Compact Disc Digital Audio is the standard format for audio compact discs. The standard is defined in the Red Book, one of a series of "Rainbow Books" (named for their binding colors) that contain the technical specifications for all CD formats.
The Red Book specifies the physical parameters and properties of the CD, the optical "stylus" parameters, deviations and error rate, modulation system (eight-to-fourteen modulation, EFM) and error correction facility (cross-interleaved Reed–Solomon coding, CIRC), and the eight subcode channels. These parameters are common to all compact discs and used by all logical formats, such as CD-ROM. The standard also specifies the form of digital audio encoding: 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz. Although rarely used, the specification allows for discs to be mastered with a form of emphasis.
The first edition of the Red Book was released in 1980 by Philips and Sony; it was adopted by the Digital Audio Disc Committee and ratified by the International Electrotechnical Commission Technical Committee 100, as an International Standard in 1987 with the reference IEC 60908. The second edition of IEC 60908 was published in 1999 and it cancels and replaces the first edition, amendment 1 (1992) and the corrigendum to amendment 1. The IEC 60908, however, does not contain all the information for extensions that is available in the Red Book, such as the details for CD-Text, CD+G, and CD+EG.
The standard is not freely available and must be licensed. It is available from Philips and the IEC. As of 2013, Philips outsources licensing of the standard to Adminius, which charges US$100 for the Red Book, plus US$50 each for the Subcode Channels R-W and CD-Text Mode annexes.