Ampex Corporation

Walter J Cheney

Alan G Grace

James W Jones

A magnetic disc has a plurality of video track segments for storing distinct fields of video information. A look-up track is provided on the disc and segmented to store indirect address data which may be represented by random numbers, and which are related to the video information fields. Both the look-up track segments and the video track segments are numbered sequentially. Each video track segment is permanently associated with a look-up track segment. A movable transducer is associated with both the video tracks and the look-up track. A counter circuit is provided to indicate periodically the instant look-up segment numbers with respect to the instant position of the rotating cyclical storage device and in synchronism therewith. A first comparator circuit compares an indirect address input request with the indirect addresses recorded on the look-up track. Responsive to an output from the first comparator circuit, a buffer circuit stores an instant look-up segment number and transfers it to a control circuit. A control signal from the control circuit is sent to a transducer positioning device which moves the transducer to the corresponding video track segment. A look-up decoder circuit is designed to sense a first empty segment automatically and periodically. A new video picture information is stored on the video track segment corresponding to that first empty look-up track segment. Data bits are stored on the back porch of the horizontal sync pulses on consecutive lines of the video information. A circuit is provided to extract these data bits and restore the look-up track if accidentally erased.

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Portola Valley, CA, United States of America

Walter J Cheney