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'''High Efficiency AAC aka HE-AAC aka aacPlus'''
{{wikipedia|HE-AAC}}


'''High Efficiency AAC''' (aka '''aacPlus'''), is a [[lossy]] data compression scheme for audio streams, and is part of the '''[[MPEG-4]] Part 3''' specification.


'''aacPlus'''  is a [[lossy data compression]] scheme for [[audio stream]]s. It is based on [[MPEG-4]], and combines three techniques: [[Advanced Audio Coding]] (AAC), [[Spectral Band Replication]] (SBR), and [[parametric stereo]] (PS).  
HE-AAC combines [[Advanced Audio Coding]] (AAC), [[Spectral Band Replication]] (SBR) and, since version 2 (or Enhanced aacPlus), [[parametric stereo]] (PS). The [[codec]] can operate at very low bitrates and is good for [[internet radio]] streaming.  A 48 kilobit-per-second stream is considered to have higher quality than 128 [[kbit/s]] [[MP3]].


aacPlus was standardized by the [[MPEG]] as part of the MPEG-4 Part 3 specification, under the '''High Efficiency AAC''' ('''HE-AAC''') name.
VLC supports HE-AAC through the [[FAAD2]] library.
For details on the MPEG-4 Part 3 specification, see [http://en.wikipedia.org/wiki/MPEG-4_Part_3 wikipedia:MPEG-4_Part_3].


The [[codec]] can operate at very low bitrates and is good for [[Internet radio]] streaming.  A 48 kilobit-per-second stream is considered to have higher quality than 128 [[kbit/s]] [[MP3]].


In HE-AAC, Spectral Band Replication (SBR)  technology has been applied to AAC, and was incorporated into the standard to form High Efficiency AAC v1 (HE-AAC v1), (sometimes known as  aacPlus v1).
==External links==
 
Another recent introduction to AAC is  Parametric Stereo  ( aacPlus v2  or  Enhanced aacPlus ). These technologies significantly improve the performance of AAC at lower bitrates, and are used, for example, in  Digital Radio Mondiale .
 
====Support====
HE-AAC is supported in the [[free software|free]] [[FAAD2|FAAD2 decoding library]], and hence in many free players, and in [[Winamp]] and [[foobar2000]].
 
==See also==
*[[.m4a|.m4a file extension]] (the "mpeg4-audio" extenstion popularized by Apple iTunes)
 
===External links===
* [http://www.tuner2.com/ Tuner2.com] list of Internet radio stations using aacPlus
* [http://www.tuner2.com/ Tuner2.com] list of Internet radio stations using aacPlus
* [http://www.codingtechnologies.com/products/aacPlus.htm aacPlus explained]
* [http://www.codingtechnologies.com/products/aacPlus.htm aacPlus explained]
* [http://www.audiocoding.com/ Open Source AAC codec] FAAC (encoder) and FAAD2 (decoder)
* [http://www.audiocoding.com/ Open Source AAC codec] FAAC (encoder) and FAAD2 (decoder)

Revision as of 15:58, 12 February 2006

Wikipedia has information on this entry:
HE-AAC

High Efficiency AAC (aka aacPlus), is a lossy data compression scheme for audio streams, and is part of the MPEG-4 Part 3 specification.

HE-AAC combines Advanced Audio Coding (AAC), Spectral Band Replication (SBR) and, since version 2 (or Enhanced aacPlus), parametric stereo (PS). The codec can operate at very low bitrates and is good for internet radio streaming. A 48 kilobit-per-second stream is considered to have higher quality than 128 kbit/s MP3.

VLC supports HE-AAC through the FAAD2 library.


External links

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