Macrovision said its anti-piracy technologies have now been employed on 100 million music CDs, mostly in Europe and Asia. The company’s software creates what are known as “dual-session” discs, which have the music encoded both in standard Red Book audio format and in another, copy-protected, format.
If the disc is put into a computer, software on the disc plays the copy-protected version of the songs, preventing them from being burned to the computer’s hard drive or rewritable CD copies.
Dual-session approaches have been controversial, with some users reporting problems getting the discs to play in regular CD players. Some have been able to defeat copy protections by covering key areas of the disc with a black marker or precisely applied sticky note.