Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | AES3-2003. AES standard for digital audio — Digital input-output interfacing — Serial transmission format for two-channel linearly represented digital audio data (formal name) AES3 (common name) |
| Description | Audio Engineering Society interface format for serial digital transmission of stereo or two-channel LPCM (Linear Pulse Code Modulated) sound. The data is sent in audio blocks, each of which is made up of 192 frames numbered 0 to 191. Each frame is divided in 2 subframes (or channels): A (left) and B (right). Each subframe contains the information for one single sample of the PCM audio. LCPM data is "expected" to be sampled at the preferred frequencies recommended in AES5; see Notes below. A method for inserting standardized unique identifiers into the AES3 stream is specified in AES52-2006, specifically covering the UMID (Unique Material Identifier specified in SMPTE 330M-2000) and the UUID (Universally Unique Identifier as documented in ISO/IEC 11578:1996 and IETF RFC 4122). An extension of the AES3 interface has been developed by the Society of Motion Picture and Television Engineers (AES3_SMPTE), and it specifies a method for using the interface to transmit non-PCM AC3 compressed audio and other data. The main thrust of AES3 concerns cabling and the physical interface between devices (see Notes below); this Web site is primarily devoted to formats pertaining to the storage of digital content bitstreams and to related file, wrapper, or bundling formats. |
| Production phase | Interface format that may be used at any point in a production life cycle. |
| Relationship to other formats | |
| Contains | LPCM, Linear Pulse Code Modulated Audio |
| Has earlier version | AES3-1985 and -1992 (also published as ANSI S4.40-1985 and -1992), not documented here. |
| LC experience or existing holdings | See LPCM |
| LC preference | See LPCM |
| Disclosure | Open standard. Developed by the Audio Engineering Society. |
| Documentation | AES3-2003. AES standard for digital audio — Digital input-output interfacing — Serial transmission format for two-channel linearly represented digital audio data. |
| Adoption | Widely adopted. |
| Licensing and patent claims | None. |
| Transparency | See LPCM |
| Self-documentation | Not applicable. Metadata can be embedded in some file formats that incorporate LPCM bitstreams. |
| External dependencies | The specification covers wiring and cable connectors. |
| Technical protection considerations | None |
| Normal rendering | Good support. |
| Fidelity (support for high audio resolution) | Fidelity considerations reflect the use of linear PCM encoding; see LPCM. |
| Support for multiple sound channels | AES3 supports the interleaving of two LPCM streams. |
| Support for downloadable or user-defined sounds, samples, and patches | Not applicable |
| Functionality beyond normal sound rendering | Not applicable |
| Tag type | Value | Note |
| Filename Extension | See note | Generally depends upon the wrapper used for the "storage" version of LPCM. LPCM data may be stored in "raw" form, with ".raw" as a possible file extension. A variant of this encoding is captured by devices manufactured by Snell & Wilcox, reportedly carring an ".aes" extension. |
| Internet Media Type | Not applicable | |
| Magic numbers | None found |
| General | The main body of AES3 specifies signal transmission via a single shielded twisted wire pair. Annex D, however, discusses the carriage of AES3 signals on structured wiring, e.g., the "category 5" cables associated with computer network installations, a topic that receives extended treatment in AES47, which specifies the method of carrying multiple channels of audio in linear PCM or AES3 format across an asynchronous transfer mode (ATM) network. Elaborations on audio signal transfer are the topics of AES10-2003, AES Recommended Practice for Digital Audio Engineering &8221; Serial Multichannel Audio Digital Interface (MADI) (Revision of AES10-1991), and AES50-2005: AES standard for digital audio engineering &8221; High-resolution multi-channel audio interconnection.
Certain sampling frequencies are recommended by the AES in AES5, pp. 5-6: The recommended sampling frequency for digital audio encoding shall be 48 kHz ± 10 parts per million. This frequency is compatible with television and motion picture systems, and it permits the encoding of audio programs with full 20-kHz bandwidth. It is recommended for all applications of program origination, processing, and interchange. To maintain synchronization whenever digital audio using the standard 48-kHz sampling frequency is utilized in conjunction with television or motion pictures, the average number of samples per frame shall be [as follows: nominal frame rate of 24, then 2,000 samples per frame; 25 frames, then 1,920 samples; 30 frames, 1,600 samples; and 30/1,001 frames, 8008/5 samples]. For an application directly related to certain consumer products, a sampling frequency of 44,1 kHz may be used. This application may include the interchange of program material prepared specifically for such products. For broadcast and transmission-related applications with restricted channel capacity and where a nominal audio bandwidth of 15 kHz is considered adequate, a sampling frequency of 32 kHz may be used, in accordance with ITU-T Recommendation J.53. For applications with an audio bandwidth greater than 20 kHz or in order to permit the use of a wider transition region in the anti-alias filtering a rate of 96 kHz ± 10 parts per million may be used. Techniques have come into common use since the above frequencies were defined which use very high sampling frequencies, typically more than 100 times higher than 48 kHz. Where such sampling frequencies appear at an interface, only multiples representing some factor of two of the sampling frequencies identified in AES5 should be used. |
| History |
URLs
• Relevant Audio Engineering Society standards, including AES3 and AES5, are sold from http://www.aes.org/publications/standards/.
• AES3-2003. AES standard for digital audio — Digital input-output interfacing — Serial transmission format for two-channel linearly represented digital audio data.
• AES5-2003. AES recommended practice for professional digital audio — Preferred sampling frequencies for applications employing pulse-code modulation.
• AES52-2006. AES standard for digital audio engineering — Insertion of unique identifiers into the AES3 transport stream
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URLs
• Wikipedia article on AES3 (http://en.wikipedia.org/wiki/AES/EBU)
• RFC 4122, IETF document pertaining to the UUID (http://www.ietf.org/rfc/rfc4122.txt)
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• SMPTE 330M-2000. Unique Material Identifier (UMID).
• ISO/IEC 11578:1996. Universally Unique Identifier (UUID)
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