Re: [AV Media Matters] CD-R vs. R-DAT

[mollyw@gslis.utexas.edu]

I recently took a course, Basics in Audio Preservation and Reformatting,
here at the University of Texas at Austin, as part of my archives
cirriculum. In this class we covered this very issue, CD-R vs. R-DAT.

While many people are using R-DATs for their preservation copies of
sound
recordings, they pose a serious problem.

Since R-DATs are a helical scan tape technology, the tracks are recorded
as diagonal stripes along the tape. The fundamental perservation issue
in
this is that  stored data at any given point along a track, since it is
not linear, differs so much from the data on the neighboring track.
This can then cause migration, as the polarities will attempt to adjust,
and information lost will have a much bigger effect on the integrity
of the DAT tape than it would a tape with linear tracks. So, it seems
as though CD-Rs are a wiser choice for preservation purposes.

I hope this helps.

Molly Wheeler
Student, University of Texas at Austin

Moderators Comment:
Well you need to talk to your professor - and tell him/her that almost
all recordings these days are helical, and that almost all recordings
these days don't have guard bands between tracks (space between them)
and therefore have one magnetic area right next to another and
furthermore use azimuth recording techniques which mean that tracks are
laid up right against one another. But almost NO recordings have bits
that spontaneously move around and change polarity. T there are many
techniques used to spread the data and make it redundant so that data
loss is recoverable, but usually the loss is not the type you mention
anyhow. Magnetic fields generally don't "migrate" unless there is a
reason to. You might consider print through a migration of sorts, but it
is not the type of migration you mention, but it is an artifact where an
area of high energy is in DIRECT proximity/contact with an area of low
energy. The migration (or lack thereof) will also depend on the
coercivity of the tape being used. Most modern media is high coercivity
which means that a relatively strong field is needed to reverse an
existing field of magnetic energy on a tape. So if a positively biased
particle is next to a negatively biased one - on a high coercivity tape
- it will be very unusual for either to just change polarity. BUT having
said all that. There is no question that CD'r are the choice because the
alternative is almost an obsolete format - clearly endangered. 
 
Right answer - wrong reason. But don't tangle with the prof. yourself -
send him/her to me!! We don't want you're "A" for the course to
spontaneously turn into a "B"  - or for that matter the prof's paycheck
to go from $5,000 to $500 after it was stored for a while would we??
 
Jim lindner
 

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