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Copy Control

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Copy control logo
Copy control logo

Copy control is the name of a compact disc copy-protection system used on recent EMI CD releases in some regions. The system is intended to prevent digital audio extraction from the protected CDs, and thus stop the file-sharing of ripped music. The techniques used are:

  • Multisession (Blue Book) information is included which effectively hides the audio tracks from most CD-ROM drives;
  • Error-correction codes for the audio data are corrupted, which may introduce audible errors to ripped copies.
  • The data area of the disc usually includes DRM-protected copies of the audio content, which are compatible with some major Operating systems such as Microsoft Windows.

It should be noted that the techniques used by Copy control make the discs incompliant with the Red Book standard for CD audio; hence, the discs cannot technically or officially be called 'Compact Discs'.

Circumvention

A copy-controlled disc will appear as a mixed-mode disc, with audio and data content. Under Windows, inserting the disc will usually autorun an audio player utility, which plays the DRM-protected audio files provided. (You may choose to temporarily disable this action by holding down SHIFT while inserting the CD.)

The ability to extract the CD-Audio tracks is otherwise largely dependent on the disc drive used. The first obstacle is the 'fake' Table of Contents (ToC), which is intended to mask the audio tracks from CD-ROM drives. On the other hand, CD-R/RW drives, and similar, can usually access all session data on a disc, and thus can properly read the audio segment. (It has been reported that the fake ToC may also be bypassed by obscuring the outer 2-4cm of the disc with a temporary felt-tip marker.)

The other major obstacle is the corrupted error-correction data. Again, the effect of this is dependent on the disc drive; some drives will be able to read the data without problems, but others will produce audio files with loud pops every few seconds. (A related problem is that copy-controlled discs will probably be less resilient to scratching.)

See also

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