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| latest release version = ISO/IEC 13818-3:1998
| latest release date = {{Start date and age|1998|04|df=y}}
| type = [[Lossy compression|Lossy]] [[Audio file format|audio]]
| container for =
| contained by = [[MPEG-ES]]
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}}
 
'''MP3''' (formally '''MPEG-1 Audio Layer III''' or '''MPEG-2 Audio Layer III''')<ref name="rfc5219" /> is a [[audio coding format|coding format]] for [[digital audio]] developed largely by the [[Fraunhofer Society]] in Germany under the lead of [[Karlheinz Brandenburg]],.<ref>{{Cite web|url=https://www.youtube.com/watch?v=cuU16whZ-Fs|title=73. "Father" of the MP3, Karlheinz Brandenburg|date=13 July 2015 |via=www.youtube.com|access-date=2 January 2023|archive-date=2 January 2023|archive-url=https://web.archive.org/web/20230102160404/https://www.youtube.com/watch?v=cuU16whZ-Fs|url-status=live}}</ref><ref>{{Cite web|url=https://www.internethistorypodcast.com/2015/07/on-the-20th-birthday-of-the-mp3-an-interview-with-the-father-of-the-mp3-karlheinz-brandenburg/|title=On the 20th Birthday of the MP3, An Interview With The "Father" of the MP3, Karlheinz Brandenburg|access-date=2 January 2023|archive-date=2 January 2023|archive-url=https://web.archive.org/web/20230102160403/https://www.internethistorypodcast.com/2015/07/on-the-20th-birthday-of-the-mp3-an-interview-with-the-father-of-the-mp3-karlheinz-brandenburg/|url-status=live}}</ref> withIt supportwas fromdesigned otherto digitalgreatly scientistsreduce inthe otheramount countries.of Originallydata definedrequired asto the thirdrepresent audio, formatyet still sound like a faithful reproduction of the original [[MPEG-1uncompressed]] standard,audio itto wasmost retainedlisteners; andfor furtherexample, extended—definingcompared additionalto bit[[Compact ratesDisc andDigital supportAudio|CD-quality for moredigital [[surround channels|audio channels]]—as, theMP3 thirdcompression audiocan formatcommonly ofachieve thea subsequent75–95% reduction in size, depending on the [[MPEG-2bit rate]] standard.<ref>{{cite Aweb third|date=27 version,July known2017 as|title=MP3 (MPEG Layer III Audio Encoding) |url=https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml |url-2status=live |archive-url=https://web.archive.org/web/20170814015755/https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.5—extendedshtml to|archive-date=14 betterAugust support2017 lower|access-date=9 November 2017 |publisher=The Library of Congress}}</ref> In popular usage, ''MP3'' often refers to [[bitComputer ratefile|files]]s—is commonlyof implementedsound butor ismusic notrecordings astored in the MP3 [[file format]] (.mp3) on consumer recognizedelectronic standarddevices.
 
ConcerningOriginally defined in 1991 as the third audio format of the [[audioMPEG-1]] compressionstandard, (data)it was retained and further extended—defining additional bit rates and support for more [[surround channels|audio compressionchannels]]—as (the aspectthird audio format of the subsequent [[MPEG-2]] standard. mostMP3 apparentas toa end[[file format]] commonly designates files containing an [[elementary stream]] of MPEG-users1 andAudio foror whichMPEG-2 itAudio isencoded bestdata, knownwithout other complexities of the MP3 standard. Concerning [[audio compression (data)|audio compression]], which is its most apparent element to end-users, MP3 uses [[lossy compression]] to encode data using inexact approximations and the partial discarding of data., Thisallowing allowsfor a large reduction in [[File size|file sizes]] when compared to uncompressed audio. The combination of small size and acceptable fidelity led to a boom in the distribution of music over the [[Internet]] in the mid-to-late 1990s, with MP3 serving as an enabling technology at a time when [[Bandwidth (computing)|bandwidth]] and storage were still at a premium. The MP3 format soon became associated with controversies surrounding [[copyright infringement]], [[music piracy]], and the file-[[ripping]] and [[file sharing|sharing]] services [[MP3.com#Original_version|MP3.com]] and [[Napster]], among others. With the advent of [[portable media player]]s (including "MP3 players"), a product category also including [[smartphones]], MP3 support remains near-universal and a [[De facto standard|''de facto'' standard]] for digital audio.▼
'''MP3''' (or '''mp3''') as a [[file format]] commonly designates files containing an [[elementary stream]] of MPEG-1 Audio or MPEG-2 Audio encoded data, without other complexities of the MP3 standard.
 
▲Concerning [[audio compression (data)|audio compression]] (the aspect of the standard most apparent to end-users and for which it is best known), MP3 uses [[lossy compression]] to encode data using inexact approximations and the partial discarding of data. This allows a large reduction in file sizes when compared to uncompressed audio. The combination of small size and acceptable fidelity led to a boom in the distribution of music over the Internet in the mid-to-late 1990s, with MP3 serving as an enabling technology at a time when bandwidth and storage were still at a premium. The MP3 format soon became associated with controversies surrounding [[copyright infringement]], [[music piracy]], and the file-[[ripping]] and [[file sharing|sharing]] services [[MP3.com#Original_version|MP3.com]] and [[Napster]], among others. With the advent of [[portable media player]]s, a product category also including [[smartphones]], MP3 support remains near-universal.
 
MP3 compression works by reducing the accuracy of certain components of sound that are considered (by psychoacoustic analysis) to be beyond the [[Hearing range#Humans|hearing capabilities]] of most humans. This method is commonly referred to as perceptual coding or [[psychoacoustic]] modeling.<ref name="Jayant1993" /> The remaining audio information is then recorded in a space-efficient manner using [[MDCT]] and [[FFT]] algorithms. Compared to [[Compact Disc Digital Audio|CD-quality digital audio]], MP3 compression can commonly achieve a 75–95% reduction in size. For example, an MP3 encoded at a constant bit rate of 128&nbsp;kbit/s would result in a file approximately 9% the size of the original CD audio.<ref>{{cite web |url= https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml |title= MP3 (MPEG Layer III Audio Encoding) |date= 27 July 2017 |publisher= The Library of Congress |access-date= 9 November 2017 |archive-date= 14 August 2017 |archive-url= https://web.archive.org/web/20170814015755/https://www.loc.gov/preservation/digital/formats/fdd/fdd000012.shtml |url-status= live }}</ref> In the early 2000s, compact disc players increasingly adopted support for playback of MP3 files on data CDs.
 
== History ==▼
The [[Moving Picture Experts Group]] (MPEG) designed MP3 as part of its [[MPEG-1]], and later [[MPEG-2]], standards. MPEG-1 Audio (MPEG-1 Part 3), which included MPEG-1 Audio Layer I, II, and III, was approved as a committee draft for an [[ISO]]/[[IEC]] standard in 1991,<ref name="cd-1991" /><ref name="neuron2-cd-1991" /> finalized in 1992,<ref name="dis-1992" /> and published in 1993 as ISO/IEC 11172-3:1993.<ref name="11172-3" /> An MPEG-2 Audio (MPEG-2 Part 3) extension with lower sample and bit rates was published in 1995 as ISO/IEC 13818-3:1995.<ref name="13818-3" /><ref name="mpeg-audio-faq-bc" /> It requires only minimal modifications to existing MPEG-1 decoders (recognition of the MPEG-2 bit in the header and addition of the new lower sample and bit rates).
 
▲== History ==
=== Background ===
{{See|Linear predictive coding|Modified discrete cosine transform}}
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The MP3 [[lossy compression]] algorithm takes advantage of a perceptual limitation of human hearing called [[auditory masking]]. In 1894, the American physicist [[Alfred M. Mayer]] reported that a tone could be rendered inaudible by another tone of lower frequency.<ref name="Mayer1894" /> In 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon.<ref name="Ehmer1959" /> Between 1967 and 1974, [[Eberhard Zwicker]] did work in the areas of tuning and masking of critical frequency-bands,<ref name="Zwicker" /><ref name="Eberhard" /> which in turn built on the fundamental research in the area from [[Harvey Fletcher]] and his collaborators at [[Bell Labs]].<ref name="Fletcher" />
 
Perceptual coding was first used for [[speech coding]] compression with [[linear predictive coding]] (LPC),<ref name="Schroeder2014">{{cite book |last1= Schroeder |first1= Manfred R. |title= Acoustics, Information, and Communication: Memorial Volume in Honor of Manfred R. Schroeder |date= 2014 |publisher= Springer |isbn= 978-3-319-05660-9 |chapter= Bell Laboratories |page= 388 |chapter-url= https://books.google.com/books?id=d9IkBAAAQBAJ&pg=PA388}}</ref> which has origins in the work of [[Fumitada Itakura]] ([[Nagoya University]]) and Shuzo Saito ([[Nippon Telegraph and Telephone]]) in 1966.<ref>{{cite journal |last1= Gray |first1= Robert M. |title= A History of Realtime Digital Speech on Packet Networks: Part II of Linear Predictive Coding and the Internet Protocol |journal= Found. Trends Signal Process. |date= 2010 |volume= 3 |issue= 4 |pages= 203–303 |doi= 10.1561/2000000036 |url= https://ee.stanford.edu/~gray/lpcip.pdf |issn= 1932-8346 |doi-access= free |access-date= 14 July 2019 |archive-date= 9 October 2022 |archive-url= https://ghostarchive.org/archive/20221009/https://ee.stanford.edu/~gray/lpcip.pdf |url-status= live }}</ref> In 1978, [[Bishnu S. Atal]] and [[Manfred R. Schroeder]] at Bell Labs proposed an LPC speech [[codec]], called [[adaptive predictive coding]], that used a [[psychoacoustic]] coding-algorithm exploiting the masking properties of the human ear.<ref name="Schroeder2014"/><ref>{{cite book |last1= Atal |first1= B. |last2= Schroeder |first2= M. |title= ICASSP '78. IEEE International Conference on Acoustics, Speech, and Signal Processing |chapter= Predictive coding of speech signals and subjective error criteria |date= 1978 |volume= 3 |pages= 573–576 |doi= 10.1109/ICASSP.1978.1170564}}</ref> Further optimization by Schroeder and Atal with J.L. Hall was later reported in a 1979 paper.<ref name="Schroeder1979"/> That same year, a psychoacoustic masking codec was also proposed by M. A. Krasner,<ref name="Krasner" /> who published and produced hardware for speech (not usable as music bit-compression), but the publication of his results in a relatively obscure [[Lincoln Laboratory]] Technical Report<ref>{{cite web|last1= Krasner|first1= M. A.|title= Digital Encoding of Speech Based on the Perceptual Requirement of the Auditory System (Technical Report 535)|url= https://apps.dtic.mil/dtic/tr/fulltext/u2/a077355.pdf|ref= Lincoln Laboratory, MIT|date= 18 June 1979|url-status= live|archive-url= https://web.archive.org/web/20170903070321/https://www.dtic.mil/dtic/tr/fulltext/u2/a077355.pdf|archive-date= 3 September 2017}}</ref> did not immediately influence the mainstream of psychoacoustic codec-development.
 
The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for lossy compression, proposed by [[N. Ahmed|Nasir Ahmed]] in 1972, was developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973; they published their results in 1974.<ref name="Ahmed">{{cite journal |last= Ahmed |first= Nasir |author-link= N. Ahmed |title= How I Came Up With the Discrete Cosine Transform |journal= [[Digital Signal Processing (journal)| Digital Signal Processing]] |date= January 1991 |volume= 1 |issue= 1 |pages= 4–5 |doi= 10.1016/1051-2004(91)90086-Z |bibcode= 1991DSP.....1....4A |url= https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform |access-date= 19 November 2019 |archive-date= 10 June 2016 |archive-url= https://web.archive.org/web/20160610013109/https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform |url-status= live }}</ref><ref name="pubDCT">{{Citation |first1= Nasir |last1= Ahmed |author1-link= N. Ahmed |first2= T. |last2= Natarajan |first3= K. R. |last3= Rao |title= Discrete Cosine Transform |journal= IEEE Transactions on Computers |date= January 1974 |volume= C-23 |issue= 1 |pages= 90–93 |doi= 10.1109/T-C.1974.223784|s2cid= 149806273 }}</ref><ref name="pubRaoYip">{{Citation |last1= Rao |first1= K. R. |author-link1= K. R. Rao |last2= Yip |first2= P. |title= Discrete Cosine Transform: Algorithms, Advantages, Applications |publisher= Academic Press |location= Boston |year= 1990 |isbn= 978-0-12-580203-1}}</ref> This led to the development of the [[modified discrete cosine transform]] (MDCT), proposed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987,<ref>J. P. Princen, A. W. Johnson und A. B. Bradley: ''Subband/transform coding using filter bank designs based on time domain aliasing cancellation'', IEEE Proc. Intl. Conference on Acoustics, Speech, and Signal Processing (ICASSP), 2161–2164, 1987</ref> following earlier work by Princen and Bradley in 1986.<ref>John P. Princen, Alan B. Bradley: ''Analysis/synthesis filter bank design based on time domain aliasing cancellation'', IEEE Trans. Acoust. Speech Signal Processing, ''ASSP-34'' (5), 1153–1161, 1986</ref> The MDCT later became a core part of the MP3 algorithm.<ref name="Guckert">{{cite web |last1= Guckert |first1= John |title= The Use of FFT and MDCT in MP3 Audio Compression |url= http://www.math.utah.edu/~gustafso/s2012/2270/web-projects/Guckert-audio-compression-svd-mdct-MP3.pdf |website= [[University of Utah]] |date= Spring 2012 |access-date= 14 July 2019 |archive-date= 12 February 2021 |archive-url= https://web.archive.org/web/20210212022237/http://www.math.utah.edu/~gustafso/s2012/2270/web-projects/Guckert-audio-compression-svd-mdct-MP3.pdf |url-status= live }}</ref>
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=== Encoding and decoding ===
In short, MP3 compression works by reducing the accuracy of certain components of sound that are considered (by psychoacoustic analysis) to be beyond the [[Hearing range#Humans|hearing capabilities]] of most humans. This method is commonly referred to as perceptual coding or [[psychoacoustic]] modeling.<ref name="Jayant1993" /> The remaining audio information is then recorded in a space-efficient manner using [[MDCT]] and [[FFT]] algorithms.
 
The MP3 encoding algorithm is generally split into four parts. Part 1 divides the audio signal into smaller pieces, called frames, and an MDCT filter is then performed on the output. Part 2 passes the sample into a 1024-point [[fast Fourier transform]] (FFT), then the [[psychoacoustic]] model is applied and another MDCT filter is performed on the output. Part 3 quantifies and encodes each sample, known as noise allocation, which adjusts itself to meet the bit rate and [[sound masking]] requirements. Part 4 formats the [[bitstream]], called an audio frame, which is made up of 4 parts, the [[Header (computing)|header]], [[Error checking|error check]], [[audio data]], and [[#Ancillary data|ancillary data]].<ref name="Guckert"/>
 
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{{reflist|30em|refs=
<ref name="mp3-name">{{cite web | url = http://www.businesswire.com/news/home/20050712005686/en/Fraunhofer-IIS-Happy-Birthday-MP3! | title = Happy Birthday MP3! | publisher = Fraunhofer IIS | date = 12 July 2005 | access-date = 18 July 2010 | archive-date = 11 December 2014 | archive-url = https://web.archive.org/web/20141211110033/http://www.businesswire.com/news/home/20050712005686/en/Fraunhofer-IIS-Happy-Birthday-MP3! | url-status = livedead }}</ref>
<ref name="audio/mpeg">{{cite journal | url = http://tools.ietf.org/html/rfc3003 | title = The audio/mpeg Media Type&nbsp;— RFC 3003 | publisher = IETF | date = November 2000 | doi = 10.17487/RFC3003 | access-date = 7 December 2009 | last1 = Nilsson | first1 = M. | archive-date = 13 April 2012 | archive-url = https://web.archive.org/web/20120413074234/http://tools.ietf.org/html/rfc3003 | url-status = live }}</ref>
<ref name="RTP">{{cite journal | url = http://tools.ietf.org/html/rfc3555#page-24 | title = MIME Type Registration of RTP Payload Formats&nbsp;— RFC 3555 | publisher = IETF | date = July 2003 | doi = 10.17487/RFC3555 | access-date = 7 December 2009 | last1 = Casner | first1 = S. | last2 = Hoschka | first2 = P. | archive-date = 14 January 2012 | archive-url = https://web.archive.org/web/20120114154203/http://tools.ietf.org/html/rfc3555#page-24 | url-status = live }}</ref>
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* [https://www.mp3-history.com/ MP3-history.com] {{Webarchive|url=https://web.archive.org/web/20200211201051/https://www.mp3-history.com/ |date=11 February 2020 }}, The Story of MP3: How MP3 was invented, by Fraunhofer IIS.<!-- https://web.archive.org/web/20070610231859/http://www.iis.fraunhofer.de/EN/bf/amm/mp3history/mp3history03.jsp -->▼
* {{Curlie|Computers/Multimedia/Music_and_Audio/Audio_Formats/MP3/}}
▲* [https://www.mp3-history.com/ MP3-history.com] {{Webarchive|url=https://web.archive.org/web/20200211201051/https://www.mp3-history.com/ |date=11 February 2020 }}, The Story of MP3: How MP3 was invented, by Fraunhofer IIS.
* [https://www.mp3newswire.net/sect/archive.htm MP3 News Archive]. {{Webarchive|url=https://web.archive.org/web/20190303201456/https://www.mp3newswire.net/sect/archive.htm |date=3 March 2019 }} – over 1000 articles from 1999 to 2011 focused on MP3 and digital audio.
* [https://www.mpeg.chiariglione.org/ MPEG.chiariglione.org] {{Webarchive|url=https://web.archive.org/web/20240410005848/https://mpeg.chiariglione.org/ |date=10 April 2024 }} – MPEG official website
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