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An enhanced AAC format from Coding Technologies (www.codingtechnologies.com) that extends Low Complexity AAC (AAC LC) to deliver near CD-quality sound in as little as 32 Kbps. Also known as "High Efficiency AAC" (HE-AAC).

Version 1 - AAC+ (HE-AAC v1)
Using Spectral Band Replication (SBR), AAC+ is a proprietary technique that halves the sampling rate but encodes the missing higher frequencies at a rate of 1.5 Kbps and stores them in the auxiliary data fields of the MPEG format. SBR is also used in the mp3PRO format (see mp3PRO).

Version 2 - eAAC+ (HE-AAC v2)
Used for stereo signals, eAAC+ supports Parametric Stereo (PS), which works similar to SBR. PS encodes the differences between left and right channels as a 3 Kbps data stream that it sends along with the monaural representation of the channels. See AAC and MP3.

Spectral Band Replication (SBR)
SBR encodes the high frequencies and stores them in the auxiliary data fields. The decoder restores the high frequencies from the SBR data.

Parametric Stereo (PS)
Parametric Stereo combines the left and right channels into a monaural signal and encodes the differences between channels as parametric data at a bit rate up to 3Kbps. The decoder turns the monaural stream back into stereo from the parametric data.
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According to Coding Technologies aacPlus has been proven in several tests to offer the highest quality at lowest possible bit rates.
561 Dolby Digital Plus Encoder OEM Module with Dolby E, Dolby Digital, Dolby Digital Plus, and aacPlus by Dolby audio formats.
We've offered our customers stereo AAC-LC and aacPlus decoders for several years with great success in the handheld and portable device markets, and we're now seeing strong demand for multi-channel versions in home entertainment multimedia products," stated Larry Przywara, Tensilica's marketing director for mobile/multimedia products.
Supported audio packages include: Dolby[R] Digital AC-3 and Dolby Digital Plus, MP3, MPEG-2/4 AAC LC, MPEG-4 aacPlus V1 and V2, Ogg Vorbis, WMA, AMR, G.
Dolby also showed aacPlus, a high-quality, highly efficient audio compression format designed for download, streaming, and broadcast applications on mobile phones.
The demo supports MP3, AAC, aacPlus and WMA decode as well as SRS WOW-XT, X-Space 3D, AM3D stereo expansion and 3D effects.