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 ...

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 siz ...

of digital audio defined as an

MPEG-4 Audio MPEG-4 Part 3 or MPEG-4 Audio (formally ISO/IEC 14496-3) is the third part of the ISO/IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods. The first version of ISO/IEC 14496-3 was publish ...

profile in

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...

14496–3. 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 Streaming media is multimedia that is delivered and consumed in a continuous manner from a source, with little or no intermediate storage in network elements. ''Streaming'' refers to the delivery method of content, rather than the content it ...

. The usage profile HE-AAC v1 uses

spectral band replication Spectral band replication (SBR) is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain. It can be combined with any audio compression codec: the codec itself tra ...

(SBR) to enhance the modified discrete cosine transform (MDCT) compression efficiency in the

frequency domain In physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency, rather than time. Put simply, a time-domain graph shows how a s ...

. The usage profile HE-AAC v2 couples SBR with

Parametric Stereo Parametric Stereo (abbreviated as PS) is an audio compression algorithm used as an audio coding format for digital audio. It is considered an Audio Object Type of MPEG-4 Part 3 (MPEG-4 Audio) that serves to enhance the coding efficiency of low band ...

(PS) to further enhance the compression efficiency of stereo signals. HE-AAC is used in digital radio standards like HD Radio, DAB+ and Digital Radio Mondiale.

History

The progenitor of HE-AAC was developed by

Coding Technologies Coding Technologies AB was a Swedish technology company that pioneered the use of spectral band replication in Advanced Audio Coding. Its MPEG-2 AAC-derived codec, called aacPlus, was published in 2001 and submitted to the MPEG for standardizati ...

by combining MPEG-2 AAC-LC with a proprietary mechanism for

(SBR), to be used by

XM Radio XM Satellite Radio (XM) was one of the three satellite radio ( SDARS) and online radio services in the United States and Canada, operated by Sirius XM Holdings. It provided pay-for-service radio, analogous to subscription cable television. Its s ...

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 ISO and IEC that sets standards for media coding, including compression coding of audio, video, graphics, and genomic data; and transmission and f ...

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 The root-mean-square deviation (RMSD) or root-mean-square error (RMSE) is a frequently used measure of the differences between values (sample or population values) predicted by a model or an estimator and the values observed. The RMSD represents ...

into account, is a tie between

mp3PRO mp3PRO is an unmaintained proprietary audio compression codec that combines the MP3 audio format with the spectral band replication (SBR) compression method. At the time it was developed it could reduce the size of a stereo MP3 by as much as 50% ...

, 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. Vorbis is most commonly used in conjun ...

. 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 kbit/s). In 2011, a public listening test comparing the two best-rated HE-AAC encoders at the time to

Opus ''Opus'' (pl. ''opera'') is a Latin word meaning "work". Italian equivalents are ''opera'' (singular) and ''opere'' (pl.). Opus or OPUS may refer to: Arts and entertainment Music * Opus number, (abbr. Op.) specifying order of (usually) publicatio ...

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 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 Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression. Designed to be the successor of the MP3 format, AAC generally achieves higher sound quality than MP3 encoders at the same bit rate. AAC has been stand ...

/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 (USAC) is an audio compression format and 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 by Moving Picture Experts Group (MPEG ...

Unified Speech and Audio Coding Unified Speech and Audio Coding (USAC) is an audio compression format and 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 by Moving Picture Experts Group (MPE ...

. 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 the fifth Roman emperor and final emperor of the Julio-Claudian dynasty, reigning from AD 54 unti ...

has released a free-of-charge command line HE-AAC encoder,

Nero AAC Codec __NOTOC__ Nero AAC Codec is a set of software tools for encoding and decoding Advanced Audio Coding (AAC) format audio, and editing MPEG-4 metadata. It was developed and distributed by Nero AG, and is available at no cost for Windows and Linux f ...

, 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 operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

as well as

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ser ...

. The 3GPP consortium released source code of a reference HE-AACv2 encoder that appears to offer competitive quality.

Winamp Winamp is a 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 Radionomy in 2014. Sinc ...

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 Nokia PC Suite is a discontinued software package used to establish an interface between Nokia mobile devices and computers that run the Microsoft Windows operating system. Its first release was in 1997, originally called Nokia Data Suite. I ...

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 Fraunhofer FDK AAC is an open-source library for encoding and decoding digital audio in the Advanced Audio Coding (AAC) format. Fraunhofer IIS, developed this library for Android 4.1. It supports several Audio Object Types including MPEG-2 and ...

library in Android 4.1 and later versions.

Decoding

HE-AAC is supported in the open source FAAD/

FAAD2 FAAC or Freeware Advanced Audio Coder is a software project which includes the AAC encoder FAAC and decoder FAAD2. It supports MPEG-2 AAC as well as MPEG-4 AAC. It supports several MPEG-4 Audio object types (LC, Main, LTP for encoding and S ...

decoding library and all players incorporating it, such as

VLC media player VLC media player (previously the VideoLAN Client and commonly known as simply VLC) is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for desk ...

, foobar2000, Audacious Media Player and

SonicStage SonicStage is a discontinued software product from Sony that is used for managing portable devices when they are plugged into a computer running Microsoft Windows. It comprises a music player and library manager, similar to iTunes, Windows Media ...

. The

supports decoding HE and HEv2 AAC. HE-AAC is also used by

AOL Radio AOL Radio powered by Slacker (formerly AOL Radio powered by CBS Radio, and prior AOL Radio featuring XM) was an online radio service available in the United States only. It had over 200 free internet radio stations. History Roots AOL Radio ...

and

Pandora Radio Pandora is a subscription-based music streaming service owned by Sirius XM Holdings based in Oakland, California, United States. The service carries a focus on recommendations based on the " Music Genome Project" — a means of classifying indi ...

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. 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

since Android version 4.1.

Clients

Promotion aspects

Commercial trademarks and labeling

HE-AAC is marketed under the trademark aacPlus by

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 at least two 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 ...

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 3GPP technical specifications for 3G

UMTS The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the In ...

multimedia services and should be supported in IP Multimedia Subsystem (IMS), Multimedia Messaging Service (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 3GPP for 3G UMTS multimedia services in September 2004 (3GPP TS 26.401). HE-AAC and HE-AAC v2 audio coding for

DVB Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) o ...

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 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 ISDB-T International, or SBTVD, short for Sistema Brasileiro de Televisão Digital ( en, Brazilian Digital Television System), is a technical standard for digital television broadcast used in Brazil, Argentina, Peru, Botswana, Chile, Honduras, Ve ...

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:

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