/* OpenCL lowres subpel Refine */

/* Each thread performs 8x8 SAD.  4 threads per MB, so the 4 DIA HPEL offsets are
 * calculated simultaneously */
int sad_8x8_ii_hpel( read_only image2d_t fenc, int2 fencpos, read_only image2d_t fref_planes, int2 qpos )
{
    int2 frefpos = qpos >> 2;
    int hpel_idx = ((qpos.x & 2) >> 1) + (qpos.y & 2);
    uint mask_shift = 8 * hpel_idx;

    uint4 cost4 = 0;

    for( int y = 0; y < 8; y++ )
    {
        uint4 enc, val4;
        enc = read_imageui( fenc, sampler, fencpos + (int2)(0, y));
        val4.s0 = (read_imageui( fref_planes, sampler, frefpos + (int2)(0, y)).s0 >> mask_shift) & 0xFF;
        val4.s1 = (read_imageui( fref_planes, sampler, frefpos + (int2)(1, y)).s0 >> mask_shift) & 0xFF;
        val4.s2 = (read_imageui( fref_planes, sampler, frefpos + (int2)(2, y)).s0 >> mask_shift) & 0xFF;
        val4.s3 = (read_imageui( fref_planes, sampler, frefpos + (int2)(3, y)).s0 >> mask_shift) & 0xFF;
        cost4 += abs_diff( enc, val4 );

        enc = read_imageui( fenc, sampler, fencpos + (int2)(4, y));
        val4.s0 = (read_imageui( fref_planes, sampler, frefpos + (int2)(4, y)).s0 >> mask_shift) & 0xFF;
        val4.s1 = (read_imageui( fref_planes, sampler, frefpos + (int2)(5, y)).s0 >> mask_shift) & 0xFF;
        val4.s2 = (read_imageui( fref_planes, sampler, frefpos + (int2)(6, y)).s0 >> mask_shift) & 0xFF;
        val4.s3 = (read_imageui( fref_planes, sampler, frefpos + (int2)(7, y)).s0 >> mask_shift) & 0xFF;
        cost4 += abs_diff( enc, val4 );
    }

    return cost4.s0 + cost4.s1 + cost4.s2 + cost4.s3;
}

/* One thread measures 8x8 SAD cost at a QPEL offset into an HPEL plane */
int sad_8x8_ii_qpel( read_only image2d_t fenc, int2 fencpos, read_only image2d_t fref_planes, int2 qpos )
{
    int2 frefApos = qpos >> 2;
    int hpelA = ((qpos.x & 2) >> 1) + (qpos.y & 2);

    int2 qposB = qpos + ((qpos & 1) << 1);
    int2 frefBpos = qposB >> 2;
    int hpelB = ((qposB.x & 2) >> 1) + (qposB.y & 2);

    uint mask_shift0 = 8 * hpelA, mask_shift1 = 8 * hpelB;

    int cost = 0;

    for( int y = 0; y < 8; y++ )
    {
        for( int x = 0; x < 8; x++ )
        {
            uint enc = read_imageui( fenc, sampler, fencpos + (int2)(x, y)).s0;
            uint vA = (read_imageui( fref_planes, sampler, frefApos + (int2)(x, y)).s0 >> mask_shift0) & 0xFF;
            uint vB = (read_imageui( fref_planes, sampler, frefBpos + (int2)(x, y)).s0 >> mask_shift1) & 0xFF;
            cost += abs_diff( enc, rhadd( vA, vB ) );
        }
    }

    return cost;
}

/* Four threads measure 8x8 SATD cost at a QPEL offset into an HPEL plane
 *
 * Each thread collects 1/4 of the rows of diffs and processes one quarter of
 * the transforms
 */
int satd_8x8_ii_qpel_coop4( read_only image2d_t fenc,
                            int2 fencpos,
                            read_only image2d_t fref_planes,
                            int2 qpos,
                            local sum2_t *tmpp,
                            int idx )
{
    volatile local sum2_t( *tmp )[4] = (volatile local sum2_t( * )[4])tmpp;
    sum2_t b0, b1, b2, b3;

    // fencpos is full-pel position of original MB
    // qpos is qpel position within reference frame
    int2 frefApos = qpos >> 2;
    int hpelA = ((qpos.x&2)>>1) + (qpos.y&2);

    int2 qposB = qpos + (int2)(((qpos.x&1)<<1), ((qpos.y&1)<<1));
    int2 frefBpos = qposB >> 2;
    int hpelB = ((qposB.x&2)>>1) + (qposB.y&2);

    uint mask_shift0 = 8 * hpelA, mask_shift1 = 8 * hpelB;

    uint vA, vB;
    uint a0, a1;
    uint enc;
    sum2_t sum = 0;

#define READ_DIFF( OUT, X )\
    enc = read_imageui( fenc, sampler, fencpos + (int2)(X, idx) ).s0;\
    vA = (read_imageui( fref_planes, sampler, frefApos + (int2)(X, idx) ).s0 >> mask_shift0) & 0xFF;\
    vB = (read_imageui( fref_planes, sampler, frefBpos + (int2)(X, idx) ).s0 >> mask_shift1) & 0xFF;\
    OUT = enc - rhadd( vA, vB );

#define READ_DIFF_EX( OUT, a, b )\
    {\
        READ_DIFF( a0, a );\
        READ_DIFF( a1, b );\
        OUT = a0 + (a1<<BITS_PER_SUM);\
    }
#define ROW_8x4_SATD( a, b )\
    {\
        fencpos.y += a;\
        frefApos.y += b;\
        frefBpos.y += b;\
        READ_DIFF_EX( b0, 0, 4 );\
        READ_DIFF_EX( b1, 1, 5 );\
        READ_DIFF_EX( b2, 2, 6 );\
        READ_DIFF_EX( b3, 3, 7 );\
        HADAMARD4( tmp[idx][0], tmp[idx][1], tmp[idx][2], tmp[idx][3], b0, b1, b2, b3 );\
        HADAMARD4( b0, b1, b2, b3, tmp[0][idx], tmp[1][idx], tmp[2][idx], tmp[3][idx] );\
        sum += abs2( b0 ) + abs2( b1 ) + abs2( b2 ) + abs2( b3 );\
    }
    ROW_8x4_SATD( 0, 0 );
    ROW_8x4_SATD( 4, 4 );

#undef READ_DIFF
#undef READ_DIFF_EX
#undef ROW_8x4_SATD
    return (((sum_t)sum) + (sum>>BITS_PER_SUM)) >> 1;
}

constant int2 hpoffs[4] =
{
    {0, -2}, {-2, 0}, {2, 0}, {0, 2}
};

/* sub pixel refinement of motion vectors, output MVs and costs are moved from
 * temporary buffers into final per-frame buffer
 *
 * global launch dimensions:  [mb_width * 4, mb_height]
 *
 * With X being the source 16x16 pixels, F is the lowres pixel used by the
 * motion search.  We will now utilize the H V and C pixels (stored in separate
 * planes) to search at half-pel increments.
 *
 * X X X X X X
 *  F H F H F
 * X X X X X X
 *  V C V C V
 * X X X X X X
 *  F H F H F
 * X X X X X X
 *
 * The YX HPEL bits of the motion vector selects the plane we search in.  The
 * four planes are packed in the fref_planes 2D image buffer.  Each sample
 * returns:  s0 = F, s1 = H, s2 = V, s3 = C */
kernel void subpel_refine( read_only image2d_t   fenc,
                           read_only image2d_t   fref_planes,
                           const global short2  *in_mvs,
                           const global int16_t *in_sad_mv_costs,
                           local int16_t        *cost_local,
                           local sum2_t         *satd_local,
                           local short2         *mvc_local,
                           global short2        *fenc_lowres_mv,
                           global int16_t       *fenc_lowres_mv_costs,
                           int                   mb_width,
                           int                   lambda,
                           int                   b,
                           int                   ref,
                           int                   b_islist1 )
{
    int mb_x = get_global_id( 0 ) >> 2;
    if( mb_x >= mb_width )
        return;
    int mb_height = get_global_size( 1 );

    int mb_i = get_global_id( 0 ) & 3;
    int mb_y = get_global_id( 1 );
    int mb_xy = mb_y * mb_width + mb_x;

    /* fenc_lowres_mv and fenc_lowres_mv_costs are large buffers that
     * hold many frames worth of motion vectors.  We must offset into the correct
     * location for this frame's vectors.  The kernel will be passed the correct
     * directional buffer for the direction of the search: list1 or list0
     *
     *   CPU equivalent: fenc->lowres_mvs[0][b - p0 - 1]
     *   GPU equivalent: fenc_lowres_mvs[(b - p0 - 1) * mb_count] */
    fenc_lowres_mv +=       (b_islist1 ? (ref-b-1) : (b-ref-1)) * mb_width * mb_height;
    fenc_lowres_mv_costs += (b_islist1 ? (ref-b-1) : (b-ref-1)) * mb_width * mb_height;

    /* Adjust pointers into local memory buffers for this thread's data */
    int mb_in_group = get_local_id( 1 ) * (get_local_size( 0 ) >> 2) + (get_local_id( 0 ) >> 2);
    cost_local += mb_in_group * 4;
    satd_local += mb_in_group * 16;
    mvc_local += mb_in_group * 4;

    int i_mvc = 0;

    mvc_local[0] = mvc_local[1] = mvc_local[2] = mvc_local[3] = 0;

#define MVC( DX, DY ) mvc_local[i_mvc++] = in_mvs[mb_width * (mb_y + DY) + (mb_x + DX)];
    if( mb_x > 0 )
        MVC( -1, 0 );
    if( mb_y > 0 )
    {
        MVC( 0, -1 );
        if( mb_x < mb_width - 1 )
            MVC( 1, -1 );
        if( mb_x > 0 )
            MVC( -1, -1 );
    }
#undef MVC
    int2 mvp = (i_mvc <= 1) ? convert_int2_sat(mvc_local[0]) : x264_median_mv( mvc_local[0], mvc_local[1], mvc_local[2] );

    int bcost =  in_sad_mv_costs[mb_xy];
    int2 coord = (int2)(mb_x, mb_y) << 3;
    int2 bmv = convert_int2_sat( in_mvs[mb_xy] );

    /* Make mvp and bmv QPEL MV */
    mvp <<= 2; bmv <<= 2;

#define HPEL_QPEL( ARR, FUNC )\
    {\
        int2 trymv = bmv + ARR[mb_i];\
        int2 qpos = (coord << 2) + trymv;\
        int cost = FUNC( fenc, coord, fref_planes, qpos ) + lambda * mv_cost( abs_diff( trymv, mvp ) );\
        cost_local[mb_i] = (cost<<2) + mb_i;\
        cost = min( cost_local[0], min( cost_local[1], min( cost_local[2], cost_local[3] ) ) );\
        if( (cost>>2) < bcost )\
        {\
            bmv += ARR[cost&3];\
            bcost = cost>>2;\
        }\
    }

    HPEL_QPEL( hpoffs, sad_8x8_ii_hpel );
    HPEL_QPEL( dia_offs, sad_8x8_ii_qpel );
    fenc_lowres_mv[mb_xy] = convert_short2_sat( bmv );

    /* remeasure cost of bmv using SATD */
    int2 qpos = (coord << 2) + bmv;
    cost_local[mb_i] = satd_8x8_ii_qpel_coop4( fenc, coord, fref_planes, qpos, satd_local, mb_i );
    bcost = cost_local[0] + cost_local[1] + cost_local[2] + cost_local[3];
    bcost += lambda * mv_cost( abs_diff( bmv, mvp ) );

    fenc_lowres_mv_costs[mb_xy] = min( bcost, LOWRES_COST_MASK );
}