Macrovision Corporation

Andrew B Mellows

Ronald Quan

John O Ryan

Gerow D Brill

William J Wrobleski

A technique is disclosed for preventing unauthorized playback of scrambled video/audio signals recorded on, for example, a video tape cassette, which technique includes several cooperating processes and apparatus which further prevent the playback of recorded video/audio when the playback apparatus is in a still or pause mode of operation. The technique includes selected combinations of processes of inverting and re-clamping the luminance component of the video signal just prior to FM modulation; blanking an overscan portion, or portions, of the video signal and adding a video retrace signal to the overscan portion(s); inverting the normal control track signal and position modulating the normally unused edge; and selectively scrambling the audio signal and recording the scrambled audio signal in an audio track or in a Hi-Fi track. A selected user specific authorization code is recording in and recovered from the audio track. The recorded scrambled video/audio signal is recovered via a modified combo VCR/TV unit with no external video/audio jacks, which reverses the scrambling processes mentioned above, but only if the descrambling apparatus is authorized by having the proper recovered authorization code.

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Palo Alto, CA, United States of America

Andrew B Mellows