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The success of CD audio in the consumer market has been made possible, in part, by the licensing of the fundamental technologies to all who wanted to enter the market. The resulting competition for market share has generated a wide variety of low-cost consumer CD products and a large established manufacturing capacity for CD media. The success of the basic CD audio technology has vastly improved the viability of several spin-off technologies by generating extensive technical proficiency related to CDs in the engineering community, as well as providing the necessary production volumes to amortize most of the manufacturing capacity required to support the production of other CD-related products and publications.
The so-called "Red Book" specification formally describes the CD-DA media size and structure, data encoding technology (including a sophisticated error-correction scheme), and low-level data recording mechanisms. CDs are a purely digital medium, which has allowed extension of the technology to support distribution of digital computer data. The general computer data version, CD-ROM, is described in a document known as the "Yellow Book." This document was released, and early development of a commercial CD-ROM market begun, in the mid-1980s.
Computer data requires substantially higher data reliability than audio data does, so the fundamental difference between CD-DA and CD-ROM encoding involves a second layer of error correction, which brings the data integrity up to a level competitive with hard disks. Mixed-Mode disks can also be created where the first track on the disk contains CD-ROM format digital data and all other tracks contain CD-DA format audio data. While a CD audio player will treat the data track as useless noise, a CD-ROM player with audio outputs can usually play the audio tracks under computer control, but generally cannot read the audio tracks as digital data without hardware modifications to the drive.
COMPACT DISK-INTERACTIVE
A third CD-based format, known as Compact Disk-Interactive, or CD-I, targets entertainment, educational and commercial applications of basic multimedia technology. Unlike the previously mentioned formats, the CD-I "Green Book" did not restrict itself to media and data recording specifications, but proceeded to define virtually all aspects of the entire receiving system, including the microprocessor, operating system and major data formats to be used While such attention to details may have been necessary to realistically...