Sustainability of Digital Formats
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Advanced Audio Coding (MPEG-2), Audio Data Interchange Format

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Formal name (from MPEG-2 documentation that specifies both the AAC_MP2 bitstream and the ADIF file structure.): ISO/IEC 13818-7:2003. Information technology -- Generic coding of moving pictures and associated audio information -- Part 7: Advanced Audio Coding (AAC). Common names: AAC and ADIF.
Description Bitstream encoding and file format designed for efficient distribution of sound files over moderate bandwidth connections; may be used at higher data rates for better fidelity. ADIF stands for Audio Data Interchange Format and consists of a brief header that precedes AAC data in a file. Note that the compression approach in AAC_MP2 (used in this format) was subsequently refined as AAC_MP4, which requires a different decoder.
Production phase Generally used for final-state, end-user delivery.
Relationship to other formats
    Subtype of MPEG-2, MPEG-2 Video Encoding (H.262)
    Contains AAC_MP2, Advanced Audio Coding (MPEG-2)

Local use Explanation of format description terms

LC experience or existing holdings None
LC preference The Broadcast WAVE format (either version, WAVE_BWF_1 or WAVE_BWF_2), wrapping LPCM, is preferred as the archival master format for mono and stereo audio when reformatting analog sound recordings. Preferences for born-digital acquisitions have not been formally established as of this writing, but acceptable formats will certainly include WAVE, MP3, AAC, and possibly others.

Sustainability factors Explanation of format description terms

Disclosure Open standard. Developed through ISO technical program JTC 1/SC 29 for coding of audio, picture, multimedia and hypermedia information by Working Group 11 (WG11) aka the Motion Pictures Expert Group (MPEG).
    Documentation ISO/IEC 13818-7:2003. Information technology -- Generic coding of moving pictures and associated audio information -- Part 7: Advanced Audio Coding (AAC). See also MPEG-2.
Adoption See AAC_MP2.
    Licensing and patents See AAC_MP2.
Transparency See AAC_MP2.
Self-documentation

According to the Audio Coding Wiki, which is no longer available as of June, 2010, the ADIF format actually is just one header at the beginning of the AAC file. And the rest of the data are consecutive raw data blocks. This file format is meant for simple local storing purposes unlike ADTS or LATM which are meant for streaming AAC. The ADIF header is made up of the following tagged elements; the field size in bits is provided in the parentheses, followed by a comment:

  • adif_id/ (32). Always has value "ADIF"
  • copyright_id_present (1).
  • copyright_id (72). Only present if copyright_id_present has value 1
  • original_copy (1).
  • home (1).
  • bitstream_type (1). 0 for CBR; 1 for VBR
  • bitrate (23). For CBR: bitrate; for VBR: peak bitrate; 0 means unknown
  • num_program_config_elements (4).

The next two elements are repeated (num_program_config_elements+1) times:

  • buffer_fullness (20). Only if bitstream_type has value 0
  • program_config_element (VAR).
External dependencies  
Technical protection considerations  

Quality and functionality factors Explanation of format description terms

Sound
Normal rendering Good support.
Fidelity (high audio resolution) See AAC_MP2.
Multiple channels See AAC_MP2.
Support for user-defined sounds, samples, and patches See AAC_MP2.
Functionality beyond normal rendering See AAC_MP2.

File type signifiers Explanation of format description terms

Tag Value Note
Filename extension aac
From The File Extension Source.
Internet Media Type Not found.  Comments welcome.  None identified as of 2004-05-26.

Notes Explanation of format description terms

General  
History  

Format specifications Explanation of format description terms


Useful references

URLs


Last Updated: Monday, 10-Feb-2014 22:12:20 EST