Other Portable Audio

Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. AAC is promoted as the successor to the MP3 format by MP3’s creator, Fraunhofer IIS. more...

Home
A/V Accessories & Cables
Apple iPod, MP3 Players
DVD & Home Theater
Gadgets & Other Electronics
Home Audio
MP3 Accessories
Portable Audio/Video
Boomboxes
Cassette Players
CD Players
MiniDisc Players
Other Portable Audio
Portable A/V Accessories
Portable DVD Players
Portable Media Centers
Portable Radios
Speakers
Voice Recorders
Radios: CB, Ham & Shortwave
Satellite Radio
Satellite, Cable TV
Telephones & Pagers
Televisions

Depending on the encoder used, AAC generally achieves better sound quality than MP3 at the same bitrate, particularly below 192 kbit/s.

AAC’s most famous usage is as the default audio format of Apple's iPhone, iPod, iTunes, and the format used for all iTunes Store audio (with extensions for proprietary Digital Rights Management (DRM) where used).

AAC is also the standard audio format for Sony’s PlayStation 3 and the MPEG-4 video standard. HE-AAC is part of digital radio standards like DAB+ and Digital Radio Mondiale.

History

AAC was developed with the cooperation and contributions of companies including Dolby, Fraunhofer IIS, AT&T, Sony and Nokia, and was officially declared an international standard by the Moving Pictures Experts Group in April 1997.

Standardization

It is specified both as Part 7 of the MPEG-2 standard, and Part 3 of the MPEG-4 standard. As such, it can be referred to as MPEG-2 Part 7 and MPEG-4 Part 3 depending on its implementation, however it is most often referred to as MPEG-4 AAC, or AAC for short.

AAC was first specified in the standard MPEG-2 Part 7 (known formally as ISO/IEC 13818-7:1997) in 1997 as a new "part" (distinct from ISO/IEC 13818-3) in the MPEG-2 family of international standards.

It was updated in MPEG-4 Part 3 (known formally as ISO/IEC 14496-3:1999) in 1999. The reference software is specified in MPEG-4 Part 4 and the conformance bitstreams are specified in MPEG-4 Part 5. A notable addition in this version of the standard is Perceptual Noise Substitution (PNS).

HE-AAC (AAC with SBR) was first standardized in ISO/IEC 14496-3:2001/Amd.1. HE-AAC v2 (AAC with Parametric Stereo) was first specified in ISO/IEC 14496-3:2001/Amd.4.

The current version of the AAC standard is ISO/IEC 14496-3:2005 (with 14496-3:2005/Amd.2. for HE-AAC v2)

AacPlus v2 is also standardized by ETSI (European Telecommunications Standards Institute) as TS 102005.

The MPEG4 standard also contains other ways of compressing sound. These are low bit rate and generally used for speech.

AAC’s improvements over MP3

AAC was designed to have better performance than MP3 (which was specified in MPEG-1 and MPEG-2) by the ISO/IEC in 11172-3 and 13818-3.

Read more at Wikipedia.org