Method and system for scrambling and descrambling audio information signals
First Claim
1. A method of scrambling audio information signals having frequency components lying within an original frequency spectrum, said method comprising the steps of:
- (a) frequency shifting original time domain audio information signals to produce scrambled audio information signals;
(b) generating a pilot signal of a preselected frequency; and
(c) recording both the scrambled audio information signals and the pilot signal on a common recording medium so that any frequency variations introduced in the scrambled audio signals upon playback are tracked by the pilot signal.
3 Assignments
0 Petitions
Accused Products
Abstract
Audio signals are scrambled by inverting the original; frequency spectrum so that frequency portions originally lying at the lower end of the audio frequency band are shifted to the upper end while those portions originally lying near the upper end of the band are shifted to the lower end. A pilot tone of known frequency is recorded along with the frequency shifted audio signals, along with accompanying video signal portions. Upon reproduction, any variations in phase and frequency introduction by the recording or reproduction process are tracked by the pilot tone, which is used to generate the demodulation signal for restoring the original frequency content of the audio signals.
18 Citations
22 Claims
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1. A method of scrambling audio information signals having frequency components lying within an original frequency spectrum, said method comprising the steps of:
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(a) frequency shifting original time domain audio information signals to produce scrambled audio information signals; (b) generating a pilot signal of a preselected frequency; and (c) recording both the scrambled audio information signals and the pilot signal on a common recording medium so that any frequency variations introduced in the scrambled audio signals upon playback are tracked by the pilot signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of descrambling audio information signals previously scrambled by frequency shifting original time domain audio information signals having frequency components lying within an original frequency spectrum and recording the frequency shifted audio information signals along with a pilot signal having a preselected frequency, said descrambling method comprising the steps of:
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(a) reproducing the scrambled audio information signal and the pilot signal; (b) using the pilot signal to generate a frequency restoring demodulation signal containing any frequency variations introduced by step (a); and (c) demodulating the reproduced scrambled audio information signals with the demodulation signal from step (b) to produce final audio information signals lying within the original frequency spectrum. - View Dependent Claims (9, 10, 11)
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12. A system for scrambling audio information signals having frequency components lying within an original frequency spectrum, said system comprising:
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means for frequency shifting original time domain audio information signals to produce scrambled audio information signals; means for generating a pilot signal of a preselected frequency; and means for combining the scrambled audio information signal and the pilot signal prior to recording on a common recording medium so that any frequency variations introduced in the scrambled audio signals upon playback are tracked by the pilot signal. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A system for descrambling audio information signals previously scrambled by frequency shifting original time domain audio information signals having frequency components lying within an original frequency spectrum and recording the frequency shifted audio information signals along with a pilot signal having a predetermined frequency, said descrambling system comprising:
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means for reproducing the scrambled audio information signals and the pilot signal; means responsive to the pilot signal for generating a frequency restoring demodulation signal; and means responsive to the demodulation signal for demodulating the reproduced scrambled audio information signals to produce final audio information signals lying within the original frequency spectrum and substantially devoid of any frequency variations introduced in the scrambled audio information signals upon reproduction. - View Dependent Claims (20, 21, 22)
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Specification