Katana VentraIP

High-Efficiency Advanced Audio Coding

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.[3] The usage profile HE-AAC v2 couples SBR with Parametric Stereo (PS) to further enhance the compression efficiency of stereo signals.

"EAAC" redirects here. For the airline, see European Aviation Air Charter.

Filename extensions

MPEG/3GPP Container

Apple Container

  • .m4a, .m4b, .m4p, .m4r, .m4v

ADTS Stream - NOT raw - Contains Headers

  • .aac

audio/aac
audio/aacp
audio/3gpp
audio/3gpp2
audio/mp4

ISO

Audio compression format

MPEG-4 Part 14, 3GP and 3G2, ISO base media file format, Audio Data Interchange Format (ADIF), Audio Data Transport Stream (ADTS)

AAC

HE-AAC is used in digital radio standards like HD Radio,[4] DAB+ and Digital Radio Mondiale.

History[edit]

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 and published as part of the ISO/IEC 14496-3:2001/Amd 1:2003[5] specification.


The HE-AAC v2 profile was standardized in 2006 as per ISO/IEC 14496-3:2005/Amd 2:2006.[1][6]


Parts of the HE-AAC specification had previously been standardized and published by various bodies in 3GPP TS 26.401 ,[7] ETSI TS 126 401 V6.1.0 ,[8] ISO/IEC 14496-3:2001/Amd.1:2003 and ISO/IEC 14496-3:2001/Amd 2:2004. [9]


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[edit]

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.[10][11][12][13] 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[14] 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 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[edit]

Encoding[edit]

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.[15][16]


Nero has released a free-of-charge command line HE-AAC encoder, Nero AAC Codec,[17] 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 Windows.


The 3GPP consortium released source code of a reference HE-AACv2 encoder that appears to offer competitive quality.[18]


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.[19]


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.[20]

Decoding[edit]

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.

Promotion aspects[edit]

Commercial trademarks and labeling[edit]

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[edit]

Companies holding patents for HE-AAC have formed a patent pool administered by Via Licensing Corporation[27] 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.[28] Unlike the MP3 format before April 23, 2017,[29] content owners are not required to pay license fees to distribute content in HE-AAC.

LC means

low complexity

SBR means

spectral band replication

PS means

parametric stereo

USAC means

unified speech and audio coding

Advanced Audio Coding

Digital Radio Mondiale

Radio Streaming Provider that provides every stream in HE-AACv2

Stream.Media

article in the EBU technical review (01/2006) giving explanations on HE-AAC.

MPEG-4 HE-AAC v2 — audio coding for today's digital media world

list of Internet radio stations using aacPlus

Tuner2.com

UK terrestrial radio stations streaming online in aacPlus format

RadioFeeds UK & Ireland (AAC+)

aacPlus explained

FAAC (encoder) and FAAD2 (decoder)

Open Source AAC codec

aacplusenc (Windows binary aacplusenc.exe only goes to 51 kbit/s.)

Reworked HE-AAC encoder

Archived 2012-01-03 at the Wayback Machine for Nero Encoder e.g. AAC-LC, HE-AAC, HE-AACv2 e.g.(Van Halen's Panama HE-AAC maxed at 205 kbit/s)

SNG 1.3 Front-end

- the Nero Encoder back-end for the SNG 1.3 front-end.

neroAacEnc.exe

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).

Winamp.com

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.

EZ CD Audio Converter

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.

Die Plattenkiste

Archived 2017-02-02 at the Wayback Machine - includes graphs comparing high-frequency performance for MP3pro (similar to HE-AAC+)

mp3PRO vs MP3

Official MPEG web site

- HE-AAC Patent Pool

Via Licensing Corporation

 4281 - The Codecs Parameter for "Bucket" Media Types

RFC

Fraunhofer AAC Test Site