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.