General Instrument Corporation

General Instrument Corporation Jerrold Communications

General Instrument Corporation, Jerrold Communications Division

John T Griffin

David Grubb

Joseph B Glaab

Jeffrey S Hamilton

David E Zeidler

A novel method and apparatus for scrambling a television signal includes using a synchronization separator to separate a synchronization signal from an input audio-visual signal. The synchronization signal is then used to regulate an oscillator producing an audio carrier signal. In this manner, the audio-visual signal is transmitted without the component synchronization signal rendering it useless to a conventional television receiver. The descrambler and descrambling method of the invention involve removing the audio carrier signal from the scrambled signal and using the audio carrier signal to generate the color sub-carrier signal and a vertical time frame reference signal necessary to synchronize the transmitted audio visual signal for display.

Method and apparatus for television signal scrambling using the replacement of synchronizing and color subcarrier signals with an alternative time base inherent in a QPSK audio subcarrier

A method and apparatus for scrambling an original analog video signal samples predetermined portions of the original video signal at a first rate and stores the sampled portions of the original video signal within a memory device. The stored video signal is read out of the memory device at a second rate, which is less than the first rate, to produce a time expanded scrambled video signal. A predetermined code is inserted into the time expanded scrambled video signal which is then converted into an analog scrambled video signal and transmitted through a channel. A method and apparatus for descrambling the scrambled video signal to produce a reconstructed video signal samples the scrambled video signal at the second rate, stores the sampled scrambled video signal into a memory and reads the sampled scrambled video signal out of the memory at the first rate. Replicas of the eliminated portions of the original video signal are reinserted into the sampled video signal to produce a digital version of the original video signal which is then converted to analog to produce the reconstructed video signal. The code word within the scrambled video signal is used to align each frame of the reconstructed video signal with the frame of the incoming scrambled video signal to keep the reconstructed video signal synchronized with the scrambled video signal.

Method and apparatus for television signal scrambling using a line

A method and apparatus for scrambling video signals to obtain the secure transmission of video information. A block of video lines in a television raster is divided into top and bottom sub-block portions. The top and bottom sub-block portions are switched in position. The sequence of video lines within the sub-blocks are shuffled so that the resulting scrambled video signal contains blocks of video lines which have been block portion switched and shuffled from their original block portion position and their original line sequences. The size of the first block of video lines can grow and/or shrink in time so that the video appears to roll down or up the display. A pseudo-random number of sequence controls the shuffling sequence. A descrambler receives the scrambled video signal and a code identifying the shuffling sequence of the scrambled video for descrambling the video signal and returning the block portions and the video lines to their original sequences.

Method and apparatus for television signal scrambling using block

An encrypted video distribution system includes a signal originating station which distributes television signals in a format unrecoverable by a standard television receiver. In particular, the normally occurring vertical and horizontal synchronizing pulses are deleted and, optionally also, video information is selectively inverted about a voltage reference potential intermediate the black and white levels. To permit synchronization restoration, a keying pulse is transmitted once each video field, and a synchronizing digital code burst transmitted once each frame--all at a fixed, predetermined intra-frame timed relationship. At each authorized subscriber location, the keying pulse and digital code burst are employed to lock a receiver frame clock which derivatively gives rise to all requisite reception-permitting synchronizing pulses. The transmitted information also contains information sufficient to restore the inverted video program content.

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Doylestown, PA, United States of America

John T Griffin