An apparatus and method for encoding and decoding a television signal are disclosed in which the horizontal sync pulses and the first section of the video signal are inverted, and the inverted horizontal sync pulses and video signals are reduced in amplitude by a predetermined amount.

A video signal is modified so that a television receiver still produces a normal color picture from the modified signal, whereas a videotape recording of this signal produces generally unacceptable pictures. This invention relies on the fact that videotape recorders feature some form of automatic level control circuit. These automatic level control circuits measure the sync pulse level in the video signal and develop a gain correction signal for keeping the video level applied to an FM modulator in the videotape recording system at a fixed predetermined value. In accordance with the present invention either a positive or a negative pulse is added to the video signal immediately following the trailing edge of sync. The effect of these added pulses is to cause the automatic level control circuit in the recorder to assess the video level at either many times its actual value or as a fraction of its actual value. The gain correction signal applied to the amplifier in the automatic level control circuit thus causes recording of a signal which is either not strong enough to properly synchronize a television receiver's scanning circuits or is so high to result in clipping and signal distortion. The sync pulses themselves can also be at a reduced level, and means are disclosed for boosting the black level in the video signal so as to not degrade normal reproduction of the video signal on a television receiver.

A satellite TV system including a plurality of channel strips and a control computer wherein each channel strip includes a tuner and a modulator matched to each other and are both computer controlled. The tuner selects the particular satellite signal and the modulator selects the particular channel position on the TV. Both tuner and modulator circuits include a divide by 2 component which permits use of lower cost electronic components while producing high quality TV pictures or other outputs.

A method of scrambling a television signal and a method of and apparatus for descrambling a television signal is provided. An audio signal is used on which a key signal containing compression information and information concerning the position of a vertical blanking interval is superimposed on a portion of the audio signal corresponding to a horizontal blanking interval. In addition, a pseudo-key signal is superimposed on the audio signal at a portion which corresponds to a vertical blanking interval, so that the vertical blanking interval cannot be detected through the detection of the audio signal. As a result, an expansion signal for expanding the signal in the horizontal blanking interval and vertical blanking interval compressed by scrambling cannot be formed in its normal position. Thus, unauthorized access is difficult. Descrambling can be performed by detecting the vertical blanking interval based on the information concerning the position of the vertical blanking interval contained in the key signal, and decoding the information for the position which is transmitted in the form of out-band data. Compression information can then be extracted from the key signal based on the detected vertical blanking interval, and an expansion signal for expanding the signal in the horizontal and vertical blanking periods can be generated.

Anti-copying protection for video material is provided wherein at least one high-amplitude pulse is inserted into various lines of the video signal, in and immediately preceding the vertical interval associated with each field, during the process of preparing a master recording for use in the high-speed duplication of legitimate recordings of the video material. A preferred embodiment of the present system and method is directed to videotape-to-videotape anti-copying protection. A high-amplitude pulse is inserted in the back porch region of horizontal sync pulses, and immediately following certain equalizing and vertical sync pulses, at an intermediate stage in the mastering process, whereby the pulse is inserted into a separated luminance component of the video signal, which is later recombined with the chromenance signal. Such method allows for the insertion of an higher amplitude pulse than would otherwise be possible, and yields a pulse of the desired final width, without the occurrence of such undesirable effects as loss of color lock or darkening of the picture with respect to legitimate recordings. The resulting modified video material may be viewed properly on a TV receiver or other display, but when coping from the legitimate source is attempted, the copy will yield a video signal which is too distorted for proper viewing. A further modification of the value of negative-going horizontal sync pulses provides additional synchronization error in recorded copies of legitimately recorded video material so as to further render such materials effectively non-copiable.