Patent ID: 6718501
Filing Date: 2004-04-06
Classification: G11B

Abstract:
A method for producing a copy-protected audio compact disc containing a plurality of symbols within error-correction codewords representing audio data samples of an audio signal, by including latent noise on the copy-protected audio compact disc which does not interfere with the playback of the audio signal from the audio compact disc on an ordinary audio player, but which interferes with the unauthorized copying of the audio compact disc on an ordinary CD recorder and with the playback of an unauthorized copy of the audio compact disc made on an ordinary CD recorder, the method comprising the steps of:(a) selecting at least one audio data sample of the audio signal; (b) locating the data symbols representing said at least one audio data sample; (c) overwriting said data symbols with erroneous symbols; (d) locating the error-correction codewords which contain said data symbols; and (e) disabling the error-correction of said error-correction codewords.