A system for determining the sequential position of video fields of a received video signal that was derived from a film having successive image frames in accordance with the 3:2 pulldown method, wherein the video fields are produced at a greater rate than the film frame rate and in a predetermined repetitive sequentially varying relationship to the film frames wherein at predetermined positions in the sequence a video field is identical to the video field that preceded it by the duration of two video fields. The system includes means for delaying each field of the received video signal; means for comparing each received video field with a video field that has been delayed by the duration of two video fields; and means for comparing the results of a successive number of said comparisons with the predetermined sequence to determine when identical fields are located in only said predetermined positions in a sequence of the compared received video fields. A video signal processing system is synchronized by said determination that identical fields are located in only said predetermined positions in a sequence of the compared received video fields, for inserting indications of sequential video field position in the vertical blanking intervals preceding video fields that are received subsequent to said synchronizing determination. A counter times said comparisons of said compared results with the predetermined sequence and provides an indication that the received video fields were not so derived from film when a determination that identical fields are located in only said predetermined positions in a sequence of the compared received video fields, is not made within a predetermined time. This indication is used to set the mode of operation of a system for providing a progressive-scan video display in accordance with whether or not the received video signal was derived from film.