Eidak Corporation

Karoly Budai

Eugene Leonard

Bill Perlman

William R Dolson

Graham S Stubbs

William J Buynak

Augmenting pulses are added to the horizontal sync pulse intervals of a video signal to prevent a copy of the thus modified video signal from being satisfactorily displayed. The magnitude of the augmenting pulses is chosen so that the modified signal containing these pulses can be displayed without distortion. When the modified video signal is recorded and then reproduced by a typical VCR (i.e., when the modified video signal is copied), attenuation of the augmenting pulses and the remaining portions of the horizontal sync pulse occurs so that a television receiver cannot properly detect horizontal sync in the copied modified video signal, resulting in an unsatisfactory display.

Horizontal pulse augmentation of a video signal

Counting circuitry in the vertical synchronizing circuit of a video receiver is prevented from generating vertical control signals at a fixed, standard periodicity when the video signal transmitted to that receiver exhibits a changing field interval which varies above and below that standard period. At least one of the vertical pulses in the vertical period of each field interval as well as plural equalizing pulses in the post equalizing period in that field interval are deleted from the video signal. To minimize perturbations in the video picture displayed from that video signal, the time of occurrence of the first vertical pulse in selected field intervals is shifted.

Anti-copying video signal processing

A composite television signal is modified to inhibit the reproduction of an unauthorized recording thereof by conventional video recorders but enable the display of a video picture therefrom on a television receiver. The length of a frame (more particularly, the length of each field in a frame) is increased or decreased from standard length, either by changing the time duration of the respective horizontal line intervals included in each frame while keeping a constant, standard (e.g. 525) number of lines per frame, or by changing the number of horizontal line intervals which constitute a frame while maintaining the standard duration of each line interval (e.g. 63.5 microseconds). A profile pattern representing the variation of the video frame duration, or vertical period, (whether by changing the horizontal line durations or the number of lines in a frame) with respect to time is adjustable to correspondingly control the rate at which the vertical period (i.e. frame length) changes, the maximum and minimum vertical period and the ratio of increased to decreased vertical periods. Accordingly, substantially the same electronics responsive to the profile pattern may be used to modify the television signal; and the profile pattern itself may be changed easily, such as by simple software modifications, to accommodate different circumstances and to satisfy different conditions.

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Danbury, CT, United States of America

Karoly Budai