TheBlue Book is acompact disc standard developed in 1995 byPhilips andSony. It defines theEnhanced Music CD format (E-CD, also known asCD-Extra,CD-Plus andCD+), which combinesaudio tracks anddata tracks on the same disc.[1] The format was created as a way to solve the problem ofmixed mode CDs, which were not properly supported by manyCD players.[1]
E-CDs are created through thestamped multisession technology, which creates twosessions on a disc. The first session of an E-CD contains audio tracks according to theRed Book. As a consequence, existingcompact disc players can play back this first session as an audio disc. The second session containsCD-ROM data files with content often related to the audio tracks in the first session. The second session will only be used by computer systems equipped with a CD-ROM drive, or by special “Enhanced CD players”.[1]
The second session of a E-CD contains one track inCD-ROM XA Mode 2, Form 1 format. It must contain certain specific files inside anISO 9660file system, though anHFS file system may also be included for compatibility with theclassic Mac OS. The mandatory files and directories include anautorun.inf file compatible with theWindows 95 AutoRun feature; a CDPLUS and a PICTURES directories; and an optional DATA directory.[2]
The technology was originally developed byAlbhy Galuten who, along with Ty Roberts brought the idea to the majorrecord labels where it was built into commercial releases. There were other technologies that solved the same problem, but they were not compatible with many existing CD players and so this approach was brought to Sony and Philips where it was written into the Blue Book standard.
The term "enhanced CD" is also an umbrella term and a certification mark used to refer to different CD formats that support audio and data content, includingmixed mode CDs,CD-i andCD-i Ready.