A digital electronic device which synchronises two or more video signals. The frame synchronizer uses one of its inputs as a reference and genlocks the other video signals to the reference's sync and colour burst signals. By delaying the other signals so that each line and field starts at the same time, two or more video images can be blended, wiped and otherwise processed together. (A TBC takes this a step further by synchronising both signals to a stable reference, eliminating time base errors from both sources.)