mpeg12.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.7平台上编译为嵌入式图形界面操作系统。

    int code, bit_size, l, m, bits, range, sign;

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

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

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

    common_init(s);

    if(!done){
        int f_code;
        int mv;
	int i;

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

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

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

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

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

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

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

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

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

        for(f_code=MAX_FCODE; f_code>0; f_code--){
            for(mv=-(8<<f_code); mv<(8<<f_code); mv++){
                fcode_tab[mv+MAX_MV]= f_code;
            }
        }
    }
    s->mv_penalty= mv_penalty;
    s->fcode_tab= fcode_tab;
    s->min_qcoeff=-255;
    s->max_qcoeff= 255;
    s->intra_quant_bias= 3<<(QUANT_BIAS_SHIFT-3); //(a + x*3/8)/x
    s->inter_quant_bias= 0;
}

static inline void encode_dc(MpegEncContext *s, int diff, int component)
{
    if (component == 0) {
        put_bits(
	    &s->pb, 
	    mpeg1_lum_dc_uni[diff+255]&0xFF,
	    mpeg1_lum_dc_uni[diff+255]>>8);
    } else {
        put_bits(
            &s->pb, 
	    mpeg1_chr_dc_uni[diff+255]&0xFF,
	    mpeg1_chr_dc_uni[diff+255]>>8);
    }
}

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

    last_index = s->block_last_index[n];

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

    /* now quantify & encode AC coefs */
    last_non_zero = i - 1;

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

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

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

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

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

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

    if (!done) {
        done = 1;

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

        init_2d_vlc_rl(&rl_mpeg1);
        init_2d_vlc_rl(&rl_mpeg2);
    }
}

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

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

/* motion type (for mpeg2) */
#define MT_FIELD 1
#define MT_FRAME 2
#define MT_16X8  2
#define MT_DMV   3

static int mpeg_decode_mb(MpegEncContext *s,
                          DCTELEM block[6][64])
{
    int i, j, k, cbp, val, mb_type, motion_type;
    
    dprintf("decode_mb: x=%d y=%d\n", s->mb_x, s->mb_y);

    if (--s->mb_incr != 0) {
        /* skip mb */
        s->mb_intra = 0;
        for(i=0;i<6;i++)
            s->block_last_index[i] = -1;
        s->mv_type = MV_TYPE_16X16;
        if (s->pict_type == P_TYPE) {
            /* if P type, zero motion vector is implied */
            s->mv_dir = MV_DIR_FORWARD;
            s->mv[0][0][0] = s->mv[0][0][1] = 0;
            s->last_mv[0][0][0] = s->last_mv[0][0][1] = 0;
            s->last_mv[0][1][0] = s->last_mv[0][1][1] = 0;
        } else {
            /* if B type, reuse previous vectors and directions */
            s->mv[0][0][0] = s->last_mv[0][0][0];
            s->mv[0][0][1] = s->last_mv[0][0][1];
            s->mv[1][0][0] = s->last_mv[1][0][0];
            s->mv[1][0][1] = s->last_mv[1][0][1];
        }
        s->mb_skiped = 1;
        return 0;
    }

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

    if (mb_type & MB_QUANT) {
        s->qscale = get_qscale(s);
    }
    if (mb_type & MB_INTRA) {
        if (s->concealment_motion_vectors) {
            /* just parse them */
            if (s->picture_structure != PICT_FRAME) 
                skip_bits1(&s->gb); /* field select */
            mpeg_decode_motion(s, s->mpeg_f_code[0][0], 0);
            mpeg_decode_motion(s, s->mpeg_f_code[0][1], 0);
        }
        s->mb_intra = 1;
        cbp = 0x3f;
        memset(s->last_mv, 0, sizeof(s->last_mv)); /* reset mv prediction */
    } else {
        s->mb_intra = 0;
        cbp = 0;
    }
    /* special case of implicit zero motion vector */