vc9.c

ffmpeg源码分析

    {
    case P_TYPE: status = decode_p_picture_secondary_header(v); break;
    case B_TYPE: status = decode_b_picture_secondary_header(v); break;
    case BI_TYPE:
    case I_TYPE: status = decode_i_picture_secondary_header(v); break;
    }
    if (status<0) return FRAME_SKIPPED;

    /* AC Syntax */
    v->c_ac_table_index = decode012(gb);
    if (v->s.pict_type == I_TYPE || v->s.pict_type == BI_TYPE)
    {
        v->y_ac_table_index = decode012(gb);
    }
    /* DC Syntax */
    v->s.dc_table_index = decode012(gb);

    return 0;
}
#endif
/** @} */ //End for adv_frame_hdr

/***********************************************************************/
/**
 * @defgroup block VC9 Block-level functions
 * @see 7.1.4, p91 and 8.1.1.7, p(1)04
 * @todo TODO: Integrate to MpegEncContext facilities
 * @{
 */

/**
 * @def GET_MQUANT
 * @brief Get macroblock-level quantizer scale
 * @warning XXX: qdiff to the frame quant, not previous quant ?
 * @fixme XXX: Don't know how to initialize mquant otherwise in last case
 */
#define GET_MQUANT()                                           \
  if (v->dquantfrm)                                            \
  {                                                            \
    if (v->dqprofile == DQPROFILE_ALL_MBS)                     \
    {                                                          \
      if (v->dqbilevel)                                        \
      {                                                        \
        mquant = (get_bits(gb, 1)) ? v->pq : v->altpq;         \
      }                                                        \
      else                                                     \
      {                                                        \
        mqdiff = get_bits(gb, 3);                              \
        if (mqdiff != 7) mquant = v->pq + mqdiff;              \
        else mquant = get_bits(gb, 5);                         \
      }                                                        \
    }                                                          \
    else mquant = v->pq;                                       \
  }

/**
 * @def GET_MVDATA(_dmv_x, _dmv_y)
 * @brief Get MV differentials
 * @see MVDATA decoding from 8.3.5.2, p(1)20
 * @param _dmv_x Horizontal differential for decoded MV
 * @param _dmv_y Vertical differential for decoded MV
 * @todo TODO: Use MpegEncContext arrays to store them
 */
#define GET_MVDATA(_dmv_x, _dmv_y)                                  \
  index = 1 + get_vlc2(gb, vc9_mv_diff_vlc[s->mv_table_index].table,\
                       VC9_MV_DIFF_VLC_BITS, 2);                    \
  if (index > 36)                                                   \
  {                                                                 \
    mb_has_coeffs = 1;                                              \
    index -= 37;                                                    \
  }                                                                 \
  else mb_has_coeffs = 0;                                           \
  s->mb_intra = 0;                                                  \
  if (!index) { _dmv_x = _dmv_y = 0; }                              \
  else if (index == 35)                                             \
  {                                                                 \
    _dmv_x = get_bits(gb, v->k_x);                                  \
    _dmv_y = get_bits(gb, v->k_y);                                  \
    s->mb_intra = 1;                                                \
  }                                                                 \
  else                                                              \
  {                                                                 \
    index1 = index%6;                                               \
    if (s->mspel && index1 == 5) val = 1;                           \
    else                         val = 0;                           \
    val = get_bits(gb, size_table[index1] - val);                   \
    sign = 0 - (val&1);                                             \
    _dmv_x = (sign ^ ((val>>1) + offset_table[index1])) - sign;     \
                                                                    \
    index1 = index/6;                                               \
    if (s->mspel && index1 == 5) val = 1;                           \
    else                          val = 0;                          \
    val = get_bits(gb, size_table[index1] - val);                   \
    sign = 0 - (val&1);                                             \
    _dmv_y = (sign ^ ((val>>1) + offset_table[index1])) - sign;     \
  }

/** Get predicted DC value
 * prediction dir: left=0, top=1
 * @param s MpegEncContext
 * @param[in] n block index in the current MB
 * @param dc_val_ptr Pointer to DC predictor
 * @param dir_ptr Prediction direction for use in AC prediction
 * @todo TODO: Actually do it the VC9 way
 * @todo TODO: Handle properly edges
 */
static inline int vc9_pred_dc(MpegEncContext *s, int n,
                              uint16_t **dc_val_ptr, int *dir_ptr)
{
    int a, b, c, wrap, pred, scale;
    int16_t *dc_val;
    static const uint16_t dcpred[31] = {
        1024,  512,  341,  256,  205,  171,  146,  128,
         114,  102,   93,   85,   79,   73,   68,   64,
          60,   57,   54,   51,   49,   47,   45,   43,
          41,   39,   38,   37,   35,   34,   33
    };

    /* find prediction - wmv3_dc_scale always used here in fact */
    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: Rule B is used only for I and BI frames in S/M/C profile
     *      with overlap filtering off
     */
    if ((s->pict_type == I_TYPE || s->pict_type == BI_TYPE) &&
        1 /* XXX: overlap filtering off */)
    {
        /* Set outer values */
        if (s->first_slice_line && n!=2) b=c=dcpred[scale];
        if (s->mb_x == 0) b=a=dcpred[scale];
    }
    else
    {
        /* Set outer values */
        if (s->first_slice_line && n!=2) b=c=0;
        if (s->mb_x == 0) b=a=0;

        /* XXX: Rule A needs to know if blocks are inter or intra :/ */
        if (0)
        {
            /* update predictor */
            *dc_val_ptr = &dc_val[0];
            dir_ptr = 0;
            return a;
        }
    }

    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;
}

/** Decode one block, inter or intra
 * @param v The VC9 context
 * @param block 8x8 DCT block
 * @param n Block index in the current MB (<4=>luma)
 * @param coded If the block is coded
 * @param mquant Quantizer step for the current block
 * @see Inter TT: Table 21, p73 + p91-85
 * @see Intra TT: Table 20, p72 + p(1)05-(1)07
 * @todo TODO: Process the blocks
 * @todo TODO: Use M$ MPEG-4 cbp prediction
 */
static int vc9_decode_block(VC9Context *v, DCTELEM block[64], int n, int coded, int mquant)
{
    GetBitContext *gb = &v->s.gb;
    MpegEncContext *s = &v->s;
    int ttblk; /* Transform Type per Block */
    int subblkpat; /* Sub-block Transform Type Pattern */
    int dc_pred_dir; /* Direction of the DC prediction used */
    int run_diff, i;

    /* XXX: Guard against dumb values of mquant */
    mquant = (mquant < 1) ? 0 : ( (mquant>31) ? 31 : mquant );

    /* Set DC scale - y and c use the same */
    s->y_dc_scale = s->y_dc_scale_table[mquant];
    s->c_dc_scale = s->c_dc_scale_table[mquant];

    if (s->mb_intra)
    {
        int dcdiff;
        uint16_t *dc_val;

        /* Get DC differential */
        if (n < 4) {
            dcdiff = get_vlc2(&s->gb, ff_msmp4_dc_luma_vlc[s->dc_table_index].table, DC_VLC_BITS, 3);
        } else {
            dcdiff = get_vlc2(&s->gb, ff_msmp4_dc_chroma_vlc[s->dc_table_index].table, DC_VLC_BITS, 3);
        }
        if (dcdiff < 0){
            av_log(s->avctx, AV_LOG_ERROR, "Illegal DC VLC\n");
            return -1;
        }
        if (dcdiff)
        {
            if (dcdiff == 119 /* ESC index value */)
            {
                /* TODO: Optimize */
                if (mquant == 1) dcdiff = get_bits(gb, 10);
                else if (mquant == 2) dcdiff = get_bits(gb, 9);
                else dcdiff = get_bits(gb, 8);
            }
            else
            {
                if (mquant == 1)
                  dcdiff = (dcdiff<<2) + get_bits(gb, 2) - 3;
                else if (mquant == 2)
                  dcdiff = (dcdiff<<1) + get_bits(gb, 1) - 1;
            }
            if (get_bits(gb, 1))
              dcdiff = -dcdiff;
        }

        /* Prediction */
        dcdiff += vc9_pred_dc(s, n, &dc_val, &dc_pred_dir);
        *dc_val = dcdiff;
        /* Store the quantized DC coeff, used for prediction */

        if (n < 4) {
            block[0] = dcdiff * s->y_dc_scale;
        } else {
            block[0] = dcdiff * s->c_dc_scale;
        }
        if (block[0] < 0) {
#if TRACE
            //av_log(s->avctx, AV_LOG_ERROR, "DC=%i<0\n", dcdiff);
#endif
            //return -1;
        }
        /* Skip ? */
        run_diff = 0;
        i = 0;
        if (!coded) {
            goto not_coded;
        }
    }
    else
    {
        mquant = v->pq;

        /* Get TTBLK */
        if (v->ttmb < 8) /* per block */
            ttblk = get_vlc2(gb, vc9_ttblk_vlc[v->tt_index].table, VC9_TTBLK_VLC_BITS, 2);
        else /* Per frame */
          ttblk = 0; //FIXME, depends on ttfrm

        /* Get SUBBLKPAT */
        if (ttblk == v->ttblk4x4) /* 4x4 transform for that qp value */
            subblkpat = 1+get_vlc2(gb, vc9_subblkpat_vlc[v->tt_index].table,
                                   VC9_SUBBLKPAT_VLC_BITS, 2);
        else /* All others: 8x8, 4x8, 8x4 */
            subblkpat = decode012(gb);
    }

    //TODO AC Decoding
    i = 63; //XXX: nothing done yet


 not_coded:
    if (s->mb_intra) {
        mpeg4_pred_ac(s, block, n, dc_pred_dir);
        if (s->ac_pred) {
            i = 63; /* XXX: not optimal */
        }
    }
    if(i>0) i=63; //FIXME/XXX optimize
    s->block_last_index[n] = i;
    return 0;
}

/** @} */ //End for group block

/***********************************************************************/
/**
 * @defgroup std_mb VC9 Macroblock-level functions in Simple/Main Profiles
 * @see 7.1.4, p91 and 8.1.1.7, p(1)04
 * @todo TODO: Integrate to MpegEncContext facilities
 * @{
 */

static inline int vc9_coded_block_pred(MpegEncContext * s, int n, uint8_t **coded_block_ptr)
{
    int xy, wrap, pred, a, b, c;

    xy = s->block_index[n];
    wrap = s->b8_stride;

    /* 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;
}

/** Decode one I-frame MB (in Simple/Main profile)
 * @todo TODO: Extend to AP
 */
static int vc9_decode_i_mb(VC9Context *v, DCTELEM block[6][64])
{
    int i, cbp, val;
    uint8_t *coded_val;
//    uint32_t * const mb_type_ptr= &v->s.current_picture.mb_type[ v->s.mb_x + v->s.mb_y*v->s.mb_stride ];

    v->s.mb_intra = 1;
    cbp = get_vlc2(&v->s.gb, ff_msmp4_mb_i_vlc.table, MB_INTRA_VLC_BITS, 2);
    if (cbp < 0) return -1;
    v->s.ac_pred = get_bits(&v->s.gb, 1);

    for (i=0; i<6; i++)
    {
        val = ((cbp >> (5 - i)) & 1);
        if (i < 4) {
            int pred = vc9_coded_block_pred(&v->s, i, &coded_val);
            val = val ^ pred;
            *coded_val = val;
        }
        cbp |= val << (5 - i);
        if (vc9_decode_block(v, block[i], i, val, v->pq) < 0) //FIXME Should be mquant
        {
            av_log(v->s.avctx, AV_LOG_ERROR,
                   "\nerror while decoding block: %d x %d (%d)\n", v->s.mb_x, v->s.mb_y, i);
            return -1;
        }
    }
    return 0;
}

/** Decode one P-frame MB (in Simple/Main profile)
 * @todo TODO: Extend to AP
 * @fixme FIXME: DC value for inter blocks not set
 */
static int vc9_decode_p_mb(VC9Context *v, DCTELEM block[6][64])
{
    MpegEncContext *s = &v->s;
    GetBitContext *gb = &s->gb;
    int i, mb_offset = s->mb_x + s->mb_y*s->mb_width; /* XXX: mb_stride */
    int cbp; /* cbp decoding stuff */
    int hybrid_pred; /* Prediction types */
    int mv_mode_bit = 0;
    int mqdiff, mquant; /* MB quantization */
    int ttmb; /* MB Transform type */
    int status;
    uint8_t *coded_val;

    static const int size_table[6] = { 0, 2, 3, 4, 5, 8 },
      offset_table[6] = { 0, 1, 3, 7, 15, 31 };
    int mb_has_coeffs = 1; /* last_flag */
    int dmv_x, dmv_y; /* Differential MV components */
    int index, index1; /* LUT indices */
    int val, sign; /* temp values */

    mquant = v->pq; /* Loosy initialization */

    if (v->mv_type_mb_plane.is_raw)
        v->mv_type_mb_plane.data[mb_offset] = get_bits(gb, 1);
    if (v->skip_mb_plane.is_raw)
        v->skip_mb_plane.data[mb_offset] = get_bits(gb, 1);
    if (!mv_mode_bit) /* 1MV mode */
    {
        if (!v->skip_mb_plane.data[mb_offset])
        {
            GET_MVDATA(dmv_x, dmv_y);

            /* hybrid mv pred, 8.3.5.3.4 */
            if (v->mv_mode == MV_PMODE_1MV ||
                v->mv_mode == MV_PMODE_MIXED_MV)
                hybrid_pred = get_bits(gb, 1);
            /* FIXME Set DC val for inter block ? */
            if (s->mb_intra && !mb_has_coeffs)
            {
                GET_MQUANT();
                s->ac_pred = get_bits(gb, 1);
                /* XXX: how to handle cbp ? */
                cbp = 0;
                for (i=0; i<6; i++)
                {
                     s->coded_block[s->block_index[i]] = 0;
                     vc9_decode_block(v, block[i], i, 0, mquant);
                }