VFT
par->VFT = par->VBB + (lower_margin * 2 - 1) - 1;
par->VSS = par->VFT + 1 - (vsync_len * 2 - 1);
par->VFT++;
vfreq = (hfreq * 2) / (par->VFT + 1);
(hfreq * 2) / (par->VFT + 1 + 4 * lines - 2 * yres) >
(hfreq * 2) / (par->VFT + 1 + 4 * lines) >
(hfreq * 2) / (par->VFT + 1 + 4 * lines) >
vdb = current_par.VFT + 1;
vss = current_par.VFT + 1;