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 | Library of Congress Extension to the Digital Talking Book specification to include AMR-WB+ Codec |
| Description | Extension 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 | OEBF, Open Ebook Forum Publication Structure 1.0.1 |
| Based on | XML_DTD, XML Document Type Definition |
| May contain | AMR-WB+, AMR-WB+, Extended Adaptive Multi-Rate - Wideband Speech Codec |
| May contain | WAVE_LPCM, WAVE Audio File with LPCM Audio |
| May contain | MP3_ENC, MP3 Audio Encoding |
| May contain | AAC_MP4, Advanced Audio Coding (MPEG-4) |
| Other | DTB, DTB (Digital Talking Book), main specification, omits AMR-WB+ speech codec |
| 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_Ext incorporating the full text of a work is among the preferred XML-based formats for textual works. |
| 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 July 2004, none of the NLS talking books include full text and there are no plans to produce books with full text. |
| Licensing and patent claims | None |
| Transparency | See information on the encoding formats employed for the files that comprise a DTB file set: XML, AMR-WB+, LPCM, MP3, AAC_MP4. XML and LPCM both rate highly for transparency. |
| 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 are likely to 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. |
| Sound | |
|---|---|
| Normal rendering for sound | Good support. |
| Fidelity (support for high audio resolution) | Depends upon encoding used. Not intended for audio quality beyond CD quality. Moderate quality (appropriate for speech) when AMR-WB+ is used. For LPCM and MP3, DTB players support sample rates of 44.1, 22.05, and 11.025 kHz at a depth of 16 bits per sample; the output sampling rate is restricted to one of the above three rates, with a constant bit rate. |
| Support for multiple sound channels | DTB Players are not required to support multiple channels, but must recognize stereo and render at least as monaural. |
| Support for downloadable or user-defined sounds, samples, and patches | Not investigated at this time. |
| Beyond normal rendering for sound | Synchronization with text transcription. |
| Text | |
| Normal rendering for text | Good support. |
| Integrity of structure | The logical structure of a document is an important part of a DTB with textual content. See DAISY Structure Guidelines. |
| Integrity of layout | 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. |
| Integrity of rendering of equations, etc. | Not supported |
| Beyond normal rendering for text | Supports embedding of audio, images, and synchronization of text with audio of the text being read. |
| Tag type | 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. |
| General | The NISO standard supports several classes of digital talking book and these presumably also apply to the Library of Congress extension. See DTB for more information on: • Audio with Title element only: DTB without structure. • Audio with NCX only (Navigation Control): DTB with structure. • Audio with NCX and partial text: DTB with structure and some additional text. • Audio and full text: DTB with structure and complete text and audio. • Full text and some audio: DTB with structure, complete text and limited audio. • Text and no audio: E-text with structure. |
| History | See DTB. |
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