void ff_xvmc_decode_mb(MpegEncContext *s)

{

    XvMCMacroBlock *mv_block;

    struct xvmc_pix_fmt *render;

    int i, cbp, blocks_per_mb;



    const int mb_xy = s->mb_y * s->mb_stride + s->mb_x;





    if (s->encoding) {

        av_log(s->avctx, AV_LOG_ERROR, "XVMC doesn't support encoding!!!\n");

        return;

    }



    // from ff_mpv_decode_mb(), update DC predictors for P macroblocks

    if (!s->mb_intra) {

        s->last_dc[0] =

        s->last_dc[1] =

        s->last_dc[2] =  128 << s->intra_dc_precision;

    }



    // MC doesn't skip blocks

    s->mb_skipped = 0;





    // Do I need to export quant when I could not perform postprocessing?

    // Anyway, it doesn't hurt.

    s->current_picture.qscale_table[mb_xy] = s->qscale;



    // start of XVMC-specific code

    render = (struct xvmc_pix_fmt*)s->current_picture.f->data[2];

    assert(render);

    assert(render->xvmc_id == AV_XVMC_ID);

    assert(render->mv_blocks);



    // take the next free macroblock

    mv_block = &render->mv_blocks[render->start_mv_blocks_num +

                                  render->filled_mv_blocks_num];



    mv_block->x        = s->mb_x;

    mv_block->y        = s->mb_y;

    mv_block->dct_type = s->interlaced_dct; // XVMC_DCT_TYPE_FRAME/FIELD;

    if (s->mb_intra) {

        mv_block->macroblock_type = XVMC_MB_TYPE_INTRA; // no MC, all done

    } else {

        mv_block->macroblock_type = XVMC_MB_TYPE_PATTERN;



        if (s->mv_dir & MV_DIR_FORWARD) {

            mv_block->macroblock_type |= XVMC_MB_TYPE_MOTION_FORWARD;

            // PMV[n][dir][xy] = mv[dir][n][xy]

            mv_block->PMV[0][0][0] = s->mv[0][0][0];

            mv_block->PMV[0][0][1] = s->mv[0][0][1];

            mv_block->PMV[1][0][0] = s->mv[0][1][0];

            mv_block->PMV[1][0][1] = s->mv[0][1][1];

        }

        if (s->mv_dir & MV_DIR_BACKWARD) {

            mv_block->macroblock_type |= XVMC_MB_TYPE_MOTION_BACKWARD;

            mv_block->PMV[0][1][0] = s->mv[1][0][0];

            mv_block->PMV[0][1][1] = s->mv[1][0][1];

            mv_block->PMV[1][1][0] = s->mv[1][1][0];

            mv_block->PMV[1][1][1] = s->mv[1][1][1];

        }



        switch(s->mv_type) {

            case  MV_TYPE_16X16:

                mv_block->motion_type = XVMC_PREDICTION_FRAME;

                break;

            case  MV_TYPE_16X8:

                mv_block->motion_type = XVMC_PREDICTION_16x8;

                break;

            case  MV_TYPE_FIELD:

                mv_block->motion_type = XVMC_PREDICTION_FIELD;

                if (s->picture_structure == PICT_FRAME) {

                    mv_block->PMV[0][0][1] <<= 1;

                    mv_block->PMV[1][0][1] <<= 1;

                    mv_block->PMV[0][1][1] <<= 1;

                    mv_block->PMV[1][1][1] <<= 1;

                }

                break;

            case  MV_TYPE_DMV:

                mv_block->motion_type = XVMC_PREDICTION_DUAL_PRIME;

                if (s->picture_structure == PICT_FRAME) {



                    mv_block->PMV[0][0][0] = s->mv[0][0][0];      // top from top

                    mv_block->PMV[0][0][1] = s->mv[0][0][1] << 1;



                    mv_block->PMV[0][1][0] = s->mv[0][0][0];      // bottom from bottom

                    mv_block->PMV[0][1][1] = s->mv[0][0][1] << 1;



                    mv_block->PMV[1][0][0] = s->mv[0][2][0];      // dmv00, top from bottom

                    mv_block->PMV[1][0][1] = s->mv[0][2][1] << 1; // dmv01



                    mv_block->PMV[1][1][0] = s->mv[0][3][0];      // dmv10, bottom from top

                    mv_block->PMV[1][1][1] = s->mv[0][3][1] << 1; // dmv11



                } else {

                    mv_block->PMV[0][1][0] = s->mv[0][2][0];      // dmv00

                    mv_block->PMV[0][1][1] = s->mv[0][2][1];      // dmv01

                }

                break;

            default:

                assert(0);

        }



        mv_block->motion_vertical_field_select = 0;



        // set correct field references

        if (s->mv_type == MV_TYPE_FIELD || s->mv_type == MV_TYPE_16X8) {

            mv_block->motion_vertical_field_select |= s->field_select[0][0];

            mv_block->motion_vertical_field_select |= s->field_select[1][0] << 1;

            mv_block->motion_vertical_field_select |= s->field_select[0][1] << 2;

            mv_block->motion_vertical_field_select |= s->field_select[1][1] << 3;

        }

    } // !intra

    // time to handle data blocks

    mv_block->index = render->next_free_data_block_num;



    blocks_per_mb = 6;

    if (s->chroma_format >= 2) {

        blocks_per_mb = 4 + (1 << s->chroma_format);

    }



    // calculate cbp

    cbp = 0;

    for (i = 0; i < blocks_per_mb; i++) {

        cbp += cbp;

        if (s->block_last_index[i] >= 0)

            cbp++;

    }



    if (s->avctx->flags & AV_CODEC_FLAG_GRAY) {

        if (s->mb_intra) {                                   // intra frames are always full chroma blocks

            for (i = 4; i < blocks_per_mb; i++) {

                memset(s->pblocks[i], 0, sizeof(*s->pblocks[i]));  // so we need to clear them

                if (!render->unsigned_intra)

                    *s->pblocks[i][0] = 1 << 10;

            }

        } else {

            cbp &= 0xf << (blocks_per_mb - 4);

            blocks_per_mb = 4;                               // luminance blocks only

        }

    }

    mv_block->coded_block_pattern = cbp;

    if (cbp == 0)

        mv_block->macroblock_type &= ~XVMC_MB_TYPE_PATTERN;



    for (i = 0; i < blocks_per_mb; i++) {

        if (s->block_last_index[i] >= 0) {

            // I do not have unsigned_intra MOCO to test, hope it is OK.

            if (s->mb_intra && (render->idct || !render->unsigned_intra))

                *s->pblocks[i][0] -= 1 << 10;

            if (!render->idct) {

                s->idsp.idct(*s->pblocks[i]);

                /* It is unclear if MC hardware requires pixel diff values to be

                 * in the range [-255;255]. TODO: Clipping if such hardware is

                 * ever found. As of now it would only be an unnecessary

                 * slowdown. */

            }

            // copy blocks only if the codec doesn't support pblocks reordering

            if (s->avctx->xvmc_acceleration == 1) {

                memcpy(&render->data_blocks[render->next_free_data_block_num*64],

                       s->pblocks[i], sizeof(*s->pblocks[i]));

            }

            render->next_free_data_block_num++;

        }

    }

    render->filled_mv_blocks_num++;



    assert(render->filled_mv_blocks_num     <= render->allocated_mv_blocks);

    assert(render->next_free_data_block_num <= render->allocated_data_blocks);

    /* The above conditions should not be able to fail as long as this function

     * is used and the following 'if ()' automatically calls a callback to free

     * blocks. */





    if (render->filled_mv_blocks_num == render->allocated_mv_blocks)

        ff_mpeg_draw_horiz_band(s, 0, 0);

}
