Session (CD)

Session (CD)

Compact Disc Digital Audio (CDDA or CD-DA) 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 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 as IEC 60908 (published in 1987). 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 standard is not freely available and must be licensed from Philips.

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.

It also specifies the form of digital audio encoding: 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz. This sampling rate is adapted from that attained when recording digital audio on a PAL (or NTSC) videotape with a PCM adaptor, an earlier way of storing digital audio. An audio CD can represent frequencies up to 22.05 kHz, the Nyquist frequency of the 44.1 kHz sample rate. Each sample is a signed 16-bit two's complement integer, sample values range from −32768 to +32767. Although rarely used, the specification allows for discs to be mastered with a form of emphasis.