msmpeg4.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

    int pred, extquant;
    int extrabits = 0;

    if(s->msmpeg4_version==1){
        int32_t *dc_val;
        pred = msmpeg4v1_pred_dc(s, n, &dc_val);

        /* update predictor */
        *dc_val= level;
    }else{
        int16_t *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;

    if(s->msmpeg4_version<=2){
        if (n < 4) {
            put_bits(&s->pb,
                     v2_dc_lum_table[level+256][1],
                     v2_dc_lum_table[level+256][0]);
        }else{
            put_bits(&s->pb,
                     v2_dc_chroma_table[level+256][1],
                     v2_dc_chroma_table[level+256][0]);
        }
    }else{
        sign = 0;
        if (level < 0) {
            level = -level;
            sign = 1;
        }
        code = level;
        if (code > DC_MAX)
            code = DC_MAX;
        else if( s->msmpeg4_version>=6 ) {
            if( s->qscale == 1 ) {
                extquant = (level + 3) & 0x3;
                code  = ((level+3)>>2);
            } else if( s->qscale == 2 ) {
                extquant = (level + 1) & 0x1;
                code  = ((level+1)>>1);
            }
        }

        if (s->dc_table_index == 0) {
            if (n < 4) {
                put_bits(&s->pb, ff_table0_dc_lum[code][1], ff_table0_dc_lum[code][0]);
            } else {
                put_bits(&s->pb, ff_table0_dc_chroma[code][1], ff_table0_dc_chroma[code][0]);
            }
        } else {
            if (n < 4) {
                put_bits(&s->pb, ff_table1_dc_lum[code][1], ff_table1_dc_lum[code][0]);
            } else {
                put_bits(&s->pb, ff_table1_dc_chroma[code][1], ff_table1_dc_chroma[code][0]);
            }
        }

        if(s->msmpeg4_version>=6 && s->qscale<=2)
            extrabits = 3 - s->qscale;

        if (code == DC_MAX)
            put_bits(&s->pb, 8 + extrabits, level);
        else if(extrabits > 0)//== VC1 && s->qscale<=2
            put_bits(&s->pb, extrabits, extquant);

        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.
 */
void ff_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;
    const uint8_t *scantable;

    if (s->mb_intra) {
        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 = s->msmpeg4_version>=4;
        scantable= s->intra_scantable.permutated;
    } else {
        i = 0;
        rl = &rl_table[3 + s->rl_table_index];
        if(s->msmpeg4_version<=2)
            run_diff = 0;
        else
            run_diff = 1;
        scantable= s->inter_scantable.permutated;
    }

    /* recalculate block_last_index for M$ wmv1 */
    if(s->msmpeg4_version>=4 && s->msmpeg4_version<6 && s->block_last_index[n]>0){
        for(last_index=63; last_index>=0; last_index--){
            if(block[scantable[last_index]]) break;
        }
        s->block_last_index[n]= last_index;
    }else
        last_index = s->block_last_index[n];
    /* AC coefs */
    last_non_zero = i - 1;
    for (; i <= last_index; i++) {
        j = scantable[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;
            }

            if(level<=MAX_LEVEL && run<=MAX_RUN){
                s->ac_stats[s->mb_intra][n>3][level][run][last]++;
            }
#if 0
else
    s->ac_stats[s->mb_intra][n>3][40][63][0]++; //esc3 like
#endif
            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+1, level);
                    if (s->msmpeg4_version == 4 && code == rl->n)
                        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);
                        if(s->msmpeg4_version>=4){
                            if(s->esc3_level_length==0){
                                s->esc3_level_length=8;
                                s->esc3_run_length= 6;
                                //ESCLVLSZ + ESCRUNSZ
                                if(s->qscale<8)
                                    put_bits(&s->pb, 6 + (s->msmpeg4_version>=6), 3);
                                else
                                    put_bits(&s->pb, 8, 3);
                            }
                            put_bits(&s->pb, s->esc3_run_length, run);
                            put_bits(&s->pb, 1, sign);
                            put_bits(&s->pb, s->esc3_level_length, level);
                        }else{
                            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[4];
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;
static VLC v1_intra_cbpc_vlc;
static VLC v1_inter_cbpc_vlc;
static VLC inter_intra_vlc;

/* This table is practically identical to the one from h263
 * except that it is inverted. */
static void init_h263_dc_for_msmpeg4(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 h263 */
            uni_code= DCtab_lum[size][0];
            uni_len = DCtab_lum[size][1];
            uni_code ^= (1<<uni_len)-1; //M$ does not 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$ does not 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 ff_msmpeg4_decode_init(MpegEncContext *s)
{
    static int done = 0;
    int i;
    MVTable *mv;

    common_init(s);

    if (!done) {
        done = 1;

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

        init_vlc(&ff_msmp4_dc_luma_vlc[0], DC_VLC_BITS, 120,
                 &ff_table0_dc_lum[0][1], 8, 4,
                 &ff_table0_dc_lum[0][0], 8, 4, 1);
        init_vlc(&ff_msmp4_dc_chroma_vlc[0], DC_VLC_BITS, 120,
                 &ff_table0_dc_chroma[0][1], 8, 4,
                 &ff_table0_dc_chroma[0][0], 8, 4, 1);
        init_vlc(&ff_msmp4_dc_luma_vlc[1], DC_VLC_BITS, 120,
                 &ff_table1_dc_lum[0][1], 8, 4,
                 &ff_table1_dc_lum[0][0], 8, 4, 1);
        init_vlc(&ff_msmp4_dc_chroma_vlc[1], DC_VLC_BITS, 120,
                 &ff_table1_dc_chroma[0][1], 8, 4,
                 &ff_table1_dc_chroma[0][0], 8, 4, 1);

        init_vlc(&v2_dc_lum_vlc, DC_VLC_BITS, 512,
                 &v2_dc_lum_table[0][1], 8, 4,
                 &v2_dc_lum_table[0][0], 8, 4, 1);
        init_vlc(&v2_dc_chroma_vlc, DC_VLC_BITS, 512,
                 &v2_dc_chroma_table[0][1], 8, 4,
                 &v2_dc_chroma_table[0][0], 8, 4, 1);

        init_vlc(&cbpy_vlc, CBPY_VLC_BITS, 16,
                 &cbpy_tab[0][1], 2, 1,
                 &cbpy_tab[0][0], 2, 1, 1);
        init_vlc(&v2_intra_cbpc_vlc, V2_INTRA_CBPC_VLC_BITS, 4,
                 &v2_intra_cbpc[0][1], 2, 1,
                 &v2_intra_cbpc[0][0], 2, 1, 1);
        init_vlc(&v2_mb_type_vlc, V2_MB_TYPE_VLC_BITS, 8,
                 &v2_mb_type[0][1], 2, 1,
                 &v2_mb_type[0][0], 2, 1, 1);
        init_vlc(&v2_mv_vlc, V2_MV_VLC_BITS, 33,
                 &mvtab[0][1], 2, 1,
                 &mvtab[0][0], 2, 1, 1);

        for(i=0; i<4; i++){
            init_vlc(&mb_non_intra_vlc[i], MB_NON_INTRA_VLC_BITS, 128,
                     &wmv2_inter_table[i][0][1], 8, 4,
                     &wmv2_inter_table[i][0][0], 8, 4, 1); //FIXME name?
        }

        init_vlc(&ff_msmp4_mb_i_vlc, MB_INTRA_VLC_BITS, 64,
                 &ff_msmp4_mb_i_table[0][1], 4, 2,
                 &ff_msmp4_mb_i_table[0][0], 4, 2, 1);

        init_vlc(&v1_intra_cbpc_vlc, V1_INTRA_CBPC_VLC_BITS, 8,
                 intra_MCBPC_bits, 1, 1,
                 intra_MCBPC_code, 1, 1, 1);
        init_vlc(&v1_inter_cbpc_vlc, V1_INTER_CBPC_VLC_BITS, 25,
                 inter_MCBPC_bits, 1, 1,
                 inter_MCBPC_code, 1, 1, 1);

        init_vlc(&inter_intra_vlc, INTER_INTRA_VLC_BITS, 4,
                 &table_inter_intra[0][1], 2, 1,
                 &table_inter_intra[0][0], 2, 1, 1);
    }

    switch(s->msmpeg4_version){
    case 1:
    case 2:
        s->decode_mb= msmpeg4v12_decode_mb;
        break;
    case 3:
    case 4:
        s->decode_mb= msmpeg4v34_decode_mb;
        break;
    case 5:
        s->decode_mb= wmv2_decode_mb;
    case 6:
        //FIXME + TODO VC1 decode mb
        break;
    }

    s->slice_height= s->mb_height; //to avoid 1/0 if the first frame is not a keyframe

    return 0;
}

int msmpeg4_decode_picture_header(MpegEncContext * s)
{
    int code;

#if 0
{
int i;
for(i=0; i<s->gb.size_in_bits; i++)
    av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
//    get_bits1(&s->gb);
av_log(s->avctx, AV_LOG_DEBUG, "END\n");
return -1;
}
#endif

    if(s->msmpeg4_version==1){
        int start_code, num;
        start_code = (get_bits(&s->gb, 16)<<16) | get_bits(&s->gb, 16);