Synchronizing signal reproducing circuit in a disc playback device

Abstract

A synchronizing signal reproducing circuit in a disc playback device for playing back discs such as a video disc and Compact Disc comprises an assumed synchronizing signal detection circuit for taking out an assumed synchronizing signal having possibility of being a true synchronizing signal from a signal reproduced from a disc, a window establishing circuit for establishing a window which, on the basis of a preceding true synchronizing signal, includes a timing at which a true synchronizing signal is expected to occur, and a synchronizing signal picking up circuit for picking up the assumed synchronizing signal as a true synchronizing signal if it occurs in the window. The window is so established that a future side range becomes wider than a past side range with respect to the timing at which the true synchronizing signal is expected to occur. The window establishing circuit may comprise a counter counting the number of times the synchronizing signal has not consecutively been detected in the window and operate in such a manner that, when count of the counter has reached a predetermined value, the window is enlarged to pick up the synchronizing signal in the enlarged window and, when the synchronizing signal has not been found even in this enlarged window, the window is removed for further detection of the synchronizing signal.