RE: [AV Media Matters] CD-R error specs

[kbradley@nla.gov.au]

>Kevin Irelan wrote>	For those of you using CD-R for long term
>preservation and who use
>analyzers (e.g. Clover Systems) to grade discs, what error rates do you
>deem
>acceptable?  Specifically, what is your upper limit for E11, E21, E31, and
>E22, beyond which you will not keep a disc?  Also, do you have any
>criteria
>(apart from Orange Book specs) for physical perameters like Beta,
>Assymetry,
>I3, I11?

We use three testers, CD Errormonitor, which is an error collection
software which runs on a standard PC and a hardware connection that
is connected to a CD Audio player with a Sony error correction chip.
This measures BLER, BERL, E32s and other error parameters only. EC-2
CD tester, which is a professional machine dedicated to CD testing
which measures BLER, BERL, E32s and other error parameters only.  We
also have access to a CD CATS SA3 Advanced CD-R tester, (loan),
which measures all CD parameters, and is in many respects the
industry standard.  We periodically check the measurements of the
other testers against the CD CATS and also do analytical tests on
the CD CATS.  The CD Errormonitor correlates very well with the
error measurements provided by the CD CATS.

We have a max peak of 50 for BLER and 6 for BERL, we are looking at
specifiying the average BLER, but it is always below 1.  No E32, and
we would start to worry if we detected any E31 or E22.  However, the
lower level errors are part of the system and dont need to be
specified, just analysed.

It is quite reasonable to expect that almost any fault in a CD will
eventually be represented in errors.  However any error measurement
that approaches the fail levels will, in our collection, require
testing on a machine that has greater analytical capabilities.  With
error measurement you can grade, but without the extended test
regime, you cant analyse.  In practice, experienced operators can
interpret the graphical information provided in a simple error test,
making it possible to determine problems in a CD and apply remedial
action well before it becomes marginal.

Any discs identified in this way can, if necessary, be analysed on a
CD tester with greater analytical capability.  The CD CATS for
example, while an extremely expensive piece of equipment,
nonetheless complies with, and tests, all aspects of a CDs
performance defined in the standard, and has, in addition, developed
some other parameters that highlight possible problems that are not
defined in the standard, particularly in the area of blank CD
testing.  A device that carries out full analytical tests enables
the determination of cause of failure, be it the media, the writing
devices, the storage, or damage.

I summary, we dont specify other than orange book (or red) for all
the parameters (except errors), because if we are measuring them,
then we are analysing, not grading.

Kevin Bradley
Manager: Digital and Audio Preservation Resources
National Library of Australia
Canberra   ACT 2600
AUSTRALIA
Tel:  +61-2 6262-1381
Fax: + 61-2 6262-1653
Email: kbradley@nla.gov.au
NLA home page: http://www.nla.gov.au
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