the range for motion search

[adknight]

These statements are in x264 .I don't understand them ,is there anybody who can tell me the meaning of them.thank you.

h->mb.mv_min_fpel[0] = -8*h->mb.i_mb_x - 4;
h->mb.mv_max_fpel[0] = 8*( h->sps->i_mb_width - h->mb.i_mb_x - 1 ) + 4;
h->mb.mv_min_spel[0] = 4*( h->mb.mv_min_fpel[0] - 8 );
h->mb.mv_max_spel[0] = 4*( h->mb.mv_max_fpel[0] + 8 );
if( h->mb.i_mb_x <= 1 )
{
h->mb.mv_min_fpel[1] = -8*h->mb.i_mb_y - 4;
h->mb.mv_max_fpel[1] = 8*( h->sps->i_mb_height - h->mb.i_mb_y - 1 ) + 4;
h->mb.mv_min_spel[1] = 4*( h->mb.mv_min_fpel[1] - 8 );
h->mb.mv_max_spel[1] = 4*( h->mb.mv_max_fpel[1] + 8 );
}