Recording medium having copying protection signals recorded in superposition on main signals
First Claim
1. A reproducing apparatus for reproducing a recording medium having recorded thereon, as a Σ
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modulated 1-bit digital signal, an audio signal having a first band containing an audible range and a copying protection signal having a pre-set frequency in a second band separated from said first band and outside of the audible range of the audio signal, comprising;
reproducing means for reproducing the 1-bit digital signal containing said audio signal and said copying protection signal from said recording medium;
output means for outputting the 1-bit digital signal reproduced by said reproducing means;
first extraction means for extracting the audio signal having the first band from the 1-bit digital signal reproduced by said reproducing means;
second extraction means for extracting the copying protection signal contained in the second band from the 1-bit digital signal reproduced by said reproducing means; and
control means for inhibiting outputting of the 1-bit digital signal from said output means based on a presence of the copying protection signal extracted by said second extraction means, wherein said second extraction means includes;
filtering means for extracting the copying protection signal having the pre-set frequency contained in said second band from the 1-bit digital signal; and
comparator means for comparing a level of the copying protection signal extracted by said filtering means to a reference level, wherein when said comparator means finds that the level of the copying protection signal extracted by said filtering means is larger than said reference level said control means inhibits outputting of the 1-bit digital signal.
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Accused Products
Abstract
A signal processing apparatus in which an analog signal having a first band is summed to a copying protection signal having a pre-set frequency in a second band sufficiently separated from the first band and the resulting sum signal is converted into a 1-bit digital signal which is then recorded on a recording medium. Therefore, if a user annuls the copying protection on purpose, the sum signal is converted into a multi-bit signal at the time of removing the pre-set frequency, preventing the original 1-bit signal from being copied. Thus it becomes possible to inhibit copying of the 1-bit digital signal in the high-band high-quality state proper to the 1-bit digital signal.
35 Citations
3 Claims
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1. A reproducing apparatus for reproducing a recording medium having recorded thereon, as a Σ
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modulated 1-bit digital signal, an audio signal having a first band containing an audible range and a copying protection signal having a pre-set frequency in a second band separated from said first band and outside of the audible range of the audio signal, comprising;reproducing means for reproducing the 1-bit digital signal containing said audio signal and said copying protection signal from said recording medium; output means for outputting the 1-bit digital signal reproduced by said reproducing means; first extraction means for extracting the audio signal having the first band from the 1-bit digital signal reproduced by said reproducing means; second extraction means for extracting the copying protection signal contained in the second band from the 1-bit digital signal reproduced by said reproducing means; and control means for inhibiting outputting of the 1-bit digital signal from said output means based on a presence of the copying protection signal extracted by said second extraction means, wherein said second extraction means includes; filtering means for extracting the copying protection signal having the pre-set frequency contained in said second band from the 1-bit digital signal; and comparator means for comparing a level of the copying protection signal extracted by said filtering means to a reference level, wherein when said comparator means finds that the level of the copying protection signal extracted by said filtering means is larger than said reference level said control means inhibits outputting of the 1-bit digital signal. - View Dependent Claims (2, 3)
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Specification