RE: [AV Media Matters] Archival?

[Jim Wheeler <Jimwheeler@aol.com>]

Adam

I wrote an article for a recent AMIA  newsletter on this topic so I
will attach the article here.  Basically, a true "archival" medium
must not degrade the original and compression degrades the video.

Jim

ARCHIVAL vs Acquisition/Distribution/Viewing
or
ARCHIVAL Requirements not the Same as forAcquisition/Distribution/Viewing

By Jim Wheeler
August 1999

We are in a digital revolution and archivists are being told to jump
on the digital train.  Most technical people are advising archivists
to transfer their video material to one of the small digital
videotape formats, such as DV or DVC-PRO.  These formats make nice
looking pictures, the cassettes are small, and the cost of the
equipment is reasonable.

Or, why not DVD?  Anyone who has viewed a movie on DVD has to be
impressed with the picture quality.

All of the Post-Production houses have gone digital, so everything
that we see on television today has been digitized in some way.

So, if everyone else is switching to digital, why shouldn't
archivists?

The simple answer is that archivists have a different agenda then
consumers and the people in the broadcast television business.
Archivists must select a medium that has the best chance of
surviving for many years, AND archivists must select a system that
will not alter the recorded material.

There is nothing wrong with digital, per se.  Weither or not a
particular digital videotape format is adequate as an archival
medium depends on the durability of the tape being used and how the
audio/video signals are processed.

The main problem with the low-cost digital formats is that they are
heavily compressed.  That is okay with most people but a no-no for
archivists. Also, all of the low-cost formats sample the incoming
signal at a low rate and that means that much of the detail is lost.
A good sample rate is 10 bit at 4:2:2 and none of the low-cost
formats can handle that rate.  Additional issues are those of thin
tape and the robustness of the cassette.

There are several possible problems with DVD as a video archival
medium. One is that DVDs use heavy compression, and compression
discards some of the finer details of the original.  The second
problem is that archivists will use the recordable DVD and there
have been no tests that prove that a disc recorded on a machine made
by one manufacturer will play on machines made by other
manufacturers.  There is also the potential problem for DVDs to
delaminate.  Some DVDs have an adhesive to hold the two halves
together and adhesives have a bad habit of coming unglued after a
few years.

The main problem with the high-quality digital videotape formats
used by the post-production houses is that the equipment is very
expensive.  The cheapest is D3, and a D3 tape machine costs around
$30,000 US.  D5 is a great format but a D5 machine costs
$60,000-$70,000 US.  For most archives, the high price associated
with the high-quality digital videotape machines make them
unattainable.  Digital Betacam is 4:2:2 at 10 bits but it does have
some compression.

These prices are for Standard Definition Television (SDTV) which is
NTSC, PAL, and SECAM.  You can double or triple the price if you
want a High Definition Television (HDTV) machine.  In the HDTV
world, Panasonic has a modified D5 that records 1080i HDTV, Toshiba
has a D6 machine that records 1080i, and Sony has a 1080i machine.

Why isn't there a good archival digital videotape format?  The
answer is that consumer and broadcast television are the big
markets--not archives.  There are only two companies making
videotape recorders and they are Sony and Matsushita (Panasonic and
JVC).  For them to manufacturer a machine for the archival market,
they must be convinced that there is a market there.  To show that
would require a survey that would indicate how many machines would
be sold over X years at a cost of Y dollars each.

Until there is a good archival digital videotape format, it is best
to stay with analog.  Betacam-SP is the best of the analog formats,
but some of the cheaper Betacam-SP machines have quality problems.

For acquisition, distribution, and viewing, several of the digital
videotape formats would work.  If you do not have a technical person
on your staff who can assess the pros and cons of each of the
low-cost digital videotape formats, a call to the chief engineer at
a local TV station should do it.