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Writable compact discs

Recordable CD

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Recordable Compact Discs, CD-Rs, are injection-molded with a "blank" data spiral. A photosensitive dye is then applied, after which the discs are metalized and lacquer-coated. The write laser of the CD recorder changes the colour of the dye to allow the read laser of a standard CD player to see the data, just as it would with a standard stamped disc. The resulting discs can be read by most CD-ROM drives and played in most audio CD players. CD-Rs follow the Orange Book standard.

CD-R recordings are designed to be permanent. Over time, the dye's physical characteristics may change causing read errors and data loss until the reading device cannot recover with error correction methods. The design life is from 20 to 100 years, depending on the quality of the discs, the quality of the writing drive, and storage conditions. However, testing has demonstrated such degradation of some discs in as little as 18 months under normal storage conditions.<ref name="AutoMR-14" /><ref name="AutoMR-15" /> This failure is known as disc rot, for which there are several, mostly environmental, reasons.<ref name="clir" />

The recordable audio CD is designed to be used in a consumer audio CD recorder. These consumer audio CD recorders use SCMS (Serial Copy Management System), an early form of digital rights management (DRM), to conform to the AHRA (Audio Home Recording Act). The Recordable Audio CD is typically somewhat more expensive than CD-R due to lower production volume and a 3% AHRA royalty used to compensate the music industry for the making of a copy.<ref name="McFadden" />

High-capacity recordable CD is a higher-density recording format that can hold 90 or 99 minutes of audio on a {{safesubst:#invoke:convert|convert}} disc (compared to about 80 minutes for Red Book audio) or 30 minutes of audio on an {{safesubst:#invoke:convert|convert}} disc (compared to about 24 minutes for Red Book audio).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The higher capacity is incompatible with some recorders and recording software.<ref name="cdrfaq">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

ReWritable CD

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CD-RW is a re-recordable medium that uses a metallic alloy instead of a die. The write laser in this case is used to heat and alter the properties (amorphous vs. crystalline) of the alloy, and hence change its reflectivity. A CD-RW does not have as great a difference in reflectivity as a pressed CD or a CD-R, and so many earlier CD audio players cannot read CD-RW discs, although most later CD audio players and stand-alone DVD players can. CD-RWs follow the Orange Book standard.

The ReWritable Audio CD is designed to be used in a consumer audio CD recorder, which will not (without modification) accept standard CD-RW discs. These consumer audio CD recorders use the Serial Copy Management System (SCMS), an early form of digital rights management (DRM), to conform to the United States' Audio Home Recording Act (AHRA). The ReWritable Audio CD is typically somewhat more expensive than CD-RW due to (a) lower volume and (b) a 3% AHRA royalty used to compensate the music industry for the making of a copy.<ref name="McFadden" />

Speed

Due to technical limitations, the original ReWritable CD could be written no faster than 4x speed. High Speed ReWritable CD has a different design, which permits writing at speeds ranging from 4x to 12x. Original CD-RW drives can only write to original ReWritable CDs. High Speed CD-RW drives can typically write to both original ReWritable CDs and High Speed ReWritable CDs. Both types of CD-RW discs can be read in most CD drives. Higher speed CD-RW discs, Ultra Speed (16x to 24x write speed) and Ultra Speed+ (32x write speed) are now available.


Compact disc sections
Intro   History    Physical details    Logical formats    Manufacture    Writable compact discs    Copy protection    See also    References    Further reading    External links   

Writable compact discs
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