Abstract: A system for synchronizing data streams meant to be displayed concurrently at an end station, but delivered by separate delivery networks is disclosed. In one aspect, apparatus and methods for marking one of the data streams relative to the other are taught, including insertion of frame numbers in vertical and horizontal blanking intervals, the numbers referring to frames in the other stream and related to timing markers, and inserting such numbers by pixel data alteration. In another aspect, apparatus and methods are taught for receiving and re-synchronizing the data streams at a delivery point, including decoding of the relationship data inserted in one data stream referring to the other data stream. Re-synchronization is accomplished by controlling the separate data streams in separate buffer pipelines by a single controller. In a preferred embodiment one data stream is a live video data stream and the other is an annotation stream having added material to be displayed with the live video data stream.