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US 2002/0159591 A1Published application
The copy protection of digital audio compact discs
OwnerRichard AA Heylen, Roger Edwardinventors
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OwnerRichard AA Heylen, Roger Edwardinventors
Estimating the term…
The ability of a data reader to access, extract, or otherwise read the data on a CD-DA provides a problem for the music industry. A user can use his CD-ROM drive to read the data from an audio disc into a computer file, and then that data can be copied. Therefore, errors are deliberately introduced into the encoded data, these errors being of a type which are generally transparent to an audio player but which will interfere with the extraction or reading of the audio data by a data reader. The data on a CD is encoded into frames by EFM (eight to fourteen modulation), and each frame includes 24 bytes of audio data. There are 8 sub-code bits contained in every frame which enable 8 different subchannels, P to W, to be formed. The P- and Q-subchannels incorporate timing and navigation data for the tracks on the disc, and generally are the only subchannels utilised on an audio disc. It is the timing and/or navigation data in the P- and Q-subchannels which is rendered incorrect or inaccurate to provide the copy protection.
A method of copy protecting a digital audio compact disc, wherein control data is encoded on the compact disc, the copy protection method comprising the step of rendering selected control data incorrect and/or inaccurate whereby the incorrect and/or inaccurate control data interferes with the reading of audio data from the digital audio compact disc.
A copy protection method as claimed in any preceding claim, wherein the data encoded on the compact disc which has been rendered incorrect is navigation and/or timing data.
A copy protection method as claimed in any preceding claim, for use where frames of control data are read into a frame content buffer of a data reader, wherein the number of data frames in a sector with incorrect control data is arranged to exceed the number of data frames which can be held in the frame content buffer.
A copy protection method as claimed in any preceding claim, wherein the control data encoded on the compact disc is altered prior to mastering of the disc.
A copy protected digital audio compact disc, wherein control data is encoded on the compact disc, and wherein selected control data has been rendered incorrect and/or inaccurate, the incorrect and/or inaccurate control data being arranged to interfere with the reading of audio data from the digital audio compact disc.
A method of copy protecting a digital audio compact disc substantially as hereinbefore described with reference to the accompanying drawings.
A copy protected digital audio compact disc substantially as hereinbefore described with reference to the accompanying drawings.
Dependencies are inferred from the claim text.