Compact Disc subcode
Subcode or subchannel data (called control bytes in the CD-ROM specification) is data contained in a compact disc (CD) in addition to digital audio or user data, which is used for control and playback of the CD. The original specification was defined in the Red Book standard for Compact Disc Digital Audio, though further specifications have extended their use (including the CD-ROM, CD Text and CD+G specifications). == Structure == Subchannel data is multiplexed with the digital audio or user digital data.