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{{Use dmy dates|date=October 2021}}
{{Use American English|date=May 2024}}
{{Infobox storage medium
| name = Compact Disc Digital Audio
| logo = [[File:CDDAlogo.svg
| image =
| caption =
| type = [[Optical disc]]
| encoding = 2 channels of [[LPCM]] audio, each [[signedness|signed]] 16-[[bit]] values sampled at 44100 [[Hz]]
| capacity =
| read =
| write =
| standard =
| owner = [[Sony]] & [[Philips]]
| use = Audio storage
| released = {{Start date and age|1982}}
| extended from =
| extended to = [[CD-Text]]{{,}}[[CD+G]]{{,}}{{nowrap|[[DVD-Audio]]}}
}}
{{optical disc authoring}}
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'''Compact Disc Digital Audio''' ('''CDDA''' or '''CD-DA'''), also known as '''Digital Audio Compact Disc''' or simply as '''Audio CD''', is the [[standardization|standard]] format for audio [[compact disc]]s. The standard is defined in the ''[[Rainbow Books|Red Book]]'' [[technical specification]]s, which is why the format is also dubbed ''"Redbook audio"'' in some contexts.<ref>{{Cite web |title=Redbook Audio (Concept) |url=https://www.giantbomb.com/redbook-audio/3015-6487/ |access-date=2024-08-28 |website=Giant Bomb |language=en}}</ref> CDDA utilizes [[pulse-code modulation]] (PCM) and uses a [[44,100 Hz]] sampling frequency and 16-bit resolution, and was originally specified to store up to 74 minutes of [[stereo]] audio per disc.
The first commercially available audio [[CD player]], the [[Sony CDP-101]], was released in October 1982 in Japan. The format gained worldwide acceptance in 1983–84, selling more than a million CD players in its first two years, to play 22.5 million discs,<ref>{{cite book |last=Pohlmann |first=Ken C. |title=Principles of Digital Audio |date=2000 |publisher=McGraw-Hill |isbn=978-0-07-134819-5 |page=244}}</ref> before overtaking [[phonograph record|records]] and [[Cassette tape|cassette tapes]] to become the dominant standard for commercial music. Peaking around year 2000, the audio CD contracted over the next decade due to rising popularity and revenue from [[Music download|digital downloading]], and during the 2010s by [[Music streaming service|digital music streaming]],<ref>{{cite news |date=14 April 2015 |title=IFPI publishes Digital Music Report 2015 |url=https://www.ifpi.org/news/Global-digital-music-revenues-match-physical-format-sales-for-first-time |url-status=live |archive-url=https://web.archive.org/web/20150414194629/https://www.ifpi.org/news/Global-digital-music-revenues-match-physical-format-sales-for-first-time |archive-date=14 April 2015 |access-date=1 July 2016}}</ref> but has remained as one of the primary distribution methods for the [[music industry]].<ref name="AutoMR-2">{{cite news |last=Plambeck |first=Joseph |date=30 May 2010 |title=As CD Sales Wane, Music Retailers Diversify |url=https://www.nytimes.com/2010/05/31/business/media/31bestbuy.html |url-status=live |archive-url=https://web.archive.org/web/20170501175846/https://www.nytimes.com/2010/05/31/business/media/31bestbuy.html |archive-date=1 May 2017 |work=The New York Times}}</ref> In the United States, phonograph record revenues surpassed the CD in 2020 for the first time since the 1980s,<ref>{{cite news |date=10 September 2020 |title=Vinyl Outsells CDs For the First Time in Decades |url=https://pitchfork.com/news/vinyl-outsells-cds-for-the-first-time-in-decades
In the music industry, audio CDs have been generally sold as either a [[CD single]] (now largely dormant), or as full-length [[album]]s, the latter of which has been more commonplace since the 2000s.<ref>{{Cite web |title=1999: The Year the Record Industry Lost Control |url=https://theafterword.co.uk/1999-the-year-the-record-industry-lost-control/ |access-date=2024-05-03 |website=theafterword.co.uk}}</ref> The format has also been influential in the progression of [[video game music]], used in [[Mixed Mode CD|mixed mode]] [[CD-ROM|CD-ROMs]], providing CD-quality audio popularized during the 1990s on hardware such as [[PlayStation (console)|PlayStation]], [[Sega Saturn]] and [[personal
== History ==
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* The first ''public demonstration'' was on the [[BBC]] television programme ''[[Tomorrow's World]]'' in 1981, when the [[Bee Gees]]' album ''[[Living Eyes (Bee Gees album)|Living Eyes]]'' (1981) was played.<ref name="AutoMR-4">{{cite book| last = Bilyeu|first = Melinda|author2=Hector Cook |author3=Andrew Môn Hughes |publisher = Omnibus Press|year = 2004| isbn = 978-1-84449-057-8| title = The Bee Gees:tales of the brothers Gibb| page = 519 }}</ref>
* The first ''commercial'' compact disc was produced on 17 August 1982, a 1979 recording of [[Frédéric Chopin|Chopin]] waltzes performed by [[Claudio Arrau]].<ref>{{Cite AV media |date=20 July 2010 |title=1985 News Story on Debut of the Compact Disc (CD) |url=https://www.youtube.com/watch?v=vwrU8s-M-gc |access-date=25 June 2022 |publisher=acmestreamingDOTcom |via=YouTube |language=en-US |archive-date=25 June 2022 |archive-url=https://web.archive.org/web/20220625184512/https://www.youtube.com/watch?v=vwrU8s-M-gc |url-status=live }}</ref>
* The first 50 titles were ''released'' in Japan on 1 October 1982,<ref name="AutoMR-6">{{cite web|url=https://www.sony.net/Fun/SH/1-20/h5.html|archive-url=https://web.archive.org/web/20080802133849/https://www.sony.net/Fun/SH/1-20/h5.html|archive-date=2 August 2008|title=Sony History: A Great Invention 100 Years On|publisher=[[Sony]]|access-date=28 February 2012 }}</ref> the first of which was a re-release of
* The first CD played on BBC Radio was in October 1982.{{citation needed|date=September 2024}}
*The Japanese launch was followed on 14 March 1983 by the introduction of CD players and discs to Europe<ref>[https://www.newscenter.philips.com/main/standard/about/news/press/20070816_25th_anniversary_cd.wpd "Philips celebrates 25th anniversary of the Compact Disc"]{{webarchive|url=https://wayback.archive-it.org/all/20150817154431/https://www.newscenter.philips.com/main/standard/about/news/press/20070816_25th_anniversary_cd.wpd |date=17 August 2015 }}, Philips Media Release, 16 August 2007. Retrieved 6 October 2013.</ref> and North America where CBS Records released sixteen titles.<ref name="G&M 1983-03-05">{{cite news
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}}</ref>
The first artist to sell a million copies on CD was [[Dire Straits]], with their 1985 album ''[[Brothers in Arms (album)|Brothers in Arms]]''.<ref name="AutoMR-7">''[[Maxim (magazine)|Maxim]]'', 2004</ref> One of the first CD markets was devoted to reissuing popular music whose commercial potential was already proven. The first major artist to have their entire catalog converted to CD was [[David Bowie]], whose first fourteen studio albums (up to ''[[Scary Monsters (and Super Creeps)]]'') of (then) sixteen were made available by [[RCA Records]] in February 1985, along with four greatest hits albums; his fifteenth and sixteenth albums (''[[Let's Dance (David Bowie album)|Let's Dance]]'' and ''[[Tonight (David Bowie album)|Tonight]]'', respectively) had already been issued on CD by [[EMI Records]] in 1983 and 1984, respectively.<ref name="AutoMR-8">The New Schwann Record & Tape Guide Volume 37 No. 2 February 1985</ref> On 26 February 1987, the first four UK albums by [[the Beatles]] were released in mono on compact disc.<ref name="BeatlesCD">{{cite web |url=https://www.nytimes.com/1987/02/25/arts/now-on-cd-s-first-4-beatles-albums.html |title=NOW ON CD'S, FIRST 4 BEATLES ALBUMS |author=JON PARELES |date=25 February 1987 |work=[[The New York Times]] |access-date=6 February 2017 |archive-url=https://web.archive.org/web/20170310202959/https://www.nytimes.com/1987/02/25/arts/now-on-cd-s-first-4-beatles-albums.html |archive-date=10 March 2017 |url-status=live }}</ref>
The growing acceptance of the CD in 1983
=== Further development ===
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With the advent and popularity of [[Digital distribution|Internet-based distribution]] of files in [[Lossy compression|lossy-compressed]] [[audio format]]s such as [[MP3]], sales of CDs began to decline in the 2000s. For example, between 2000 and 2008, despite overall growth in music sales and one anomalous year of increase, major-label CD sales declined overall by 20%.<ref name="AutoMR-11">{{cite news |first=Ethan |last=Smith |title=Music Sales Decline for Seventh Time in Eight Years: Digital Downloads Can't Offset 20% Plunge in CD Sales |url=https://www.wsj.com/articles/SB123075988836646491?mod=rss_whats_news_technology&mg=com-wsj |newspaper=Wall Street Journal |date=2 January 2009 |access-date=4 March 2009 |url-status=live |archive-url=https://web.archive.org/web/20171020191140/https://www.wsj.com/articles/SB123075988836646491?mod=rss_whats_news_technology&mg=com-wsj |archive-date=20 October 2017 }}</ref> Despite rapidly declining sales year-over-year, the pervasiveness of the technology lingered for a time, with companies placing CDs in pharmacies, supermarkets, and filling station convenience stores to target buyers less likely to be able to use Internet-based distribution.<ref name="AndItsEnd" />
In 2012, CDs and DVDs made up only 34% of music sales in the United States.<ref>{{cite web|url=https://www.tokyotimes.com/buying-cds-continues-to-be-a-tradition-in-japan/|title=Buying CDs continues to be a tradition in Japan – Tokyo Times|date=23 August 2013|access-date=30 December 2016|url-status=live|archive-url=https://web.archive.org/web/20161220150903/https://www.tokyotimes.com/buying-cds-continues-to-be-a-tradition-in-japan/|archive-date=20 December 2016}}</ref> By 2015, only 24% of music in the United States was purchased on physical media, two thirds of this consisting of CDs;<ref>{{Cite web|url=https://riaa.com/media/238E8AC7-3810-A95C-44DC-B6DEB46A3C6E.pdf|title=News and Notes on 2015 Mid-Year RIAA Shipment and Revenue Statistics|last=Friedlander|first=Joshua P.|year=2015|publisher=Recording Industry Association of America|archive-url=https://web.archive.org/web/20150930135150/https://riaa.com/media/238E8AC7-3810-A95C-44DC-B6DEB46A3C6E.pdf|archive-date=30 September 2015}}</ref> however, in the same year in Japan, over 80% of music was bought on CDs and other physical formats.<ref>Sisaro, Ben. ''New York Times'' 11 June 2015: {{cite news|url=https://www.nytimes.com/2015/06/12/business/media/line-music-a-new-streaming-service-aims-at-japanese-market.html?_r=0|title=Music Streaming Service Aims at Japan, Where CD Is Still King|newspaper=The New York Times|date=11 June 2015|archive-url=https://web.archive.org/web/20171020191923/https://www.nytimes.com/2015/06/12/business/media/line-music-a-new-streaming-service-aims-at-japanese-market.html?_r=0|archive-date=20 October 2017|url-status=live|access-date=26 August 2017|last1=Sisario|first1=Ben}}</ref> In 2018, U.S. CD sales were 52 million units—less than 6% of the peak sales volume in 2000.<ref name="statista" /> In the UK, 32 million units were sold, almost 100 million fewer than in 2008.<ref>{{citation |title=Is this the end of owning music? |work=BBC News |date=3 January 2019 |url=https://www.bbc.com/news/entertainment-arts-46735093 |access-date=3 March 2021 |archive-date=8 November 2020 |archive-url=https://web.archive.org/web/20201108002704/https://www.bbc.com/news/entertainment-arts-46735093 |url-status=live }}</ref> In 2018, [[Best Buy]] announced plans to decrease their focus on CD sales, however, while continuing to sell records, sales of which are growing during the [[vinyl revival]].<ref name="bestverge">{{cite web |last=Ong |first=Thuy |date=6 February 2018 |title=Best Buy will stop selling CDs as digital music revenue continues to grow |url=https://www.theverge.com/2018/2/6/16973538/bestbuy-target-cd-sales-vinyl-cassette |url-status=live |archive-url=https://web.archive.org/web/20180206181746/https://www.theverge.com/2018/2/6/16973538/bestbuy-target-cd-sales-vinyl-cassette |archive-date=6 February 2018 |access-date=6 February 2018 |website=[[The Verge]]}}</ref><ref>{{cite news |last=Owsinski |first=Bobby |date=7 July 2018 |title=Best Buy, Winding Down CD Sales, Pounds Another Nail Into The Format's Coffin |url=https://www.forbes.com/sites/bobbyowsinski/2018/07/07/best-buy-cd-sales
During the 2010s, the increasing popularity of solid-state media and music streaming services caused automakers to remove automotive CD players in favor of [[minijack]] auxiliary inputs, wired connections to USB devices and wireless [[Bluetooth]] connections.<ref name="Biersdorfer">{{cite news |last1=Biersdorfer |first1=J.D. |title=Hand Me the AUX Cord |url=https://www.nytimes.com/2017/03/17/technology/personaltech/hand-me-the-aux-cord.html |access-date=12 January 2022 |work=The New York Times |date=March 17, 2017 |archive-date=12 January 2022 |archive-url=https://web.archive.org/web/20220112053206/https://www.nytimes.com/2017/03/17/technology/personaltech/hand-me-the-aux-cord.html |url-status=live }}</ref> Automakers viewed CD players as using up valuable space and taking up weight which could be reallocated to more popular features, like large touchscreens.<ref name="Ramey">{{cite news |last1=Ramey |first1=Jay |title=Do You Want a CD Player in a New Car? |url=https://www.autoweek.com/car-life/classic-cars/a35459280/do-you-want-a-cd-player-in-a-new-car/ |access-date=12 January 2022 |work=Autoweek |date=February 9, 2021 |archive-date=27 August 2023 |archive-url=https://web.archive.org/web/20230827104052/https://www.autoweek.com/car-life/classic-cars/a35459280/do-you-want-a-cd-player-in-a-new-car/ |url-status=live }}</ref> By 2021, only [[Lexus]] and [[General Motors]] were still including CD players as standard equipment with certain vehicles.<ref name="Ramey" />
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CDs continued to be strong in some markets such as Japan where 132 million units were produced in 2019.<ref>{{Cite web|url=https://www.nippon.com/en/japan-data/h00740/|title=Physical Formats Still Dominate Japanese Music Market|date=24 June 2020|website=nippon.com|access-date=14 November 2022|archive-date=28 October 2022|archive-url=https://web.archive.org/web/20221028183640/https://www.nippon.com/en/japan-data/h00740/|url-status=live}}</ref>
The decline in CD sales has slowed in recent years; in 2021, CD sales increased in the US for the first time since 2004,<ref>{{cite web | url=https://www.strata-gee.com/lets-get-physical-vinyl-sales-up-51-cd-sales-up-for-first-time-in-17-yrs/ | title=Let's Get Physical! Vinyl Sales up >51%, CD Sales up for First Time in 17-yrs | website=Strata-gee.com | date=26 January 2022 | access-date=14 November 2022 | archive-date=14 November 2022 | archive-url=https://web.archive.org/web/20221114140242/https://www.strata-gee.com/lets-get-physical-vinyl-sales-up-51-cd-sales-up-for-first-time-in-17-yrs/ | url-status=live }}</ref> with [[Axios (website)|Axios]] citing its rise to "young people who are finding they like hard copies of music in the digital age".<ref>{{Cite web|url=https://www.makeuseof.com/cd-sales-are-rising-again-but-why/|title=CD Sales Are Rising Again, but Why?|first=Patrick|last=Kariuki|date=18 March 2022|website=Makeuseof.com|access-date=14 November 2022|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104056/https://www.makeuseof.com/cd-sales-are-rising-again-but-why/|url-status=live}}</ref> It came at the same time as both vinyl and cassette reached sales levels not seen in 30 years.<ref>{{Cite web|url=https://www.officialcharts.com/chart-news/vinyl-and-cassette-uk-sales-continue-to-surge-to-30-year-high-as-cd-sales-decline-slows__34839/|title=Vinyl and cassette UK sales continue to surge to 30 year high|website=Officialcharts.com|access-date=14 November 2022|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104058/https://www.officialcharts.com/chart-news/vinyl-and-cassette-uk-sales-continue-to-surge-to-30-year-high-as-cd-sales-decline-slows__34839/|url-status=live}}</ref> The [[Recording Industry Association of America|RIAA]] reported that CD revenue made a dip in 2022, before increasing again in 2023 and overtook downloading for the first time in over a decade.<ref>{{cite report |last=Bass |first=Matthew |date=2024 |title=Year-end 2023 RIAA Revenue Statistics |url=https://www.riaa.com/wp-content/uploads/2024/03/2023-Year-End-Revenue-Statistics.pdf
In the US, 33.4 million CD albums were sold in the year 2022.<ref>{{Cite web |title=Physical album shipments in the U.S. 2022 |url=https://www.statista.com/statistics/186772/album-shipments-in-the-us-music-industry-since-1999/ |access-date=2024-05-03 |website=Statista |language=en}}</ref> In [[France]] in 2023, 10.5 million CDs were sold, almost double that of vinyl, but both of them represented generated 12% each of the French music industry revenues.<ref>{{Cite web |last=Bazoge |first=Mickaël |date=2024-03-27 |title=En France comme aux États-Unis, les vinyles en position de force face aux CD |url=https://www.01net.com/actualites/en-france-comme-aux-etats-unis-les-vinyles-en-position-de-force-face-aux-cd.html |access-date=2024-05-03 |website=01net.com |language=fr-FR}}</ref>
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There was a long debate over the use of 16-bit (Sony) or 14-bit (Philips) [[Quantization (signal processing)|quantization]], and 44,056 or 44,100 samples/s (Sony) or approximately 44,000 samples/s (Philips). When the Sony/Philips task force designed the Compact Disc, Philips had already developed a 14-bit [[D/A converter]] (DAC), but Sony insisted on 16-bit. In the end Sony won, so 16 bits and 44.1 kilosamples per second prevailed. Philips found a way to produce 16-bit quality using its 14-bit DAC by using four times [[oversampling]].<ref name=Immink />
Some early CDs were mastered with [[pre-emphasis]], an artificial boost of high audio frequencies. The pre-emphasis improves the apparent signal-to-noise ratio by making better use of the channel's dynamic range. On playback, the player applies a de-emphasis filter to restore the frequency response curve to an overall flat one. Pre-emphasis time constants are 50 μs and 15 μs (9.49 dB boost at 20 kHz), and a binary flag in the disc [[subcode]] instructs the player to apply de-emphasis filtering if appropriate. Playback of such discs in a computer or [[CD ripper|ripping]] to [[WAV]] files typically does not take into account the pre-emphasis, so such files play back with an incorrect frequency response.{{citation needed|date=January 2022}} [[FFmpeg]] has a filter to remove (or apply) the pre-emphasis in order to create standard WAV files, or to create CDs with pre-emphasis.<ref>{{cite web |title=FFmpeg Filters Documentation |url=https://ffmpeg.org/ffmpeg-filters.html#aemphasis |website=FFmpeg |publisher=FFmpeg project |access-date=6 January 2024 |archive-date=28 March 2017 |archive-url=https://web.archive.org/web/20170328021020/https://ffmpeg.org/ffmpeg-filters.html#aemphasis |url-status=live }}</ref>
Four-channel, or [[quadraphonic]], support was originally intended to be included in CD-DA.<ref>{{Cite book|url = https://books.google.com/books?id=jqwgBQAAQBAJ&q=Four-channel+Compact+Disc+Digital+Audio&pg=PA108|title = Digital Audio and Compact Disc Technology|isbn = 978-1-4831-4039-1|last1 = Baert|first1 = Luc|last2 = Theunissen|first2 = Luc|last3 = Vergult|first3 = Guido|date = 2013-10-22| publisher=Newnes |access-date = 27 August 2023|archive-date = 27 August 2023|archive-url = https://web.archive.org/web/20230827104057/https://books.google.com/books?id=jqwgBQAAQBAJ&q=Four-channel+Compact+Disc+Digital+Audio&pg=PA108|url-status = live}}</ref> The ''Red Book'' specification briefly mentioned a four-channel mode in its June 1980,<ref name="RedBook1980">"Red Book" Audio CD specification, June 1980, Sony/Philips</ref> September 1983,<ref name="RedBook1983">"Red Book" Audio CD specification, September 1983, Sony/Philips</ref> and November 1991<ref name="RedBook1991">"Red Book" Audio CD specification, November 1991, Sony/Philips</ref> editions. On the first page, it lays out the "Main parameters" of the CD system, including: "Number of channels: 2 and/or 4 simultaneously[*] sampled." The footnote says, "In the case of more than two channels the encoder and decoder diagrams have to be adapted."
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According to a ''[[Sunday Tribune]]'' interview,<ref name="ferguscassidy" /> the story is slightly more involved. In 1979, Philips owned [[PolyGram]], one of the world's largest music distributors. PolyGram had set up a large experimental CD plant in [[Hannover]], Germany, which could produce huge numbers of CDs having a diameter of 115 mm. Sony did not yet have such a facility. If Sony had agreed on the 115-mm disc, Philips would have had a significant competitive edge in the market. The long playing time of Beethoven's Ninth Symphony imposed by [[Norio Ohga|Ohga]] was used to push Philips to accept 120 mm, so that Philips' PolyGram lost its edge on disc fabrication.<ref name="ferguscassidy" />
The 74:33 playing time of a CD, which is longer than the 22 minutes per side<ref name="Auto45-7" /><ref name="Auto45-8" /> typical of [[long-playing]] (LP) [[vinyl album]]s, was often used to the CD's advantage during the early years when CDs and LPs vied for commercial sales. CDs would often be released with one or more [[bonus track]]s, enticing consumers to buy the CD for the extra material. However, attempts to combine double LPs onto one CD occasionally resulted in the opposite situation in which the CD would instead offer less audio than the LP. One such example was with [[DJ Jazzy Jeff & The Fresh Prince]]'s double album ''[[He's the DJ, I'm the Rapper]]'', in which initial CD releases of the album had multiple tracks edited down for length to fit on a single disc; recent CD reissues package the album across two discs as a result. Furthermore, early CD releases were restricted by the 72-minute limit of 3/4
Playing times beyond 74:33 are achieved by decreasing track pitch (the distance separating the track as it spirals the disc). However, most players can still accommodate the more closely spaced data if it is still within ''Red Book'' tolerances.<ref name="Auto45-9" /> Manufacturing processes used in the final years of CD technology allowed an audio CD to contain up to
{| class="wikitable sortable"
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| 1988 || 80:08<ref name="Auto45-11" />
| ''Mission of Burma'' (compilation) || [[Mission of Burma]] || [[Rykodisc]]
|-
| 1990
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| [[Richard Marlow]]
| Mirabilis Records
|-
| 2004 || 82:34<ref name="Auto45-10" />
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The audio data stream in an audio CD is continuous but has three parts. The main portion, further divided into playable audio tracks, is the ''program area''. This section is preceded by a ''lead-in'' track and followed by a ''lead-out'' track. The lead-in and lead-out tracks encode only silent audio, but all three sections contain [[subcode]] data streams.
The lead-in's subcode contains repeated copies of the disc's table of contents (TOC), which provides an index of the start positions of the tracks in the program area and of the lead-out. The track positions are referenced by absolute [[timecode]], relative to the start of the program area, in MSF format: minutes, seconds, and fractional seconds called ''frames''. Each ''timecode frame'' is one seventy-fifth of a second, and corresponds to a block of 98 ''channel-data
==== Tracks ====
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The largest entity on a CD is called a [[Track (optical disc)|track]]. A CD can contain up to 99 tracks (including a data track for [[Mixed Mode CD|mixed mode discs]]). Each track can in turn have up to 100 indexes, though players that still support this feature have become rarer over time. The vast majority of songs are recorded under index 1, with the [[pregap]] being index 0. Sometimes [[hidden track]]s are placed at the end of the last track of the disc, often using index 2 or 3, or using the pregap as index 0 (this latter usage will result in the track playing as the time counter counts down to time 0:00 at the start of the track, index 1.) This is also the case with some discs offering "101 sound effects", with 100 and 101 being indexed as two and three on track 99. The index, if used, is occasionally put on the track listing as a decimal part of the track number, such as 99.2 or 99.3.{{efn|[[Information Society (band)|Information Society]]'s ''[[Hack (album)|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.
Tracks, in turn, are divided into timecode frames
==== Frames and timecode frames ====
{{
The smallest entity in a CD is a channel-data ''frame'', which consists of 33 bytes and contains six complete 16-bit stereo samples: 24 bytes for the audio (two bytes × two channels × six samples = 24 bytes), eight CIRC error-correction bytes, and one [[subcode]] byte. As described in {{slink||Data encoding}}, after the EFM modulation the number of bits in a frame totals 588.
On a ''Red Book'' audio CD, data is addressed using the ''MSF scheme'', with [[timecode]]s expressed in minutes, seconds and another type of ''frames'' (mm:ss:ff), where one frame corresponds to 1/
In the 1990s, [[CD-ROM]] and related [[
The following table shows the relation between tracks, timecode frames (sectors) and channel-data frames:
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=== Bit rate ===
The audio [[bit rate]] for a ''Red Book'' audio CD is 1,411,200 [[bits per second]] (1,411 kbit/s) or 176,400 [[bytes per second]]; 2 channels
=== Data access from computers ===
Unlike on a [[DVD]] or
In a process called [[CD ripper|ripping]], digital audio extraction software can be used to read CD-DA audio data and store it in files. Common [[audio file format]]s for this purpose include
== Format variations ==
Recording publishers have created CDs that violate the ''Red Book'' standard. Some do so for the purpose of [[copy
[[Super Audio CD]] was a standard published in 1999 that aimed to provide better audio quality than CDs. [[DVD-Audio]] emerged at around the same time.<ref name="Auto45-12" /> Both formats were designed to feature audio of higher fidelity by using a higher sampling rate and [[DVD]] media. Neither format was widely accepted.
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