Format Description Categories >>
Browse Alphabetical List
Advanced Audio Coding (MPEG-2), Audio Data Interchange Format
>> Back
Format Description Properties
• ID: fdd000112
• Short name: AAC_ADIF
• Content categories: sound
• Format category: file format, bitstream encoding
• Last significant update: 2005-11-09
• Draft status: Full
Identification and description 
| Full name | ISO/IEC 13818-7:2003. Information technology -- Generic coding of moving pictures and associated audio information -- Part 7: Advanced Audio Coding (AAC). (Formal name; from MPEG-2 documentation that specifies both the AAC_MP2 bitstream and the ADIF file structure.)
AAC and ADIF (common names) |
| 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 |
| Contains | AAC_MP2 bitstream encoding |
Local use
| LC experience or existing holdings | None |
| LC preference | General preference for recorded sound is WAVE_LCPM. For compressed sound, AAC_ADIF is acceptable. |
Sustainability factors
| Disclosure | Open standard. Developed by ISO technical program JTC 1/SC 29 (WG11), aka the Motion Pictures Expert Group (MPEG), Coding of audio, picture, multimedia and hypermedia information. |
| 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 patent claims | See AAC_MP2. |
| Transparency | See AAC_MP2. |
| Self-documentation | According to the AudioCodingWiki, 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 fields:
| Field name | Field size in bits | Comment |
| adif_id | 32 | Always: "ADIF" |
| copyright_id_present | 1 | |
| copyright_id | 72 | only if copyright_id_present == 1 |
| original_copy | 1 | |
| home | 1 | |
| bitstream_type | 1 | 0: CBR, 1: VBR |
| bitrate | 23 | for CBR: bitrate, for VBR: peak bitrate, 0 means unknown |
| num_program_config_elements | 4 | |
The next 2 fields come (num_program_config_elements+1) times
|
| buffer_fullness | 20 | only if bitstream_type == 0 |
| program_config_element | VAR | |
See also AAC_MP2. |
| External dependencies | See AAC_MP2. |
| Technical protection considerations | See AAC_MP2. |
Quality and functionality factors
| Normal rendering | Good support. |
| Fidelity (support for high audio resolution) | See AAC_MP2. |
| Support for multiple sound channels | See AAC_MP2. |
| Support for downloadable or user-defined sounds, samples, and patches | See AAC_MP2. |
| Functionality beyond normal rendering | See AAC_MP2. |
File type signifiers
Notes
Format specifications
URLs
Print
• ISO/IEC 13818-7:2003 Information technology -- Generic coding of moving pictures and associated audio information -- Part 7: Advanced Audio Coding (AAC).
Useful references
URLs
• MPEG-2/MPEG-4 AAC page from MP3-tech.org (www.mp3-tech.org/aac.html)
• "MP3 and AAC Explained," by Karlheinz Brandenburg, Fraunhofer Institute, Erlangen, Germany (http://www.aes.org/publications/downloadDocument.cfm?accessID=14703162000122117).
Print
Last Updated: 03/ 7/2007
