Video scrambling, audio masking and data transmission methods for wireless cable systems
First Claim
1. In a television system of the type including a modulator receiving input signals from a video source and an audio source and providing a video intermediate frequency video modulating signal and an audio intermediate frequency modulating signal to a transmitter, said transmitter being responsive to said intermediate frequency video and audio modulating signals for transmitting a modulated radio frequency signal to a plurality of receiving sites, each of said receiving sites having a television receiver, the improvement comprising:
- said modulator including encoder means for scrambling the video and masking the audio intermediate frequency modulation signals, said encoder means further generating data signals as a sequence of binary "1s" and "0s", said data signals phase modulating video carrier during a horizontal blanking period, said modulator further including means for combining said scrambled video signals with said phase modulated video carrier, and said transmitter transmitting the combined video signal with said masked audio signal to said plurality of receiving sites; and
each of said receiving sites including a means for receiving said combined video signal and detecting said data signals and a converter responsive to said detected data signals for descrambling said video and unmasking said audio portions of received signals.
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Accused Products
Abstract
Video scrambling is accomplished by attenuating the video carrier during the horizontal blanking interval and/or by omitting horizontal sync pulses, vertical serration pulses and equalizing pulses. The method of scrambling can be dynamically changed, but this is done only at the change of scenes. Audio masking and data transmission is accomplished via phase modulation of the video carrier. At the receiver, timing signals for unscrambling video and unmasking audio are obtained from the transmitted data. The system addresses problems that exist in wireless cable systems, but are not present in cabled systems.
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Citations
40 Claims
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1. In a television system of the type including a modulator receiving input signals from a video source and an audio source and providing a video intermediate frequency video modulating signal and an audio intermediate frequency modulating signal to a transmitter, said transmitter being responsive to said intermediate frequency video and audio modulating signals for transmitting a modulated radio frequency signal to a plurality of receiving sites, each of said receiving sites having a television receiver, the improvement comprising:
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said modulator including encoder means for scrambling the video and masking the audio intermediate frequency modulation signals, said encoder means further generating data signals as a sequence of binary "1s" and "0s", said data signals phase modulating video carrier during a horizontal blanking period, said modulator further including means for combining said scrambled video signals with said phase modulated video carrier, and said transmitter transmitting the combined video signal with said masked audio signal to said plurality of receiving sites; and each of said receiving sites including a means for receiving said combined video signal and detecting said data signals and a converter responsive to said detected data signals for descrambling said video and unmasking said audio portions of received signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An encryptor for a transmitter of a television system comprising:
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buffer means for receiving baseband video signals; video scrambling means connected to said buffer means for scrambling video signals; data insertion means connected to said video scrambling means for phase modulating a video carrier during a horizontal blanking period to represent a sequence of binary "1s" and "0"; and audio masking means connected to said video scrambling means for reversing the phase of said video carrier during a portion of each field thereby masking audio signals which are transmitted with said video signals; said sequence of binary "1s" and "0s" conveying data for descrambling said video signals and unmasking said audio signals. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A converter for use in a television system of the type wherein video signals are scrambled and audio signals are masked and composite signals are transmitted with data signals as a sequence of binary "1s" and "0s", said data signals phase modulating a video carrier during a horizontal blanking period, said converter comprising:
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tuner means for receiving transmitted composite signals and separating audio signals from video signals into intermediate frequency audio and video signals; data signal detecting means connected to said tuner means and responsive to said video intermediate frequency signals for detecting said data signals; descrambling means connected to tuner means and responsive to said data signals for descrambling said video signals; and unmasking means connected to said descrambling means and responsive to said data signals for unmasking audio signals. - View Dependent Claims (33, 34, 35, 36)
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37. A phase modulator for a television transmitter, said phase modulator being used to mask the audio in a television signal and comprising:
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means for generating data signals as a sequence of binary "1s" and "0s"; means for phase modulating a video carrier of said television transmitter with said data signals during a horizontal blanking period, wherein said means for phase modulating the video carrier produces two or more phase changes in said video carrier during a horizontal blanking period and wherein a relative position of one of said phase changes with respect to another of said phase changes is varied to represent a binary bit of data; and said television transmitter transmitting the phase modulated video carrier.
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38. A phase modulator for a television transmitter, said phase modulator being used to mask the audio in a television signal and comprising:
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means for generating data signals as a sequence of binary "1s" and "0s"; means for phase modulating a video carrier of said television transmitter with said data signals during a horizontal blanking period, wherein the phase changes representing binary "1s" and "0s" differ in magnitude and wherein said means for phase modulating the video carrier produces two or more phase changes in said video carrier during a horizontal blanking period, each of said phase changes representing a binary bit of data, and wherein a relative position of one of said phase changes with respect to another of said phase changes is varied to represent a binary bit of data; and said television transmitter transmitting the phase modulated video carrier.
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39. A phase modulator for a television transmitter, said phase modulator being used to mask the audio in a television signal and comprising:
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means for generating data signals as a sequence of binary "1s" and "0s"; means for phase modulating a video carrier of said television transmitter with said data signals during a horizontal blanking period, wherein the phase changes representing binary "1s" and "0s" differ in polarity; and said television transmitter transmitting the phase modulated video carrier. - View Dependent Claims (40)
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Specification