static inline void qpel_motion(MpegEncContext *s,

                               uint8_t *dest_y,

                               uint8_t *dest_cb,

                               uint8_t *dest_cr,

                               int field_based, int bottom_field,

                               int field_select, uint8_t **ref_picture,

                               op_pixels_func (*pix_op)[4],

                               qpel_mc_func (*qpix_op)[16],

                               int motion_x, int motion_y, int h)

{

    uint8_t *ptr_y, *ptr_cb, *ptr_cr;

    int dxy, uvdxy, mx, my, src_x, src_y, uvsrc_x, uvsrc_y, v_edge_pos;

    ptrdiff_t linesize, uvlinesize;



    dxy   = ((motion_y & 3) << 2) | (motion_x & 3);



    src_x = s->mb_x *  16                 + (motion_x >> 2);

    src_y = s->mb_y * (16 >> field_based) + (motion_y >> 2);



    v_edge_pos = s->v_edge_pos >> field_based;

    linesize   = s->linesize   << field_based;

    uvlinesize = s->uvlinesize << field_based;



    if (field_based) {

        mx = motion_x / 2;

        my = motion_y >> 1;

    } else if (s->workaround_bugs & FF_BUG_QPEL_CHROMA2) {

        static const int rtab[8] = { 0, 0, 1, 1, 0, 0, 0, 1 };

        mx = (motion_x >> 1) + rtab[motion_x & 7];

        my = (motion_y >> 1) + rtab[motion_y & 7];

    } else if (s->workaround_bugs & FF_BUG_QPEL_CHROMA) {

        mx = (motion_x >> 1) | (motion_x & 1);

        my = (motion_y >> 1) | (motion_y & 1);

    } else {

        mx = motion_x / 2;

        my = motion_y / 2;

    }

    mx = (mx >> 1) | (mx & 1);

    my = (my >> 1) | (my & 1);



    uvdxy = (mx & 1) | ((my & 1) << 1);

    mx  >>= 1;

    my  >>= 1;



    uvsrc_x = s->mb_x *  8                 + mx;

    uvsrc_y = s->mb_y * (8 >> field_based) + my;



    ptr_y  = ref_picture[0] + src_y   * linesize   + src_x;

    ptr_cb = ref_picture[1] + uvsrc_y * uvlinesize + uvsrc_x;

    ptr_cr = ref_picture[2] + uvsrc_y * uvlinesize + uvsrc_x;



    if ((unsigned)src_x > FFMAX(s->h_edge_pos - (motion_x & 3) - 16, 0) ||

        (unsigned)src_y > FFMAX(v_edge_pos - (motion_y & 3) - h, 0)) {

        s->vdsp.emulated_edge_mc(s->sc.edge_emu_buffer, ptr_y,

                                 s->linesize, s->linesize,

                                 17, 17 + field_based,

                                 src_x, src_y << field_based,

                                 s->h_edge_pos, s->v_edge_pos);

        ptr_y = s->sc.edge_emu_buffer;

        if (!CONFIG_GRAY || !(s->avctx->flags & AV_CODEC_FLAG_GRAY)) {

            uint8_t *uvbuf = s->sc.edge_emu_buffer + 18 * s->linesize;

            s->vdsp.emulated_edge_mc(uvbuf, ptr_cb,

                                     s->uvlinesize, s->uvlinesize,

                                     9, 9 + field_based,

                                     uvsrc_x, uvsrc_y << field_based,

                                     s->h_edge_pos >> 1, s->v_edge_pos >> 1);

            s->vdsp.emulated_edge_mc(uvbuf + 16, ptr_cr,

                                     s->uvlinesize, s->uvlinesize,

                                     9, 9 + field_based,

                                     uvsrc_x, uvsrc_y << field_based,

                                     s->h_edge_pos >> 1, s->v_edge_pos >> 1);

            ptr_cb = uvbuf;

            ptr_cr = uvbuf + 16;

        }

    }



    if (!field_based)

        qpix_op[0][dxy](dest_y, ptr_y, linesize);

    else {

        if (bottom_field) {

            dest_y  += s->linesize;

            dest_cb += s->uvlinesize;

            dest_cr += s->uvlinesize;

        }



        if (field_select) {

            ptr_y  += s->linesize;

            ptr_cb += s->uvlinesize;

            ptr_cr += s->uvlinesize;

        }

        // damn interlaced mode

        // FIXME boundary mirroring is not exactly correct here

        qpix_op[1][dxy](dest_y, ptr_y, linesize);

        qpix_op[1][dxy](dest_y + 8, ptr_y + 8, linesize);

    }

    if (!CONFIG_GRAY || !(s->avctx->flags & AV_CODEC_FLAG_GRAY)) {

        pix_op[1][uvdxy](dest_cr, ptr_cr, uvlinesize, h >> 1);

        pix_op[1][uvdxy](dest_cb, ptr_cb, uvlinesize, h >> 1);

    }

}
