Patent ID: 7023785

Claim:
A method for manufacturing a record carrier which can be copied with the aid of a copying apparatus, whilst the copied record carrier is unreadable, which original record carrier is provided with a series of binary data bits which has been encoded into a series of binary channel bits, which series of data bits has been divided into consecutive blocks ( 5 ) of m data bits each, which blocks ( 5 ) have been encoded into consecutive blocks ( 2 ) of (n 1 +n 2 ) channel bits ((n 1 +n 2 )>m), which blocks of channel bits ( 2 ) each comprise a block ( 3 ) of n 1 information bits and a block ( 4 ) of n 2 merge bits, wherein consecutive blocks of information bits ( 3 ) are separated in each case by a block of merge bits, while during copying with the aid of the copying apparatus, the merge bits are selected such that consecutive channel bits of a first type, the type “1”, are separated by at least Ia and at most Ib consecutive and continuous bits of the second type, the type “0”, and vice versa, characterized in that the original record carrier, at least over a number of neighboring blocks of channel bits ( 2 ), is provided with specific blocks of merge bits ( 4 ), while consecutive channel bits of one type are separated by at most Ic or at least Id consecutive bits of the other type, with Ic<Ia and Id>Ib, as a result of which, in a record carrier copied with the aid of the copying apparatus, a digital sum variance, which is proportional to a difference, present over a number of blocks of channel bits, between the number of channel bits of the one type and the number of channel bits of the other type, becomes impermissibly large.