Advanced Audio Coding

AACAAC-LCMPEG-4 AAC.aacAAC/AAC+/eAAC+ADTSAAC audioAAC/ADTSAAC/MP4/M4A/M4BLC-AAC
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression.wikipedia
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Audio coding format

audio codingaudio coding standardaudio compression format
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression.
Examples of audio coding formats include MP3, AAC, Vorbis, FLAC, and Opus.

Data compression

compressionvideo compressioncompressed
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression.
DCT is the most widely used lossy compression method, and is used in multimedia formats for images (such as JPEG and HEIF), video (such as MPEG, AVC and HEVC) and audio (such as MP3, AAC and Vorbis).

MPEG-4

MPEG4MPEG 44
AAC has been standardized by ISO and IEC, as part of the MPEG-2 and MPEG-4 specifications.
AAC (Advanced Audio Coding) was standardized as an adjunct to MPEG-2 (as Part 7) before MPEG-4 was issued.

Digital audio

digital musicdigitalaudio
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression.
Audio data compression techniques, such as MP3, Advanced Audio Coding, Ogg Vorbis, or FLAC, are commonly employed to reduce the file size.

Discrete cosine transform

DCTiDCTinverse discrete cosine transform
The discrete cosine transform (DCT), a type of transform coding for lossy compression, was proposed by Nasir Ahmed in 1972, and developed by Ahmed with T. Natarajan and K. R. Rao in 1973, publishing their results in 1974.
It is used in most digital media, including digital images (such as JPEG and HEIF, where small high-frequency components can be discarded), digital video (such as MPEG, H.26x and Vorbis), digital audio (such as Dolby Digital, MP3 and AAC), digital television (such as SDTV, HDTV and VOD), digital radio (such as AAC+ and DAB+), and speech coding (such as AAC-LD, Siren and Opus).

Joint encoding

Joint stereochannel couplingintensity encoded
The quality for stereo is satisfactory to modest requirements at 96 kbit/s in joint stereo mode; however, hi-fi transparency demands data rates of at least 128 kbit/s (VBR).
Two forms are described here, both of which are implemented in various ways with different codecs, such as MP3, AAC and Ogg Vorbis.

Variable bitrate

VBRvariable bit ratevariable
The quality for stereo is satisfactory to modest requirements at 96 kbit/s in joint stereo mode; however, hi-fi transparency demands data rates of at least 128 kbit/s (VBR).
MP3, WMA and AAC audio files can optionally be encoded in VBR, while Opus, Vorbis are always in VBR.

Modified discrete cosine transform

MDCTModulated Lapped Transformtime-domain aliasing cancellation
AAC uses a purely modified discrete cosine transform (MDCT) algorithm, giving it higher compression efficiency than MP3, which uses a hybrid coding algorithm that is part MDCT and part FFT.
It is employed in most modern audio coding standards, including MP3, Dolby Digital (AC-3), Vorbis (Ogg), Windows Media Audio (WMA), ATRAC, Cook, Advanced Audio Coding (AAC), LDAC, Dolby AC-4, MPEG-H 3D Audio, as well as speech coding standards such as AAC-LD (LD-MDCT), G.722.1, G.729.1, CELT, and Opus.

Wii Menu

Mii ChannelForecast ChannelNews Channel
It is supported on PlayStation Vita, Wii (with the Photo Channel 1.1 update installed), Sony Walkman MP3 series and later, Android and BlackBerry.
The update replaced MP3 support with support for MPEG-4 encoded audio files encoded with AAC in the .m4a extension.

ITunes

Apple iTunesApple PodcastsiTunes India
AAC is the default or standard audio format for iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS, iTunes, DivX Plus Web Player, PlayStation 3 and various Nokia Series 40 phones.
iTunes supports WAV, AIFF, Apple Lossless, AAC, and MP3 audio formats.

High-Efficiency Advanced Audio Coding

AAC+HE-AACeAAC+
Part of AAC, HE-AAC ("AAC+"), is part of MPEG-4 Audio and also adopted into digital radio standards DAB+ and Digital Radio Mondiale, as well as mobile television standards DVB-H and ATSC-M/H. The HE-AAC Profile (AAC LC with SBR) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.
It is an extension of Low Complexity AAC (AAC LC) optimized for low-bitrate applications such as streaming audio.

AAC-LD

AAC-ELDAAC LD
The MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000) defined new audio object types: the low delay AAC (AAC-LD) object type, bit-sliced arithmetic coding (BSAC) object type, parametric audio coding using harmonic and individual line plus noise and error resilient (ER) versions of object types.
It is closely derived from the MPEG-2 Advanced Audio Coding (AAC) standard.

FAAC

FAAD2Freeware Advanced Audio Decoderlibfaac
For this reason, free and open source software implementations such as FFmpeg and FAAC may be distributed in source form only, in order to avoid patent infringement.
FAAC or Freeware Advanced Audio Coder is a software project which includes the AAC encoder FAAC and decoder FAAD2.

Digital Audio Broadcasting

DABDAB+DAB Digital Radio
Part of AAC, HE-AAC ("AAC+"), is part of MPEG-4 Audio and also adopted into digital radio standards DAB+ and Digital Radio Mondiale, as well as mobile television standards DVB-H and ATSC-M/H.
(For comparison, BBC Radio 3 and all other BBC radio stations are now streamed using AAC at 320 kbit/s, described as 'HD', on BBC Radio iPlayer after a period when it was available at two different bit rates.)

IPod

iPodsApple iPodiPod Touch
AAC is the default or standard audio format for iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS, iTunes, DivX Plus Web Player, PlayStation 3 and various Nokia Series 40 phones.
The iPod line can play several audio file formats including MP3, AAC/M4A, Protected AAC, AIFF, WAV, Audible audiobook, and Apple Lossless.

FFmpeg

SnowLAV Filterslibavformat
For this reason, free and open source software implementations such as FFmpeg and FAAC may be distributed in source form only, in order to avoid patent infringement.
In 2016 the native AAC encoder was considered stable, removing support for the two external AAC encoders from VisualOn and FAAC.

Wii

Nintendo WiiWii MiniSensor Bar
It is supported on PlayStation Vita, Wii (with the Photo Channel 1.1 update installed), Sony Walkman MP3 series and later, Android and BlackBerry.
Version 1.1 of the Photo Channel removed MP3 playback in favor of AAC support.

Nintendo DSi

DSiNintendo DSi XLDSiWare
AAC is the default or standard audio format for iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS, iTunes, DivX Plus Web Player, PlayStation 3 and various Nokia Series 40 phones.
The DSi has more extensive multimedia features than previous models; AAC audio files from other devices, pictures, and downloadable software can be stored to an SD card.

ITunes Store

iTunesiTunes Music StoreiTunes U
Customers could download music in a closed-source Digital Rights Management (DRM)-restricted form of AAC (see FairPlay) via the iTunes Store or create files without DRM from their own CDs using iTunes.
Music in the store is in the Advanced Audio Coding (AAC) format, which is the MPEG-4-specified successor to MP3.

Nasir Ahmed (engineer)

Nasir AhmedN. Ahmed
The discrete cosine transform (DCT), a type of transform coding for lossy compression, was proposed by Nasir Ahmed in 1972, and developed by Ahmed with T. Natarajan and K. R. Rao in 1973, publishing their results in 1974.
A DCT variant, the modified discrete cosine transform (MDCT), is used in modern audio compression formats such as MP3, Advanced Audio Coding (AAC), and Vorbis (OGG).

Spectral band replication

SBRMPEG-4 V3 SBR
The HE-AAC Profile (AAC LC with SBR) and AAC Profile (AAC LC) were first standardized in ISO/IEC 14496-3:2001/Amd 1:2003.
A Swedish company, Coding Technologies (acquired by Dolby in 2007), developed and pioneered the use of SBR in its MPEG-2 AAC derived codec called aacPlus, which first appeared in 2001.

FairPlay

.m4pAAC-DRMan open letter
Customers could download music in a closed-source Digital Rights Management (DRM)-restricted form of AAC (see FairPlay) via the iTunes Store or create files without DRM from their own CDs using iTunes.
FairPlay is a digital rights management (DRM) technology developed by Apple Inc. It is built into the MP4 multimedia file format as an encrypted AAC audio layer, and is used by the company to protect copyrighted works sold through iTunes Store, allowing only authorized devices to play the content.

MP3

.mp3MP3 downloadMP3 files
Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at the same bit rate.
Among these, Advanced Audio Coding (AAC) is the most widely used, and was designed to be the successor to MP3.

DivX

DivX Media FormatXSUB.divx
AAC is the default or standard audio format for iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS, iTunes, DivX Plus Web Player, PlayStation 3 and various Nokia Series 40 phones.
DivX Plus HD files contain an H.264 video bitstream, AAC surround sound audio, and a number of XML-based attachments defining chapters, subtitles and meta data.

MPEG-4 SLS

Scalable Lossless CodingHD-AACMPEG-4 Scalable To Lossless (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).