Editing Compact Disc Digital Audio (section)

== Format variations ==
Recording publishers have created CDs that violate the ''Red Book'' standard. Some do so for the purpose of [[copy prevention]], using systems like [[Copy Control]]. Some do so for extra features such as [[DualDisc]], which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9&nbsp;mm, than required by the ''Red Book'', which stipulates a nominal 1.2&nbsp;mm, but at least 1.1&nbsp;mm. Philips and many other companies have stated that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement.

[[Super Audio CD]] was a standard published in 1999 that aimed to provide better audio quality than CDs. [[DVD-Audio]] emerged at around the same time.<ref name="Auto45-12" /> Both formats were designed to feature audio of higher fidelity by using a higher sampling rate and [[DVD]] media. Neither format was widely accepted.