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[AV Media Matters] RE:Optical compact disc media failure mechanisms and life exp


I would like to refer to and add some perspective to a recent posting
reporting on the SMPTE V16.07 WG Redondo Beach meeting that I chaired.
Recognizing that some manufacturers are coming forward to point out that
they now have products that have improved features, such as better dye
stability, for which we do not even have a test method yet. And improved
scratch resistance, for which we do not have a test method other than a
description of an unidentified cloth wound around an undefined pointed
object weighted down to one kilogram weight, rubbed across the protective
layer for an arbitrary number of times. I still do not believe that the
accelerated 'Sauna Survival Test' (SST) as I have somewhat irreverently
phrased it, should be used as an indicator of CD or DVD life expectancy.
There are many other factors that impact optical disc media and content
signal life expectancy, and I have not seen any other manufacturer's system
qualification test reports about the impact on content life expectancy that
would confirm the long life typically claimed by the hasty and superficial
hype of marketing people, based on a simplistic single test method.
Virtually all manufacturer's data we have, if it has been published at all
without having 'Confidential' all over it, is based on engineering
calculations and projections that have had too little time to be confirmed
in real life and when they are not confirmed, we will not read about them.
Another life expectancy risk factor, is the constant flood of new products,
many of them made at low cost and with no indication that they meet the
lofty expectations expressed by the most reputable manufacturers. As a
leading scientist at one of the primary license-holding Companies expressed
it to me: "No optical disc medium has been designed to survive longer than a
human life, after 30 years the polycarbonate and lacquer layer will allow
oxygen to get to the reflective layer, that is a constraint imposed by the
laws of physics." We all witness that enabling technologies have a life
cycle of no more than 25 years. No optical compact disc player, other than
those very sophisticated and expensive ones used for testing, will show the
error-rate condition of a disc, hence users should be prepared for, as again
I have formulated it somewhat irreverently, 'disgraceful degradation'. This
basically means that you find out that a disc has reached its 'end-of-life'
when your disc fails to play your recorded signals back. The disturbing
reports of independent testing services for optical compact discs indicate
that an increasing percentage of new and large numbers of newly written
discs have the life-reducing characteristics already in them. This means
that optical disc media are not presently serious players in those
applications where extended life expectancy is a requirement. It also means,
besides never using a disc (after quality assurance and control
measurements)that is intended to preserve content during its archiving, a
digital data back-up tape of the highly compressed disc content is a prudent
practice, if any content life expectancy is required. It is recognized
again, no magnetic or optical tape is archival yet, so expect to migrate it
to newer technology every decade or so.

There was no evidence presented at our SMPTE V16.07 WG meeting referred to,
that addressed concerns about bonding failure of DVD media, hence I remain
sceptical about the impact of this potential failure mechanism.

For the record, I have just completed drafting a comprehensive proposed ISO
document, its contents having been prioritized by the Optical Disc working
group of the ISO/AES/PIMA Joint Technical Commission, entitled: "Imaging
materials-Extending life expectancy of information stored on recordable
compact disc systems-The evaluation and measurement of life cycle
determining factors that indicate degradation, stress and failure, their
causes and effects, and preventive measures." I have invited experts from a
wide variety of disciplines in the optical disc industry to critique the
document, to assure that it adequately and competently covers each
specialist discipline in the systems manufacturing and use, testing and
measurement processes, so we can produce a truly realistic and helpful
document. This document will be presented to the ISO/AES/PIMA Joint
Technical Commission and SMPTE V.1607 WG in the near future.

Thanks for considering this perspective. Any experts interested in
contributing to this project, are invited to contact me.

Best regards,

Ed H. Zwaneveld,
Technological Research and Development,
National Film Board of Canada
3155 Chemin de la Cote de Liesse
Saint Laurent, QC., Canada
H4N 2N4
Tel: +1-514-283-9143
Fax: +1-514-283-0278
E-mail: e.ha.zwaneveld@nfb.ca
January 29, 2001

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