Advanced Audio Coding - Revision history

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	The reference software for MPEG-4 Part 3 is specified in MPEG-4 Part 5 and the conformance bit-streams are specified in MPEG-4 Part 4. MPEG-4 Audio remains [[backward-compatible]] with MPEG-2 Part 7.<ref name="mpeg4audio-mpeg2audio">{{cite web\|url=http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|title=MPEG-4 Natural Audio Coding - General Audio Coding (AAC based) \|first1=Karlheinz \|last1=Brandenburg \|first2=Oliver \|last2=Kunz \|first3=Akihiko \|last3=Sugiyama \|website=chiariglione.org \|year=1999 \|access-date=2009-10-06 \|url-status=dead \|archive-url=https://web.archive.org/web/20100219233137/http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|archive-date=2010-02-19 }}</ref>		The reference software for MPEG-4 Part 3 is specified in MPEG-4 Part 5 and the conformance bit-streams are specified in MPEG-4 Part 4. MPEG-4 Audio remains [[backward-compatible]] with MPEG-2 Part 7.<ref name="mpeg4audio-mpeg2audio">{{cite web\|url=http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|title=MPEG-4 Natural Audio Coding - General Audio Coding (AAC based) \|first1=Karlheinz \|last1=Brandenburg \|first2=Oliver \|last2=Kunz \|first3=Akihiko \|last3=Sugiyama \|website=chiariglione.org \|year=1999 \|access-date=2009-10-06 \|url-status=dead \|archive-url=https://web.archive.org/web/20100219233137/http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|archive-date=2010-02-19 }}</ref>

	The MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000) defined new audio object types: the low delay AAC ([[AAC-LD]]) object type, bit-sliced arithmetic coding (BSAC) object type, parametric audio coding using [[Harmonic and Individual Lines and Noise\|harmonic and individual line plus noise]] and error resilient (ER) versions of object types.<ref name="mpeg4audio-iso-2-amd">{{cite web \| url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| title=ISO/IEC 14496-3:1999/Amd 1:2000 - Audio extensions \| publisher=[[ISO]] \| year=2000 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606215234/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| archive-date=2011-06-06 }}</ref><ref name="mpeg4audio-version2">{{~~cite~~ ~~web~~ \| url=ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf \| title=ISO/IEC 14496-3:/Amd.1 - Final Committee Draft - MPEG-4 Audio Version 2 ~~\| publisher=[[ISO]]/[[IEC]] JTC 1/SC 29/WG 11~~ \| date=July 1999 \| access-date=2009-10-07 \| ~~archive~~-~~url~~=~~http://webarchive.loc.gov/all/20120801161551/ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf~~ \| ~~archive-date~~=~~2012-08-01~~ \| ~~url-status=dead~~ }}</ref><ref name="mpeg4audio2">{{cite web\|url=https://sound.media.mit.edu/resources/mpeg4/audio/general/aes108_6-Parametric.pdf\|title=MPEG-4 Version 2 Audio Workshop:HILN - Parametric Audio Coding\|at=AES 108th Convention: MPEG-4 Version 2 Audio What is it about?\|location=Paris\| first1=Heiko \|last1=Purnhagen \| date=19 February 2000 \| access-date=2009-10-07}}</ref> It also defined four new audio profiles: High Quality Audio Profile, Low Delay Audio Profile, Natural Audio Profile and Mobile Audio Internetworking Profile.<ref name="mpeg4-profiles">{{cite web\|url=http://www.m4if.org/resources/profiles/audio.php \|archive-url=http://webarchive.loc.gov/all/20100108152236/http://www.m4if.org/resources/profiles/audio.php \|url-status=dead \|archive-date=2010-01-08 \|title=Levels for Audio Profiles \|first1=Fernando \|last1=Pereira \|publisher=MPEG Industry Forum \|date=October 2001 \|access-date=2009-10-15 }}</ref>		The MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000) defined new audio object types: the low delay AAC ([[AAC-LD]]) object type, bit-sliced arithmetic coding (BSAC) object type, parametric audio coding using [[Harmonic and Individual Lines and Noise\|harmonic and individual line plus noise]] and error resilient (ER) versions of object types.<ref name="mpeg4audio-iso-2-amd">{{cite web \| url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| title=ISO/IEC 14496-3:1999/Amd 1:2000 - Audio extensions \| publisher=[[ISO]] \| year=2000 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606215234/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| archive-date=2011-06-06 }}</ref><ref name="mpeg4audio-version2">{{Cite FTP \| url=ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf \| title=ISO/IEC 14496-3:/Amd.1 - Final Committee Draft - MPEG-4 Audio Version 2 \| date=July 1999 \| access-date=2009-10-07 \| url-status=dead \| server=[[ISO]]/[[IEC]] JTC 1/SC 29/WG 11 }}</ref><ref name="mpeg4audio2">{{cite web\|url=https://sound.media.mit.edu/resources/mpeg4/audio/general/aes108_6-Parametric.pdf\|title=MPEG-4 Version 2 Audio Workshop:HILN - Parametric Audio Coding\|at=AES 108th Convention: MPEG-4 Version 2 Audio What is it about?\|location=Paris\| first1=Heiko \|last1=Purnhagen \| date=19 February 2000 \| access-date=2009-10-07}}</ref> It also defined four new audio profiles: High Quality Audio Profile, Low Delay Audio Profile, Natural Audio Profile and Mobile Audio Internetworking Profile.<ref name="mpeg4-profiles">{{cite web\|url=http://www.m4if.org/resources/profiles/audio.php \|archive-url=http://webarchive.loc.gov/all/20100108152236/http://www.m4if.org/resources/profiles/audio.php \|url-status=dead \|archive-date=2010-01-08 \|title=Levels for Audio Profiles \|first1=Fernando \|last1=Pereira \|publisher=MPEG Industry Forum \|date=October 2001 \|access-date=2009-10-15 }}</ref>

	The [[HE-AAC]] Profile (AAC LC with [[Spectral band replication\|SBR]]) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.<ref name="he-aac-amd1">{{cite web \| url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| title=ISO/IEC 14496-3:2001/Amd 1:2003 - Bandwidth extension \| publisher=[[ISO]] \| year=2003 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606054451/http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| archive-date=2011-06-06 }}</ref> The HE-AAC v2 Profile (AAC LC with SBR and Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016">{{cite web\|url=http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|title=Text of ISO/IEC 14496-3:2001/FPDAM 4, Audio Lossless Coding (ALS), new audio profiles and BSAC extensions \|format=DOC \|publisher=[[ISO]]/[[IEC]] JTC1/SC29/WG11/N7016 \|date=11 January 2005 \|access-date=2009-10-09 \|url-status=dead \|archive-url=https://web.archive.org/web/20140512215821/http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|archive-date=12 May 2014 }}</ref><ref name="ISO 14496-3:2005/Amd.2">{{cite web \| title=Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, ISO/IEC 14496-3:2005/Amd 2:2006 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| publisher=[[ISO]] \| year=2006 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104072435/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| archive-date=2012-01-04 }}</ref><ref name="embedded">{{cite web \| title=Audio compression gets better and more complex \| url=http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| first=Mihir \| last=Mody \| website=Embedded.com \| date=6 June 2005 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20160208004827/http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| archive-date=8 February 2016 }}</ref> The Parametric Stereo audio object type used in HE-AAC v2 was first defined in ISO/IEC 14496-3:2001/Amd 2:2004.<ref name="CT-whitepaper">{{cite web\|url=http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|title=MPEG-4 aacPlus - Audio coding for today's digital media world\|access-date=2007-01-29 \|url-status=dead \|archive-url=https://web.archive.org/web/20061026031407/http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|archive-date=2006-10-26 }}</ref><ref name="parametric">{{cite web \| title=Parametric coding for high-quality audio, ISO/IEC 14496-3:2001/Amd 2:2004 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| publisher=[[ISO]] \| year=2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104071002/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| archive-date=2012-01-04 }}</ref><ref name="3gpp26401">{{cite web \| title=3GPP TS 26.401 V6.0.0 (2004-09), General Audio Codec audio processing functions; Enhanced aacPlus General Audio Codec; General Description (Release 6) \| url=http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| format=DOC \| publisher=3GPP \| date=30 September 2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20060819083421/http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| archive-date=19 August 2006 }}</ref>		The [[HE-AAC]] Profile (AAC LC with [[Spectral band replication\|SBR]]) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.<ref name="he-aac-amd1">{{cite web \| url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| title=ISO/IEC 14496-3:2001/Amd 1:2003 - Bandwidth extension \| publisher=[[ISO]] \| year=2003 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606054451/http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| archive-date=2011-06-06 }}</ref> The HE-AAC v2 Profile (AAC LC with SBR and Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016">{{cite web\|url=http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|title=Text of ISO/IEC 14496-3:2001/FPDAM 4, Audio Lossless Coding (ALS), new audio profiles and BSAC extensions \|format=DOC \|publisher=[[ISO]]/[[IEC]] JTC1/SC29/WG11/N7016 \|date=11 January 2005 \|access-date=2009-10-09 \|url-status=dead \|archive-url=https://web.archive.org/web/20140512215821/http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|archive-date=12 May 2014 }}</ref><ref name="ISO 14496-3:2005/Amd.2">{{cite web \| title=Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, ISO/IEC 14496-3:2005/Amd 2:2006 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| publisher=[[ISO]] \| year=2006 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104072435/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| archive-date=2012-01-04 }}</ref><ref name="embedded">{{cite web \| title=Audio compression gets better and more complex \| url=http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| first=Mihir \| last=Mody \| website=Embedded.com \| date=6 June 2005 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20160208004827/http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| archive-date=8 February 2016 }}</ref> The Parametric Stereo audio object type used in HE-AAC v2 was first defined in ISO/IEC 14496-3:2001/Amd 2:2004.<ref name="CT-whitepaper">{{cite web\|url=http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|title=MPEG-4 aacPlus - Audio coding for today's digital media world\|access-date=2007-01-29 \|url-status=dead \|archive-url=https://web.archive.org/web/20061026031407/http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|archive-date=2006-10-26 }}</ref><ref name="parametric">{{cite web \| title=Parametric coding for high-quality audio, ISO/IEC 14496-3:2001/Amd 2:2004 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| publisher=[[ISO]] \| year=2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104071002/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| archive-date=2012-01-04 }}</ref><ref name="3gpp26401">{{cite web \| title=3GPP TS 26.401 V6.0.0 (2004-09), General Audio Codec audio processing functions; Enhanced aacPlus General Audio Codec; General Description (Release 6) \| url=http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| format=DOC \| publisher=3GPP \| date=30 September 2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20060819083421/http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| archive-date=19 August 2006 }}</ref>

OAbot: Open access bot: url-access updated in citation with #oabot.

2025-05-24T07:29:55Z

Open access bot: url-access updated in citation with #oabot.

← Previous revision		Revision as of 07:29, 24 May 2025
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	==History==		==History==
	===Background===		===Background===
	The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed\|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing 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}}</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 [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<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}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web \|last=Borland \|first=John \|date=March 18, 2004 \|title=The sound of science \|url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ \|access-date=2023-04-21 \|website=CNET \|language=en}}</ref>		The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed\|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing 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\|url-access=subscription }}</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 [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<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}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web \|last=Borland \|first=John \|date=March 18, 2004 \|title=The sound of science \|url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ \|access-date=2023-04-21 \|website=CNET \|language=en}}</ref>

	AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society\|Fraunhofer IIS]] (who developed MP3) and [[Sony\|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report \|url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio \|date=1 September 2009 \|access-date=2009-10-07 \|archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|url-status=live \|archive-date=14 June 2011 \|publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone\|NTT]].<ref name="aac-licensors">{{cite web \|title=AAC Licensors \|url=https://www.via-corp.com/licensing/aac/aac-licensors/ \|access-date=15 January 2020 \|website=Via Corp}}</ref><ref name="businesswire">{{cite web \|date=5 January 2009 \|title=Via Licensing Announces Updated AAC Joint Patent License \|url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License \|access-date=18 June 2019 \|website=[[Business Wire]]}}</ref>		AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society\|Fraunhofer IIS]] (who developed MP3) and [[Sony\|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report \|url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio \|date=1 September 2009 \|access-date=2009-10-07 \|archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|url-status=live \|archive-date=14 June 2011 \|publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone\|NTT]].<ref name="aac-licensors">{{cite web \|title=AAC Licensors \|url=https://www.via-corp.com/licensing/aac/aac-licensors/ \|access-date=15 January 2020 \|website=Via Corp}}</ref><ref name="businesswire">{{cite web \|date=5 January 2009 \|title=Via Licensing Announces Updated AAC Joint Patent License \|url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License \|access-date=18 June 2019 \|website=[[Business Wire]]}}</ref>

Snow Lion Fenian at 02:56, 20 May 2025

2025-05-20T02:56:59Z

← Previous revision		Revision as of 02:56, 20 May 2025
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	{{Infobox file format		{{Infobox file format
	\| name = Advanced Audio Coding		\| name = Advanced Audio Coding
	\| icon = AAC original logo.~~png~~		\| icon = AAC original logo.svg
	\| icon_size = 125		\| icon_size = 125
	\| screenshot =		\| screenshot =

BattyBot: Removed/fixed incorrect author parameter(s), performed general fixes

2025-05-07T04:22:12Z

Removed/fixed incorrect author parameter(s), performed general fixes

← Previous revision		Revision as of 04:22, 7 May 2025
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	The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed\|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing 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}}</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 [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<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}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web \|last=Borland \|first=John \|date=March 18, 2004 \|title=The sound of science \|url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ \|access-date=2023-04-21 \|website=CNET \|language=en}}</ref>		The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed\|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing 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}}</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 [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<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}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web \|last=Borland \|first=John \|date=March 18, 2004 \|title=The sound of science \|url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ \|access-date=2023-04-21 \|website=CNET \|language=en}}</ref>

	AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society\|Fraunhofer IIS]] (who developed MP3) and [[Sony\|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report \|url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio \|date=1 September 2009 \|access-date=2009-10-07 \|archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|url-status=live \|archive-date=14 June 2011 \|publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone\|NTT]].<ref name="aac-licensors">{{cite web \|title=AAC Licensors \|url=https://www.via-corp.com/licensing/aac/aac-licensors/ \|access-date=15 January 2020 \|website=Via Corp}}</ref><ref name="businesswire">{{cite web \|date=5 January 2009 \|title=Via Licensing Announces Updated AAC Joint Patent License \|url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License \|access-date=18 June 2019 \|website=[[Business Wire]]}}</ref>		AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society\|Fraunhofer IIS]] (who developed MP3) and [[Sony\|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report \|url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio \|date=1 September 2009 \|access-date=2009-10-07 \|archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|url-status=live \|archive-date=14 June 2011 \|publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone\|NTT]].<ref name="aac-licensors">{{cite web \|title=AAC Licensors \|url=https://www.via-corp.com/licensing/aac/aac-licensors/ \|access-date=15 January 2020 \|website=Via Corp}}</ref><ref name="businesswire">{{cite web \|date=5 January 2009 \|title=Via Licensing Announces Updated AAC Joint Patent License \|url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License \|access-date=18 June 2019 \|website=[[Business Wire]]}}</ref>

	===Standardization===		===Standardization===
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	[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web \|last=RadioWorld \|date=2002-03-26 \|title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program \|url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program \|access-date=2025-04-11 \|website=Radio World \|language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].		[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web \|last=RadioWorld \|date=2002-03-26 \|title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program \|url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program \|access-date=2025-04-11 \|website=Radio World \|language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].

	Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web \|title=Carrying A Tune With Nokia Phones \|url=https://www.forbes.com/2001/08/30/0830tentech.html \|access-date=2025-04-11 \|website=Forbes \|language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite magazine \|~~last~~=Staff ~~\|first=WIRED~~ \|title=A Music File by Any Other Name \|url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite magazine \|last=Buskirk \|first=Eliot Van \|title=In EMI-ITunes Deal, the Big Loser May Be Microsoft \|url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref>		Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web \|title=Carrying A Tune With Nokia Phones \|url=https://www.forbes.com/2001/08/30/0830tentech.html \|access-date=2025-04-11 \|website=Forbes \|language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite magazine \|author=WIRED Staff \|title=A Music File by Any Other Name \|url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite magazine \|last=Buskirk \|first=Eliot Van \|title=In EMI-ITunes Deal, the Big Loser May Be Microsoft \|url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref>

	By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web \|author1=What Hi-Fi Admin \|date=2017-05-15 \|title=Home \|url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref>		By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web \|author1=What Hi-Fi Admin \|date=2017-05-15 \|title=Home \|url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref>

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← Previous revision		Revision as of 18:03, 4 May 2025
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	\| standard = [[ISO/IEC 13818-7]],<br/>[[ISO/IEC 14496-3]]		\| standard = [[ISO/IEC 13818-7]],<br/>[[ISO/IEC 14496-3]]
	}}		}}
	'''Advanced Audio Coding''' ('''AAC''') is an [[audio coding standard]] for [[lossy]] [[digital audio]] [[Audio data compression\|compression]]. It was developed by [[Dolby]], [[AT&T Labs\|AT&T]], [[Fraunhofer Society\|Fraunhofer]] and [[Sony]],<ref name=":3">{{Cite web \|date=2002-06-09 \|title=AAC in the Chips \|url=https://www.stereophile.com/news/11361/index.html \|access-date=2025-04-11 \|website=Stereophile.com \|language=en}}</ref><ref>{{Cite web \|date=2000 \|title=Dolby Laboratories Announces AAC Support Program \|url=https://web.archive.org/web/20000823164039/http://www.aac-audio.com/pdf/m.pr.0003.AACInauguration.pdf}}</ref><ref>{{Cite web \|date=2001-04-17 \|title=MP3's Competitors Line Up \|url=https://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=63900 \|access-date=2025-04-11 \|website=Streaming Media Magazine \|language=en-US}}</ref> originally as part of the [[MPEG-2]] specification but later improved under [[MPEG-4]].<ref name="mpeg2">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345 ISO/IEC 13818-7:2006 – Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)] {{webarchive\|url=https://web.archive.org/web/20160303183701/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345\|date=2016-03-03}}, Retrieved on 2009-08-06</ref><ref name="mpeg4">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739 ISO/IEC 14496-3:2005 – Information technology — Coding of audio-visual objects — Part 3: Audio] {{webarchive\|url=https://web.archive.org/web/20160413224040/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739\|date=2016-04-13}}, Retrieved on 2009-08-06</ref> AAC was designed to be the successor of the [[MP3]] format (MPEG-2 Audio Layer III) and generally achieves higher sound quality than MP3 at the same [[bit rate]].<ref name="brandenburg">{{cite web \|last=Brandenburg \|first=Karlheinz \|year=1999 \|title=MP3 and AAC Explained \|url=http://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|url-status=dead \|archive-url=https://web.archive.org/web/20170213191747/https://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|archive-date=2017-02-13}}</ref> AAC encoded audio files are typically packaged in an [[MPEG-4 Part 14\|MP4]] [[Container format\|container]] most commonly using the [[filename extension]] <code>.m4a</code>.<ref>{{Cite news \|title=Apple seeking coder to port iTunes to Windows \|url=https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-url=http://web.archive.org/web/20240908131507/https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-date=2024-09-08 \|access-date=2025-04-11 \|language=en}}</ref><ref>{{Cite web \|last=says \|first=James \|date=2021-10-17 \|title=MP3 vs. AAC (.m4a) with Allan Tépper – PES 120 – Podcast Engineering School \|url=https://podcastengineeringschool.com/mp3-vs-aac-m4a-with-allan-tepper-pes-120/ \|access-date=2025-04-11 \|language=en-US}}</ref>		'''Advanced Audio Coding''' ('''AAC''') is an [[audio coding standard]] for [[lossy]] [[digital audio]] [[Audio data compression\|compression]]. It was developed by [[Dolby]], [[AT&T Labs\|AT&T]], [[Fraunhofer Society\|Fraunhofer]] and [[Sony]],<ref name=":3">{{Cite web \|date=2002-06-09 \|title=AAC in the Chips \|url=https://www.stereophile.com/news/11361/index.html \|access-date=2025-04-11 \|website=Stereophile.com \|language=en}}</ref><ref>{{Cite web \|date=2000 \|title=Dolby Laboratories Announces AAC Support Program \|url=http://www.aac-audio.com/pdf/m.pr.0003.AACInauguration.pdf\|archive-url=https://web.archive.org/web/20000823164039/http://www.aac-audio.com/pdf/m.pr.0003.AACInauguration.pdf \|archive-date=23 August 2000 }}</ref><ref>{{Cite web \|date=2001-04-17 \|title=MP3's Competitors Line Up \|url=https://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=63900 \|access-date=2025-04-11 \|website=Streaming Media Magazine \|language=en-US}}</ref> originally as part of the [[MPEG-2]] specification but later improved under [[MPEG-4]].<ref name="mpeg2">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345 ISO/IEC 13818-7:2006 – Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)] {{webarchive\|url=https://web.archive.org/web/20160303183701/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345\|date=2016-03-03}}, Retrieved on 2009-08-06</ref><ref name="mpeg4">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739 ISO/IEC 14496-3:2005 – Information technology — Coding of audio-visual objects — Part 3: Audio] {{webarchive\|url=https://web.archive.org/web/20160413224040/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739\|date=2016-04-13}}, Retrieved on 2009-08-06</ref> AAC was designed to be the successor of the [[MP3]] format (MPEG-2 Audio Layer III) and generally achieves higher sound quality than MP3 at the same [[bit rate]].<ref name="brandenburg">{{cite web \|last=Brandenburg \|first=Karlheinz \|year=1999 \|title=MP3 and AAC Explained \|url=http://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|url-status=dead \|archive-url=https://web.archive.org/web/20170213191747/https://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|archive-date=2017-02-13}}</ref> AAC encoded audio files are typically packaged in an [[MPEG-4 Part 14\|MP4]] [[Container format\|container]] most commonly using the [[filename extension]] <code>.m4a</code>.<ref>{{Cite news \|title=Apple seeking coder to port iTunes to Windows \|url=https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-url=http://web.archive.org/web/20240908131507/https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-date=2024-09-08 \|access-date=2025-04-11 \|language=en}}</ref><ref>{{Cite web \|last=says \|first=James \|date=2021-10-17 \|title=MP3 vs. AAC (.m4a) with Allan Tépper – PES 120 – Podcast Engineering School \|url=https://podcastengineeringschool.com/mp3-vs-aac-m4a-with-allan-tepper-pes-120/ \|access-date=2025-04-11 \|language=en-US}}</ref>

	The basic profile of AAC (both MPEG-4 and MPEG-2) is called '''AAC-LC''' (''Low Complexity''). It is widely supported in the industry and has been adopted as the default or standard audio format on products including [[Apple Inc.\|Apple]]'s [[iTunes Store]], [[Nintendo]]'s [[Wii]],<ref>{{Cite web \|last=Caron \|first=Frank \|date=2007-11-14 \|title=Wii Photo Channel update adds customization, removes MP3 playback \|url=https://arstechnica.com/gaming/2007/11/wii-photo-channel-update-adds-customization-removes-mp3-playback/ \|access-date=2025-04-11 \|website=Ars Technica \|language=en-US}}</ref> [[Nintendo DSi\|DSi]] and [[Nintendo 3DS\|3DS]] and [[Sony]]'s [[PlayStation 3]].<ref>{{Cite web \|title=PS3™ {{!}} Importing audio CDs to the system storage \|url=https://manuals.playstation.net/document/en/ps3/current/music/cdimport.html \|access-date=2025-04-11 \|website=manuals.playstation.net}}</ref> It is also further supported on various other devices and software such as [[iPhone]], [[iPod]], [[PlayStation Portable]] and [[PlayStation Vita\|Vita]], [[PlayStation 5]], [[Android (operating system)\|Android]] and older cell phones,<ref>{{Cite web \|date=2006-05-10 \|title=Sony to support AAC -- heck not to freeze over \|url=https://www.engadget.com/2006-05-10-sony-to-support-aac-heck-not-to-freeze-over.html \|access-date=2025-04-11 \|website=Engadget \|language=en-US}}</ref> digital audio players like [[Sony Walkman]] and [[SanDisk Clip]], media players such as [[VLC media player\|VLC]], [[Winamp]] and [[Windows Media Player]], various in-dash [[Vehicle audio\|car audio]] systems,<ref>{{Cite web \|title=Pioneer Releases Car Audio Package for a Limited Time in the Overseas Markets to Commemorate the 80th Anniversary of its Foundation {{!}} News Releases {{!}} News and Events {{!}} About Us {{!}} Pioneer \|url=https://global.pioneer/en/corp/news/press/index/2175/ \|access-date=2025-04-11 \|website=Pioneer Corporation \|language=en}}</ref> and is used on [[Spotify]],<ref>{{cite web \|title=Audio file formats for Spotify \|url=https://artists.spotify.com/help/article/audio-file-formats \|access-date=20 September 2021 \|website=Spotify}}</ref> [[Apple Music]],{{efn\|only used on web player, [[Google Home]], [[Amazon Alexa]], and [[Microsoft Windows]] app.}} and [[YouTube]] web streaming services.<ref>{{Cite web \|last=updated \|first=Joe Svetlik Contributions from Becky Scarrott last \|date=2022-07-25 \|title=MP3, AAC, WAV, FLAC: all the audio file formats explained \|url=https://www.whathifi.com/advice/mp3-aac-wav-flac-all-the-audio-file-formats-explained \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref> AAC has been further extended into [[HE-AAC]] (''High Efficiency'', or AAC+), which improves efficiency over AAC-LC.<ref>{{Cite web \|date=2004 \|title=Dolby adds High-Efficiency AAC to MPEG 4 patent pool \|url=https://www.theregister.com/2004/07/20/aac_he_licensing/}}</ref> Another variant is [[AAC-LD]] (''Low Delay'').<ref>{{Cite web \|last=Rose \|first=Matthias \|date=2012-06-28 \|title=Understanding MPEG Audio Codecs From mp3 To xHE-AAC \|url=https://www.electronicdesign.com/technologies/embedded/article/21796123/understanding-mpeg-audio-codecs-from-mp3-to-xhe-aac \|access-date=2025-04-11 \|website=Electronic Design \|language=en}}</ref>		The basic profile of AAC (both MPEG-4 and MPEG-2) is called '''AAC-LC''' (''Low Complexity''). It is widely supported in the industry and has been adopted as the default or standard audio format on products including [[Apple Inc.\|Apple]]'s [[iTunes Store]], [[Nintendo]]'s [[Wii]],<ref>{{Cite web \|last=Caron \|first=Frank \|date=2007-11-14 \|title=Wii Photo Channel update adds customization, removes MP3 playback \|url=https://arstechnica.com/gaming/2007/11/wii-photo-channel-update-adds-customization-removes-mp3-playback/ \|access-date=2025-04-11 \|website=Ars Technica \|language=en-US}}</ref> [[Nintendo DSi\|DSi]] and [[Nintendo 3DS\|3DS]] and [[Sony]]'s [[PlayStation 3]].<ref>{{Cite web \|title=PS3™ {{!}} Importing audio CDs to the system storage \|url=https://manuals.playstation.net/document/en/ps3/current/music/cdimport.html \|access-date=2025-04-11 \|website=manuals.playstation.net}}</ref> It is also further supported on various other devices and software such as [[iPhone]], [[iPod]], [[PlayStation Portable]] and [[PlayStation Vita\|Vita]], [[PlayStation 5]], [[Android (operating system)\|Android]] and older cell phones,<ref>{{Cite web \|date=2006-05-10 \|title=Sony to support AAC -- heck not to freeze over \|url=https://www.engadget.com/2006-05-10-sony-to-support-aac-heck-not-to-freeze-over.html \|access-date=2025-04-11 \|website=Engadget \|language=en-US}}</ref> digital audio players like [[Sony Walkman]] and [[SanDisk Clip]], media players such as [[VLC media player\|VLC]], [[Winamp]] and [[Windows Media Player]], various in-dash [[Vehicle audio\|car audio]] systems,<ref>{{Cite web \|title=Pioneer Releases Car Audio Package for a Limited Time in the Overseas Markets to Commemorate the 80th Anniversary of its Foundation {{!}} News Releases {{!}} News and Events {{!}} About Us {{!}} Pioneer \|url=https://global.pioneer/en/corp/news/press/index/2175/ \|access-date=2025-04-11 \|website=Pioneer Corporation \|language=en}}</ref> and is used on [[Spotify]],<ref>{{cite web \|title=Audio file formats for Spotify \|url=https://artists.spotify.com/help/article/audio-file-formats \|access-date=20 September 2021 \|website=Spotify}}</ref> [[Apple Music]],{{efn\|only used on web player, [[Google Home]], [[Amazon Alexa]], and [[Microsoft Windows]] app.}} and [[YouTube]] web streaming services.<ref>{{Cite web \|last=updated \|first=Joe Svetlik Contributions from Becky Scarrott last \|date=2022-07-25 \|title=MP3, AAC, WAV, FLAC: all the audio file formats explained \|url=https://www.whathifi.com/advice/mp3-aac-wav-flac-all-the-audio-file-formats-explained \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref> AAC has been further extended into [[HE-AAC]] (''High Efficiency'', or AAC+), which improves efficiency over AAC-LC.<ref>{{Cite web \|date=2004 \|title=Dolby adds High-Efficiency AAC to MPEG 4 patent pool \|url=https://www.theregister.com/2004/07/20/aac_he_licensing/}}</ref> Another variant is [[AAC-LD]] (''Low Delay'').<ref>{{Cite web \|last=Rose \|first=Matthias \|date=2012-06-28 \|title=Understanding MPEG Audio Codecs From mp3 To xHE-AAC \|url=https://www.electronicdesign.com/technologies/embedded/article/21796123/understanding-mpeg-audio-codecs-from-mp3-to-xhe-aac \|access-date=2025-04-11 \|website=Electronic Design \|language=en}}</ref>
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	=== Adoption ===		=== Adoption ===
	While the MP3 format has near-universal hardware and software support, primarily because MP3 was the format of choice during the crucial first few years of widespread music [[file-sharing]]/distribution over the internet, AAC remained a strong contender due to some unwavering industry support.<ref>{{cite web \|title=AAC \|url=http://wiki.hydrogenaud.io/index.php?title=AAC \|url-status=live \|archive-url=https://web.archive.org/web/20140706172307/http://wiki.hydrogenaud.io/index.php?title=AAC \|archive-date=2014-07-06 \|access-date=2011-01-24 \|publisher=Hydrogenaudio}}</ref> Due to MP3's dominance, adoption of AAC was initially slow. The first commercialization was in 1997 when [[AT&T Labs]] (a co-owner of AAC patents) launched a digital music store with songs encoded in MPEG-2 AAC.<ref name=":2">{{Cite web \|date=2001-08-08 \|title=News: A higher standard for digital music \|url=https://web.archive.org/web/20010808234826/https://www.zdnet.com/zdnn/stories/comment/0,5859,2699666,00.html \|~~access~~-date=~~2025-04-11~~ ~~\|website=web.archive.org~~}}</ref> HomeBoy for Windows was one of the earliest available AAC encoders and decoders.<ref>{{Cite web \|title=ReallyRareWares - HomeBoy AAC encoder \|url=https://www.rarewares.org/rrw/homeboy.php \|access-date=2025-04-11 \|website=www.rarewares.org}}</ref>		While the MP3 format has near-universal hardware and software support, primarily because MP3 was the format of choice during the crucial first few years of widespread music [[file-sharing]]/distribution over the internet, AAC remained a strong contender due to some unwavering industry support.<ref>{{cite web \|title=AAC \|url=http://wiki.hydrogenaud.io/index.php?title=AAC \|url-status=live \|archive-url=https://web.archive.org/web/20140706172307/http://wiki.hydrogenaud.io/index.php?title=AAC \|archive-date=2014-07-06 \|access-date=2011-01-24 \|publisher=Hydrogenaudio}}</ref> Due to MP3's dominance, adoption of AAC was initially slow. The first commercialization was in 1997 when [[AT&T Labs]] (a co-owner of AAC patents) launched a digital music store with songs encoded in MPEG-2 AAC.<ref name=":2">{{Cite web \|date=2001-08-08 \|title=News: A higher standard for digital music \|website=[[ZDNet]] \|url=https://www.zdnet.com/zdnn/stories/comment/0,5859,2699666,00.html \|access-date=2025-04-11 \|archive-url=https://web.archive.org/web/20010808234826/https://www.zdnet.com/zdnn/stories/comment/0,5859,2699666,00.html \|archive-date=8 August 2001 }}</ref> HomeBoy for Windows was one of the earliest available AAC encoders and decoders.<ref>{{Cite web \|title=ReallyRareWares - HomeBoy AAC encoder \|url=https://www.rarewares.org/rrw/homeboy.php \|access-date=2025-04-11 \|website=www.rarewares.org}}</ref>

	[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web \|last=RadioWorld \|date=2002-03-26 \|title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program \|url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program \|access-date=2025-04-11 \|website=Radio World \|language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].		[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web \|last=RadioWorld \|date=2002-03-26 \|title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program \|url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program \|access-date=2025-04-11 \|website=Radio World \|language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].

	Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web \|title=Carrying A Tune With Nokia Phones \|url=https://www.forbes.com/2001/08/30/0830tentech.html \|access-date=2025-04-11 \|website=Forbes \|language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite ~~news~~ \|last=Staff \|first=WIRED \|title=A Music File by Any Other Name \|url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ \|access-date=2025-04-11 \|~~work~~=Wired \|language=en-US \|issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite ~~news~~ \|last=Buskirk \|first=Eliot Van \|title=In EMI-ITunes Deal, the Big Loser May Be Microsoft \|url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ \|access-date=2025-04-11 \|~~work~~=Wired \|language=en-US \|issn=1059-1028}}</ref>		Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web \|title=Carrying A Tune With Nokia Phones \|url=https://www.forbes.com/2001/08/30/0830tentech.html \|access-date=2025-04-11 \|website=Forbes \|language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite magazine \|last=Staff \|first=WIRED \|title=A Music File by Any Other Name \|url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite magazine \|last=Buskirk \|first=Eliot Van \|title=In EMI-ITunes Deal, the Big Loser May Be Microsoft \|url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref>

	By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web \|~~last=published \|first~~=What Hi-Fi Admin \|date=2017-05-15 \|title=Home \|url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref>		By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web \|author1=What Hi-Fi Admin \|date=2017-05-15 \|title=Home \|url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref>

	==Functionality==		==Functionality==

Agendapeel: /* External links */

2025-04-26T00:45:21Z

External links

← Previous revision		Revision as of 00:45, 26 April 2025
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	==External links==		==External links==
	*[~~http~~://www.iis.fraunhofer.de/en/bf/amm/produkte/audiocodec.html Fraunhofer audio codecs]		*[https://www.iis.fraunhofer.de/en/bf/amm/produkte/audiocodec.html Fraunhofer audio codecs]
	*[~~http~~://www.audiocoding.com/ AudioCoding.com] {{Webarchive\|url=https://web.archive.org/web/20060825230111/~~http~~://www.audiocoding.com/ \|date=2006-08-25 }} – home of FAAC and FAAD2		*[https://www.audiocoding.com/ AudioCoding.com] {{Webarchive\|url=https://web.archive.org/web/20060825230111/https://www.audiocoding.com/ \|date=2006-08-25 }} – home of FAAC and FAAD2
	*[~~http~~://mpeg.chiariglione.org/ Official MPEG web site]		*[https://mpeg.chiariglione.org/ Official MPEG web site]
	*[[commons:File:AAC profiles.svg\|AAC improvements and extensions (2004)]]		*[[commons:File:AAC profiles.svg\|AAC improvements and extensions (2004)]]
	*{{IETF RFC\|3016}} - RTP Payload Format for MPEG-4 Audio/Visual Streams		*{{IETF RFC\|3016}} - RTP Payload Format for MPEG-4 Audio/Visual Streams

Mpaytw: /* Products that support AAC */

2025-04-17T20:21:53Z

Products that support AAC

Show changes

Mpaytw: .adif .adts

2025-04-17T20:00:12Z

.adif .adts

← Previous revision		Revision as of 20:00, 17 April 2025
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	\| screenshot =		\| screenshot =
	\| caption =		\| caption =
	\| extension = {{code\|.3gp, .aac, .m4a, .m4b, .m4p, .m4r, .mp4}}		\| extension = {{code\|.3gp, .aac, .adif, .adts, .m4a, .m4b, .m4p, .m4r, .mp4}}
	\| _noextcode = 1		\| _noextcode = 1
	\| mime = audio/aac <br /> audio/aacp <br /> audio/3gpp <br /> audio/3gpp2 <br /> audio/mp4 <br /> audio/mp4a-latm <br /> audio/mpeg4-generic		\| mime = audio/aac <br /> audio/aacp <br /> audio/3gpp <br /> audio/3gpp2 <br /> audio/mp4 <br /> audio/mp4a-latm <br /> audio/mpeg4-generic
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	'''Advanced Audio Coding''' ('''AAC''') is an [[audio coding standard]] for [[lossy]] [[digital audio]] [[Audio data compression\|compression]]. It was developed by [[Dolby]], [[AT&T Labs\|AT&T]], [[Fraunhofer Society\|Fraunhofer]] and [[Sony]],<ref name=":3">{{Cite web \|date=2002-06-09 \|title=AAC in the Chips \|url=https://www.stereophile.com/news/11361/index.html \|access-date=2025-04-11 \|website=Stereophile.com \|language=en}}</ref><ref>{{Cite web \|date=2000 \|title=Dolby Laboratories Announces AAC Support Program \|url=https://web.archive.org/web/20000823164039/http://www.aac-audio.com/pdf/m.pr.0003.AACInauguration.pdf}}</ref><ref>{{Cite web \|date=2001-04-17 \|title=MP3's Competitors Line Up \|url=https://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=63900 \|access-date=2025-04-11 \|website=Streaming Media Magazine \|language=en-US}}</ref> originally as part of the [[MPEG-2]] specification but later improved under [[MPEG-4]].<ref name="mpeg2">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345 ISO/IEC 13818-7:2006 – Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)] {{webarchive\|url=https://web.archive.org/web/20160303183701/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345\|date=2016-03-03}}, Retrieved on 2009-08-06</ref><ref name="mpeg4">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739 ISO/IEC 14496-3:2005 – Information technology — Coding of audio-visual objects — Part 3: Audio] {{webarchive\|url=https://web.archive.org/web/20160413224040/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739\|date=2016-04-13}}, Retrieved on 2009-08-06</ref> AAC was designed to be the successor of the [[MP3]] format (MPEG-2 Audio Layer III) and generally achieves higher sound quality than MP3 at the same [[bit rate]].<ref name="brandenburg">{{cite web \|last=Brandenburg \|first=Karlheinz \|year=1999 \|title=MP3 and AAC Explained \|url=http://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|url-status=dead \|archive-url=https://web.archive.org/web/20170213191747/https://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|archive-date=2017-02-13}}</ref> AAC encoded audio files are typically packaged in an [[MPEG-4 Part 14\|MP4]] [[Container format\|container]] most commonly using the [[filename extension]] <code>.m4a</code>.<ref>{{Cite news \|title=Apple seeking coder to port iTunes to Windows \|url=https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-url=http://web.archive.org/web/20240908131507/https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-date=2024-09-08 \|access-date=2025-04-11 \|language=en}}</ref><ref>{{Cite web \|last=says \|first=James \|date=2021-10-17 \|title=MP3 vs. AAC (.m4a) with Allan Tépper – PES 120 – Podcast Engineering School \|url=https://podcastengineeringschool.com/mp3-vs-aac-m4a-with-allan-tepper-pes-120/ \|access-date=2025-04-11 \|language=en-US}}</ref>		'''Advanced Audio Coding''' ('''AAC''') is an [[audio coding standard]] for [[lossy]] [[digital audio]] [[Audio data compression\|compression]]. It was developed by [[Dolby]], [[AT&T Labs\|AT&T]], [[Fraunhofer Society\|Fraunhofer]] and [[Sony]],<ref name=":3">{{Cite web \|date=2002-06-09 \|title=AAC in the Chips \|url=https://www.stereophile.com/news/11361/index.html \|access-date=2025-04-11 \|website=Stereophile.com \|language=en}}</ref><ref>{{Cite web \|date=2000 \|title=Dolby Laboratories Announces AAC Support Program \|url=https://web.archive.org/web/20000823164039/http://www.aac-audio.com/pdf/m.pr.0003.AACInauguration.pdf}}</ref><ref>{{Cite web \|date=2001-04-17 \|title=MP3's Competitors Line Up \|url=https://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=63900 \|access-date=2025-04-11 \|website=Streaming Media Magazine \|language=en-US}}</ref> originally as part of the [[MPEG-2]] specification but later improved under [[MPEG-4]].<ref name="mpeg2">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345 ISO/IEC 13818-7:2006 – Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)] {{webarchive\|url=https://web.archive.org/web/20160303183701/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43345\|date=2016-03-03}}, Retrieved on 2009-08-06</ref><ref name="mpeg4">ISO (2006) [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739 ISO/IEC 14496-3:2005 – Information technology — Coding of audio-visual objects — Part 3: Audio] {{webarchive\|url=https://web.archive.org/web/20160413224040/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42739\|date=2016-04-13}}, Retrieved on 2009-08-06</ref> AAC was designed to be the successor of the [[MP3]] format (MPEG-2 Audio Layer III) and generally achieves higher sound quality than MP3 at the same [[bit rate]].<ref name="brandenburg">{{cite web \|last=Brandenburg \|first=Karlheinz \|year=1999 \|title=MP3 and AAC Explained \|url=http://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|url-status=dead \|archive-url=https://web.archive.org/web/20170213191747/https://graphics.ethz.ch/teaching/mmcom12/slides/mp3_and_aac_brandenburg.pdf \|archive-date=2017-02-13}}</ref> AAC encoded audio files are typically packaged in an [[MPEG-4 Part 14\|MP4]] [[Container format\|container]] most commonly using the [[filename extension]] <code>.m4a</code>.<ref>{{Cite news \|title=Apple seeking coder to port iTunes to Windows \|url=https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-url=http://web.archive.org/web/20240908131507/https://www.theregister.com/2003/04/30/apple_seeking_coder_to_port/ \|archive-date=2024-09-08 \|access-date=2025-04-11 \|language=en}}</ref><ref>{{Cite web \|last=says \|first=James \|date=2021-10-17 \|title=MP3 vs. AAC (.m4a) with Allan Tépper – PES 120 – Podcast Engineering School \|url=https://podcastengineeringschool.com/mp3-vs-aac-m4a-with-allan-tepper-pes-120/ \|access-date=2025-04-11 \|language=en-US}}</ref>

	The basic profile of MPEG-4 ~~AAC~~ is ~~commonly~~ called '''AAC-LC''' (''Low Complexity''). It is widely supported in the industry and has been adopted as the default or standard audio format on products including [[Apple Inc.\|Apple]]'s [[iTunes Store]], [[Nintendo]]'s [[Wii]],<ref>{{Cite web \|last=Caron \|first=Frank \|date=2007-11-14 \|title=Wii Photo Channel update adds customization, removes MP3 playback \|url=https://arstechnica.com/gaming/2007/11/wii-photo-channel-update-adds-customization-removes-mp3-playback/ \|access-date=2025-04-11 \|website=Ars Technica \|language=en-US}}</ref> [[Nintendo DSi\|DSi]] and [[Nintendo 3DS\|3DS]] and [[Sony]]'s [[PlayStation 3]].<ref>{{Cite web \|title=PS3™ {{!}} Importing audio CDs to the system storage \|url=https://manuals.playstation.net/document/en/ps3/current/music/cdimport.html \|access-date=2025-04-11 \|website=manuals.playstation.net}}</ref> It is also further supported on various other devices and software such as [[iPhone]], [[iPod]], [[PlayStation Portable]] and [[PlayStation Vita\|Vita]], [[PlayStation 5]], [[Android (operating system)\|Android]] and older cell phones,<ref>{{Cite web \|date=2006-05-10 \|title=Sony to support AAC -- heck not to freeze over \|url=https://www.engadget.com/2006-05-10-sony-to-support-aac-heck-not-to-freeze-over.html \|access-date=2025-04-11 \|website=Engadget \|language=en-US}}</ref> digital audio players like [[Sony Walkman]] and [[SanDisk Clip]], media players such as [[VLC media player\|VLC]], [[Winamp]] and [[Windows Media Player]], various in-dash [[Vehicle audio\|car audio]] systems,<ref>{{Cite web \|title=Pioneer Releases Car Audio Package for a Limited Time in the Overseas Markets to Commemorate the 80th Anniversary of its Foundation {{!}} News Releases {{!}} News and Events {{!}} About Us {{!}} Pioneer \|url=https://global.pioneer/en/corp/news/press/index/2175/ \|access-date=2025-04-11 \|website=Pioneer Corporation \|language=en}}</ref> and is used on [[Spotify]],<ref>{{cite web \|title=Audio file formats for Spotify \|url=https://artists.spotify.com/help/article/audio-file-formats \|access-date=20 September 2021 \|website=Spotify}}</ref> [[Apple Music]],{{efn\|only used on web player, [[Google Home]], [[Amazon Alexa]], and [[Microsoft Windows]] app.}} and [[YouTube]] web streaming services.<ref>{{Cite web \|last=updated \|first=Joe Svetlik Contributions from Becky Scarrott last \|date=2022-07-25 \|title=MP3, AAC, WAV, FLAC: all the audio file formats explained \|url=https://www.whathifi.com/advice/mp3-aac-wav-flac-all-the-audio-file-formats-explained \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref> AAC has been further extended into [[HE-AAC]] (''High Efficiency'', or AAC+), which improves efficiency over AAC-LC.<ref>{{Cite web \|date=2004 \|title=Dolby adds High-Efficiency AAC to MPEG 4 patent pool \|url=https://www.theregister.com/2004/07/20/aac_he_licensing/}}</ref> Another variant is [[AAC-LD]] (''Low Delay'').<ref>{{Cite web \|last=Rose \|first=Matthias \|date=2012-06-28 \|title=Understanding MPEG Audio Codecs From mp3 To xHE-AAC \|url=https://www.electronicdesign.com/technologies/embedded/article/21796123/understanding-mpeg-audio-codecs-from-mp3-to-xhe-aac \|access-date=2025-04-11 \|website=Electronic Design \|language=en}}</ref>		The basic profile of AAC (both MPEG-4 and MPEG-2) is called '''AAC-LC''' (''Low Complexity''). It is widely supported in the industry and has been adopted as the default or standard audio format on products including [[Apple Inc.\|Apple]]'s [[iTunes Store]], [[Nintendo]]'s [[Wii]],<ref>{{Cite web \|last=Caron \|first=Frank \|date=2007-11-14 \|title=Wii Photo Channel update adds customization, removes MP3 playback \|url=https://arstechnica.com/gaming/2007/11/wii-photo-channel-update-adds-customization-removes-mp3-playback/ \|access-date=2025-04-11 \|website=Ars Technica \|language=en-US}}</ref> [[Nintendo DSi\|DSi]] and [[Nintendo 3DS\|3DS]] and [[Sony]]'s [[PlayStation 3]].<ref>{{Cite web \|title=PS3™ {{!}} Importing audio CDs to the system storage \|url=https://manuals.playstation.net/document/en/ps3/current/music/cdimport.html \|access-date=2025-04-11 \|website=manuals.playstation.net}}</ref> It is also further supported on various other devices and software such as [[iPhone]], [[iPod]], [[PlayStation Portable]] and [[PlayStation Vita\|Vita]], [[PlayStation 5]], [[Android (operating system)\|Android]] and older cell phones,<ref>{{Cite web \|date=2006-05-10 \|title=Sony to support AAC -- heck not to freeze over \|url=https://www.engadget.com/2006-05-10-sony-to-support-aac-heck-not-to-freeze-over.html \|access-date=2025-04-11 \|website=Engadget \|language=en-US}}</ref> digital audio players like [[Sony Walkman]] and [[SanDisk Clip]], media players such as [[VLC media player\|VLC]], [[Winamp]] and [[Windows Media Player]], various in-dash [[Vehicle audio\|car audio]] systems,<ref>{{Cite web \|title=Pioneer Releases Car Audio Package for a Limited Time in the Overseas Markets to Commemorate the 80th Anniversary of its Foundation {{!}} News Releases {{!}} News and Events {{!}} About Us {{!}} Pioneer \|url=https://global.pioneer/en/corp/news/press/index/2175/ \|access-date=2025-04-11 \|website=Pioneer Corporation \|language=en}}</ref> and is used on [[Spotify]],<ref>{{cite web \|title=Audio file formats for Spotify \|url=https://artists.spotify.com/help/article/audio-file-formats \|access-date=20 September 2021 \|website=Spotify}}</ref> [[Apple Music]],{{efn\|only used on web player, [[Google Home]], [[Amazon Alexa]], and [[Microsoft Windows]] app.}} and [[YouTube]] web streaming services.<ref>{{Cite web \|last=updated \|first=Joe Svetlik Contributions from Becky Scarrott last \|date=2022-07-25 \|title=MP3, AAC, WAV, FLAC: all the audio file formats explained \|url=https://www.whathifi.com/advice/mp3-aac-wav-flac-all-the-audio-file-formats-explained \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref> AAC has been further extended into [[HE-AAC]] (''High Efficiency'', or AAC+), which improves efficiency over AAC-LC.<ref>{{Cite web \|date=2004 \|title=Dolby adds High-Efficiency AAC to MPEG 4 patent pool \|url=https://www.theregister.com/2004/07/20/aac_he_licensing/}}</ref> Another variant is [[AAC-LD]] (''Low Delay'').<ref>{{Cite web \|last=Rose \|first=Matthias \|date=2012-06-28 \|title=Understanding MPEG Audio Codecs From mp3 To xHE-AAC \|url=https://www.electronicdesign.com/technologies/embedded/article/21796123/understanding-mpeg-audio-codecs-from-mp3-to-xhe-aac \|access-date=2025-04-11 \|website=Electronic Design \|language=en}}</ref>

	AAC supports inclusion of 48 full-[[Bandwidth (computing)\|bandwidth]] (up to 96 kHz) [[audio channel]]s in one stream plus 16 low frequency effects ([[Low-frequency effects\|LFE]], limited to 120 Hz) channels, up to 16 "coupling" or dialog channels, and up to 16 data streams. The quality for stereo is satisfactory to modest requirements at 96 kbit/s in [[joint stereo]] mode; however, [[Transparency (data compression)\|hi-fi transparency]] demands data rates of at least 128 kbit/s ([[Variable bitrate\|VBR]]). Tests{{which\|date=December 2021}} of MPEG-4 audio have shown that AAC meets the requirements referred to as "transparent" for the [[ITU]] at 128 kbit/s for stereo, and 384 kbit/s for [[5.1]] audio.<ref>{{cite web\|url=https://www.iis.fraunhofer.de/content/dam/iis/de/doc/ame/wp/FraunhoferIIS_White-Paper_AAC-Broadcast-CableTV.pdf\|title=The AAC Audio Coding Family For Broadcast and Cable TV\|author=<!--Not stated-->\|year=2013\|page=6\|access-date=2024-01-29\|archive-url=https://web.archive.org/web/20230928013141/https://www.iis.fraunhofer.de/content/dam/iis/de/doc/ame/wp/FraunhoferIIS_White-Paper_AAC-Broadcast-CableTV.pdf\|archive-date=2023-09-28}}</ref> AAC uses only a [[modified discrete cosine transform]] (MDCT) algorithm, giving it higher compression efficiency than MP3, which uses a hybrid coding algorithm that is part MDCT and part [[FFT]].<ref name="brandenburg"/>		AAC supports inclusion of 48 full-[[Bandwidth (computing)\|bandwidth]] (up to 96 kHz) [[audio channel]]s in one stream plus 16 low frequency effects ([[Low-frequency effects\|LFE]], limited to 120 Hz) channels, up to 16 "coupling" or dialog channels, and up to 16 data streams. The quality for stereo is satisfactory to modest requirements at 96 kbit/s in [[joint stereo]] mode; however, [[Transparency (data compression)\|hi-fi transparency]] demands data rates of at least 128 kbit/s ([[Variable bitrate\|VBR]]). Tests{{which\|date=December 2021}} of MPEG-4 audio have shown that AAC meets the requirements referred to as "transparent" for the [[ITU]] at 128 kbit/s for stereo, and 384 kbit/s for [[5.1]] audio.<ref>{{cite web\|url=https://www.iis.fraunhofer.de/content/dam/iis/de/doc/ame/wp/FraunhoferIIS_White-Paper_AAC-Broadcast-CableTV.pdf\|title=The AAC Audio Coding Family For Broadcast and Cable TV\|author=<!--Not stated-->\|year=2013\|page=6\|access-date=2024-01-29\|archive-url=https://web.archive.org/web/20230928013141/https://www.iis.fraunhofer.de/content/dam/iis/de/doc/ame/wp/FraunhoferIIS_White-Paper_AAC-Broadcast-CableTV.pdf\|archive-date=2023-09-28}}</ref> AAC uses only a [[modified discrete cosine transform]] (MDCT) algorithm, giving it higher compression efficiency than MP3, which uses a hybrid coding algorithm that is part MDCT and part [[FFT]].<ref name="brandenburg"/>

Durziil89: Undid revision 1285612292 by 2600:1000:B16D:756F:0:5D:D17F:DF01 (talk)

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	{{Prose\|date=June 2024}}		{{Prose\|date=June 2024}}
	{{about\|the [[audio coding format]]\|collegiate athletic conference\|American Athletic Conference}}
	{{Infobox file format		{{Infobox file format
	\| name = Advanced Audio Coding		\| name = Advanced Audio Coding

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	{{Prose\|date=June 2024}}		{{Prose\|date=June 2024}}
			{{about\|the [[audio coding format]]\|collegiate athletic conference\|American Athletic Conference}}
	{{Infobox file format		{{Infobox file format
	\| name = Advanced Audio Coding		\| name = Advanced Audio Coding

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	The reference software for MPEG-4 Part 3 is specified in MPEG-4 Part 5 and the conformance bit-streams are specified in MPEG-4 Part 4. MPEG-4 Audio remains [[backward-compatible]] with MPEG-2 Part 7.<ref name="mpeg4audio-mpeg2audio">{{cite web\|url=http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|title=MPEG-4 Natural Audio Coding - General Audio Coding (AAC based) \|first1=Karlheinz \|last1=Brandenburg \|first2=Oliver \|last2=Kunz \|first3=Akihiko \|last3=Sugiyama \|website=chiariglione.org \|year=1999 \|access-date=2009-10-06 \|url-status=dead \|archive-url=https://web.archive.org/web/20100219233137/http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|archive-date=2010-02-19 }}</ref>		The reference software for MPEG-4 Part 3 is specified in MPEG-4 Part 5 and the conformance bit-streams are specified in MPEG-4 Part 4. MPEG-4 Audio remains [[backward-compatible]] with MPEG-2 Part 7.<ref name="mpeg4audio-mpeg2audio">{{cite web\|url=http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|title=MPEG-4 Natural Audio Coding - General Audio Coding (AAC based) \|first1=Karlheinz \|last1=Brandenburg \|first2=Oliver \|last2=Kunz \|first3=Akihiko \|last3=Sugiyama \|website=chiariglione.org \|year=1999 \|access-date=2009-10-06 \|url-status=dead \|archive-url=https://web.archive.org/web/20100219233137/http://mpeg.chiariglione.org/tutorials/papers/icj-mpeg4-si/09-natural_audio_paper/gacoding.html \|archive-date=2010-02-19 }}</ref>

	The MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000) defined new audio object types: the low delay AAC ([[AAC-LD]]) object type, bit-sliced arithmetic coding (BSAC) object type, parametric audio coding using [[Harmonic and Individual Lines and Noise\|harmonic and individual line plus noise]] and error resilient (ER) versions of object types.<ref name="mpeg4audio-iso-2-amd">{{cite web \| url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| title=ISO/IEC 14496-3:1999/Amd 1:2000 - Audio extensions \| publisher=[[ISO]] \| year=2000 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606215234/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| archive-date=2011-06-06 }}</ref><ref name="mpeg4audio-version2">{{~~cite~~ ~~web~~ \| url=ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf \| title=ISO/IEC 14496-3:/Amd.1 - Final Committee Draft - MPEG-4 Audio Version 2 ~~\| publisher=[[ISO]]/[[IEC]] JTC 1/SC 29/WG 11~~ \| date=July 1999 \| access-date=2009-10-07 \| ~~archive~~-~~url~~=~~http://webarchive.loc.gov/all/20120801161551/ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf~~ \| ~~archive-date~~=~~2012-08-01~~ \| ~~url-status=dead~~ }}</ref><ref name="mpeg4audio2">{{cite web\|url=https://sound.media.mit.edu/resources/mpeg4/audio/general/aes108_6-Parametric.pdf\|title=MPEG-4 Version 2 Audio Workshop:HILN - Parametric Audio Coding\|at=AES 108th Convention: MPEG-4 Version 2 Audio What is it about?\|location=Paris\| first1=Heiko \|last1=Purnhagen \| date=19 February 2000 \| access-date=2009-10-07}}</ref> It also defined four new audio profiles: High Quality Audio Profile, Low Delay Audio Profile, Natural Audio Profile and Mobile Audio Internetworking Profile.<ref name="mpeg4-profiles">{{cite web\|url=http://www.m4if.org/resources/profiles/audio.php \|archive-url=http://webarchive.loc.gov/all/20100108152236/http://www.m4if.org/resources/profiles/audio.php \|url-status=dead \|archive-date=2010-01-08 \|title=Levels for Audio Profiles \|first1=Fernando \|last1=Pereira \|publisher=MPEG Industry Forum \|date=October 2001 \|access-date=2009-10-15 }}</ref>		The MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000) defined new audio object types: the low delay AAC ([[AAC-LD]]) object type, bit-sliced arithmetic coding (BSAC) object type, parametric audio coding using [[Harmonic and Individual Lines and Noise\|harmonic and individual line plus noise]] and error resilient (ER) versions of object types.<ref name="mpeg4audio-iso-2-amd">{{cite web \| url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| title=ISO/IEC 14496-3:1999/Amd 1:2000 - Audio extensions \| publisher=[[ISO]] \| year=2000 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606215234/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=31568 \| archive-date=2011-06-06 }}</ref><ref name="mpeg4audio-version2">{{Cite FTP \| url=ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2803/w2803_n.pdf \| title=ISO/IEC 14496-3:/Amd.1 - Final Committee Draft - MPEG-4 Audio Version 2 \| date=July 1999 \| access-date=2009-10-07 \| url-status=dead \| server=[[ISO]]/[[IEC]] JTC 1/SC 29/WG 11 }}</ref><ref name="mpeg4audio2">{{cite web\|url=https://sound.media.mit.edu/resources/mpeg4/audio/general/aes108_6-Parametric.pdf\|title=MPEG-4 Version 2 Audio Workshop:HILN - Parametric Audio Coding\|at=AES 108th Convention: MPEG-4 Version 2 Audio What is it about?\|location=Paris\| first1=Heiko \|last1=Purnhagen \| date=19 February 2000 \| access-date=2009-10-07}}</ref> It also defined four new audio profiles: High Quality Audio Profile, Low Delay Audio Profile, Natural Audio Profile and Mobile Audio Internetworking Profile.<ref name="mpeg4-profiles">{{cite web\|url=http://www.m4if.org/resources/profiles/audio.php \|archive-url=http://webarchive.loc.gov/all/20100108152236/http://www.m4if.org/resources/profiles/audio.php \|url-status=dead \|archive-date=2010-01-08 \|title=Levels for Audio Profiles \|first1=Fernando \|last1=Pereira \|publisher=MPEG Industry Forum \|date=October 2001 \|access-date=2009-10-15 }}</ref>

	The [[HE-AAC]] Profile (AAC LC with [[Spectral band replication\|SBR]]) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.<ref name="he-aac-amd1">{{cite web \| url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| title=ISO/IEC 14496-3:2001/Amd 1:2003 - Bandwidth extension \| publisher=[[ISO]] \| year=2003 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606054451/http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| archive-date=2011-06-06 }}</ref> The HE-AAC v2 Profile (AAC LC with SBR and Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016">{{cite web\|url=http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|title=Text of ISO/IEC 14496-3:2001/FPDAM 4, Audio Lossless Coding (ALS), new audio profiles and BSAC extensions \|format=DOC \|publisher=[[ISO]]/[[IEC]] JTC1/SC29/WG11/N7016 \|date=11 January 2005 \|access-date=2009-10-09 \|url-status=dead \|archive-url=https://web.archive.org/web/20140512215821/http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|archive-date=12 May 2014 }}</ref><ref name="ISO 14496-3:2005/Amd.2">{{cite web \| title=Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, ISO/IEC 14496-3:2005/Amd 2:2006 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| publisher=[[ISO]] \| year=2006 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104072435/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| archive-date=2012-01-04 }}</ref><ref name="embedded">{{cite web \| title=Audio compression gets better and more complex \| url=http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| first=Mihir \| last=Mody \| website=Embedded.com \| date=6 June 2005 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20160208004827/http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| archive-date=8 February 2016 }}</ref> The Parametric Stereo audio object type used in HE-AAC v2 was first defined in ISO/IEC 14496-3:2001/Amd 2:2004.<ref name="CT-whitepaper">{{cite web\|url=http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|title=MPEG-4 aacPlus - Audio coding for today's digital media world\|access-date=2007-01-29 \|url-status=dead \|archive-url=https://web.archive.org/web/20061026031407/http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|archive-date=2006-10-26 }}</ref><ref name="parametric">{{cite web \| title=Parametric coding for high-quality audio, ISO/IEC 14496-3:2001/Amd 2:2004 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| publisher=[[ISO]] \| year=2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104071002/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| archive-date=2012-01-04 }}</ref><ref name="3gpp26401">{{cite web \| title=3GPP TS 26.401 V6.0.0 (2004-09), General Audio Codec audio processing functions; Enhanced aacPlus General Audio Codec; General Description (Release 6) \| url=http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| format=DOC \| publisher=3GPP \| date=30 September 2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20060819083421/http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| archive-date=19 August 2006 }}</ref>		The [[HE-AAC]] Profile (AAC LC with [[Spectral band replication\|SBR]]) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.<ref name="he-aac-amd1">{{cite web \| url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| title=ISO/IEC 14496-3:2001/Amd 1:2003 - Bandwidth extension \| publisher=[[ISO]] \| year=2003 \| access-date=2009-10-07 \| url-status=live \| archive-url=https://web.archive.org/web/20110606054451/http://www.iso.org/iso/catalogue_detail.htm?csnumber=38148 \| archive-date=2011-06-06 }}</ref> The HE-AAC v2 Profile (AAC LC with SBR and Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016">{{cite web\|url=http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|title=Text of ISO/IEC 14496-3:2001/FPDAM 4, Audio Lossless Coding (ALS), new audio profiles and BSAC extensions \|format=DOC \|publisher=[[ISO]]/[[IEC]] JTC1/SC29/WG11/N7016 \|date=11 January 2005 \|access-date=2009-10-09 \|url-status=dead \|archive-url=https://web.archive.org/web/20140512215821/http://kikaku.itscj.ipsj.or.jp/sc29/open/29view/29n6475t.doc \|archive-date=12 May 2014 }}</ref><ref name="ISO 14496-3:2005/Amd.2">{{cite web \| title=Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, ISO/IEC 14496-3:2005/Amd 2:2006 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| publisher=[[ISO]] \| year=2006 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104072435/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43026 \| archive-date=2012-01-04 }}</ref><ref name="embedded">{{cite web \| title=Audio compression gets better and more complex \| url=http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| first=Mihir \| last=Mody \| website=Embedded.com \| date=6 June 2005 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20160208004827/http://www.embedded.com/design/real-time-and-performance/4025543/Audio-compression-gets-better-and-more-complex \| archive-date=8 February 2016 }}</ref> The Parametric Stereo audio object type used in HE-AAC v2 was first defined in ISO/IEC 14496-3:2001/Amd 2:2004.<ref name="CT-whitepaper">{{cite web\|url=http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|title=MPEG-4 aacPlus - Audio coding for today's digital media world\|access-date=2007-01-29 \|url-status=dead \|archive-url=https://web.archive.org/web/20061026031407/http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf \|archive-date=2006-10-26 }}</ref><ref name="parametric">{{cite web \| title=Parametric coding for high-quality audio, ISO/IEC 14496-3:2001/Amd 2:2004 \| url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| publisher=[[ISO]] \| year=2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20120104071002/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39382 \| archive-date=2012-01-04 }}</ref><ref name="3gpp26401">{{cite web \| title=3GPP TS 26.401 V6.0.0 (2004-09), General Audio Codec audio processing functions; Enhanced aacPlus General Audio Codec; General Description (Release 6) \| url=http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| format=DOC \| publisher=3GPP \| date=30 September 2004 \| access-date=2009-10-13 \| url-status=live \| archive-url=https://web.archive.org/web/20060819083421/http://www.3gpp.org/ftp/Specs/archive/26_series/26.401/26401-600.zip \| archive-date=19 August 2006 }}</ref>

← Previous revision		Revision as of 04:22, 7 May 2025
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	The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed\|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing 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}}</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 [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<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}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web \|last=Borland \|first=John \|date=March 18, 2004 \|title=The sound of science \|url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ \|access-date=2023-04-21 \|website=CNET \|language=en}}</ref>		The [[discrete cosine transform]] (DCT), a type of [[transform coding]] for [[lossy compression]], was proposed by [[N. Ahmed\|Nasir Ahmed]] in 1972, and developed by Ahmed with T. Natarajan and [[K. R. Rao]] in 1973, publishing 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}}</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 [[MP3]] [[audio coding standard]] introduced in 1992 used a hybrid coding algorithm that is part MDCT and part [[FFT]].<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}}</ref> AAC uses a purely MDCT algorithm, giving it higher compression efficiency than MP3.<ref name="brandenburg"/> Development further advanced when [[Lars Liljeryd]] introduced a method that radically shrank the amount of information needed to store the digitized form of a song or speech.<ref>{{Cite web \|last=Borland \|first=John \|date=March 18, 2004 \|title=The sound of science \|url=https://www.cnet.com/tech/services-and-software/the-sound-of-science/ \|access-date=2023-04-21 \|website=CNET \|language=en}}</ref>

	AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society\|Fraunhofer IIS]] (who developed MP3) and [[Sony\|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report \|url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio \|date=1 September 2009 \|access-date=2009-10-07 \|archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|url-status=live \|archive-date=14 June 2011 \|publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone\|NTT]].<ref name="aac-licensors">{{cite web \|title=AAC Licensors \|url=https://www.via-corp.com/licensing/aac/aac-licensors/ \|access-date=15 January 2020 \|website=Via Corp}}</ref><ref name="businesswire">{{cite web \|date=5 January 2009 \|title=Via Licensing Announces Updated AAC Joint Patent License \|url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License \|access-date=18 June 2019 \|website=[[Business Wire]]}}</ref>		AAC was developed with the cooperation between [[AT&T Labs]], [[Dolby]], [[Fraunhofer Society\|Fraunhofer IIS]] (who developed MP3) and [[Sony\|Sony Corporation]].<ref name=":3" /> AAC was officially declared an international standard by the [[Moving Picture Experts Group]] in April 1997. It is specified both as ''Part 7 of the MPEG-2 standard'', and ''Subpart 4 in Part 3 of the MPEG-4 standard''.<ref name="mpeg4audio-version4-2009">{{Cite tech report \|url=http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|title=ISO/IEC 14496-3:2009 - Information technology -- Coding of audio-visual objects -- Part 3: Audio \|date=1 September 2009 \|access-date=2009-10-07 \|archive-url=https://web.archive.org/web/20110614010613/http://webstore.iec.ch/preview/info_isoiec14496-3%7Bed4.0%7Den.pdf \|url-status=live \|archive-date=14 June 2011 \|publisher=[[ISO]]/[[IEC]]}}</ref> Further companies have contributed to development in later years including [[Bell Labs]], [[LG Electronics]], [[NEC]], [[Nokia]], [[Panasonic]], [[ETRI]], [[JVC Kenwood]], [[Philips]], [[Microsoft]], and [[Nippon Telegraph and Telephone\|NTT]].<ref name="aac-licensors">{{cite web \|title=AAC Licensors \|url=https://www.via-corp.com/licensing/aac/aac-licensors/ \|access-date=15 January 2020 \|website=Via Corp}}</ref><ref name="businesswire">{{cite web \|date=5 January 2009 \|title=Via Licensing Announces Updated AAC Joint Patent License \|url=https://www.businesswire.com/news/home/20090105005026/en/Licensing-Announces-Updated-AAC-Joint-Patent-License \|access-date=18 June 2019 \|website=[[Business Wire]]}}</ref>

	===Standardization===		===Standardization===
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	[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web \|last=RadioWorld \|date=2002-03-26 \|title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program \|url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program \|access-date=2025-04-11 \|website=Radio World \|language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].		[[Dolby Laboratories]] came in charge of AAC licensing in 2000.<ref name=":2" /> A new licensing model was launched by Dolby in 2002, while [[Nokia]] became a fifth co-licenser of the format.<ref>{{Cite web \|last=RadioWorld \|date=2002-03-26 \|title=Dolby Laboratories Reveals MPEG-4 AAC Licensing Program \|url=https://www.radioworld.com/news-and-business/dolby-laboratories-reveals-mpeg4-aac-licensing-program \|access-date=2025-04-11 \|website=Radio World \|language=en-US}}</ref> Dolby itself also marketed its own coding format, [[Dolby AC-3]].

	Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web \|title=Carrying A Tune With Nokia Phones \|url=https://www.forbes.com/2001/08/30/0830tentech.html \|access-date=2025-04-11 \|website=Forbes \|language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite magazine \|~~last~~=Staff ~~\|first=WIRED~~ \|title=A Music File by Any Other Name \|url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite magazine \|last=Buskirk \|first=Eliot Van \|title=In EMI-ITunes Deal, the Big Loser May Be Microsoft \|url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref>		Nokia started supporting AAC playback on devices as early as 2001,<ref>{{Cite web \|title=Carrying A Tune With Nokia Phones \|url=https://www.forbes.com/2001/08/30/0830tentech.html \|access-date=2025-04-11 \|website=Forbes \|language=en}}</ref> but it was the exclusive use of AAC by Apple Computer for their [[iTunes Store]] which accelerated attention to AAC. Soon the format was also supported by Sony for their [[PlayStation Portable]] (albeit Sony continued promoting its proprietary [[ATRAC]]), and music-oriented cell phones from [[Sony Ericsson]] beginning with the [[Sony Ericsson W800]].<ref>{{Cite magazine \|author=WIRED Staff \|title=A Music File by Any Other Name \|url=https://www.wired.com/2005/12/a-music-file-by-any-other-name/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref> The [[Windows Media Audio]] (WMA) format, from Microsoft, was considered to be AAC's main competitor.<ref>{{Cite magazine \|last=Buskirk \|first=Eliot Van \|title=In EMI-ITunes Deal, the Big Loser May Be Microsoft \|url=https://www.wired.com/2007/04/in-emi-itunes-deal-the-big-loser-may-be-microsoft/ \|access-date=2025-04-11 \|magazine=Wired \|language=en-US \|issn=1059-1028}}</ref>

	By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web \|author1=What Hi-Fi Admin \|date=2017-05-15 \|title=Home \|url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref>		By 2017, AAC was considered to have become a ''de facto'' industry standard for lossy audio.<ref>{{Cite web \|author1=What Hi-Fi Admin \|date=2017-05-15 \|title=Home \|url=https://www.whathifi.com/news/mp3-dead-creators-end-licensing-programme \|access-date=2025-04-11 \|website=whathifi \|language=en}}</ref>