Method for producing copy protected recorded videotape having uncopyable vertical synchronizing signal partition

DETAILED DESCRIPTION It is an object of the present invention to provide a copy protected recorded videotape that is effective with presently marketed VTRs.
The present invention provides copy protection of recorded videotape by recording composite synchronizing signals on at least a part of the tape, wherein the width of the vertical synchronizing pulses discernible by the vertical synchronizing signal separating circuit of a television receiver has a pulse width in the range of 1-20 micro-seconds.
All other vertical synchronizing pulses in the vertical synchronizing signal partition, all the equalizing pulses and at least a part of the horizontal synchronizing pulses following the vertical synchronizing signal partition in the composite synchronizing signal with a signal height less than a predetermined pedestal level of the synchronizing signals.
More specifically, the present invention is directed to a copy protected pre-recorded videotape intended for playback by a helical scanning rotary head videotape machine for viewing on a television receiver, copy protection being provided by recording on the videotape a television field signal including a composite synchronizing signal for controlling the image produced by the television receiver, the composite synchronizing signal comprising: a vertical synchronizing pulse in the vertical synchronizing signal partition having a pulse width in the range of 1-20 micro-seconds and a pulse height discernible by a vertical synchronizing signal separating circuit of the television receiver; and all other vertical synchronizing pulses in the vertical synchronizing signal partition, all equalizing pulses in the equalizing signal partition following the vertical synchronizing signal partition and at least a part of the horizontal synchronizing pulses in the horizontal synchronizing signal partition following the equalizing signal partition in the composite synchronizing signal having a pulse height less than a predetermined pedestal level of the standard television signal