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Re: preservation of DVD



I know I'm stepping into this a bit late, but I'd like to make a few
comments beginning with some general ones followed by some specific to
the project originally mentioned.

At my institution we will testing DVD within a month or two. I won't
have anything to say about image quality until I have seen things for
myself.

One issue in that regard is the codec used for compression. I do not
think "longevity" of a codec is a concern because that is a relatively
simple matter of ensuring that conversion software is available, which
is a pretty obvious thing to do in a digital preservation management
process.  Ditto for hardware availability.  However, I have seen
concerns raised about loss of quality in conversion of digital video
(and audio) from one form of encoding to another due at least in part to
poorly designed conversion software.  I think that needs to be looked at
carefully in the context of long-term data migration.

In terms of longevity of the recording medium, we will continue to
monitor the situation.  I have seen no convincing evidence that DVD is
better or worse than recordings on magnetic tape.

I think it is very risky to make blanket statements about any recording
medium because formulations are manufacturers' secrets, subject to
change without notice. There are also the issues of batch-to-batch
variation and undocumented outsourcing by manufacturers.

Note that long-term availability of hardware is at least as much of an
issue for professional video formats as it is for DVDs.  There will be
far more DVD drives manufactured than was ever the case for Betacam
players, and they are a hell of a lot cheaper.

One of the comments below raised the issue of the probable introduction
of new formats in the near future. That will always be the case.  It is
in the nature of technology in a free marketplace.

It should be remembered that we do not always have to achieve
perfection. Excellence is often good enough.  There is no point is
waiting for perfect archival technology if your recordings are piles of
dust by the time it arrives.

Examples of questions we should ask are:

1. What are our realistic quality requirements?

2. Which currently available products meet our requirements in a
cost-effective manner?

3. Which of the products meeting the above requirements are mainstream,
widely used systems that will enable high-quality and cost-effective
migration to a new medium?

With regard to the project described in the original question:

The original Super VHS tapes should be kept as long as they are
playable.  They will probably last as long as any other type of tape
recording.

The suggestion about making new masters on Betacam is sensible, along
with spinning off VHS reference copies.  The Betacam format is
high-quality and will keep generational loss to a minimum.  Note,
however, that Betacam is still a magnetic tape medium and very far from
a permanent preservation format.

If you are thinking about using your proposed VHS copies for permanent
preservation, that's a big no-no.  You will see a major quality loss.
Use the VHS copies for reference copies, limiting playback of the Super
VHS originals to the production of new archival masters.

I think you would be wise to look at digitization as a permanent
preservation approach, but should take a year or two to examine the
issues fully rather than jumping head-first into a specific project.

In short, my opinion is that DVD is probably a good bet as a first step
in permanent preservation but that you should be a bit conservative for
this particular project and go the route of keeping the originals,
making backup masters on Betacam, and using VHS copies for access.


John Poirier
Coordinator of Technical Services
Northwest Territories Archives

-----Original Message-----
From: Laura.Katz.Smith /unix [mailto:Laura.Katz.Smith@UCONN.EDU]
Sent: Wednesday, August 29, 2001 9:03 AM
To: ARCHIVES /unix
Cc: Laura.Katz.Smith /unix
Subject: preservation of DVD


Hi, everyone.  I recently got an inquiry from a donor about the
permanence
of DVD.  He is donating a set of Super-VHS tapes, which we intend to
convert
to regular VHS, but he wondered if DVD might be a better choice.  I
wasn't
sure what how to respond.  Do any of you have any thoughts or knowledge
of
this situation?

Laura Katz Smith
Thomas J. Dodd Research Center
University of Connecticut Libraries

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