The "Red Book" is the standard for audio CDs (Compact Disc Digital Audio system, or CDDA). The printed book has red covers - hence the name - and is one of a set of color-bound books that contain the technical specifications for all CD and CD-ROM formats.
The first edition of the "Red Book" was released in June 1980 by Philips and Sony; it was adopted by the Digital Audio Disc Committee and ratified as IEC 908. The standard is not freely available and CDGFix Crew has it licensed from Philips.
More specific the "Red Book" consists of three separate parts:
A specification of the physical parameters and properties of the CD, the optical "stylus" parameters, deviations and error rate, modulation system (Eight-to-Fourteen Modulation, EFM) and error correction (Cross-interleaved Reed-Solomon coding, CIRC).
Subcode/Control and Display System, channels R..W for CD TEXT mode - describing how text, for example titles and artist names, can be embedded on the CD.
Subcode/Control and Display System, channels R..W for CD GRAPHICS (CDG) - describing how graphics, for example lyrics, can be embedded on the CD.
CDGFix 3 Super relies on part 1 in the implementation of a software Reed Solomon error detection and correction module to provide error free ripping of CDG discs using almost any CD or DVD drive.
Part 3 of the "Red Book", that describes the CDG graphics format, was a requirement for correct implementation of a CDG playback engine. None of the CDG descriptions available at different locations on the Internet are fully correct when it comes to more or less subtle details in the instructions. Licensing the "Red Book" was therefore the only reasonable solution to developing a correct implementation CDG player. Also, while the "default" CDG implementation supports 16 colors only, the full CDG standard as described by the "Red Book" includes support for 256-color graphics. There are yet to be seen CDG discs utilizing the full 256 color capability, and should they appear they will play in a 16 color CDG decoder as well since the standard accounts for seamless reduction from 256 to 16 colors when the full range is not supported. While there are no immediate plans for it, a future version of CDGFix may support the 256 color extended CDG format.