View source for HE-AAC

'''High Efficiency AAC aka HE-AAC aka aacPlus'''


'''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). 

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

(See also [[.mp4|.mp4 file extension]])

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). 

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]].

===External links===
* [http://www.tuner2.com/ Tuner2.com] list of Internet radio stations using aacPlus
* [http://www.codingtechnologies.com/products/aacPlus.htm aacPlus explained]
* [http://www.audiocoding.com/ Open Source AAC codec] FAAC (encoder) and FAAD2 (decoder)