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Glossary
Digital Formats in use by NDLP
American Memory collections incorporate:
- Images (including images of textual materials)
- Text (for reproductions of historical documents,
finding aids, and descriptive materials)
- Sound
- Moving Images
This page lists the digital formats in use and describes very briefly how
and when they are used. For more information about particular
standards, try the NDLP glossary.
File formats in use include:
- GIF -- For presentation. For "inline" thumbnail
images of pictorial items within HTML presentations, including item-level
results generated from searches in pictorial collections. Accessible with
any image-capable WWW browser.
- JPEG/JFIF -- For presentation and archiving. Images are
compressed with the JPEG algorithm and stored in JFIF files. Used for two
categories of reproduction: (1) reference versions of pictorial materials
and (2) certain documents and book pages.
Accessible by some WWW browsers or by a spawned viewer.
- TIFF -- For presentation and archiving. Images with TIFF
(Tagged Image File Format) headers are used for various types of images,
especially bitonal images of documents and book pages and
uncompressed-archival versions of pictorial images. Accessible by a
spawned viewer, e.g., DocuView.
More information on use of image viewers
with American Memory materials is available on the public American
Memory web-site.
Related reading from outside the Library of Congress:
Formats in use for searchable text include:
- HTML -- Primarily for presentation. Texts
marked up
to conform to HTML (HyperText Markup Language) guidelines for two
categories of content: (1) for texts in the primary
collection-presentation framework, including most introductory materials,
and (2) searchable-text reproductions of certain textual originals (to run
in parallel with the SGML versions; q.v.). Accessible with any WWW browser.
- SGML -- For presentation and archiving. Texts marked up to
conform to SGML (Standard Generalized Markup Language) guidelines for two
categories of content: (1) searchable-text reproductions of certain
textual originals, using the American Memory DTD, and (2) for
finding aids, using the Encoded Archival
Descriptions (EAD) DTD. Accessible by a spawned viewer, e.g., Panorama.
More information on viewing SGML text is available on
the public American Memory site.
Archival copies of sound recordings that have been digitized
have been made on DAT audio tape. Formats in use for sound presentation
include:
- WAV -- Recorded sound files in the
WAV format. Accessible through recent browser versions or a spawned
"viewer."
- RAM -- RealAudio (TM) for streaming audio. RealAudio viewer
is bundled with popular browsers.
More information on Audio
playback is available from the pubilc American Memory site.
Archival copies of video materials digitized for American
Memory have been made in high-quality analog formats. Presentation
formats in use for moving images include:
- AVI --
AVI format, produced with the INDEO codec. Accessible by a spawned viewer,
e.g., the Windows multimedia player. The Library is planning to
reformat current and future moving image collections using MPEG
compression and will discontinue use of the AVI format.
- MPEG -- Moving image files in the
MPEG format. Accessible by a spawned viewer.
- QuickTime -- Moving image files in the
QuickTime format. Accessible by a spawned viewer.
Information in Video playback is
available from the public American Memory site.
Delve deeper for further discussion of:
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Documentation.
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About --
Start --
Index --
Glossary
NDLP Digital Formats
National Digital Library Program
Comments: caar@loc.gov
(05/02/97)