High-Efficiency Advanced Audio Coding

Last updated
High-Efficiency Advanced Audio Coding
Filename extensions MPEG/3GPP Container

Apple Container

  • .m4a, .m4b, .m4p, .m4r, .m4v

ADTS Stream - NOT raw - Contains Headers

  • .aac
Internet media type audio/aac
audio/aacp
audio/3gpp
audio/3gpp2
audio/mp4
Developed by ISO
Type of formatAudio 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)
Extended from AAC
Standard ISO/IEC 14496-3
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. HE-AAC and HE-AAC v2.svg
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.
Evolution from MPEG-2 AAC-LC (Low Complexity) Profile and MPEG-4 AAC-LC Object Type to HE-AAC v2 Profile. AAC profiles.svg
Evolution from MPEG-2 AAC-LC (Low Complexity) Profile and MPEG-4 AAC-LC Object Type to HE-AAC v2 Profile.

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.

Contents

HE-AAC is used in digital radio standards like HD Radio, [4] 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 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

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 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.

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. [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]

Die Plattenkiste and 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

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.

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.

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:

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. [20] Decoding is handled by Fraunhofer FDK AAC since Android version 4.1.

Clients

ApplicationPlatformDescription
AIMP WindowsA Winamp-like alternative music player. [22]
Adobe Flash Player Windows, macOS, Chrome OS, LinuxBrowser plug-in. [23] [24] 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.) [lower-alpha 1]
Amarok (software) Windows, LinuxOpen-source music player.
Audacious Media Player Windows, LinuxOpen-source music player.
Deadbeef Linux, AndroidOpen-source music player.
Die Plattenkiste WindowsFreeware internet radio application (in German).
foobar2000 WindowsFreeware music player.
fre:ac Windows, macOS, LinuxOpen-source audio converter.
FStream macOS, iOSInternet radio application.
GuguRadio iOSInternet radio application.
Internet Radio Player AndroidInternet radio player.
Internet Radio Box iOSInternet radio application.
iTunes Windows, macOSFreeware music player. Pre-installed on Mac computers.
JetAudio Windows, AndroidShareware media player.
MediaHuman Audio Converter Windows, macOSFreeware audio converter.
(Supports conversion of MP3, AAC, AIFF, WAV etc.)
MPlayer Windows, macOS and LinuxOpen-source media player.
Mpv (media player) Windows, macOS and LinuxOpen-source media player.
Rockbox Various portable media devicesAlternate firmware for various portable media-players, such as Apple iPod and Creative Zen.
QuickTime X macOSMedia player pre-installed on Mac OS X Snow Leopard or later.
RealPlayer Windows, macOS, Linux, AndroidFreemium media player.
(HE-AAC v2 will only play in mono) [26]
Rhythmbox LinuxOpen-source music player.
Snowtape macOSShareware internet radio application.
streamWriter WindowsOpen-source internet radio application.
StreamS HiFi Radio iOSPaidware internet radio player.
Tunein radio iOS, Android, Windows Phone, BlackberryInternet radio player.
VLC media player Windows, macOS, Linux, iOS, AndroidOpen-source media player.
Winamp Windows, macOS, AndroidFreeware media player.
XiiaLive Android, iOSInternet radio player.
Kodi Windows, Linux, macOS, AndroidOpen-source media player.
Media Player Classic WindowsOpen-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 ]

Licensing and patents

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.

Standards

HE-AAC profile was first standardized in ISO/IEC 14496-3:2001/Amd 1:2003. [5] HE-AAC v2 profile (HE-AAC with Parametric Stereo) was first specified in ISO/IEC 14496-3:2005/Amd 2:2006. [1] [6] [30] 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. [9] [7]

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). [31] [32] [33] [34] 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). [35]

HE-AAC and HE-AAC v2 audio coding for DVB applications is standardized by TS 101 154. [36] [37] AacPlus v2 by Coding Technologies [38] 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.

Versions

The following is the summary of the different versions of HE-AAC:

VersionCommon trade namesCodec featureStandards
HE-AAC v1aacPlus v1, eAAC, AAC+, CT-aacPlusAAC-LC + SBRISO/IEC 14496-3:2001/Amd 1:2003
HE-AAC v2aacPlus v2, eAAC+, AAC++, Enhanced AAC+AAC-LC + SBR + PSISO/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
[39]

See also

Notes

  1. 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. [25]

Related Research Articles

MPEG-2 Video encoding standard

MPEG-2 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, which permit storage and transmission of movies using currently available storage media and transmission bandwidth. While MPEG-2 is not as efficient as newer standards such as H.264/AVC and H.265/HEVC, backwards compatibility with existing hardware and software means it is still widely used, for example in over-the-air digital television broadcasting and in the DVD-Video standard.

MPEG-4 is a method of defining compression of audio and visual (AV) digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of AV data for Internet video and CD distribution, voice and broadcast television applications. The MPEG-4 standard was developed by a group led by Touradj Ebrahimi and Fernando Pereira.

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 at the same bit rate.

MPEG-4 Part 3 or MPEG-4 Audio 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 published in 1999.

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.

Adaptive Multi-Rate Wideband (AMR-WB) is a patented wideband speech audio coding standard developed based on Adaptive Multi-Rate encoding, using similar methodology as algebraic code excited linear prediction (ACELP). AMR-WB provides improved speech quality due to a wider speech bandwidth of 50–7000 Hz compared to narrowband speech coders which in general are optimized for POTS wireline quality of 300–3400 Hz. AMR-WB was developed by Nokia and VoiceAge and it was first specified by 3GPP.

3GP is a multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones.

Harmonic Vector Excitation Coding, abbreviated as HVXC is a speech coding algorithm specified in MPEG-4 Part 3 standard for very low bit rate speech coding. HVXC supports bit rates of 2 and 4 kbit/s in the fixed and variable bit rate mode and sampling frequency 8 kHz. It also operates at lower bitrates, such as 1.2 - 1.7 kbit/s, using a variable bit rate technique. The total algorithmic delay for the encoder and decoder is 36 ms.

TwinVQ is an audio compression technique developed by Nippon Telegraph and Telephone Corporation (NTT) Human Interface Laboratories in 1994. The compression technique has been used in both standardized and proprietary designs.

MPEG-4 Part 17, or MPEG-4 Timed Text (MP4TT), or MPEG-4 Streaming text format is the text-based subtitle format for MPEG-4, published as ISO/IEC 14496-17 in 2006. It was developed in response to the need for a generic method for coding of text as one of the multimedia components within audiovisual presentations.

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, file formats, multichannel and gapless encoding/decoding and MP4 metadata tags. The encoder and decoder is compatible with standard-compliant audio applications using one or more of these object types and facilities. It also supports Digital Radio Mondiale.

MPEG-4 Audio Lossless Coding, also known as MPEG-4 ALS, is an extension to the MPEG-4 Part 3 audio standard to allow lossless audio compression. The extension was finalized in December 2005 and published as ISO/IEC 14496-3:2005/Amd 2:2006 in 2006. The latest description of MPEG-4 ALS was published as subpart 11 of the MPEG-4 Audio standard in August 2009.

MPEG-4 SLS

MPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/IEC 14496-3:2005/Amd 3:2006 (Scalable Lossless Coding), is an extension to the MPEG-4 Part 3 (MPEG-4 Audio) standard to allow lossless audio compression scalable to lossy MPEG-4 General Audio coding methods (e.g., variations of AAC). It was developed jointly by the Institute for Infocomm Research (I2R) and Fraunhofer, which commercializes its implementation of a limited subset of the standard under the name of HD-AAC. Standardization of the HD-AAC profile for MPEG-4 Audio is under development (as of September 2009).

MPEG-4 Part 14 MP4; digital format for storing video and audio

MPEG-4 Part 14 or MP4 is a digital multimedia container format most commonly used to store video and audio, but it can also be used to store other data such as subtitles and still images. Like most modern container formats, it allows streaming over the Internet. The only filename extension for MPEG-4 Part 14 files as defined by the specification is .mp4. MPEG-4 Part 14 is a standard specified as a part of MPEG-4.

The MPEG-4 Low Delay Audio Coder is audio compression standard designed to combine the advantages of perceptual audio coding with the low delay necessary for two-way communication. It is closely derived from the MPEG-2 Advanced Audio Coding (AAC) standard. It was published in MPEG-4 Audio Version 2 and in its later revisions.

MPEG Surround, also known as Spatial Audio Coding (SAC) is a lossy compression format for surround sound that provides a method for extending mono or stereo audio services to multi-channel audio in a backwards compatible fashion. The total bit rates used for the core and the MPEG Surround data are typically only slightly higher than the bit rates used for coding of the core. MPEG Surround adds a side-information stream to the core bit stream, containing spatial image data. Legacy stereo playback systems will ignore this side-information while players supporting MPEG Surround decoding will output the reconstructed multi-channel audio.

2D Plus Delta is a method of encoding 3D image listed as a part of MPEG2 and MPEG4 standards, specifically on the H.264 implementation of Multiview Video Coding extension. This technology originally started as a proprietary method for Stereoscopic Video Coding and content deployment that utilizes the Left or Right channel as the 2D version and the optimized difference or disparity (Delta) between that image channel view and a second eye image view is injected into the videostream as user_data, secondary stream, independent stream, enhancement layer or NALu for deployment. The Delta data can be either a spatial stereo disparity, temporal predictive, bidirectional or optimized motion compensation.

ISO/IEC base media file format defines a general structure for time-based multimedia files such as video and audio. The identical text is published as ISO/IEC 15444-12.

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) and was published as an international standard ISO/IEC 23003-3 and also as an MPEG-4 Audio Object Type in ISO/IEC 14496-3:2009/Amd 3 in 2012.

References

  1. 1 2 3 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
  2. Fraunhofer IIS, MPEG-4 Audio and Video Technology (PDF), retrieved 2009-10-15[ dead link ]
  3. 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.
  4. "Receiving NRSC-5". theori.io. Archived from the original on 20 August 2017. Retrieved 14 April 2018.
  5. 1 2 ISO (2003). "Bandwidth extension, ISO/IEC 14496-3:2001/Amd 1:2003". ISO. Archived from the original on 2012-01-04. Retrieved 2009-10-13.
  6. 1 2 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.
  7. 1 2 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.
  8. 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.
  9. 1 2 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.
  10. "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)
  11. "Multiformat Listening Test @ 48 kbps - FINISHED". www.hydrogenaud.io. Archived from the original on 8 July 2014. Retrieved 3 May 2018.
  12. "80 kbps personal listening test (summer 2005)". www.hydrogenaud.io. Archived from the original on 8 July 2014. Retrieved 3 May 2018.
  13. "MP3 – WMA – AAC – OGG – qualité à 96 kbps (évaluation) - Traitement Audio - Video & Son - FORUM HardWare.fr". forum.hardware.fr. Archived from the original on 15 July 2012. Retrieved 3 May 2018.
  14. "Hydrogen audio 2011 multiformat listening test unofficial results page". people.xiph.org. Archived from the original on 25 July 2012. Retrieved 3 May 2018.
  15. "Archived copy". Archived from the original on 2011-03-29. Retrieved 2011-03-29.CS1 maint: archived copy as title (link)
  16. "iTunes". Apple. Archived from the original on 29 March 2011. Retrieved 3 May 2018.
  17. "Nero AAC Codec". Archived from the original on 2009-12-11. Retrieved 2009-11-23.
  18. Bouvigne, Gabriel (2006-03-20). "48kbps AAC public test results". MP3'Tech. Archived from the original on 2008-07-24. Retrieved 2008-09-05.
  19. "Free Download Winamp Transcoder 2.0". www.free-codecs.com. Archived from the original on 20 August 2008. Retrieved 3 May 2018.
  20. 1 2 "Supported Media Formats". Google. Archived from the original on 2012-03-11. Retrieved 2013-10-10.
  21. "iPod touch: Supported file formats". Apple Support. Retrieved 2019-04-07.
  22. "AIMP". www.aimp.ru. Archived from the original on 8 November 2014. Retrieved 3 May 2018.
  23. "Adobe Flash Player". www.adobe.com. Archived from the original on 23 July 2008. Retrieved 3 May 2018.
  24. "Adobe bringing HD video, high quality audio to Flash using H.264, AAC (iPhone Flash support?) – MacDailyNews - Welcome Home". macdailynews.com. Archived from the original on 21 June 2015. Retrieved 3 May 2018.
  25. "Playing Icecast streaming audio in Flash Player - Adobe Developer Connection". www.adobe.com. Archived from the original on 16 March 2015. Retrieved 3 May 2018.
  26. "Archived copy". Archived from the original on 2015-03-18. Retrieved 2014-10-19.CS1 maint: archived copy as title (link)
  27. Via Licensing. "Licensing Programs". Archived from the original on 2017-05-13. Retrieved 2017-05-11.
  28. Via Licensing. "AAC Licensing FAQ". Archived from the original on 2017-05-22. Retrieved 2017-05-11.
  29. Thomson. "Thomson/FhG MP3 Licensing". Archived from the original on 2017-01-17.
  30. Mihir Mody (2005-06-06). "Audio compression gets better and more complex". Embedded.com. Retrieved 2009-10-13.[ permanent dead link ]
  31. 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.
  32. 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.
  33. 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.
  34. 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.
  35. 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.
  36. 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
  37. 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.
  38. "Archived copy" (PDF). Archived from the original (PDF) on 2006-10-26. Retrieved 2007-01-29.CS1 maint: archived copy as title (link)
  39. "xHE-AAC". Fraunhofer Institute for Integrated Circuits IIS. Retrieved 3 January 2021.