Editing High-Efficiency Advanced Audio Coding (section)

{{Short description|Audio codec}}
{{Redirect|EAAC|the airline|European Aviation Air Charter}}
{{Hatnote|Not to be confused with [[MPEG-4 SLS]], which is branded HD-AAC.}}
{{Infobox file format
| name                   = High-Efficiency Advanced Audio Coding
| icon                   = 
| logo                   = 
| screenshot             = 
| caption                = 
| _noextcode             = on
| extensions             =
'''MPEG/3GPP Container'''
* <code>[[.m4a]], .mp4, [[3GP|.3gp]]</code>
'''Apple Container'''
* <code>.m4a, .m4b, .m4p, .m4r, .m4v</code>
'''ADTS Stream - NOT raw - Contains Headers'''
* <code>.aac</code>
| _nomimecode            = on
| mime                   = <code>audio/aac</code> <br> <code>audio/aacp</code> <br> <code>audio/3gpp</code> <br> <code>audio/3gpp2</code> <br> <code>audio/mp4</code>
| type code              = 
| uniform type           = 
| magic                  = 
| owner                  = [[International Organization for Standardization|ISO]]
| released               = 
| latest release version = 
| latest release date    = 
| genre                  = Audio compression format
| container for          = 
| contained by           = [[MPEG-4 Part 14]], [[3GP and 3G2]], [[ISO base media file format]], Audio Data Interchange Format (ADIF), Audio Data Transport Stream (ADTS)
| extended from          = [[Advanced Audio Coding|AAC]]
| extended to            = 
| standard               = [[MPEG-4 Part 3|ISO/IEC 14496-3]]
| url                    = 
}}

[[File:HE-AAC and HE-AAC v2.svg|300px|thumb|right|Hierarchical structure of AAC profile, HE-AAC profile and HE-AAC v2 profile, and compatibility between them. The HE-AAC profile decoder is fully capable of decoding any AAC profile stream. Similarly, The HE-AAC v2 decoder can handle all HE-AAC profile streams as well as all AAC profile streams. Based on the MPEG-4 Part 3 technical specification.<ref name="mpeg4audio-n7016">{{citation|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 |author=ISO/IEC JTC1/SC29/WG11/N7016 |date=2005-01-11 |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=2014-05-12 }}</ref>]]
[[File:AAC profiles.svg|250px|thumb|right|Evolution from MPEG-2 AAC-LC (Low Complexity) Profile and MPEG-4 AAC-LC [[MPEG-4 Part 3#MPEG-4 Audio Object Types|Object Type]] to HE-AAC v2 Profile.<ref name="evolution">{{citation|url=http://www.itu.int/ITU-R/study-groups/seminars/rsg6-eng/docs/(7)%20Nikolaus%20Rettelbach.pdf |title=MPEG-4 Audio and Video Technology |author=Fraunhofer IIS |access-date=2009-10-15 }}{{dead link|date=June 2016|bot=medic}}{{cbignore|bot=medic}}</ref>]]

'''High-Efficiency Advanced Audio Coding''' ('''HE-AAC''') is an [[audio coding format]] for [[lossy data compression]] of [[digital audio]] as part of the [[MPEG-4]] standards. It is an extension of Low Complexity [[Advanced Audio Coding|AAC]] (AAC-LC) optimized for low-[[bitrate]] applications such as [[streaming audio]]. 

The usage profile HE-AAC v1 uses [[spectral band replication]] (SBR) to enhance the [[modified discrete cosine transform]] (MDCT) compression efficiency in the [[frequency domain]].<ref>{{cite journal |last1=Herre |first1=J. |last2=Dietz |first2=M. |title=MPEG-4 high-efficiency AAC coding [Standards in a Nutshell] |journal=IEEE Signal Processing Magazine |date=2008 |volume=25 |issue=3 |pages=137–142 |doi=10.1109/MSP.2008.918684|bibcode=2008ISPM...25..137H }}</ref> The usage profile HE-AAC v2 couples SBR with [[Parametric Stereo]] (PS) to further enhance the compression efficiency of stereo signals.

HE-AAC is defined as an [[MPEG-4 Audio]] profile in [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] 14496–3. HE-AAC is used in [[digital radio]] standards like [[HD Radio]],<ref name="theori">{{cite web|url=http://theori.io/research/nrsc-5-c|title=Receiving NRSC-5|website=theori.io|date=9 June 2017 |access-date=14 April 2018|url-status=live|archive-url=https://web.archive.org/web/20170820185827/http://theori.io/research/nrsc-5-c|archive-date=20 August 2017}}</ref> [[Digital Audio Broadcasting#DAB+|DAB+]] and [[Digital Radio Mondiale]].