The addition of text to the standard audio CD format. The original "Red Book" format, which came out in 1983, had no provision for storing album, artist and song titles in the disc, but CD Text added this capability in the late 1990s, although not every new CD includes the data.
The text is laid out in the Interactive Text Transmission System (ITTS) format, which is also used in digital broadcasting and MiniDiscs. ITTS text is coded and requires a translation table for display.
The ITTS-formatted text is stored in six of the eight subcode channels of the CD (R through W), each of which can hold 4MB. Subcode channels have been used by CD+G discs primarily for Karaoke lyrics. Newer drives/players read and display the subchannel text, while older units ignore it. See
music CD identification,
ID3 tag,
music search,
CD and
CD+G.