Trw Limited

Thomas G Schnerk

Gregory A Shreve

Peter L McAdam

A television signal encoding and decoding system providing a line-spin scrambled video signal with substantially reduced amplitude gaps and line tilt and a digitally-encrypted audio signal that can be transmitted within the bandwidth limitations of a conventional NTSC television signal. The television signal encoding system, located at a television transmitter, includes a video and an audio encoder. The video encoder selectively line spin scrambles, reverses and inverts certain video lines or video line segments to generate a line-spin scrambled video signal having amplitude gaps less than some desired value. The audio encoder digitally encrypts the audio signal and modulates the encrypted audio signal with a three-level partial response waveform to generate and encrypted audio signal that can be transmitted within the bandwidth limitations of a conventional NTSC television signal. The television signal decoding system, located at a television receiver, includes a video and an audio decoder. The video decoder applies line tilt compensation to the received line-spin scrambled video signal and then unscrambles the compensated scrambled video signal. The audio decoder demodulates and decrypts the received audio signal.

Secure television signal encoding and decoding system

A method and apparatus for modulating and demodulating a digitized stereo audio signal with a 3-level, partial response waveform. The 3-level, partial response waveform utilizes 3-level coded pulses rather than conventional on-off or 2-level coded pulses. This results in a bandwidth reduction of approximately 50% over the conventional 2-level coded pulses and allows the stereo audio signal to be transmitted within the bandwidth limitations of conventional television transmission systems, without first compressing or reducing the sampling rate of the stereo audio signal. For transmission over statellite-based systems, the modulated stereo audio signal is digitally up-converted to a 6.6 MHz quadrature subcarrier. For transmission over ground-based systems, the modulated audio signal is multiplexed into the video signal during the video horizontal blanking interval.

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Rancho Palos Verdes, CA, United States of America

Thomas G Schnerk