HHT
par->HHT = plen * (left_margin + xres + right_margin) /
par->HDB += par->HHT + 2 + 0x200;
par->HDE = gend1 - par->HHT - 2 - hde_off / prescale;
par->HBB = gend2 - par->HHT - 2;
par->HSS = par->HHT + 2 - plen * hsync_len / prescale;
hfreq = pclock->f / ((par->HHT + 2) * prescale * 2);
hbe = current_par.HHT + 2;
hss = current_par.HHT + 2;