Sustainability of Digital Formats
 Planning for Library of Congress Collections

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DTB (Digital Talking Book), NLS extension for AMR-WB+ Speech Codec

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Table of Contents
Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name NLS modification to ANSI/NISO Digital Talking Book specification to include AMR-WB+ Codec
Description Modification of DTB (NISO Digital Talking Book Standard, ANSI/NISO Z39.86-2002), which defines the format and content of the electronic file set that comprises a digital talking book (DTB) and establishes a limited set of requirements for DTB playback devices. The Library of Congress specification extends the NISO standard by adding the option to use AMR-WB+ compressed audio coding.
Production phase This bundle of files is likely to be used primarily as a middle-state format, with dissemination to end-users managed through publishers or aggregators who provide in a form appropriate for viewers/players that enforce limitations on access and use consistent with terms imposed by copyright holders.
Relationship to other formats
    Contains OEBPS_1_0, OEBPS, Open Ebook Forum Publication Structure 1.0.1
    Defined via XML_DTD, XML Document Type Definition (DTD)
    Contains AMR-WB+, AMR-WB+, Extended Adaptive Multi-Rate - Wideband Speech Codec
    Modification of DTB_2002, DTB (Digital Talking Book), 2002. Main specification omits AMR-WB+ speech codec

Local use Explanation of format description terms

LC experience or existing holdings The National Library Service for the Blind and Physically Handicapped (NLS), which is part of LC, is developing this standard and produces books to this specification. See Current Strategic Business Plan for the Implementation of Digital Systems, September 2006.
LC preference Preferred format for digital talking books. A DTB or DTB_2002_NLS incorporating the full text of a work is among the acceptable XML-based formats for textual works, assuming no encryption or DRM is applied.

Sustainability factors Explanation of format description terms

Disclosure Open standard
    Documentation For the DTB: ANSI/NISO Z39.86-2002. Specifications for the Digital Talking Book, ISSN: 1041-5653. Information about the extension: Current Strategic Business Plan for the Implementation of Digital Systems, September 2006. See also AMR-WB+ for links to the audio codec specification.
Adoption The National Library Service for the Blind and Physically Handicapped (NLS) is using the extended version of the DTB standard for all production of talking books. As of April 2009, none of the NLS talking books include full text and there are no plans to produce books with full text.
    Licensing and patents None
Transparency See information on the encoding formats employed for the files that comprise a DTB file set: XML, AMR-WB+. XML rates highly for transparency. For the audio, the master WAV format file used in the production process is more transparent.
Self-documentation The Package file can include Dublin Core metadata and an extended set of elements intended to record information about rights and the provenance and generation of the talking book from a source text.
External dependencies None. The format is designed to support effective use of special hardware and software players for the visually impaired, but does not require them.
Technical protection considerations None in relation to the sets of files that comply with the ANSI/NISO Z39.86-2002 specification. Digital Talking Books from NLS will be distributed to end users via mechanisms that do impose technical protections. Hence it is probable that LC will need to receive such files direct from publisher or aggregator by a special transmittal process rather than by harvesting as if an end user.

Quality and functionality factors Explanation of format description terms

Sound
Normal rendering Good support.
Fidelity (high audio resolution) Moderate quality (appropriate for speech) from AMR-WB+ encoding.
Multiple channels DTB Players are not required to support multiple channels, but must recognize stereo and render at least as monaural.
Support for user-defined sounds, samples, and patches Not investigated at this time.
Functionality beyond normal rendering Synchronization with text transcription.
Text
Normal rendering Good support.
Integrity of document structure The logical structure of a document is an important part of a DTB with textual content. See DAISY Structure Guidelines
Integrity of layout and display This standard focuses on the textual content, the logical structure, and the synchronization of text with audio of the text being read. Layout is not of primary significance in rendering for the visually impaired.
Support for mathematics, formulae, etc. Not supported
Functionality beyond normal rendering Supports embedding of audio, images, and synchronization of text with audio of the text being read.

File type signifiers Explanation of format description terms

Tag Value Note
Filename extension opf
For the required Package file. Documented in NISO standard.
Filename extension xml
For textual content files. Documented in NISO standard.
Filename extension ncx
For navigation control files. Documented in NISO standard.
Filename extension amr
For AMR-WB+ audio files. Presumed to be the case; The File Extension Source provides amr as the extension for Adaptive Multi-Rate Speech Codec files .
Filename extension aac
For AAC_MP4 audio files. Documented in NISO standard.
Filename extension mp3
For MP3 audio files. Documented in NISO standard.
Filename extension wav
For WAVE_LPCM audio files. Documented in NISO standard.

Notes Explanation of format description terms

General In addition to requiring the AMR-WB+ audio encoding using prescribed parameters and wrappped in the 3GP file format, the NLS Specification for the Production of Digital Talking Books specifies particular usage of the ANSI/NISO Z39.86:2002 standard. Required or specified features include, for example, file-naming and metadata conventions, audio-clips for spoken title and author name and to support navigation, opening announcements, and positioning of pauses.
History See DTB_2002.

Format specifications Explanation of format description terms


Useful references

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Last Updated: 02/27/2015