Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | Audible.Com File Format |
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| Description | File format for sound that wraps various audio bitstreams. Audible.Com is a seller of recorded sound products, ranging from talking books to archived radio programs, e.g., Car Talk. See Notes for more information. |
| Production phase | Used for final-state, end-user delivery. |
| Relationship to other formats | |
| Has subtype | AudCom_MP3, Audible.Com MP3 |
| Has subtype | Audible.Com HAC (hearing aid compatibility) format, not documented here |
| Has subtype | Audible.Com ACELP speech encoding, not documented here |
| Has subtype | Audible.Com files containing other sound encodings not documented here |
| May contain | MP3_ENC, MP3 Encoding |
| May contain | SONY HAC (hearing aid compatibility) encoding, not documented here |
| May contain | VoiceAge ACELP speech encoding, not documented here |
| May contain | Other sound encodings, not documented here |
| LC experience or existing holdings | None |
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| LC preference | See the Library of Congress Recommended Formats Statement for format preferences for audio works. |
| Disclosure | Not documented. Proprietary format of Audible.Com |
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| Documentation | Compilers of this document were unable to locate specifications for the wrapper format. |
| Adoption | Not known to the compilers of this document. Audible.Com is a visible player in the downloadable sound marketplace and appears to be actively distributing product. |
| Licensing and patents | Not known to the compilers of this document. |
| Transparency | Unknown; see note on technological protection below. |
| Self-documentation | Not known to the compilers of this document. Evidence at the web site suggests that the files carry some descriptive ("bibliographic") information, e.g., author, title, and duration. |
| External dependencies | Files can be played only on certain players. As of September 2015, these include applications for personal computers and many mobile devices. See Audible's "How to Listen" page and its Help Center. Audible.com previously hosted a Device Center with information about all supported devices and formats. The link to this page is available via Internet Archive capture from August 6, 2011. |
| Technical protection considerations |
From the an archived capture of theAudible Web site as it appeared in August 2020: "We apologize for the inconvenience, but Audible audio files cannot be converted into MP3 or any other file format. The reason for this is because we utilize security technologies to protect the intellectual property rights of our content providers and authors." Slightly different wording was provided at the site in 2004: "Audible created and employs a proprietary technology solution for distributing copyright-secure audio files that can be downloaded or streamed from audible.com. Audible's secure distribution system prevents a customer from passing along duplicate digital audio files to another listener." Note that there is a provision for subscribers to write/burn audio files in Audible format to CDs playable in regular CD players using iTunes [see help on listening to Audible content in a car (Page no longer available when checked in July 2021.)]. Burning to CD is only allowed once for an audio book. |
| Sound | |
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| Normal rendering | Good support. |
| Fidelity (high audio resolution) | Moderate to good, depending upon encoding selected; the web site compares the formats in terms of fidelity and other factors. (This page was no longer available when checked in July 2021, but an alternate page is available via Internet Archive capture from June 26, 2011.) |
| Multiple channels | Apparently not |
| Support for user-defined sounds, samples, and patches | Not supported |
| Functionality beyond normal rendering | None described |
| Tag | Value | Note |
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| Filename extension | aa |
Extension may be used for all Audible.Com formats [?] |
| Internet Media Type | audio/audible audio/x-pn-audibleaudio |
From The File Extension Source. None found at http://www.iana.org/assignments/media-types/. |
| Magic numbers | Not found. | Comments welcome. |
| General | The formats used by the company range from highly compressed speech encodings to less compressed MP3_ENC (MP3 encoding). The Audible.com website states, "The more information, or bits, the fuller and richer the sound." (Page available via Internet Archive capture from March 11, 2010.) Programs that feature music are not offered in the most compressed formats. More information on the Audible.com formats page (link via Internet Archive). Another page at the site reports that "Audible's preferred speech codec is licensed from VoiceAge Corporation," presumably the ACELP (Algebraic Code Excited Linear Prediction) encoding described by VoiceAge. |
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| History |
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