Method and apparatus for protection of signal copy

Claim 1

An apparatus for detecting copy protection information from a reproduced signal from a recording medium which has recorded therein a signal which is to be protected from being copied and added to an echo signal thereof as the copy protection information, said apparatus comprising: a low cut filter for removing a low frequency component from the reproduced signal; a normalizing auto-correlation function calculator for calculating an auto-correlation function from an output signal of the low cut filter; a maximum function calculator for calculating a maximum value of the auto-correlation function in a specified time period from an output of the normalizing auto-correlation function calculator; a mean function calculator for calculating a mean value of the auto-correlation function in a specified time period from the output of the normalizing auto-correlation function calculator; and a level difference discriminator for determining if a difference between said maximum value and said mean value is within a specific range, and for indicating that the copy protection information is present in the reproduced signal when said difference is within said specific range.

Claim 2

An apparatus for detecting copy protection information from a reproduced signal from a recording medium which has recorded therein a signal which is to be protected from being copied and added to an echo signal thereof as the copy protection information, said apparatus comprising: a low cut filter for removing a low frequency component from the reproduced signal; a normalizing auto-correlation function calculator for calculating an auto-correlation function from an output signal of the low cut filter; a maximum function calculator for calculating a maximum value of the auto-correlation function in a specified time period from an output of the normalizing auto-correlation function calculator; a mean function calculator for calculating a mean value of the auto-correlation function in a specified time period from the output of the normalizing auto-correlation function calculator; and a level difference discriminator for determining if a difference between said maximum value and said mean value is within a specific range, and for indicating that the copy protection information is present in the reproduced signal when said difference is within said specific range.

Claim 3

An apparatus for detecting copy protection information from a reproduced signal from a recording medium which has recorded therein a signal which is to be protected from being copied and added with an echo signal thereof as the copy protection information, said apparatus comprising: a low cut filter for removing a low frequency component from the reproduced signal; a normalizing auto-correlation function calculator for calculating a self-correlation function from an output signal of said low cut filter; and a level discriminator for comparing a level of the auto-correlation function with a specific threshold level, and for determining that the copy protection information is present in the reproduced signal when the level of the auto-correlation function is higher than the threshold level.

Claim 4

An apparatus for detecting copy protection information from a reproduced signal from a recording medium which has recorded therein a signal which is to be protected from being copied and added with an echo signal thereof as the copy protection information, said apparatus comprising: a low cut filter for removing a low frequency component from the reproduced signal; a normalizing auto-correlation function calculator for calculating a self-correlation function from an output signal of said low cut filter; and a level discriminator for comparing a level of the auto-correlation function with a specific threshold level, and for determining that the copy protection information is present in the reproduced signal when the level of the auto-correlation function is higher than the threshold level.

Claim 5

An apparatus for copying copy-protected information having copy protected information showing that the copy-protected information is protected from being copied illegally, comprising: a storage means having stored therein a limited quantity of information; a detecting means for detecting the copy protection information from the copy-protected information and for detecting whether any information is stored in said storage means, wherein said detecting means, upon detection of the copy protection information, outputs a copy allowed signal when some information is stored in said storage means and a copy prohibiting signal in the absence of information being stored in said storage means; and a copying means responsive to said copy allowed signal for copying the copy-protected information while removing from said storage means a quantity of stored information proportional to a quantity of copied information, and responsive to said copy prohibiting signal for stopping the copying operation.

Claim 6

An apparatus for copying copy-protected information having copy protected information showing that the copy-protected information is protected from being copied illegally, comprising: a storage means having stored therein a limited quantity of information; a detecting means for detecting the copy protection information from the copy-protected information and for detecting whether any information is stored in said storage means, wherein said detecting means, upon detection of the copy protection information, outputs a copy allowed signal when some information is stored in said storage means and a copy prohibiting signal in the absence of information being stored in said storage means; and a copying means responsive to said copy allowed signal for copying the copy-protected information while removing from said storage means a quantity of stored information proportional to a quantity of copied information, and responsive to said copy prohibiting signal for stopping the copying operation.