Abstract: The ability of a data reader, such as a CD-ROM drive, to access, extract, or otherwise read the data on a digital audio compact disc 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. To provide copy protection, errors are deliberately introduced into the data on a CD, but these errors are of a type which are generally transparent to an audio player but which will interfere with the reading of the audio data by a data reader. According to the standards, the data on a CD is encoded into frames by EFM (eight to fourteen modulation). Each frame has sync data, sub-code bits providing control and display symbols, data bits and parity bits, and includes 24 bytes of data, which is audio data for a CD-DA. The standard requires that 98 such frames are grouped into a sector. To provide copy protection, each is provided with a non-standard number of frames, for example, has 99 rather than 98 frames.

Abstract: 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.

Abstract: The ability of a data reader, such as a CD-ROM drive, to access, extract, or otherwise read the data on a digital audio compact disc 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. To provide copy protecton, errors are deliberately introduced into the data on a CD, but these errors are of a type which are generally transparent to an audio player but which will interfere with the reading of the audio data by a data reader. According to the standards, the data on a CD is encoded into frames by EFM (eight to fourteen modulation). Each frame has sync data, sub-code bits providing control and display symbols, data bits and parity bits, and includes 24 bytes of data, which is audio data for a CD-DA. The standard requires that 98 such frames are grouped into a sector. To provide copy protection, each is provided with a non-standard number of frames, for example, has 99 rather than 98 frames.