Compact Disc Digital Audio

Audio CDCDRed BookCD-DACD audioRed Book audioaudio CDsCDDAcompact discRedbook
Compact Disc Digital Audio (CDDA or CD-DA), also known as Audio CD, is the standard format for audio compact discs.wikipedia
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Digital audio

digital musicaudiodigital
The standard also specifies the form of digital audio encoding: 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz.
For example, in CD audio, samples are taken 44100 times per second each with 16 bit sample depth.

Rainbow Books

Orange BookRed BookRainbow book
The standard is defined in the Red Book, one of a series of "Rainbow Books" (named for their binding colors) that contain the technical specifications for all CD formats.
CD-DA (Digital Audio) – standardized as IEC 60908

CD-ROM

CDCD-ROM drives18x
These parameters are common to all compact discs and used by all logical formats, such as CD-ROM.
It was an extension of Compact Disc Digital Audio, and adapted the format to hold any form of digital data, with a storage capacity of 553 MiB.

CD-Text

The IEC 60908 however does not contain all the information for extensions that is available in the Red Book, such as the details for CD-Text, CD+G and CD+EG.
CD-Text is an extension of the Red Book Compact Disc specifications standard for audio CDs.

CD+G

CD + DVDCD+EG / CD+XG
The IEC 60908 however does not contain all the information for extensions that is available in the Red Book, such as the details for CD-Text, CD+G and CD+EG. (Information Society's Hack was one of very few CD releases to do this, following a release with an equally obscure CD+G feature.) The track and index structure of the CD were carried forward to the DVD format as title and chapter, respectively.
CD+G (also known as CD-G, CD+Graphics and TV-Graphics ) is an extension of the compact disc standard that can present low-resolution graphics alongside the audio data on the disc when played on a compatible device.

44,100 Hz

44.1 kHz44.1kHz44,100 samples per second
The standard also specifies the form of digital audio encoding: 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz.
This then became the basis for compact disc digital audio (CD-DA), defined in the Red Book standard (1980).

Kees Schouhamer Immink

Kees ImminkDr. Kees ImminkKees A. Schouhamer Immink
Kees Schouhamer Immink, Philips' chief engineer, however, denies this, claiming that the increase was motivated by technical considerations, and that even after the increase in size, the Furtwängler recording would not have fit on one of the earliest CDs.
Immink took part in the joint Sony–Philips task force, which developed the Compact Disc standard, the Red Book.

Pregap

pre-gappregap hidden trackby holding rewind at the start of track 1
The vast majority of songs are recorded under index 1, with the pre-gap being index 0.
The pregap on a Red Book audio CD is the portion of the audio track that precedes "index 01" for a given track in the table of contents (TOC).

Key2Audio

key2AudioXS
Nonstandard or corrupted TOC records are abused as a form of CD/DVD copy protection, in e.g. the key2Audio scheme.
key2audio is a copy restriction system for Audio CDs, developed by Sony DADC.

Emphasis (telecommunications)

pre-emphasispreemphasisEmphasis
Although rarely used, the specification allows for discs to be mastered with a form of emphasis.
Although rarely used, there exists the capability for standardized emphasis in Red Book CD mastering.

Mixed Mode CD

data trackenhanced portion of the discmixed mode CDs
A CD can contain up to 99 tracks (including a data track for mixed mode discs).
Typically the first track is a data track while the rest are audio tracks.

Compact Disc subcode

subcodesubcode channelssubchannel data
The Red Book specifies 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 facility (cross-interleaved Reed–Solomon coding, CIRC), and the eight subcode channels.
Subcode or subchannel data (called "control bytes" in the CD-ROM specification) refers to data contained in a compact disc (CD) in addition to digital audio or user data, which is used for control and playback of the CD. The original specification was defined in the Red Book standard for CD Digital Audio, though further specifications have extended their use (including the CD-ROM, CD Text and CD+G specifications).

Compact Disc and DVD copy protection

copy protectionCopy Protected Compact Disccopy protection measures
Nonstandard or corrupted TOC records are abused as a form of CD/DVD copy protection, in e.g. the key2Audio scheme.
The Red Book CD-DA audio specification does not include any copy protection mechanism other than a simple anti-copy flag.

Compact disc

CDCDsCD single
These parameters are common to all compact discs and used by all logical formats, such as CD-ROM. Compact Disc Digital Audio (CDDA or CD-DA), also known as Audio CD, is the standard format for audio compact discs. Some do so for extra features such as DualDisc, which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9 mm, than required by the Red Book, which stipulates a nominal 1.2 mm, but at least 1.1 mm. Philips and many other companies have stated that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement.
The format was originally developed to store and play only sound recordings (CD-DA) but was later adapted for storage of data (CD-ROM).

MP3

.mp3MP3 downloadmp3s
Common audio file formats for this purpose include WAV and AIFF, which simply preface the LPCM data with a short header; FLAC, ALAC, and Windows Media Audio Lossless, which compress the LPCM data in ways that conserve space yet allow it to be restored without any changes; and various lossy, perceptual coding formats like MP3 and AAC, which modify and compress the audio data in ways that irreversibly change the audio, but that exploit features of human hearing to make the changes difficult to discern.
Compared to CD-quality digital audio, MP3 compression can commonly achieve a 75 to 95% reduction in size.

Phonograph record

vinyl7LP
The 74-minute playing time of a CD, which is longer than the 22 minutes per side typical of long-playing (LP) vinyl albums, was often used to the CD's advantage during the early years when CDs and LPs vied for commercial sales.
According to Red Book specifications, the compact disc has a frequency response of 20 Hz up to 22,050 Hz, and most CD players measure flat within a fraction of a decibel from at least 0 Hz to 20 kHz at full output.

DualDisc

CD+DVDdual discDD
Some do so for extra features such as DualDisc, which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9 mm, than required by the Red Book, which stipulates a nominal 1.2 mm, but at least 1.1 mm. Philips and many other companies have stated that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement.
It featured an audio layer intended to be compatible with CD players (but not following the Red Book CD Specifications) on one side and a standard DVD layer on the other.

Copy Control

CCCDcopy protectedCopy-Controlled
Some do so for the purpose of copy prevention, using systems like Copy Control.
While basically intended as a means of copy-protecting compact discs, Copy Control discs cannot properly be referred to as CDs because the system introduces incompatible data, making the discs non-compliant with the Red Book standard for audio CDs.

Audio file format

audio fileaudioaudio files
Common audio file formats for this purpose include WAV and AIFF, which simply preface the LPCM data with a short header; FLAC, ALAC, and Windows Media Audio Lossless, which compress the LPCM data in ways that conserve space yet allow it to be restored without any changes; and various lossy, perceptual coding formats like MP3 and AAC, which modify and compress the audio data in ways that irreversibly change the audio, but that exploit features of human hearing to make the changes difficult to discern.
One major uncompressed audio format, LPCM, is the same variety of PCM as used in Compact Disc Digital Audio and is the format most commonly accepted by low level audio APIs and D/A converter hardware.

Super Audio CD

SACDSHM-SACDhybrid SACD
Super Audio CD was a standard published in 1999 that aimed to provide better audio quality in CDs, but it never became very popular.
A stereo SACD recording has an uncompressed rate of 5.6 Mbit/s, four times the rate for Red Book CD stereo audio.

.cda file

.cdaCD audio tracks
For example, Windows represents the CD's Table of Contents as a set of Compact Disc Audio track (CDA) files, each file containing indexing information, not audio data.
.cda is a common filename extension denoting a small (44 byte) stub file generated by Microsoft Windows for each audio track on a standard "Red Book" CD-DA format audio CD as defined by the Table of Contents (ToC) (within the lead-in's subcode).

Bit rate

bitratedata ratedata transfer rate
The audio bit rate for a Red Book audio CD is 1,411,200 bits per second or 176,400 bytes per second; 2 channels × 44,100 samples per second per channel × 16 bits per sample.
CD-DA, the standard audio CD, is said to have a data rate of 44.1 kHz/16, meaning that the audio data was sampled 44,100 times per second and with a bit depth of 16. CD-DA is also stereo, using a left and right channel, so the amount of audio data per second is double that of mono, where only a single channel is used.

DVD

DVD-ROMDVDsvideo album
Some do so for extra features such as DualDisc, which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9 mm, than required by the Red Book, which stipulates a nominal 1.2 mm, but at least 1.1 mm. Philips and many other companies have stated that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement. (Information Society's Hack was one of very few CD releases to do this, following a release with an equally obscure CD+G feature.) The track and index structure of the CD were carried forward to the DVD format as title and chapter, respectively.
It offers many channel configuration options (from mono to 5.1 surround sound) at various sampling frequencies (up to 24-bits/192 kHz versus CDDA's 16-bits/44.1 kHz).

Copy protection

anti-piracycopy-protectedcopy protected
Some do so for the purpose of copy prevention, using systems like Copy Control.
The CD Digital Audio is the oldest CD standard and forms the basic feature set beyond which dedicated audio players need no instructions.

Four-channel Compact Disc Digital Audio

four-channel audioFour-channel sound
Four-channel compact disc digital audio
The proprietary Red Book specification, as published by Sony and Philips, briefly mentions a four-channel mode in its June 1980, September 1983, and November 1991 editions.