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The CD Format
According to Red Book specifications, a standard CD is 120 mm (4.75 inches) in diameter and 1.2 mm (0.05 inches) thick and is composed of a polycarbonate plastic substrate (underlayer - this is the main body of the disc), one or more thin reflective metal (usually aluminum) layers, and a lacquer coating. CDs are divided into a lead-in area, which contains the table of contents (TOC), a program area, which contains the audio data, and a lead-out area, which contains no data. An audio CD can hold up to 74 minutes of recorded sound, and up to 99 separate tracks. Data on a CD-DA is organized into sectors (the smallest possible separately addressable block) of information. The audio information is stored in frames of 1/75 second length. 44,100 16-bit samples per second are stored, and there are two channels (left and right). This gives a sector size of 2,352 bytes per frame, which is the total size of a physical block on a CD.
CD data is not arranged in distinct physical units; data is organized into frames (consisting of 24 bytes of user data, plus synchronization, error correction, and control and display bits) which are intricately interleaved so that damage to the disc will not destroy any single frame, but only small parts of many frames.
The Red Book specifications form the basis for all later CD technologies.