Besides digital audio, a Compact Disc contains digital data called "subcode", which is multiplexed with the digital audio. The data in a CD are arranged in frames. A frame comprises 33 bytes, of which 24 are audio bytes (six full stereo samples), eight error correction, CIRC-generated, bytes plus one subcode byte. The eight bits of a subcode byte are available for control and display. The eight bits are used as eight different subcoding channels, and given letters designating their usage: P, Q, …, W. Thus each channel has a bit rate of 7.35 (=44.1/6) kbit/s. The Compact Disc logo was inspired by that of the previous Compact Cassette. ... In the Compact Disc system, error correction and detection is provided by Cross-Interleaved Reed-Solomon Code. ...

In each sector there are 2352 bytes (24×98) of audio content data and 96 bytes of subchannel data. A byte is commonly used as a unit of storage measurement in computers, regardless of the type of data being stored. ...

The 96 bytes of subchannel information in each sector contain four packets of 24 bytes apiece:

1 byte for command, 1 byte for instruction, 2 bytes for parityQ, 16 bytes for data, and 4 bytes parityP.

Each of the 96 subchannel data bytes can be thought of as being divided into eight bits. Each of these bits corresponds to a separate stream of information. These streams are called "channels", and are labeled starting with the letter P, like so: This article is about the unit of information. ...

Channel P is a simple pause/music flag, which can be used for low-cost search systems. Quite a few players ignore it in favor of the Q Channel.

Channel Q is used for control purposes of more sophisticated players. It contains positioning information, the Media Catalog Number (MCN), and International Standard Recording Code (ISRC). The ISRC is used by the media industry, and contains information about the country of origin, the year of publication, owner of the rights, as well as a serial number, and some additional tags: The International Standard Recording Code (ISRC), defined by ISO 3901, is an international standard code for uniquely identifying sound recordings and music video recordings. ...

Data

This track contains Data (rather than audio). Can be used for muting in audio CD players.

Copy Flag

Used by the Serial Copy Management System to indicate permission to digitally copy the track.

Four Channel Audio

The track uses four channel audio. This is very rarely used on Compact Discs.

Pre-Emphasis

The audio track was recorded with pre-emphasis. Used very rarely on Compact Discs.

Channels R…W are unused by Red-Book compliant CDs, and have been used for extensions to the standard. The Serial Copy Management System or SCMS was created in response to the digital audio tape (DAT) invention, in order to prevent DAT recorders from making second-generation or serial copies. ... Four Channel Compact Disc Digital Audio is a four channel audio format specified under the Compact Disc Digital Audio Red Book standard. ...

CD-Text

CD-Text is part of the CD+G extension to the Red Book standard for audio CDs. It allows for storage of additional information (e.g. album name, song name, and artist) on a standards-compliant audio CD. The information is stored in the lead-in area of the CD, where there is roughly five kilobytes of space available, or in the R through W Subchannels on the disc, which are not used by strict Red Book CDs. About 31 megabytes of information can be stored there. The text is stored in a format usable by the Interactive Text Transmission System (ITTS). ITTS is also used by Digital Audio Broadcasting or the MiniDisc. The title given to this article is incorrect due to technical limitations. ... It has been suggested that this article or section be merged with Rainbow Books. ... // Overview The MiniDisc logo A MiniDisc (MD) is a disc-based data storage device intended for storage of digitized audio. ...

Note that the CD+G or “karaoke” extension also uses the R-W subchannels or subcodes to store low resolution graphics. The title given to this article is incorrect due to technical limitations. ...