Difference between revisions of "Advanced Audio Coding"

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(Describe more common flavors)
(→‎MPEG-2/4 AAC Main: Mention other Main features)
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=== MPEG-2/4 AAC Main ===
=== MPEG-2/4 AAC Main ===
MPEG-2/4 AAC-LC plus a computationally intensive, intra-channel, inter-frame frequency domain prediction tool. The details of the prediction tool are only given in ISO/IEC 13818-7 not in ISO/IEC 14496-4. This flavor is rarely seen in the wild.
MPEG-2/4 AAC-LC plus a computationally intensive, intra-channel, inter-frame frequency domain prediction tool. Additionally this profile adds relaxation to the maximum TNS filter size, and time domain coupling. The details of the prediction tool are only given in ISO/IEC 13818-7 not in ISO/IEC 14496-4. This flavor is rarely seen in the wild.


=== MPEG-4 AAC LTP ===
=== MPEG-4 AAC LTP ===

Revision as of 16:17, 17 February 2009

Specification and reference source links.

Implementations with source code:

Other Notable Implementations:

Usually stored in an MP4 container.

See also Understanding AAC.

Common AAC Flavors

MPEG-2 AAC-LC

The basic subset of AAC that most other flavors and profiles are based on.

The AAC Profile (MPEG-4 AAC-LC)

MPEG-2 AAC-LC plus a Perceptual Noise Substitution (PNS) tool.

The HE-AAC Profile (v1 and v2)

HE-AAC (also known as by the Dolby trade name aacPlus) is MPEG-4 AAC-LC + SBR (Spectral Band Replication) and HE-AAC v2 (aacPlus v2) is MPEG-4 AAC-LC + SBR + PS (Parametric Stereo). Standard AAC-LC decoders can decode HE-AAC encoded files/streams but without SBR and PS you do not get the full quality.

MPEG-2/4 AAC Main

MPEG-2/4 AAC-LC plus a computationally intensive, intra-channel, inter-frame frequency domain prediction tool. Additionally this profile adds relaxation to the maximum TNS filter size, and time domain coupling. The details of the prediction tool are only given in ISO/IEC 13818-7 not in ISO/IEC 14496-4. This flavor is rarely seen in the wild.

MPEG-4 AAC LTP

MPEG-4 AAC-LC plus a less computationally intensive frequency domain prediction tool. This flavor is rarely seen in the wild. Despite being an MPEG-4 only flavor it can be embedded in an ADTS stream.

Extensions

GAIN headers

See http://mp3gain.sourceforge.net and MP3 GAIN header.