Red Book CD

Red Book, which defines CD-Audio, is the compact disc patriarch. Compact disc was created, after all, to be nothing more or less than a universal delivery medium for one type of content only, namely music digitized at 44,100 samples per second (44.1KHz) and in a range of 65,536 possible values (16 bits). Red Book, or Compact Disc-Digital Audio (CD-DA), was defined by Philips N.V. and Sony Corporation in 1980.

Data on an audio disc is organized into frames in order to ensure a constant read rate. Each frame consists of 24 bytes of user data, plus synchronization, error correction, and control and display bits. One of the first crucial things to understand about CD-Audio is that its data is not arranged in distinct physical units. Instead, one frame is interleaved with many other frames so that a scratch or defect in the disc will not destroy a single frame beyond correction. Rather, a scratch will destroy a small portion of many frames, all of which can be recovered.

Red Book disc itself is divided into three areas: Lead In, Program, and Lead Out. Each track's location, or address, is recorded in the disc's TOC, or Table of Contents, which is stored in the Lead In area of every disc. Because pressed CDs are read-only, the number and location of the audio tracks to be recorded is known in advance, and the TOC is written to the disc (or more accurately, to the glass master that will be used to create metal stampers to mould discs) in advance of writing the actual audio data. An audio disc can contain up to 99 tracks, which are stored in the Program area. After the Program area is the Lead Out area, which is simply 90 seconds of silence, or blank sectors. The Lead Out area on an audio disc is essentially just a ham-fisted way to let CD-Audio players know the music is over.

All of this technical detail about Red Book would be eminently forgettable, except for one small fact: the Red Book specification is the base case for all other types of compact disc. Every disc that came after Red Book in the CD family includes the specs of  Red Book or refers to them. The physical, logical, and content description details of Red Book are the basic DNA of the compact disc, and everything that follows is either a specialization of these details, an adaptation, or a work-around. For example, the original strategy of data layout for safekeeping--interleaving files--shows up as a big factor in the fixed-length versus variable-length packet writing, in the current efforts behind the adoption of UDF (the Universal Disk Format) for CD-RW (CD-Rewritable). Packet writing for rewritability is just one instance of how all issues with compact disc come back to the father of all compact discs, Red Book. (Some argue, it is true, that the children may suffer for the sins of the father.)

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Last modified: January 08, 2008