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Subject: Audio tape and videotape

Audio tape and videotape

From: Paul Messier <pmessier>
Date: Friday, May 8, 1998
Patricia Smith-Hunt <smith [at] oak__cats__ohiou__edu> writes

>Our library expects to receive a fairly sizeable collection of
>audio and video tapes soon and we are making some preliminary
>plans for its preservation and storage. The material is
>probably about 10-15 years old and has been stored in
>basements. These tapes contain scientific data; therefore, a
>faithful reproduction of the original is critical. We have also
>been cautioned about reformatting techniques that may result in
>loss of information due to compression, cleaning up, etc. The
>faculty are very interested in digital migration; however, I
>have not been able to find information that definitively
>supports this approach. Has anyone had experience with
>reformatting audio and/or video tape collects using

Based on some recent experience, my guess is that when your faculty
talks about "digital migration" what they really might have in mind
is making the source material both digital and "non-linear."

Non-linear formats allow content (text, video, still photographs,
audio etc.) to be instantly accessible using a computer, computer
network or other digital playback device.  For a non-linear system
to work well you need to have the content cataloged and it must be
placed on a medium that can deal with rapid, random, searches like
optical disks (i.e. CD-ROMs) or magnetic disks (i.e. computer hard
drives).  A good example of non-linear content is a CD-ROM
encyclopedia, where the various components, text, illustrations,
audio and video, are instantly accessible in any order based on user

By contrast "linear" playback systems format and store content in a
continuous, sequenced, stream.  From the standpoint of ready
researcher access to stored information, linear systems pose some
restrictions.  For example, trying to find a particular 2-minute
scene on a lengthy tape can take a lot of rewinding /
fast-forwarding which is not healthy for the tape. The digital
formats Jim Lindner mentions in his posting (D1, D2, D3, D5) are
linear, tape-based, formats.  Linear systems dependent on magnetic
tape have ongoing importance because tape remains unchallenged for
its high storage capacity and ability to produce the high data
transfer rates needed for uncompressed digital video.  Hard drives
and CD ROMS (with non-linear capabilities) can deal with small
quantities of uncompressed video but, from the standpoint of cost
and functionality, still do not make sense for the mass storage of

Jim also mentioned DVD, which is worth discussing because it has the
promise to be the breakthrough non-linear, digital, format that
combines high video quality, high data throughput and sufficient
storage capacity at a reasonable cost.  However, this functionality
comes at the price of data compression, the appropriateness of which
should be a matter of great interest for custodians of cultural

I looked at some of the benefits and drawbacks of digital
reformatting for a presentation I gave at the Playback Conference,
organized by the Bay Area Video Coalition and the Media Alliance in
1995.  The printed version "Assessing Digital Video as a
Preservation Medium," is a few years old (a long time in the digital
realm) but might still might prove useful.  Along with other papers
on the topic, it will be will be assembled in "Playback: A
Preservation Primer for Video" which will be available this June.
You can call the Bay Area Video Coalition at 415-861-3282 for more

    **** Moderator's comments: See also the Playback 96 pages in
    Conservation OnLine

                  Conservation DistList Instance 11:92
                  Distributed: Thursday, May 14, 1998
                       Message Id: cdl-11-92-001
Received on Friday, 8 May, 1998

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