if this MB was skipped in the next P Frame */
            if (s->next_picture.f.mbskip_table[s->mb_y * s->mb_stride + s->mb_x]) { //FIXME avoid DCT & ...
                s->skip_count++;
                s->mv[0][0][0]=
                s->mv[0][0][1]=
                s->mv[1][0][0]=
                s->mv[1][0][1]= 0;
                s->mv_dir= MV_DIR_FORWARD; //doesn't matter
                s->qscale -= s->dquant;
//                s->mb_skipped=1;

                return;
            }

            cbp= get_b_cbp(s, block, motion_x, motion_y, mb_type);

            if ((cbp | motion_x | motion_y | mb_type) ==0) {
                /* direct MB with MV={0,0} */
                av_assert2(s->dquant==0);

                put_bits(&s->pb, 1, 1); /* mb not coded modb1=1 */

                if(interleaved_stats){
                    s->misc_bits++;
                    s->last_bits++;
                }
                s->skip_count++;
                return;
            }

            put_bits(&s->pb, 1, 0);     /* mb coded modb1=0 */
            put_bits(&s->pb, 1, cbp ? 0 : 1); /* modb2 */ //FIXME merge
            put_bits(&s->pb, mb_type+1, 1); // this table is so simple that we don't need it :)
            if(cbp) put_bits(&s->pb, 6, cbp);

            if(cbp && mb_type){
                if(s->dquant)
                    put_bits(&s->pb, 2, (s->dquant>>2)+3);
                else
                    put_bits(&s->pb, 1, 0);
            }else
                s->qscale -= s->dquant;

            if(!s->progressive_sequence){
                if(cbp)
                    put_bits(&s->pb, 1, s->interlaced_dct);
                if(mb_type) // not direct mode
                    put_bits(&s->pb, 1, s->mv_type == MV_TYPE_FIELD);
            }

            if(interleaved_stats){
                s->misc_bits+= get_bits_diff(s);
            }

            if(mb_type == 0){
                av_assert2(s->mv_dir & MV_DIRECT);
                ff_h263_encode_motion_vector(s, motion_x, motion_y, 1);
                s->b_count++;
                s->f_count++;
            }else{
                av_assert2(mb_type > 0 && mb_type < 4);
                if(s->mv_type != MV_TYPE_FIELD){
                    if(s->mv_dir & MV_DIR_FORWARD){
                        ff_h263_encode_motion_vector(s, s->mv[0][0][0] - s->last_mv[0][0][0],
                                                        s->mv[0][0][1] - s->last_mv[0][0][1], s->f_code);
                        s->last_mv[0][0][0]= s->last_mv[0][1][0]= s->mv[0][0][0];
                        s->last_mv[0][0][1]= s->last_mv[0][1][1]= s->mv[0][0][1];
                        s->f_count++;
                    }
                    if(s->mv_dir & MV_DIR_BACKWARD){
                        ff_h263_encode_motion_vector(s, s->mv[1][0][0] - s->last_mv[1][0][0],
                                                        s->mv[1][0][1] - s->last_mv[1][0][1], s->b_code);
                        s->last_mv[1][0][0]= s->last_mv[1][1][0]= s->mv[1][0][0];
                        s->last_mv[1][0][1]= s->last_mv[1][1][1]= s->mv[1][0][1];
                        s->b_count++;
                    }
                }else{
                    if(s->mv_dir & MV_DIR_FORWARD){
                        put_bits(&s->pb, 1, s->field_select[0][0]);
                        put_bits(&s->pb, 1, s->field_select[0][1]);
                    }
                    if(s->mv_dir & MV_DIR_BACKWARD){
                        put_bits(&s->pb, 1, s->field_select[1][0]);
                        put_bits(&s->pb, 1, s->field_select[1][1]);
                    }
                    if(s->mv_dir & MV_DIR_FORWARD){
                        for(i=0; i<2; i++){
                            ff_h263_encode_motion_vector(s, s->mv[0][i][0] - s->last_mv[0][i][0]  ,
                                                            s->mv[0][i][1] - s->last_mv[0][i][1]/2, s->f_code);
                            s->last_mv[0][i][0]= s->mv[0][i][0];
                            s->last_mv[0][i][1]= s->mv[0][i][1]*2;
                        }
                        s->f_count++;
                    }
                    if(s->mv_dir & MV_DIR_BACKWARD){
                        for(i=0; i<2; i++){
                            ff_h263_encode_motion_vector(s, s->mv[1][i][0] - s->last_mv[1][i][0]  ,
                                                            s->mv[1][i][1] - s->last_mv[1][i][1]/2, s->b_code);
                            s->last_mv[1][i][0]= s->mv[1][i][0];
                            s->last_mv[1][i][1]= s->mv[1][i][1]*2;
                        }
                        s->b_count++;
                    }
                }
            }

            if(interleaved_stats){
                s->mv_bits+= get_bits_diff(s);
            }

            mpeg4_encode_blocks(s, block, NULL, NULL, NULL, &s->pb);

            if(interleaved_stats){
                s->p_tex_bits+= get_bits_diff(s);
            }

        }else{ /* s->pict_type==AV_PICTURE_TYPE_B */
            cbp= get_p_cbp(s, block, motion_x, motion_y);

            if ((cbp | motion_x | motion_y | s->dquant) == 0 && s->mv_type==MV_TYPE_16X16) {
                /* check if the B frames can skip it too, as we must skip it if we skip here
                   why didn't they just compress the skip-mb bits instead of reusing them ?! */
                if(s->max_b_frames>0){
                    int i;
                    int x,y, offset;
                    uint8_t *p_pic;

                    x= s->mb_x*16;
                    y= s->mb_y*16;

                    offset= x + y*s->linesize;
                    p_pic = s->new_picture.f.data[0] + offset;

                    s->mb_skipped=1;
                    for(i=0; i<s->max_b_frames; i++){
                        uint8_t *b_pic;
                        int diff;
                        Picture *pic= s->reordered_input_picture[i+1];

                        if (pic == NULL || pic->f.pict_type != AV_PICTURE_TYPE_B)
                            break;

                        b_pic = pic->f.data[0] + offset;
                        if (pic->f.type != FF_BUFFER_TYPE_SHARED)
                            b_pic+= INPLACE_OFFSET;

                        if(x+16 > s->width || y+16 > s->height){
                            int x1,y1;
                            int xe= FFMIN(16, s->width - x);
                            int ye= FFMIN(16, s->height- y);
                            diff=0;
                            for(y1=0; y1<ye; y1++){
                                for(x1=0; x1<xe; x1++){
                                    diff+= FFABS(p_pic[x1+y1*s->linesize] - b_pic[x1+y1*s->linesize]);
                                }
                            }
                            diff= diff*256/(xe*ye);
                        }else{
                            diff= s->dsp.sad[0](NULL, p_pic, b_pic, s->linesize, 16);
                        }
                        if(diff>s->qscale*70){ //FIXME check that 70 is optimal
                            s->mb_skipped=0;
                            break;
                        }
                    }
                }else
                    s->mb_skipped=1;

                if(s->mb_skipped==1){
                    /* skip macroblock */
                    put_bits(&s->pb, 1, 1);

                    if(interleaved_stats){
                        s->misc_bits++;
                        s->last_bits++;
                    }
                    s->skip_count++;

                    return;
                }
            }

            put_bits(&s->pb, 1, 0);     /* mb coded */
            cbpc = cbp & 3;
            cbpy = cbp >> 2;
            cbpy ^= 0xf;
            if(s->mv_type==MV_TYPE_16X16){
                if(s->dquant) cbpc+= 8;
                put_bits(&s->pb,
                        ff_h263_inter_MCBPC_bits[cbpc],
                        ff_h263_inter_MCBPC_code[cbpc]);

                put_bits(pb2, ff_h263_cbpy_tab[cbpy][1], ff_h263_cbpy_tab[cbpy][0]);
                if(s->dquant)
                    put_bits(pb2, 2, dquant_code[s->dquant+2]);

                if(!s->progressive_sequence){
                    if(cbp)
                        put_bits(pb2, 1, s->interlaced_dct);
                    put_bits(pb2, 1, 0);
                }

                if(interleaved_stats){
                    s->misc_bits+= get_bits_diff(s);
                }

                /* motion vectors: 16x16 mode */
                ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);

                ff_h263_encode_motion_vector(s, motion_x - pred_x,
                                                motion_y - pred_y, s->f_code);
            }else if(s->mv_type==MV_TYPE_FIELD){
                if(s->dquant) cbpc+= 8;
                put_bits(&s->pb,
                        ff_h263_inter_MCBPC_bits[cbpc],
                        ff_h263_inter_MCBPC_code[cbpc]);

                put_bits(pb2, ff_h263_cbpy_tab[cbpy][1], ff_h263_cbpy_tab[cbpy][0]);
                if(s->dquant)
                    put_bits(pb2, 2, dquant_code[s->dquant+2]);

                av_assert2(!s->progressive_sequence);
                if(cbp)
                    put_bits(pb2, 1, s->interlaced_dct);
                put_bits(pb2, 1, 1);

                if(interleaved_stats){
                    s->misc_bits+= get_bits_diff(s);
                }

                /* motion vectors: 16x8 interlaced mode */
                ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
                pred_y /=2;

                put_bits(&s->pb, 1, s->field_select[0][0]);
                put_bits(&s->pb, 1, s->field_select[0][1]);

                ff_h263_encode_motion_vector(s, s->mv[0][0][0] - pred_x,
                                                s->mv[0][0][1] - pred_y, s->f_code);
                ff_h263_encode_motion_vector(s, s->mv[0][1][0] - pred_x,
                                                s->mv[0][1][1] - pred_y, s->f_code);
            }else{
                av_assert2(s->mv_type==MV_TYPE_8X8);
                put_bits(&s->pb,
                        ff_h263_inter_MCBPC_bits[cbpc+16],
                        ff_h263_inter_MCBPC_code[cbpc+16]);
                put_bits(pb2, ff_h263_cbpy_tab[cbpy][1], ff_h263_cbpy_tab[cbpy][0]);

                if(!s->progressive_sequence){
                    if(cbp)
                        put_bits(pb2, 1, s->interlaced_dct);
                }

                if(interleaved_stats){
                    s->misc_bits+= get_bits_diff(s);
                }

                for(i=0; i<4; i++){
                    /* motion vectors: 8x8 mode*/
                    ff_h263_pred_motion(s, i, 0, &pred_x, &pred_y);

                    ff_h263_encode_motion_vector(s, s->current_picture.f.motion_val[0][ s->block_index[i] ][0] - pred_x,
                                                    s->current_picture.f.motion_val[0][ s->block_index[i] ][1] - pred_y, s->f_code);
                }
            }

            if(interleaved_stats){
                s->mv_bits+= get_bits_diff(s);
            }

            mpeg4_encode_blocks(s, block, NULL, NULL, NULL, tex_pb);

            if(interleaved_stats){
                s->p_tex_bits+= get_bits_diff(s);
            }
            s->f_count++;
        }
    } else {
        int cbp;
        int dc_diff[6];   //dc values with the dc prediction subtracted
        int dir[6];  //prediction direction
        int zigzag_last_index[6];
        uint8_t *scan_table[6];
        int i;

        for(i=0; i<6; i++){
            dc_diff[i]= ff_mpeg4_pred_dc(s, i, block[i][0], &dir[i], 1);
        }

        if(s->flags & CODEC_FLAG_AC_PRED){
            s->ac_pred= decide_ac_pred(s, block, dir, scan_table, zigzag_last_index);
        }else{
            for(i=0; i<6; i++)
                scan_table[i]= s->intra_scantable.permutated;
        }

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

        cbpc = cbp & 3;
        if (s->pict_type == AV_PICTURE_TYPE_I) {
            if(s->dquant) cbpc+=4;
            put_bits(&s->pb,
                ff_h263_intra_MCBPC_bits[cbpc],
                ff_h263_intra_MCBPC_code[cbpc]);
        } else {
            if(s->dquant) cbpc+=8;
            put_bits(&s->pb, 1, 0);     /* mb coded */
            put_bits(&s->pb,
                ff_h263_inter_MCBPC_bits[cbpc + 4],
                ff_h263_inter_MCBPC_code[cbpc + 4]);
        }
        put_bits(pb2, 1, s->ac_pred);
        cbpy = cbp >> 2;
        put_bits(pb2, ff_h263_cbpy_tab[cbpy][1], ff_h263_cbpy_tab[cbpy][0]);
        if(s->dquant)
            put_bits(dc_pb, 2, dquant_code[s->dquant+2]);

        if(!s->progressive_sequence){
            put_bits(dc_pb, 1, s->interlaced_dct);
        }

        if(interleaved_stats){
            s->misc_bits+= get_bits_diff(s);
        }

        mpeg4_encode_blocks(s, block, dc_diff, scan_table, dc_pb, tex_pb);

        if(interleaved_stats){
            s->i_tex_bits+= get_bits_diff(s);
        }
        s->i_count++;

        /* restore ac coeffs & last_index stuff if we messed them up with the prediction */
        if(s->ac_pred)
            restore_ac_coeffs(s, block, dir, scan_table, zigzag_last_index);
    }
}

/**
 * add mpeg4 stuffing bits (01...1)
 */
void ff_mpeg4_stuffing(PutBitContext * pbc)
{
    int length;
    put_bits(pbc, 1, 0);
    length= (-put_bits_count(pbc))&7;
    if(length) put_bits(pbc, length, (1<<length)-1);
}

/* must be called before writing the header */
void ff_set_mpeg4_time(MpegEncContext * s){
    if(s->pict_type==AV_PICTURE_TYPE_B){
        ff_mpeg4_init_direct_mv(s);
    }else{
        s->last_time_base= s->time_base;
        s->time_base= FFUDIV(s->time, s->avctx->time_base.den);
    }
}

static void mpeg4_encode_gop_header(MpegEncContext * s){
    int hours, minutes, seconds;
    int64_t time;

    put_bits(&s->pb, 16, 0);
    put_bits(&s->pb, 16, GOP_STARTCODE);

    time = s->current_picture_ptr->f.pts;
    if(s->reordered_input_picture[1])
        time = FFMIN(time, s->reordered_input_picture[1]->f.pts);
    time= time*s->avctx->time_base.num;
    s->last_time_base= FFUDIV(time, s->avctx->time_base.den);

    seconds= FFUDIV(time, s->avctx->time_base.den);
    minutes= FFUDIV(seconds, 60); seconds = FFUMOD(seconds, 60);
    hours  = FFUDIV(minutes, 60); minutes = FFUMOD(minutes, 60);
    hours  = FFUMOD(hours  , 24);

    put_bits(&s->pb, 5, hours);
    put_bits(&s->pb, 6, minutes);
    put_bits(&s->pb, 1, 1);
    put_bits(&s->pb, 6, seconds);

    put_bits(&s->pb, 1, !!(s->flags&CODEC_FLAG_CLOSED_GOP));
    put_bits(&s->pb, 1, 0); //broken link == NO

    ff_mpeg4_stuffing(&s->pb);
}

static void mpeg4_encode_visual_object_header(MpegEncContext * s){
    int profile_and_level_indication;
    int vo_ver_id;

    if(s->avctx->profile != FF_PROFILE_UNKNOWN){
        profile_and_level_indication = s->avctx->profile << 4;
    }else if(s->max_b_frames || s->quarter_sample){
        profile_and_level_indication= 0xF0; // adv simple
    }else{
        profile_and_level_indication= 0x00; // simple
    }

    if(s->avctx->level != FF_LEVEL_UNKNOWN){
        profile_and_level_indication |= s->avctx->level;
    }else{
        profile_and_level_indication |= 1; //level 1
    }

    if(profile_and_level_indication>>4 == 0xF){
        vo_ver_id= 5;
    }else{
        vo_ver_id= 1;
    }

    //FIXME levels

    put_bits(&s->pb, 16, 0);
    put_bits(&s->pb, 16, VOS_STARTCODE);

    put_bits(&s->pb, 8, profile_and_level_indication);

    put_bits(&s->pb, 16, 0);
    put_bits(&s->pb, 16, VISUAL_OBJ_STARTCODE);

    put_bits(&s->pb, 1, 1);
        put_bits(&s->pb, 4, vo_ver_id);
        put_bits(&s->pb, 3, 1); //priority

    put_bits(&s->pb, 4, 1); //visual obj type== video obj

    put_bits(&s->pb, 1, 0); //video signal type == no clue //FIXME

    ff_mpeg4_stuffing(&s->pb);
}

static void mpeg4_encode_vol_header(MpegEncContext * s, int vo_number, int vol_number)
{
    int vo_ver_id;

    if (!CONFIG_MPEG4_ENCODER)  return;

    if(s->max_b_frames || s->quarter_sample){
        vo_ver_id= 5;
        s->vo_type= ADV_SIMPLE_VO_TYPE;
    }else{
        vo_ver_id= 1;
        s->vo_type= SIMPLE_VO_TYPE;
    }

    put_bits(&s->pb, 16, 0);
    put_bits(&s->pb, 16, 0x100 + vo_number);        /* video obj */
    put_bits(&s->pb, 16, 0);
    put_bits(&s->pb, 16, 0x120 + vol_number);       /* video obj layer */

    put_bits(&s->pb, 1, 0);             /* random access vol */
    put_bits(&s->pb, 8, s->vo_type);    /* video obj type indication */
    if(s->workaround_bugs & FF_BUG_MS) {
        put_bits(&s->pb, 1, 0);         /* is obj layer id= no */
    } else {
        put_bits(&s->pb, 1, 1);         /* is obj layer id= yes */
        put_bits(&s->pb, 4, vo_ver_id); /* is obj layer ver id */
        put_bits(&s->pb, 3, 1);         /* is obj layer priority */
    }

    s->aspect_ratio_info= ff_h263_aspect_to_info(s->avctx->sample_aspect_ratio);

    put_bits(&s->pb, 4, s->aspect_ratio_info);/* aspect ratio info */
    if (s->aspect_ratio_info == FF_ASPECT_EXTENDED){
        av_reduce(&s->avctx->sample_aspect_ratio.num, &s->avctx->sample_aspect_ratio.den,
                   s->avctx->sample_aspect_ratio.num,  s->avctx->sample_aspect_ratio.den, 255);
        put_bits(&s->pb, 8, s->avctx->sample_aspect_ratio.num);
        put_bits(&s->pb, 8, s->avctx->sample_aspect_ratio.den);
    }

    if(s->workaround_bugs & FF_BUG_MS) { //
        put_bits(&s->pb, 1, 0);         /* vol control parameters= no @@@ */
    } else {
        put_bits(&s->pb, 1, 1);         /* vol control parameters= yes */
        put_bits(&s->pb, 2, 1);         /* chroma format YUV 420/YV12 */
        put_bits(&s->pb, 1, s->low_delay);
        put_bits(&s->pb, 1, 0);         /* vbv parameters= no */
    }

    put_bits(&s->pb, 2, RECT_SHAPE);    /* vol shape= rectangle */
    put_bits(&s->pb, 1, 1);             /* marker bit */

    put_bits(&s->pb, 16, s->avctx->time_base.den);
    if (s->time_increment_bits < 1)
        s->time_increment_bits = 1;
    put_bits(&s->pb, 1, 1);             /* marker bit */
    put_bits(&s->pb, 1, 0);             /* fixed vop rate=no */
    put_bits(&s->pb, 1, 1);             /* marker bit */
    put_bits(&s->pb, 13, s->width);     /* vol width */
    put_bits(&s->pb, 1, 1);             /* marker bit */
    put_bits(&s->pb, 13, s->height);    /* vol height */
    put_bits(&s->pb, 1, 1);             /* marker bit */
    put_bits(&s->pb, 1, s->progressive_sequence ? 0 : 1);
    put_bits(&s->pb, 1, 1);             /* obmc disable */
    if (vo_ver_id == 1) {
        put_bits(&s->pb, 1, s->vol_sprite_usage);       /* sprite enable */
    }else{
        put_bits(&s->pb, 2, s->vol_sprite_usage);       /* sprite enable */
    }

    put_bits(&s->pb, 1, 0);             /* not 8 bit == false */
    put_bits(&s->pb, 1, s->mpeg_quant); /* quant type= (0=h263 style)*/

    if(s->mpeg_quant){
        ff_write_quant_matrix(&s->pb, s->avctx->intra_matrix);
        ff_write_quant_matrix(&s->pb, s->avctx->inter_matrix);
    }

    if (vo_ver_id != 1)
        put_bits(&s->pb, 1, s->quarter_sample);
    put_bits(&s->pb, 1, 1);             /* complexity estimation disable */
    s->resync_marker= s->rtp_mode;
    put_bits(&s->pb, 1, s->resync_marker ? 0 : 1);/* resync marker disable */
    put_bits(&s->pb, 1, s->data_partitioning ? 1 : 0);
    if(s->data_partitioning){
        put_bits(&s->pb, 1, 0);         /* no rvlc */
    }

    if (vo_ver_id != 1){
        put_bits(&s->pb, 1, 0);         /* newpred */
        put_bits(&s->pb, 1, 0);         /* reduced res vop */
    }
    put_bits(&s->pb, 1, 0);             /* scalability */

    ff_mpeg4_stuffing(&s->pb);

    /* user data */
    if(!(s->flags & CODEC_FLAG_BITEXACT)){
        put_bits(&s->pb, 16, 0);
        put_bits(&s->pb, 16, 0x1B2);    /* user_data */
        avpriv_put_string(&s->pb, LIBAVCODEC_IDENT, 0);
    }
}

/* write mpeg4 VOP header */
void ff_mpeg4_encode_picture_header(MpegEncContext * s, int picture_number)
{
    int time_incr;
    int time_div, time_mod;

    if(s->pict_type==AV_PICTURE_TYPE_I){
        if(!(s->flags&CODEC_FLAG_GLOBAL_HEADER)){
            if(s->strict_std_compliance < FF_COMPLIANCE_VERY_STRICT) //HACK, the reference sw is buggy
                mpeg4_encode_visual_object_header(s);
            if(s->strict_std_compliance < FF_COMPLIANCE_VERY_STRICT || picture_number==0) //HACK, the reference sw is buggy
                mpeg4_encode_vol_header(s, 0, 0);
        }
        if(!(s->workaround_bugs & FF_BUG_MS))
            mpeg4_encode_gop_header(s);
    }

    s->partitioned_frame= s->data_partitioning && s->pict_type!=AV_PICTURE_TYPE_B;

    put_bits(&s->pb, 16, 0);                /* vop header */
    put_bits(&s->pb, 16, VOP_STARTCODE);    /* vop header */
    put_bits(&s->pb, 2, s->pict_type - 1);  /* pict type: I = 0 , P = 1 */

    time_div= FFUDIV(s->time, s->avctx->time_base.den);
    time_mod= FFUMOD(s->time, s->avctx->time_base.den);
    time_incr= time_div - s->last_time_base;
    av_assert0(time_incr >= 0);
    while(time_incr--)
        put_bits(&s->pb, 1, 1);

    put_bits(&s->pb, 1, 0);

    put_bits(&s->pb, 1, 1);                             /* marker */
    put_bits(&s->pb, s->time_increment_bits, time_mod); /* time increment */
    put_bits(&s->pb, 1, 1);                             /* marker */
    put_bits(&s->pb, 1, 1);                             /* vop coded */
    if (    s->pict_type == AV_PICTURE_TYPE_P
        || (s->pict_type == AV_PICTURE_TYPE_S && s->vol_sprite_usage==GMC_SPRITE)) {
        put_bits(&s->pb, 1, s->no_rounding);    /* rounding type */
    }
    put_bits(&s->pb, 3, 0);     /* intra dc VLC threshold */
    if(!s->progressive_sequence){
         put_bits(&s->pb, 1, s->current_picture_ptr->f.top_field_first);
         put_bits(&s->pb, 1, s->alternate_scan);
    }
    //FIXME sprite stuff

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

    if (s->pict_type != AV_PICTURE_TYPE_I)
        put_bits(&s->pb, 3, s->f_code); /* fcode_for */
    if (s->pict_type == AV_PICTURE_TYPE_B)
        put_bits(&s->pb, 3, s->b_code); /* fcode_back */
}


static void init_uni_dc_tab(void)
{
    int level, uni_code, uni_len;

    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 */
        uni_code= ff_mpeg4_DCtab_lum[size][0];
        uni_len = ff_mpeg4_DCtab_lum[size][1];

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

        /* chrominance */
        uni_code= ff_mpeg4_DCtab_chrom[size][0];
        uni_len = ff_mpeg4_DCtab_chrom[size][1];

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

    }
}

static void init_uni_mpeg4_rl_tab(RLTable *rl, uint32_t *bits_tab, uint8_t *len_tab){
    int slevel, run, last;

    av_assert0(MAX_LEVEL >= 64);
    av_assert0(MAX_RUN   >= 63);

    for(slevel=-64; slevel<64; slevel++){
        if(slevel==0) continue;
        for(run=0; run<64; run++){
            for(last=0; last<=1; last++){
                const int index= UNI_MPEG4_ENC_INDEX(last, run, slevel+64);
                int level= slevel < 0 ? -slevel : slevel;
                int sign= slevel < 0 ? 1 : 0;
                int bits, len, code;
                int level1, run1;

                len_tab[index]= 100;

                /* ESC0 */
                code= get_rl_index(rl, last, run, level);
                bits= rl->table_vlc[code][0];
                len=  rl->table_vlc[code][1];
                bits=bits*2+sign; len++;

                if(code!=rl->n && len < len_tab[index]){
                    bits_tab[index]= bits;
                    len_tab [index]= len;
                }
                /* ESC1 */
                bits= rl->table_vlc[rl->n][0];
                len=  rl->table_vlc[rl->n][1];
                bits=bits*2;    len++; //esc1
                level1= level - rl->max_level[last][run];
                if(level1>0){
                    code= get_rl_index(rl, last, run, level1);
                    bits<<= rl->table_vlc[code][1];
                    len  += rl->table_vlc[code][1];
                    bits += rl->table_vlc[code][0];
                    bits=bits*2+sign; len++;

                    if(code!=rl->n && len < len_tab[index]){
                        bits_tab[index]= bits;
                        len_tab [index]= len;
                    }
                }
                /* ESC2 */
                bits= rl->table_vlc[rl->n][0];
                len=  rl->table_vlc[rl->n][1];
                bits=bits*4+2;    len+=2; //esc2
                run1 = run - rl->max_run[last][level] - 1;
                if(run1>=0){
                    code= get_rl_index(rl, last, run1, level);
                    bits<<= rl->table_vlc[code][1];
                    len  += rl->table_vlc[code][1];
                    bits += rl->table_vlc[code][0];
                    bits=bits*2+sign; len++;

                    if(code!=rl->n && len < len_tab[index]){
                        bits_tab[index]= bits;
                        len_tab [index]= len;
                    }
                }
                /* ESC3 */
                bits= rl->table_vlc[rl->n][0];
                len = rl->table_vlc[rl->n][1];
                bits=bits*4+3;    len+=2; //esc3
                bits=bits*2+last; len++;
                bits=bits*64+run; len+=6;
                bits=bits*2+1;    len++;  //marker
                bits=bits*4096+(slevel&0xfff); len+=12;
                bits=bits*2+1;    len++;  //marker

                if(len < len_tab[index]){
                    bits_tab[index]= bits;
                    len_tab [index]= len;
                }
            }
        }
    }
}

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

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

    if (!done) {
        done = 1;

        init_uni_dc_tab();

        ff_init_rl(&ff_mpeg4_rl_intra, ff_mpeg4_static_rl_table_store[0]);

        init_uni_mpeg4_rl_tab(&ff_mpeg4_rl_intra, uni_mpeg4_intra_rl_bits, uni_mpeg4_intra_rl_len);
        init_uni_mpeg4_rl_tab(&ff_h263_rl_inter, uni_mpeg4_inter_rl_bits, uni_mpeg4_inter_rl_len);
    }

    s->min_qcoeff= -2048;
    s->max_qcoeff=  2047;
    s->intra_ac_vlc_length     = uni_mpeg4_intra_rl_len;
    s->intra_ac_vlc_last_length= uni_mpeg4_intra_rl_len + 128*64;
    s->inter_ac_vlc_length     = uni_mpeg4_inter_rl_len;
    s->inter_ac_vlc_last_length= uni_mpeg4_inter_rl_len + 128*64;
    s->luma_dc_vlc_length= uni_DCtab_lum_len;
    s->ac_esc_length= 7+2+1+6+1+12+1;
    s->y_dc_scale_table= ff_mpeg4_y_dc_scale_table;
    s->c_dc_scale_table= ff_mpeg4_c_dc_scale_table;

    if(s->flags & CODEC_FLAG_GLOBAL_HEADER){

        s->avctx->extradata= av_malloc(1024);
        init_put_bits(&s->pb, s->avctx->extradata, 1024);

        if(!(s->workaround_bugs & FF_BUG_MS))
            mpeg4_encode_visual_object_header(s);
        mpeg4_encode_vol_header(s, 0, 0);

//            ff_mpeg4_stuffing(&s->pb); ?
        flush_put_bits(&s->pb);
        s->avctx->extradata_size= (put_bits_count(&s->pb)+7)>>3;
    }
    return 0;
}

void ff_mpeg4_init_partitions(MpegEncContext *s)
{
    uint8_t *start= put_bits_ptr(&s->pb);
    uint8_t *end= s->pb.buf_end;
    int size= end - start;
    int pb_size = (((intptr_t)start + size/3)&(~3)) - (intptr_t)start;
    int tex_size= (size - 2*pb_size)&(~3);

    set_put_bits_buffer_size(&s->pb, pb_size);
    init_put_bits(&s->tex_pb, start + pb_size           , tex_size);
    init_put_bits(&s->pb2   , start + pb_size + tex_size, pb_size);
}

void ff_mpeg4_merge_partitions(MpegEncContext *s)
{
    const int pb2_len   = put_bits_count(&s->pb2   );
    const int tex_pb_len= put_bits_count(&s->tex_pb);
    const int bits= put_bits_count(&s->pb);

    if(s->pict_type==AV_PICTURE_TYPE_I){
        put_bits(&s->pb, 19, DC_MARKER);
        s->misc_bits+=19 + pb2_len + bits - s->last_bits;
        s->i_tex_bits+= tex_pb_len;
    }else{
        put_bits(&s->pb, 17, MOTION_MARKER);
        s->misc_bits+=17 + pb2_len;
        s->mv_bits+= bits - s->last_bits;
        s->p_tex_bits+= tex_pb_len;
    }

    flush_put_bits(&s->pb2);
    flush_put_bits(&s->tex_pb);

    set_put_bits_buffer_size(&s->pb, s->pb2.buf_end - s->pb.buf);
    avpriv_copy_bits(&s->pb, s->pb2.buf   , pb2_len);
    avpriv_copy_bits(&s->pb, s->tex_pb.buf, tex_pb_len);
    s->last_bits= put_bits_count(&s->pb);
}


void ff_mpeg4_encode_video_packet_header(MpegEncContext *s)
{
    int mb_num_bits= av_log2(s->mb_num - 1) + 1;

    put_bits(&s->pb, ff_mpeg4_get_video_packet_prefix_length(s), 0);
    put_bits(&s->pb, 1, 1);

    put_bits(&s->pb, mb_num_bits, s->mb_x + s->mb_y*s->mb_width);
    put_bits(&s->pb, s->quant_precision, s->qscale);
    put_bits(&s->pb, 1, 0); /* no HEC */
}

#define OFFSET(x) offsetof(MpegEncContext, x)
#define VE AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
    { "data_partitioning",       "Use data partitioning.",      OFFSET(data_partitioning), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, VE },
    { "alternate_scan",          "Enable alternate scantable.", OFFSET(alternate_scan),    AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, VE },
    FF_MPV_COMMON_OPTS
    { NULL },
};

static const AVClass mpeg4enc_class = {
    .class_name = "MPEG4 encoder",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
};

AVCodec ff_mpeg4_encoder = {
    .name           = "mpeg4",
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_MPEG4,
    .priv_data_size = sizeof(MpegEncContext),
    .init           = encode_init,
    .encode2        = ff_MPV_encode_picture,
    .close          = ff_MPV_encode_end,
    .pix_fmts       = (const enum AVPixelFormat[]){ AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE },
    .capabilities   = CODEC_CAP_DELAY | CODEC_CAP_SLICE_THREADS,
    .long_name      = NULL_IF_CONFIG_SMALL("MPEG-4 part 2"),
    .priv_class     = &mpeg4enc_class,
};