Red Book standard

The Compact Disc Digital Audio (CD-DA or just CD) standard made by Philips and Sony in the early 1980s became the de facto standard for all audio discs, and means that any CD plays on any audio CD drive.

This standard became known as the Red Book. It's specifies that the audio data is on the CD in one or more tracks. Each track is normally one song. These tracks are further subdivided into sectors that are 1/75 of a second in length and contain 2352 bytes of audio data in digital form.

A maximum of 99 audio tracks may be placed on a standard Red Book disc.

In addition to the 2352 bytes of audio data, the Red Book specifies the addition of 2 layers of error detection and error correction code (EDC/ECC). The compact disc utilises the Cross Interleave Reed-Solomon Code (CIRC) in its first two layers of error protection. If a disc gets scratched or dirty and a laser cannot read the data, the CD player uses the CIRC to recreate the music.

Each sector is also assigned 98 control bytes, which control the timing information that the CD player uses to display the length of each song.


Yellow Book standard

This standard also was introduced by Philips and Sony in 1984 which defined the Compact Disc Read Only Memory (CD-ROM) layout.

The Yellow Book further defined the Red Book by adding two new types of tracks.

The track type defined in the Red Book is:

* CD-Audio, for audio music.

The two new track types defined in the Yellow Book are:

* CD-ROM Mode 1 for computer data.

* CD-ROM Mode 2 for compressed audio data, and video/picture data. Also, usually further defined as XA (eXtended Architecture).

The CD-ROM Mode 1 and Mode 2 tracks use the Red Book specifications as a foundation. The difference between the Red Book and the Yellow Book is a redefinition of the 2352 byte Red Book data area.
The Yellow Book CD-ROM Mode 1 and Mode 2 use the same track layout as the Red Book specification, including the error correction and control bytes. The fundamental difference between the two Yellow Book CD-ROM modes is the way in which they use the main data segment.
The Yellow Book CD-ROM Mode 1 defines the ISO 9960 and non-ISO 9660 standards. The ISO 9660 compliant CD-ROMs are readable by any kind of (modern) operating systems, such as DOS, UNIX, MacOS, AmigaDOS and other OSes.

The CD-ROM Mode 1 divides the 2352 byte data area defined by the Red Book standards into the following:

* 12 bytes of synchronisation,

* 4 bytes of header information,

* 2048 bytes of user information,

* 288 bytes of error correction and detection codes.

The first 16 bytes contain the synchronisation and header information that the computer uses to determine which sector it is reading. The following 2048 bytes contain the actual user data. Together, these two subdivisions comprise the full 2352 byte portion of the Red Book standard.
The last 288 bytes carry an additional layer of error correction and direction code. This additional layer, which is found only in Mode 1, provides the reliability that is needed for certain types of computer data.
CD-ROM Mode 2 redefines the use of the 2352 byte data area as follows:

* 12 bytes of synchronisation,

* 4 bytes of header information,

* 2336 bytes of user data.

The main advantage of Mode 2 is that it provides an additional 14 per cent of the user data space per sector (2336 versus 2048 bytes). The reason is that Mode 2 does not have the additional EDC and ECC error correction data of Mode 1.

Mode 2 discs are normally used in extended architecture (XA) format. Even without XA, there are still two layers of error correction as defined in the Red Book standard. CD-ROM Mode 2 discs can be read by a standard CD-ROM drive, but require special software to decode and strip the user data from each sector.

CD-ROM Mode 2 allows compressed audio data and video/picture data to be incorporated on the disc, thanks to the alignment of the byte layout. The drawback is that a CD-ROM drive reading this data cannot read computer data while it's playing audio.

The next step in CD technology was to create a file format that lent itself to the incorporation of audio and video/picture data. To define this extension to the Yellow Book standard, Sony and Philips produced the Compact Disc Read Only Memory Extended Architecture (CD-ROM/XA). The XA disc has compressed audioand computer data interleaved on the same track, so it can read the computer data and play audio on the same time.

This was a dramatic improvement on existing Yellow Book technology, and marks the point from which application discs that made best use of CD-ROM technology started to develop. CD-ROM/XA Mode 2 is subdivided into Form 1 (for computer data) and Form 2 (for compressed audio data and video/picture data).


Green Book standard

The Compact Disc Interactive (CD-I) Media standard was released in 1987 by Philips. This standard specifies the CD-I disc layout and an operating system called CD-RTOS. This specification is known as the Green Book standard. Like CD-ROM/XA, this standard allows for the interleaving of computer data and compressed audio on the same track. The CD-I track is not shown in the table of contents on the disc. This prevents audio players from playing the CD-I track. The sector layout of a CD-I disc is identical to CD-ROM/XA. A CD-I system consists of a stand-alone CD-I player connected to a TV set.

Remember, the main drawback of a CD-ROM is, at least for some people, that it is a read-only medium (the ROM part of it's name)! Writable mediums were needed to fulfil new (created) needs.


Orange Book standard

In Frankfurt (Germany) a group was formed (guess the name) — the Frankfurt Group — which includes Philips, Sony, Kodak and others to take CD-ROM into the writable market. This became the Orange Book standard defining a CD that lets users write audio and/or data to disc.

Part 1 of the Orange Book describes a Compact Disc-Magneto Optical (CD-MO) where data can be written, erased and rewritten.

Part 2 describes a Compact Disc Write Once (CD-WO) where data can be written but not erased. The CD-WO is better known under it?s name CD-R where R stands for recordable. CD writers are becoming quite popular these days (and affordable).

Read CD-ROM hardware →