High-Efficiency Advanced Audio Coding (HE-AAC) is an

audio coding format An audio coding format (or sometimes audio compression format) is a content representation format for storage or transmission of digital audio (such as in digital television, digital radio and in audio and video files). Examples of audio coding f ...

for

lossy data compression In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...

digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...

as part of the

MPEG-4 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...

standards. It is an extension of Low Complexity AAC (AAC-LC) optimized for low-

bitrate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...

applications such as streaming audio. The usage profile HE-AAC v1 uses spectral band replication (SBR) to enhance the

modified discrete cosine transform The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where s ...

(MDCT) compression efficiency in the

frequency domain In mathematics, physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency (and possibly phase), rather than time, as in time ser ...

. 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

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

/ IEC 14496–3. HE-AAC is used in

digital radio Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services. This should not be confused with In ...

standards like

HD Radio HD Radio (HDR) is a trademark for in-band on-channel (IBOC) digital radio broadcast technology. HD radio generally simulcast, simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD R ...

DAB+ Digital Audio Broadcasting (DAB) is a digital radio international standard, standard for broadcasting digital audio radio services in many countries around the world, defined, supported, marketed and promoted by the WorldDAB organisation. T ...

and

Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—p ...

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

MPEG The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...

and published as part of the ISO/IEC 14496-3:2001/Amd 1:2003 specification. The HE-AAC v2 profile was standardized in 2006 as per ISO/IEC 14496-3:2005/Amd 2:2006. Parts of the HE-AAC specification had previously been standardized and published by various bodies in 3GPP TS 26.401 , ETSI TS 126 401 V6.1.0 , ISO/IEC 14496-3:2001/Amd.1:2003 and ISO/IEC 14496-3:2001/Amd 2:2004. 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 kbit/s HE-AAC does not quite have similar audio quality to material decoded from MP3 at 128 kbit/s using high quality encoders. The test, taking bitrate distribution and RMSD into account, is a tie between mp3PRO, HE-AAC and

Ogg Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression, libvorbis. Vorbis is most common ...

. Further controlled testing by

3GPP The 3rd Generation Partnership Project (3GPP) is an umbrella term for a number of standards organizations which develop protocols for mobile telecommunications. Its best known work is the development and maintenance of: * GSM and related 2G and ...

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 kbit/s). In 2011, a public listening test comparing the two best-rated HE-AAC encoders at the time to Opus and Ogg Vorbis indicated that Opus had statistically significant superiority at 64 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 MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU) is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods ...

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, 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 Unified Speech and Audio Coding (USAC) is an data compression#Audio, audio compression format and audio codec, codec for both music and speech or any mix of speech and audio using very low bit rates between 12 and 64 kbit/s. It was developed b ...

. 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.

Nero Nero Claudius Caesar Augustus Germanicus ( ; born Lucius Domitius Ahenobarbus; 15 December AD 37 – 9 June AD 68) was a Roman emperor and the final emperor of the Julio-Claudian dynasty, reigning from AD 54 until his ...

has released a free-of-charge command line HE-AAC encoder, Nero AAC Codec, 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 macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

as well as

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

. The

consortium released source code of a reference HE-AACv2 encoder that appears to offer competitive quality.

Winamp Winamp is a media player (software), media player for Microsoft Windows originally developed by Justin Frankel and Dmitry Boldyrev by their company Nullsoft, which they later sold to AOL in 1999 for $80 million. It was then acquired by Rad ...

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.
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 4.1 and later versions.

Decoding

HE-AAC is supported in the

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

FAAD/ FAAD2 decoding library and all players incorporating it, such as

VLC media player VLC media player (previously the VideoLAN Client) is a free and open-source software, free and open-source, software portability, portable, cross-platform media player software and streaming media Server (computing), server developed by the Vide ...

, foobar2000, Audacious Media Player and SonicStage. The Nero AAC Codec supports decoding HE and HEv2 AAC. HE-AAC is also used by

AOL Radio AOL Radio was an online radio streaming service available exclusively in the United States. Originally powered by XM Satellite Radio and later CBS Radio and Slacker, the platform offered users access to more than 200 free digital stations. H ...

and

Pandora Radio Pandora is a subscription-based music streaming service owned by the broadcasting corporation Sirius XM that is based in Oakland, California in the United States. The service carries a focus on recommendations based on the " Music Genome Proje ...

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 iTunes is a media player, media library, and mobile device management (MDM) utility developed by Apple. It is used to purchase, play, download and organize digital multimedia on personal computers running the macOS and Windows operating s ...

iPod Touch The iPod Touch (stylized as iPod touch) is a discontinued line of iOS-based mobile devices designed and formerly marketed by Apple Inc. with a touchscreen-controlled user interface. As with other iPod models, the iPod Touch can be used as a po ...

, and

iPhone The iPhone is a line of smartphones developed and marketed by Apple that run iOS, the company's own mobile operating system. The first-generation iPhone was announced by then–Apple CEO and co-founder Steve Jobs on January 9, 2007, at ...

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. These will report the track length as twice its actual length. 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. Decoding is handled by Fraunhofer FDK AAC since Android version 4.1.

Clients

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.

Licensing and patents

Companies holding patents for HE-AAC have formed a

patent pool In patent law, a patent pool is a consortium of two or more companies agreeing to cross-license patents relating to a particular technology. The creation of a patent pool can save patentees and licensees time and money, and, in case of blocking pa ...

administered by Via Licensing Corporation 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. Unlike the MP3 format before April 23, 2017, 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. HE-AAC v2 profile (HE-AAC with Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006. 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. 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

technical specifications for 3G

UMTS The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses Wideband Code Division Multiple Access, wideband code-division multiple access (W-CDMA) radio access technolog ...

multimedia services and should be supported in

IP Multimedia Subsystem The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-sty ...

(IMS),

Multimedia Messaging Service Multimedia Messaging Service (MMS) is a standard way to send messages that include multimedia content to and from a mobile phone over a cellular network. Users and providers may refer to such a message as a PXT, a picture message, or a multimedia ...

(MMS), Multimedia Broadcast/Multicast Service (MBMS) and Transparent end-to-end Packet-switched Streaming Service (PSS). HE-AAC version 2 was standardized under the name Enhanced aacPlus by

for 3G UMTS multimedia services in September 2004 (3GPP TS 26.401). HE-AAC and HE-AAC v2 audio coding for DVB applications is standardized by TS 101 154.ETSI TS 101 154 v1.5.1: Specification for the use of Video and Audio Coding in Broadcasting Applications based on the MPEG-2 Transport Stream AacPlus v2 by Coding Technologies is also standardized by the

ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization operating in the field of Information and communications technology, information and communications. ETSI supports the de ...

as TS 102 005 for Satellite services to Handheld devices (DVB-SH) below 3 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: * LC means '' low complexity'' * SBR means '' spectral band replication'' * PS means '' parametric stereo'' * USAC means ''

unified speech and audio coding Unified Speech and Audio Coding (USAC) is an data compression#Audio, audio compression format and audio codec, codec for both music and speech or any mix of speech and audio using very low bit rates between 12 and 64 kbit/s. It was developed b ...

Notes

References

External links

Stream.Media
Radio Streaming Provider that provides every stream in HE-AACv2
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.
Tuner2.com
list of Internet radio stations using aacPlus
RadioFeeds UK & Ireland (AAC+)
UK terrestrial radio stations streaming online in aacPlus format

Open Source AAC codec
FAAC (encoder) and FAAD2 (decoder)
Reworked HE-AAC encoder
aacplusenc (Windows binary aacplusenc.exe only goes to 51 kbit/s.)

for Nero Encoder e.g. AAC-LC, HE-AAC, HE-AACv2 e.g.(Van Halen's Panama HE-AAC maxed at 205 kbit/s)
neroAacEnc.exe
- the Nero Encoder back-end for the SNG 1.3 front-end.
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).
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.
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.
mp3PRO vs MP3
- includes graphs comparing high-frequency performance for MP3pro (similar to HE-AAC+)
Official MPEG web siteVia Licensing Corporation
- HE-AAC Patent Pool * - The Codecs Parameter for "Bucket" Media Types
Fraunhofer AAC Test Site
{{Audio broadcasting Audio codecs IEC standards ISO standards MPEG-4 Open standards covered by patents