Copy protection through symbol substitution and induced errors

An optical disc comprising:

• a combined data set written to the optical disc and formed from user data comprising a plurality of user data samples and a second data set comprising a plurality of second data set samples wherein each second data set sample is substituted for a corresponding one of the plurality of user data samples;
• a set of error correction codes corresponding to the combined data set;
• and
• an uncorrectable error written to each error correction code in the set of error correction codes corresponding to the second data set samples so that, when the optical disc is read by a readback system, the readback system will read each uncorrectable error and conceal the corresponding second data set sample while outputting a compensated output sample for the concealed second data set sample, wherein an unauthorized copy of the optical disc which fails to include the uncorrectable errors in the error correction codes will cause the readback system to produce an output signal comprising the user data samples with the second data set samples intermingled therein.

A digital data sequence stored on a recording medium and having a copy protection scheme encoded therein, the digital data sequence comprising:

• a combined data set formed from user data comprising a plurality of user data samples and a second data set comprising a plurality of second data set samples wherein each second data set sample is substituted for a corresponding one of the plurality of user data samples;
• a set of error correction codes corresponding to the combined data set;
• and
• an induced error written to each error correction code in the set of error correction codes corresponding to the second data set samples so that, when the data sequence is read by a readback system, the readback system will read each induced error and conceal the corresponding second data set sample while outputting a compensated output sample for the concealed second data set sample, wherein an unauthorized copy of the data sequence which fails to include the induced errors in the error correction codes will cause the readback system to produce an output signal comprising the user data samples with the second data set samples intermingled therein.