HS/VS tracking will measure the distance between HS/VS pulses and when distance is the same for three times, tracking is locked. In this mode, any HS/VS that is not in the right place (caused by noise) is corrected. If 3 consecutive pulses are wrong the tracking will try to re-lock. This mode is enabled by setting HSTRACK and VSTRACK bits (or HTRACK and VTRACK, or HVTREN bits in different deserialzers).
With MAX9286, a quad deserializer, there is no VSTRACK because VS pulses distance is varied to synchronize the the cameras. HS tracking will not work in Automatic Frame sync mode as the distance between HS pulses in this mode can vary.