High-Efficiency Advanced Audio Coding
|Filename extensions||MPEG/3GPP Container
ADTS Stream - NOT raw - Contains Headers
|Internet media type|
|Type of format||Audio compression format|
|Contained by||MPEG-4 Part 14, 3GP and 3G2, ISO base media file format, Audio Data Interchange Format (ADIF), Audio Data Transport Stream (ADTS)|
High-Efficiency Advanced Audio Coding (HE-AAC) is an audio coding format for lossy data compression of digital audio defined as an MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity 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. The usage profile HE-AAC v2 couples SBR with Parametric Stereo (PS) to further enhance the compression efficiency of stereo signals.
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.
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.
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.
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 and Ogg Vorbis indicated statistically significant superiority at 64 kbit/s for Opus 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.
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.
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 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, SonicStage and Die Plattenkiste.
The Nero AAC Codec supports decoding HE and HEv2 AAC.
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.
|AIMP||Windows||A Winamp-like alternative music player.|
|Adobe Flash Player||Windows, macOS, Chrome OS, Linux||Browser plug-in. Supports AAC+ from any RTMP source.|
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.)[a]
|Amarok (software)||Windows, Linux||Open-source music player.|
|Audacious Media Player||Windows, Linux||Open-source music player.|
|Deadbeef||Linux, Android||Open-source music player.|
|Die Plattenkiste||Windows||Freeware internet radio application (in German).|
|foobar2000||Windows||Freeware music player.|
|fre:ac||Windows, macOS, Linux||Open-source audio converter.|
|FStream||macOS, iOS||Internet radio application.|
|GuguRadio||iOS||Internet radio application.|
|Internet Radio Player||Android||Internet radio player.|
|Internet Radio Box||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.|
(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. |
(HE-AAC v2 will only play in mono)
|Rhythmbox||Linux||Open-source music player.|
|Snowtape||macOS||Shareware internet radio application.|
|streamWriter||Windows||Open-source internet radio application.|
|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.|
|XiiaLive||Android, iOS||Internet radio player.|
|Kodi||Windows, Linux, macOS, Android||Open-source media player.|
|Media Player Classic||Windows||Open-source media player|
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
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.
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 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 applications is standardized by TS 101 154. 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 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.
The following is the summary of the different versions of HE-AAC:
|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|
|xHE-AAC||aacPlus v2, eAAC+, AAC++, Enhanced AAC+||AAC-LC + SBR + PS + USAC||ISO/IEC 23003-3:2012/Amd 2:2012|
- 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). You can parse these containers and create FLV audio tags in order to use the audio file with Data Generation Mode.
- ISO/IEC JTC1/SC29/WG11/N7016 (2005-01-11), Text of ISO/IEC 14496-3:2001/FPDAM 4, Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, archived from the original (DOC) on 2014-05-12, retrieved 2009-10-09
- Fraunhofer IIS, MPEG-4 Audio and Video Technology (PDF), retrieved 2009-10-15[dead link]
- Herre, J.; Dietz, M. (2008). "MPEG-4 high-efficiency AAC coding [Standards in a Nutshell]". IEEE Signal Processing Magazine. 25 (3): 137–142. doi:10.1109/MSP.2008.918684.
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- ISO (2006). "Audio Lossless Coding (ALS), new audio profiles and BSAC extensions, ISO/IEC 14496-3:2005/Amd 2:2006". ISO. Archived from the original on 2012-01-04. Retrieved 2009-10-13.
- 3GPP (2004-09-30). "3GPP TS 26.401 V6.0.0 (2004-09), General Audio Codec audio processing functions; Enhanced aacPlus General Audio Codec; General Description (Release 6)" (DOC). 3GPP. Archived from the original on 2006-08-19. Retrieved 2009-10-13.
- 3GPP (2005-01-04). "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)". 3GPP. Retrieved 2009-10-13.
- ISO (2004). "Parametric coding for high-quality audio, ISO/IEC 14496-3:2001/Amd 2:2004". ISO. Archived from the original on 2012-01-04. Retrieved 2009-10-13.
- "Results of 64kbit/s Listening Test". archive.org. 23 June 2007. Archived from the original on 23 June 2007. Retrieved 3 May 2018.CS1 maint: bot: original URL status unknown (link)
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- "80 kbps personal listening test (summer 2005)". www.hydrogenaud.io. Archived from the original on 8 July 2014. Retrieved 3 May 2018.
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- Bouvigne, Gabriel (2006-03-20). "48kbps AAC public test results". MP3'Tech. Archived from the original on 2008-07-24. Retrieved 2008-09-05.
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- "Supported Media Formats". Google. Archived from the original on 2012-03-11. Retrieved 2013-10-10.
- "iPod touch: Supported file formats". Apple Support. Retrieved 2019-04-07.
- "AIMP". www.aimp.ru. Archived from the original on 8 November 2014. Retrieved 3 May 2018.
- "Adobe Flash Player". www.adobe.com. Archived from the original on 23 July 2008. Retrieved 3 May 2018.
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- Via Licensing. "AAC Licensing FAQ". Archived from the original on 2017-05-22. Retrieved 2017-05-11.
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- ETSI (2009-04) 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 Archived 2008-12-01 at the Wayback Machine Page 58. Retrieved on 2009-06-02.
- ETSI (2009-01) ETSI TS 126 140 V8.0.0 (2009-01); 3GPP TS 26.140; Multimedia Messaging Service (MMS); Media formats and codes Archived 2008-12-06 at the Wayback Machine Page 11. Retrieved on 2009-06-02.
- ETSI (2009-01) ETSI TS 126 141 V8.0.0 (2009-01); 3GPP TS 26.141; IP Multimedia System (IMS) Messaging and Presence; Media formats and codecs Archived 2008-10-07 at the Wayback Machine Page 10. Retrieved on 2009-06-02.
- 3GPP (2009). "ETSI TS 126 346 V8.3.0 (2009-06); 3GPP TS 26.346; Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs". ETSI. p. 85. Archived from the original on 2008-10-04. Retrieved 2009-10-13.
- 3GPP (2004). "3GPP TS 26.401 - General audio codec audio processing functions; Enhanced aacPlus general audio codec; General description". 3GPP. Archived from the original on 2008-10-04. Retrieved 2009-10-13.
- 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
- ETSI (2009-03-31). "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". ETSI. Archived from the original on 2013-04-14. Retrieved 2009-10-13.
- "Archived copy" (PDF). Archived from the original (PDF) on 2006-10-26. Retrieved 2007-01-29.CS1 maint: archived copy as title (link)
- "xHE-AAC". Fraunhofer Institute for Integrated Circuits IIS. Retrieved 3 January 2021.
- 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
- aacPlus explained
- Open Source AAC codec FAAC (encoder) and FAAD2 (decoder)
- Reworked HE-AAC encoder aacplusenc (Windows binary aacplusenc.exe only goes to 51 kbit/s.)
- SNG 1.3 Front-end 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 site
- Via Licensing Corporation - HE-AAC Patent Pool
- RFC 4281 - The Codecs Parameter for "Bucket" Media Types
- Fraunhofer AAC Test Site