Video scrambling with variable function generator
OwnerH. George Piresinventor
Life of this patent
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Abstract
A video scrambling and descrambling arrangement utilizes plural scrambling characteristics including a predetermined scrambling waveform and a selectable one of a plurality of phase relationships with respect to the video signal to be scrambled. Descrambling is achieved by combining with the scrambled video signal a correspondingly phase shifted, inverted version of the scrambling signal. Scrambling and descrambling can be implemented in analogue or digital forms. The information required to achieve descrambling is contained in the scrambled video signal, preferably in an unscrambled portion thereof.
Claims32
A system for supplying video information contained in a video signal from a sending station exclusively to a receiving station authorized to receive the video information, the system comprising:
- a scrambling system, coupled at an input thereof to the sending station for receiving the video signal, for distorting at least a portion of the video signal to produce a distorted video signal which is distorted in accordance with a selected one of a plurality of distortion modes, each distortion mode corresponding to a respective one of a plurality of predetermined angular phase variations of a predetermined video distortion characteristic to produce a corresponding distortion in said distorted video signal;
- security code encoder means coupled to said scrambling system for encoding in a portion of the video signal security data which identifies said selected one of said plurality of distortion modes being applied to the video signal to produce said distorted video signal;
- security code decoder means coupled to the receiving station for decoding said video signal security data;
- and
- a descrambling system, coupled to the receiving station for receiving the distorted video signal and to said security code decoder means, for restoring the video signal in response to said video signal security data received from said security code decoder means, whereby said selected one of said plurality of distortion modes is reversed to produce a corresponding correction in said distorted video signal.
A decoder system for receiving and descrambling a scrambled video signal, the decoder system comprising:
- signal generator means for generating a plurality of distortion mode correction signals, each distortion mode correction signal corresponding to a respective one of a plurality of predetermined angular phase variations of a predetermined video distortion characteristic of the scrambled video signal to produce a corresponding correction in the scrambled video signal;
- code detector means for providing a scramble code representing said respective one of a plurality of predetermined angular phase variations of said predetermined video distortion characteristic of the scrambled video signal;
- and
- signal combining means for combining the scrambled video signal with a respective one of said distortion mode correction signals selected in response to said code detector means.
An encoder system for receiving a video signal and forming a scrambled video signal, the encoder system comprising:
- scrambling signal generator means for generating a plurality of distortion mode signals, each distortion mode signal corresponding to a respective one of a plurality of predetermined angular phase variations of a predetermined video distortion characteristic of the scrambled video signal;
- code generator means for providing a scramble code which identifies said respective one of a plurality of predetermined angular phase variations of said predetermined video distortion characteristic of the scrambled video signal;
- and
- signal combining means for combining the video signal with said respective one of said distortion mode signals identified by said code generator means.
A method of unscrambling a scrambled video signal received at a receiving station, the scrambled video signal having a plurality of potential scramble modes, the method comprising the steps of:
- detecting a scramble code which identifies a phase-related scramble mode of the scrambled video signal;
- generating a plurality of possible phase-related correction signals, each having the capacity to correct for a respectively associated one of the plurality of potential scramble modes of the scrambled video signal;
- selecting one of said plurality of possible phase-related correction signals in response to said scramble code;
- and
- combining the scrambled video signal with said selected one of said plurality of possible phase-related correction signals, whereby the scrambled video signal is unscrambled.
A method of unscrambling a scrambled video signal received at a receiving station, the scrambled video signal having a plurality of potential scramble modes and being of the type having a plurality of sequential horizontal intervals, the method comprising the steps of:
- determining a first scramble characteristic of the scrambled video signal, said first scramble characteristic corresponding to a predetermined time displacement relationship between the sequential horizontal intervals;
- detecting a second scramble characteristic of the scrambled video signal, said second scramble characteristic corresponding to a timing phase relationship between said first scramble characteristic of the scrambled video signal and a predetermined one of the sequential horizontal intervals;
- determining in response to said step of detecting a one of a plurality of predetermined timing phase relationships between said first scramble characteristic of the scrambled video signal and a predetermined one of the sequential horizontal intervals that has been applied to the scrambled video signal;
- generating a correction signal responsive to the one of the plurality of predetermined phase relationships identified in said step of determining which has been applied to the scrambled video signal for correcting for a distortion effect in the scrambled video signal, said correction signal having a first unscramble characteristic corresponding to an inversion of said first scramble characteristic, and a second unscramble characteristic corresponding to the one of said plurality of timing phase relationships identified in said step of determining;
- and
- combining the scrambled video signal with said correction signal, whereby the scrambled video signal is unscrambled.
Dependencies are inferred from the claim text.