[Leica] Re: DVD failure

[dlr at dlridings.se (Daniel Ridings)]

In another one of their documents:

             MAKING AUDIOVISUAL CONTENTS AVAILABLE
The Analogue-to-Digital Transfer Problems: Strategies and Practical 
Solutions
                               Dietrich Sch?ller
            Phonogrammarchiv, Austrian Academy of Sciences
                                Vienna Austria


Compact discs, the most recent carriers of audio and multimedia
contents, have their own problems. In contrast to early overoptimistic 
expectations mass replicated CDs may suffer from delamination, oxidation 
of the reflective layer, and from problems of signal retrieval
resulting from scratches, fingerprints and other kind of foreign matter.
A problem of yet unknown dimension is the inherent instability of 
recordable CDs (CD-Rs), the favourable target format in digitisation 
projects of analogue documents of all kinds. The organic dyes carrying 
the information have a limited lifetime and are extremely sensitive to 
light exposure. Beyond the processes of chemical and physical decay, an 
important element of life expectancy (LE) is the rate of correctable 
errors produced during recording. Under otherwise equal conditions, the 
lower the error rate of CD-Rs, the longer the LE; the higher the error
rate, the shorter the LE. Currently, CD-Rs are undergoing further 
development, leading to problems in the compatibility between disc 
writers and blank discs. Such incompatibility inevitably leads to 
increased error rates, negatively influencing the LE of these CDs from 
the outset. These problems can only be overcome by elaborate test 
procedures which are beyond the resources of the majority of current 
CD-R users. Consequently, many of most recently produced CD-Rs may be 
lost within a very short time. While the global dimension of this 
problem is considerable, the Beijing Institute is not affected by
this phenomenon because it has, as yet, not used this format to any 
greater extent.

DVDs function on the same principle like CDs. Their situation, however, 
is aggravated by the fact that their data density is seven times higher 
than that of CDs.