View source for High-Efficiency Advanced Audio Coding

{{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]].

==History==
The progenitor of HE-AAC was developed by [[Coding Technologies]] by combining MPEG-2 AAC-LC with a proprietary mechanism for [[spectral band replication]] (SBR), to be used by [[XM Radio]] for their satellite radio service. Subsequently, Coding Technologies submitted their SBR mechanism to MPEG as a basis of what ultimately became HE-AAC.

HE-AAC v1 was standardized as a profile of MPEG-4 Audio in 2003 by [[Moving Picture Experts Group|MPEG]] and published as part of the ISO/IEC 14496-3:2001/Amd 1:2003<ref name="ISO 2003">{{cite web | title=Bandwidth extension, ISO/IEC 14496-3:2001/Amd 1:2003 | url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=38148 | author=ISO | publisher=ISO | year=2003 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20120104074607/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=38148 | archive-date=2012-01-04 }}</ref> specification.

The HE-AAC v2 profile was standardized in 2006 as per ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016" /><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 | author=ISO | 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>

Parts of the HE-AAC specification had previously been standardized and published by various bodies in
'''3GPP TS 26.401'''
,<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 | author=3GPP | publisher=3GPP | date=2004-09-30 | 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=2006-08-19 }}</ref>
'''ETSI TS 126 401 V6.1.0'''
,<ref name="3gpp126401">{{cite web | title=ETSI TS 126 401 V6.1.0 (2004-12) - Universal Mobile Telecommunications System (UMTS); General audio codec audio processing functions; Enhanced aacPlus general audio codec; General description (3GPP TS 26.401 version 6.1.0 Release 6) | url=http://webapp.etsi.org/workprogram/Report_WorkItem.asp?wki_id=21806 | author=3GPP | publisher=3GPP | date=2005-01-04 | access-date=2009-10-13}}</ref>
'''ISO/IEC 14496-3:2001/Amd.1:2003''' and 
'''ISO/IEC 14496-3:2001/Amd 2:2004'''.
<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 | author=ISO | 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>

At the time, Coding Technologies had already begun using the trade names '''AAC+''' and '''aacPlus''' for what is now known as HE-AAC v1, and '''aacPlus v2''' and '''eAAC+''' for what is now known as HE-AAC v2.

==Perceived quality==
Testing indicates that material decoded from 64&nbsp;kbit/s HE-AAC does not quite have similar audio quality to material decoded from MP3 at 128&nbsp;kbit/s using high quality encoders.<ref>{{cite web|url=http://www.rjamorim.com/test/64test/results.html|title=Results of 64kbit/s Listening Test|date=23 June 2007|access-date=3 May 2018|url-status=bot: unknown|archive-url=https://web.archive.org/web/20070623042116/http://www.rjamorim.com/test/64test/results.html|archive-date=23 June 2007}}</ref><ref>{{cite web|url=http://www.hydrogenaud.io/forums/index.php?showtopic=50888|title=Multiformat Listening Test @ 48 kbps - FINISHED|website=www.hydrogenaud.io|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20140708014541/http://www.hydrogenaud.io/forums/index.php?showtopic=50888|archive-date=8 July 2014}}</ref><ref>{{cite web|url=http://www.hydrogenaud.io/forums/index.php?showtopic=35438|title=80 kbps personal listening test (summer 2005)|website=www.hydrogenaud.io|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20140708054803/http://www.hydrogenaud.io/forums/index.php?showtopic=35438|archive-date=8 July 2014}}</ref><ref>{{cite web|url=http://forum.hardware.fr/hardwarefr/VideoSon/MP3-WMA-AAC-OGG-qualite-kbit/s-evaluation-sujet-84950-1.htm|title=MP3 – WMA – AAC – OGG – qualité à 96 kbps (évaluation) - Traitement Audio - Video & Son - FORUM HardWare.fr|website=forum.hardware.fr|access-date=3 May 2018|url-status=live|archive-url=https://archive.today/20120715145608/http://forum.hardware.fr/hardwarefr/VideoSon/MP3-WMA-AAC-OGG-qualite-kbit/s-evaluation-sujet-84950-1.htm|archive-date=15 July 2012}}</ref> The test, taking bitrate distribution and [[RMSD]] into account, is a tie between [[mp3PRO]], HE-AAC and [[Ogg Vorbis]].

Further controlled testing by [[3GPP]] during their revision 6 specification process indicates that HE-AAC and HE-AAC v2 provide "Good" audio quality for music at low bit rates (e.g., 24&nbsp;kbit/s).

In 2011, a public listening test<ref>{{cite web|url=http://people.xiph.org/~greg/opus/ha2011/|title=Hydrogen audio 2011 multiformat listening test unofficial results page|website=people.xiph.org|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20120725215759/http://people.xiph.org/~greg/opus/ha2011/|archive-date=25 July 2012}}</ref> comparing the two best-rated HE-AAC encoders at the time to [[Opus (audio format)|Opus]] and Ogg Vorbis indicated that Opus had statistically significant superiority at 64&nbsp;kbit/s over all other contenders, and second-ranked Apple's implementation of HE-AAC as statistically superior to both Ogg Vorbis and Nero HE-AAC, which were tied for third place.

[[MPEG-2]] and MPEG-4 AAC-LC decoders without SBR support will decode the AAC-LC part of the audio, resulting in audio output with only half the sampling frequency, thereby reducing the audio bandwidth. This usually results in the high-end, or [[Treble (sound)|treble]], portion of the audio signal missing from the audio product.

==Support==

===Encoding===
Orban Opticodec-PC Streaming and File Encoders were the first commercially available encoders supporting [[AAC-LC]]/HE-AAC back in 2003. They are now deprecated and replaced with StreamS Encoders from StreamS/Modulation Index with many more features, including support [[xHE-AAC]]/[[Unified Speech and Audio Coding]]. They are now in use at some of the largest content providers, and are considered to be the standard of the industry for live encoding.

Sony supports HE-AAC encoding since SonicStage version 4.

iTunes 9 supports HE-AAC encoding and playback.<ref>{{cite web|url=https://www.apple.com/itunes/features/#importing |title=Apple - iTunes - Learn about the features of iTunes 10 |access-date=2011-03-29 |url-status=dead |archive-url=https://web.archive.org/web/20110329002415/http://www.apple.com/itunes/features/#importing |archive-date=2011-03-29 }}</ref><ref>{{cite web|url=https://www.apple.com/itunes/features/#radio|title=iTunes|website=Apple|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20110329002415/http://www.apple.com/itunes/features/#radio|archive-date=29 March 2011}}</ref>

[[Nero AG|Nero]] has released a free-of-charge command line HE-AAC encoder, [[Nero AAC Codec]],<ref>{{cite web|url=http://www.nero.com/ena/technologies-aac-codec.html|title=Nero AAC Codec|access-date=2009-11-23|url-status=live|archive-url=https://web.archive.org/web/20091211174635/http://www.nero.com/ena/technologies-aac-codec.html|archive-date=2009-12-11}}</ref> and also supports HE-AAC inside the Nero software suite.

Sorenson Media's Squeeze Compression Suite includes an HE-AACv1 encoder and is available for [[macOS]] as well as [[Microsoft Windows|Windows]].

The [[3GPP]] consortium released source code of a reference HE-AACv2 encoder that appears to offer competitive quality.<ref>{{cite web|url=http://www.mp3-tech.org/tests/aac_48/results.html|title=48kbps AAC public test results|date=2006-03-20|access-date=2008-09-05|publisher=MP3'Tech|last=Bouvigne|first=Gabriel|url-status=live|archive-url=https://web.archive.org/web/20080724081344/http://www.mp3-tech.org/tests/aac_48/results.html|archive-date=2008-07-24}}</ref>

[[Winamp]] Pro also supports ripping music to HE-AAC. Using a transcoding plugin for Winamp's media library, any file can be transcoded to HE-AAC.<ref>{{cite web|url=http://www.free-codecs.com/download/Winamp_Transcoder.htm|title=Free Download Winamp Transcoder 2.0|website=www.free-codecs.com|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20080820164701/http://free-codecs.com/download/Winamp_Transcoder.htm|archive-date=20 August 2008}}</ref>

[http://tmkk.undo.jp/xld/index_e.html XLD], a macOS audio encoding program, offers encoding from any of its supported formats to HE-AAC.

[[Nokia PC Suite]] may encode audiofiles to eAAC+ format before transmitting them to mobile phone.

HE-AAC v1 and v2 encoders are provided by the [[Fraunhofer FDK AAC]] library in [[Android (operating system)|Android]] 4.1 and later versions.<ref name="Supported Media Formats">{{cite web|title=Supported Media Formats|url=http://developer.android.com/guide/appendix/media-formats.html|publisher=Google|access-date=2013-10-10|url-status=live|archive-url=https://web.archive.org/web/20120311121312/http://developer.android.com/guide/appendix/media-formats.html|archive-date=2012-03-11}}</ref>

===Decoding===
HE-AAC is supported in the [[open source]] FAAD/[[FAAD2]] decoding library and all players incorporating it, such as [[VLC media player]], [[Winamp]], [[foobar2000]], [[Audacious Media Player]] and [[SonicStage]].

The [[Nero AAC Codec]] supports decoding HE and HEv2 AAC.

HE-AAC is also used by [[AOL Radio]] and [[Pandora Radio]] clients to deliver high-fidelity music at low bitrates.

iTunes 9.2 and iOS 4 include full decoding of HE-AAC v2 parametric stereo streams.
* iTunes 9 thru 9.1, iPhone OS 3.1 and Fall 2009 iPods have support for HE-AAC playback for version 1 with no parametric stereo.
* Older versions of Apple [[iTunes]], [[iPod Touch]], and [[iPhone]] will play HE-AAC files at reduced fidelity because they ignore the spectral-band replication and parametric stereo information, instead playing them as though they were standard AAC-LC files without the high-frequency, or "treble," information that is only present in the SBR part of the signal.<ref>{{Cite web|url=https://support.apple.com/en-us/HT1709|title=iPod touch: Supported file formats|website=Apple Support|language=en|access-date=2019-04-07}}</ref> These will report the track length as twice its actual length.{{Citation needed|date=September 2009}}

Dolby released Dolby Pulse decoders and encoders in September 2008. HE-AAC v2 is the core of Dolby Pulse so files and streams encoded in Dolby Pulse will playback on AAC, HE-AAC v1 and v2 decoders. Conversely files and streams encoded in AAC, HE-AAC v1 or v2 will playback on Dolby Pulse decoders.

Dolby Pulse provides the following additional capabilities beyond HE-AAC v2:
* Ability to intelligently generate and insert reversible loudness normalization and dynamic range metadata into the encoded file/stream; this metadata can then be used to optimize the playback experience based on application and/or device.
* Ability to insert custom metadata into the encoded file, and extract this metadata on playback

Dolby has additionally released a PC decoder as an SDK suitable for integration into PC applications requiring Dolby Pulse, HE-AAC or AAC playback capabilities.

HE-AAC v2 decoders are provided in all versions of Android.<ref name="Supported Media Formats"/> Decoding is handled by [[Fraunhofer FDK AAC]] since Android version 4.1.

===Clients===
{{Incomplete list|date=September 2012}}

{| class="wikitable"
|-
! scope="col" width="150px" align="left" | Application
! scope="col" width="50px" align="left" | Platform
! scope="col" |  Description
|-
| [[AIMP]]
| Windows
| A Winamp-like alternative music player<ref>{{cite web|url=http://www.aimp.ru/|title=AIMP|website=www.aimp.ru|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20141108063032/http://www.aimp.ru/|archive-date=8 November 2014}}</ref>
|-
| [[Adobe Flash Player]]
| Windows, macOS, ChromeOS, Linux
| Browser plug-in<ref>{{cite web|url=http://www.adobe.com/products/hdvideo/supported_technologies/heaacv2.html|title=Adobe Flash Player|website=www.adobe.com|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20080723235000/http://www.adobe.com/products/hdvideo/supported_technologies/heaacv2.html|archive-date=23 July 2008}}</ref><ref>{{cite web|url=http://macdailynews.com/2007/08/21/adobe_bringing_hd_video_high_quality_audio_to_flash_using_h264_aac/|title=Adobe bringing HD video, high quality audio to Flash using H.264, AAC (iPhone Flash support?) – MacDailyNews - Welcome Home|website=macdailynews.com|date=21 August 2007 |access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20150621063328/http://macdailynews.com/2007/08/21/adobe_bringing_hd_video_high_quality_audio_to_flash_using_h264_aac/|archive-date=21 June 2015}}</ref><!--as of what date or 9.x version?--> Supports AAC+ from any [[Real Time Messaging Protocol|RTMP]] source.<br>Live streams wrapped in an ADTS container are not natively supported and have to be re-wrapped. (e.g. [[Icecast]] KH can serve streams in a [[.flv]] container, which is compatible with Flash.){{efn|name=fn1|To deliver streaming audio, AAC data is most likely carried in either the Audio Data Interchange Format (ADIF) or via Audio Data Transport Stream (ADTS). These containers can be parsed to create FLV audio tags in order to use the audio file with Data Generation Mode.<ref>{{cite web|url=http://www.adobe.com/devnet/flashplayer/articles/icecast-streams.html|title=Playing Icecast streaming audio in Flash Player - Adobe Developer Connection|website=www.adobe.com|access-date=3 May 2018|url-status=live|archive-url=https://web.archive.org/web/20150316064947/http://www.adobe.com/devnet/flashplayer/articles/icecast-streams.html|archive-date=16 March 2015}}</ref>}}
|-
| [[Amarok (software)]]
| Windows, Linux
| Open-source music player
|-
| [[Audacious Media Player]]
| Windows, Linux
| Open-source music player
|-
| [https://deadbeef.sourceforge.net/ Deadbeef]
| Linux, Android
| Open-source music player
|-
| [http://www.dieplattenkiste.de Die Plattenkiste]
| Windows
| Freeware internet radio application (in German)
|-
| [[foobar2000]]
| Windows
| Freeware music player
|-
| [[fre:ac]]
| Windows, macOS, Linux
| Open-source audio converter
|-
| [http://www.sourcemac.com/?page=fstream FStream]
| macOS, iOS
| Internet radio application
|-
| [https://web.archive.org/web/20150407162946/https://itunes.apple.com/app/guguradio/id478254813?mt=8 GuguRadio]
| iOS
| Internet radio application
|-
| [https://play.google.com/store/apps/details?id=com.media.miplayer Internet Radio Player]
| Android
| Internet radio player
|-
| [http://www.eingrad.com/products/internet-radio-box/ Internet Radio Box] {{Webarchive|url=https://web.archive.org/web/20120825170115/http://www.eingrad.com/products/internet-radio-box/ |date=2012-08-25 }}
| iOS
| Internet radio application
|-
| [[iTunes]]
| Windows, macOS
| Freeware music player. Pre-installed on Mac computers
|-
| [[JetAudio]]
| Windows, Android
| Shareware media player
|-
| [[MediaHuman Audio Converter]]
| Windows, macOS
| Freeware audio converter<br>(Supports conversion of MP3, AAC, AIFF, WAV etc.)
|-
| [[MPlayer]]
| Windows, macOS and Linux
| Open-source media player
|-
| [[Mpv (media player)]]
| Windows, macOS and Linux
| Open-source media player
|-
| [[Rockbox]]
| Various portable media devices
| Alternate firmware for various portable media-players, such as Apple iPod and Creative Zen
|-
| [[QuickTime X]]
| macOS
| Media player pre-installed on Mac OS X Snow Leopard or later
|-
| [[RealPlayer]]
| Windows, macOS, Linux, Android
| Freemium media player<br>(HE-AAC v2 will only play in mono.)<ref>{{cite web |url=http://www.orban.com/products/codec/software/opticodec-pc1020/codec/ |title=Orban Codec Products ~ Opticodec-PC 1020 Codec |access-date=2014-10-19 |url-status=dead |archive-url=https://web.archive.org/web/20150318182830/http://www.orban.com/products/codec/software/opticodec-pc1020/codec/ |archive-date=2015-03-18 }}</ref>
|-
| [[Rhythmbox]]
| Linux
| Open-source music player
|-
| [https://web.archive.org/web/20120616190656/http://vemedio.com/products/snowtape Snowtape]
| macOS
| Shareware internet radio application
|-
| [http://streamwriter.org/en/ streamWriter]
| Windows
| Open-source internet radio application
|-
| [https://apps.apple.com/app/streams-hifi-radio/id381467884 StreamS HiFi Radio]
| iOS
| Paidware internet radio player
|-
| [[Tunein radio]]
| iOS, Android, Windows Phone, Blackberry
| Internet radio player
|-
| [[VLC media player]]
| Windows, macOS, Linux, iOS, Android
| Open-source media player
|-
| [[Winamp]]
| Windows, macOS, Android
| Freeware media player
|-
| [http://www.xiialive.com/ XiiaLive]
| Android, iOS
| Internet radio player
|-
| [http://kodi.tv/ Kodi]
| Windows, Linux, macOS, Android
| Open-source media player
|-
| [http://mpc-hc.org/ Media Player Classic]
| Windows
| Open-source media player
|-
|}

==Promotion aspects==

===Commercial trademarks and labeling===
HE-AAC is marketed under the trademark aacPlus by [[Coding Technologies]] and under the trademark Nero Digital by Nero AG. Sony Ericsson, Nokia and Samsung use AAC+ to label support for HE-AAC v1 and eAAC+ to label support for HE-AAC v2 on their phones. Motorola uses AAC+ to indicate HE-AAC v1 and "AAC+ Enhanced" to indicate HE-AAC v2.{{Citation needed|date=April 2015}}

===Licensing and patents===
Companies holding patents for HE-AAC have formed a [[patent pool]] administered by Via Licensing Corporation<ref>{{cite web |url=http://www.via-corp.com/us/en/licensing.html |title=Licensing Programs |access-date=2017-05-11 |author=Via Licensing |url-status=live |archive-url=https://web.archive.org/web/20170513100143/http://www.via-corp.com/us/en/licensing.html |archive-date=2017-05-13 }}</ref> to provide a single point of license for product makers.

Patent licenses are required for end-product companies that make hardware or software products that include HE-AAC encoders and/or decoders.<ref>{{cite web |url=http://www.via-corp.com/us/en/licensing/aac/faq.html |title=AAC Licensing FAQ |access-date=2017-05-11 |author=Via Licensing |url-status=live |archive-url=https://web.archive.org/web/20170522200114/http://www.via-corp.com/us/en/licensing/aac/faq.html |archive-date=2017-05-22 }}</ref> Unlike the MP3 format before April 23, 2017,<ref>{{cite web|url=http://www.mp3licensing.com/royalty/ |title=Thomson/FhG MP3 Licensing |author=Thomson |archive-url=https://web.archive.org/web/20170117091012/http://www.mp3licensing.com/royalty/ |archive-date=2017-01-17 |url-status=dead }}</ref> content owners are not required to pay license fees to distribute content in HE-AAC.

==Standards==
HE-AAC profile was first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.<ref name="ISO 2003"/> HE-AAC v2 profile (HE-AAC with Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006.<ref name="mpeg4audio-n7016" /><ref name="ISO 14496-3:2005/Amd.2"/><ref name="embedded">{{cite web|title=Audio compression gets better and more complex |url=http://www.embedded.com/columns/specialreports/164300682?_requestid=60812 |author=Mihir Mody |publisher=Embedded.com |date=2005-06-06 |access-date=2009-10-13 }}{{dead link|date=November 2016 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The Parametric Stereo coding tool used by HE-AAC v2 was standardized in 2004 and published as ISO/IEC 14496-3:2001/Amd 2:2004.<ref name="parametric"/><ref name="3gpp26401"/>

The current version of the MPEG-4 Audio (including HE-AAC standards) is published in ISO/IEC 14496-3:2009.

Enhanced aacPlus is required audio compression format in [[3GPP]] technical specifications for [[3G]] [[UMTS]] multimedia services and should be supported in [[IP Multimedia Subsystem]] (IMS), [[Multimedia Messaging Service]] (MMS), [[Multimedia Broadcast Multicast Service|Multimedia Broadcast/Multicast Service]] (MBMS) and Transparent end-to-end Packet-switched Streaming Service (PSS).<ref>ETSI (2009-04) [http://www.3gpp.org/ftp/Specs/html-info/26234.htm ETSI TS 126 234 V8.2.0 (2009-04); 3GPP TS 26.234; Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs] {{webarchive|url=https://web.archive.org/web/20081201093237/http://www.3gpp.org/ftp/specs/html-info/26234.htm |date=2008-12-01 }} Page 58. Retrieved on 2009-06-02.</ref><ref>ETSI (2009-01) [http://www.3gpp.org/ftp/Specs/html-info/26140.htm ETSI TS 126 140 V8.0.0 (2009-01); 3GPP TS 26.140; Multimedia Messaging Service (MMS); Media formats and codes] {{webarchive|url=https://web.archive.org/web/20081206062526/http://www.3gpp.org/ftp/Specs/html-info/26140.htm |date=2008-12-06 }} Page 11. Retrieved on 2009-06-02.</ref><ref>ETSI (2009-01) [http://www.3gpp.org/ftp/Specs/html-info/26141.htm ETSI TS 126 141 V8.0.0 (2009-01); 3GPP TS 26.141; IP Multimedia System (IMS) Messaging and Presence; Media formats and codecs] {{webarchive|url=https://web.archive.org/web/20081007213730/http://www.3gpp.org/ftp/Specs/html-info/26141.htm |date=2008-10-07 }} Page 10. Retrieved on 2009-06-02.</ref><ref name="3gpp-26346">{{cite web | title=ETSI TS 126 346 V8.3.0 (2009-06); 3GPP TS 26.346; Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs | url=http://www.3gpp.org/ftp/Specs/html-info/26346.htm | page=85 | author=3GPP | author-link=3GPP | publisher=[[ETSI]] | year=2009 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20081004163354/http://www.3gpp.org/FTP/Specs/html-info/26346.htm | archive-date=2008-10-04 }}</ref> HE-AAC version 2 was standardized under the name Enhanced aacPlus by [[3GPP]] for 3G UMTS multimedia services in September 2004 (3GPP TS 26.401).<ref name="3gpp-26401">{{cite web | title=3GPP TS 26.401 - General audio codec audio processing functions; Enhanced aacPlus general audio codec; General description | url=http://www.3gpp.org/ftp/Specs/html-info/26401.htm | author=3GPP | publisher=3GPP | year=2004 | access-date=2009-10-13 | url-status=live | archive-url=https://web.archive.org/web/20081004163359/http://www.3gpp.org/FTP/Specs/html-info/26401.htm | archive-date=2008-10-04 }}</ref>

HE-AAC and HE-AAC v2 audio coding for [[Digital Video Broadcasting|DVB]] applications is standardized by TS 101 154.<ref>ETSI TS 101 154 v1.5.1: Specification for the use of Video and Audio Coding in Broadcasting Applications based on the [[MPEG transport stream|MPEG-2 Transport Stream]]</ref><ref name="etsi-101-154">{{cite web | title=TS 101 154 version 1.9.1 - Digital Video Broadcasting (DVB); Specification for the use of Video and Audio Coding in Broadcasting Applications based on the MPEG-2 Transport Stream | url=http://webapp.etsi.org/workprogram/Report_WorkItem.asp?wki_id=30945 | author=ETSI | publisher=ETSI | date=2009-03-31 | access-date=2009-10-13 | url-status=live | archive-url=https://archive.today/20130414175722/http://webapp.etsi.org/WorkProgram/Report_WorkItem.asp?WKI_ID=30945 | archive-date=2013-04-14 }}</ref> AacPlus v2 by Coding Technologies<ref name="CT-whitepaper">{{cite web|url=http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf |title=Archived copy |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> is also standardized by the [[European Telecommunications Standards Institute|ETSI]] as TS 102 005 for Satellite services to Handheld devices (DVB-SH) below 3&nbsp;GHz.

In December 2007, Brazil started broadcasting terrestrial DTV standard called International [[ISDB-Tb]] that implements video coding H.264 with audio AAC-LC on main program (single or multi) and video H.264 with audio HE-AACv2 in the 1Seg mobile sub-program.

===Versions===
The following is the summary of the different versions of HE-AAC:
{|class="wikitable"
! Version
! Common trade names
! Codec feature
! Standards
|----
| HE-AAC v1
 | aacPlus v1, eAAC, AAC+, CT-aacPlus
 | AAC-LC + SBR
 | ISO/IEC 14496-3:2001/Amd 1:2003
|----
| HE-AAC v2
 | aacPlus v2, eAAC+, AAC++, Enhanced AAC+
 | AAC-LC + SBR + PS
 | ISO/IEC 14496-3:2005/Amd 2:2006
|----
| [[Unified Speech and Audio Coding|xHE-AAC]]
 | aacPlus v2, eAAC+, AAC++, Enhanced AAC+
 | AAC-LC + SBR + PS + [[Unified Speech and Audio Coding|USAC]]
 | ISO/IEC 23003-3:2012/Amd 2:2012<br><ref>{{cite web|url=https://www.iis.fraunhofer.de/en/ff/amm/broadcast-streaming/xheaac.html|title=xHE-AAC|website=Fraunhofer Institute for Integrated Circuits IIS|access-date=3 January 2021}}</ref>
|}

* '''LC''' means ''[[Advanced Audio Coding#Modular encoding|low complexity]]''
* '''SBR''' means ''[[spectral band replication]]''
* '''PS''' means ''[[parametric stereo]]''
* '''USAC''' means ''[[unified speech and audio coding]]''

==See also==
* [[Advanced Audio Coding]]
* [[Digital Radio Mondiale]]

==Notes==
{{notelist}}

==References==
{{Reflist|30em}}

==External links==
* [https://web.archive.org/web/20150415072207/http://stream.media/ Stream.Media] Radio Streaming Provider that provides every stream in HE-AACv2
*[https://web.archive.org/web/20070316003615/http://www.ebu.ch/en/technical/trev/trev_305-moser.pdf MPEG-4 HE-AAC v2 — audio coding for today's digital media world], article in the [[EBU]] technical review (01/2006) giving explanations on HE-AAC.
* [https://web.archive.org/web/20040827034854/http://www.tuner2.com/ Tuner2.com] list of Internet radio stations using aacPlus
* [http://www.radiofeeds.co.uk/other.asp RadioFeeds UK & Ireland (AAC+)] UK terrestrial radio stations streaming online in aacPlus format
* [https://web.archive.org/web/20070220192638/http://www.codingtechnologies.com/products/aacPlus.htm aacPlus explained]
* [http://www.audiocoding.com/ Open Source AAC codec] FAAC (encoder) and FAAD2 (decoder)
* [http://teknoraver.net/software/mp4tools/ Reworked HE-AAC encoder] aacplusenc (Windows binary aacplusenc.exe only goes to 51&nbsp;kbit/s.)
*[http://www.afreecodec.com/download/simple-neroaacenc-gui-sng-46445_win1.html SNG 1.3 Front-end] {{Webarchive|url=https://web.archive.org/web/20120103111348/http://www.afreecodec.com/download/simple-neroaacenc-gui-sng-46445_win1.html |date=2012-01-03 }} for Nero Encoder e.g. AAC-LC, HE-AAC, HE-AACv2 e.g.(Van Halen's Panama HE-AAC maxed at 205&nbsp;kbit/s)
*[http://www.nero.com/eng/downloads-nerodigital-nero-aac-codec.php neroAacEnc.exe] - the Nero Encoder back-end for the SNG 1.3 front-end.
* [http://www.winamp.com/ Winamp.com] Audio player/ripper that allows you to rip CDs into HE-AAC and convert other audio files into HE-AAC (with a free add-on).
* [http://www.poikosoft.com/ EZ CD Audio Converter] CD Ripper, Audio Converter, and CD Burner that allows you to rip to AAC-LC and HE-AAC, convert to AAC-LC and HE-AAC and burn AAC-LC and HE-AAC to an Audio CD.
* [http://www.dieplattenkiste.de Die Plattenkiste] Albumplayer, Ripper, Converter, and CD Burner that allows you to rip to AAC and aacPlus, convert to AAC and aacPlus and burn AAC and aacPlus to gapless Audio-CD.
* [https://www.pricenfees.com/digit-life-archives/mp3pro-vs-mp3 mp3PRO vs MP3] {{Webarchive|url=https://web.archive.org/web/20170202062701/https://www.pricenfees.com/digit-life-archives/mp3pro-vs-mp3 |date=2017-02-02 }} - includes graphs comparing high-frequency performance for MP3pro (similar to HE-AAC+)
*[http://mpeg.chiariglione.org/ Official MPEG web site]
*[http://www.vialicensing.com/licensing/AAC_index.cfm Via Licensing Corporation] - HE-AAC Patent Pool
*{{IETF RFC|4281}} - The Codecs Parameter for "Bucket" Media Types
* [https://www2.iis.fraunhofer.de/AAC Fraunhofer AAC Test Site]
{{Compression formats}}
{{Audio broadcasting}}

[[Category:Audio codecs]]
[[Category:IEC standards]]
[[Category:ISO standards]]
[[Category:MPEG-4]]
[[Category:Open standards covered by patents]]