Digital collections should be built for the long-term. You want to create high-resolution digital objects that are as
faithful as possible to the information contained in the originals. However, digital collection building is still an
evolving service, with digital standards, display technologies and user expectations changing frequently. Your homework
needs to be current. A good rule of thumb is to digitize to the minimum standards that your local consortium requires,
so that you can share your resources with a broader audience. The New Jersey Digital Highway's updated
minimum required standards for digitization can be found here:
You will also need a metadata strategy that lets you collect and review information about how digital files were created,
what digitizing parameters were established, and what requirements for playback exist, so that as technologies change, you
can transform your digital files to newer standards and technologies.
Isaiah Beard, Digital Project Manager for the Rutgers University Libraries, provides an introduction to the technology
and standards as well as practical guidance on developing digital image collections:
Digitizing single images is a fairly straightforward process. However, when multiple images combine to create an
intellectual whole, you have moved from a simple object to a complex object, which is defined as a structured composite
object consisting of two or more single objects that exist in relationship to each other, resulting in an intellectual
whole. This is a mouthful, but easy to understand because most of us learn from complex objects every day. A book is a
complex object. It consists of pages, which are often grouped into chapters, that create an intellectual whole---the book
itself. A journal article is a complex object, which is itself part of another complex object, the journal issue. A
scrapbook is a complex object that can include both still image files and text files to create the intellectual whole.
Other complex objects include logbooks of records, diaries and multi-page letters (correspondence).
So, how do you digitize a complex object so that it makes the same sense to the user in digital form as it did in analog?
In other words, how do you bind a digital book?
There are several steps:
To prepare individual files for concatenating into a complex object, you should follow standard naming conventions. Grace Agnew, Associate University Librarian for Digital Library Systems, offers some guidance on digitizing multi-page documents:
- First you digitize each individual image to the required minimum standards for a digital archive.
- You associate each image together in a "structure map" to create complex digital objects in which each individual file is related appropriately to the other digital files in the complex objects, e.g., page two follows page one, etc.
- You display the complex object as a single object that can be navigated by the user. This can be accomplished in several ways. You can create a "page turner" that allows you to jump from one digital image to the next or to jump to the page or image that interests you. You can also use a commercial display form that relates all the images together appropriately. NJDH currently uses both Adobe PDF& #0174; and LizardTech DJVu& #0174;.
|Digitizing Multi-page Documents or Books - Grace Agnew, Rutgers University Libraries
The standards behind digitizing of photographs, text and other still image formats have been developed over many years
and widely adopted among libraries and archives.
Much attention has now turned to emerging formats for born digital images, produced from digital cameras, digital audio
and digital video.
Digital cameras are rapidly replacing analog cameras as the way to capture images of people, places and events.
Digital cameras allow instant preview of the image and support sharing in many ways, including via email, on the web or
as prints on photographic paper. Some of the problems with born digital images as an archival medium, however, include:
Isaiah Beard, Digital Project Manager for the Rutgers University Libraries, provides the minimum standards for born digital images to be placed in the New Jersey Digital Highway collection, as well as guidance on selecting a digital camera that produces high quality images conforming to the specifications:
- Lack of quality and fidelity to the information being documented. It is critical to purchase a camera that takes digital photographs with high resolution and bit depth.
- Lack of support for high quality image standards. Most analog images are digitized as high resolution TIFs. Most consumer digital cameras create images that are low-resolution JPEG or even a proprietary format that must be converted to JPEG. The preferred format for a born digital image is the Digital Negative (DNG) file format.
The following powerpoint presentation, also provided by Isaiah Beard, the future use of Born Digital still images, as well as the adoption of the Digital Negative (DNG) file format for archive preservation.
Camera selection for creating preservation-grade digital images can be difficult. To aid in equipment selection, a list of digital camera models that we know for certain meet our specifications is included here. Please note this list is not an exhaustive one, nor should the list be construed as an endorsement for any camera manufacturer or model.
Digital audio and video files bring their own complexities to the digitization process. Digital video and audio are consecutive media, meaning that information flows forward in time to create the whole. This is best illustrated by digital video, where a large number of still images, or frames, are assembled together in consecutive order, often with a synchronized audio data stream, to create a single object with meaning to the user. Each frame must appear in order and move consecutively forward in time to retain the meaning of the original:
Audio and video files tend to be extremely large, particularly if digitized in an uncompressed format, because so many consecutive frames or bits of information is needed to create the composite whole.
Audio and Video files can be shared with users in two ways:
Other forms of playback, such as continuous burst, are emerging. The most important considerations for displaying video and audio files are to recognize that users have different network and playback capabilities. Some viewers will not work equally well for PC and Mac computers. Other viewers require minimum browser versions. It is important to offer playback for video, in particular, in multiple frame sizes, resolutions and frames per second speed to provide videos that work for a wide range of users.
- Download: The complete file may be downloaded so that it can be played back on the user's computer. The benefit of downloading is that the local computer can support much greater bandwidth than the user's network or Internet connection, so the file can be played in its entirety without loss of information through jerky, blocky or pixilated playback. However, the downside is that a large file can take a long time to download, particularly if the user's network or Internet connection is not a high bandwidth connection. The user's computer will not be available for other uses and may appear to be inactive, which may cause the Internet Service Provider to disengage the connection.
- Streaming: A streaming media display will cache just enough of the file to provide playback and will begin displaying the file as soon as a meaningful portion of the file is cached on the user's computer. As the file plays, the multimedia player will continue to cache the file and feed the cached portion into the display, consecutively. Streaming is a more efficient means for display of video and audio since the user does not have to wait for full download. The drawback is that the streaming file must rely on the user's Internet or network connection to send the consecutive frames of the file for caching. With slower connections, the caching and playback can get out of sync, resulting in playback stopping until sufficient cached information is available to continue playback. Blocky, jerky playback or pauses in playback are the result, when the streaming and the caching get out of sync.
NJDH has very high standards for archival master digital video and audio files, since fidelity to the source information is required. Access or display files for users are at a much lower resolution and bit depth, to make files accessible to a large range of users.
Audio encoding standards are currently available. Video encoding standards are currently being tested and revised. The Rutgers University Libraries, with assistance from the New Jersey State Library and a grant from the Institute of Museum and Library Services have purchased a high end audio and video encoding platform, the Matrox Axio If you have sound recordings that meet the collection development policy guidelines of NJDH, you may want to request assistance in digitizing them to NJDH standards. Contact Isaiah Beard for information.
NJDH audio encoding standards and requirements are provided at the following link:
Video preservation standards have been developed and can be viewed below: