Techno Talk
Rotten luck
Mark Nelson
Bad news: disc rot is back… with a vengeance. We thought optical media would last forever, but it turns
out there is a potentially catastrophic problem with DVDs – and at this stage we’re not even certain how
widespread the problem may be.
A
re you one of those cool
dudes who has ditched your
collection of DVDs and instead
opted to stream your favourite movies
and TV programmes from the ‘Net?
Good on you! You made a wise choice
and can now save fifteen minutes of
your precious time. Skip the rest of
this article and turn the page!
Alternatively, you may have a carefully curated collection of DVDs, probably
including some impossibly hard-to-find
titles. If so, prepare to feel sick. Some of
your deeveedees may be starting to selfdestruct. To make things perfectly clear,
these reports are about ‘proper’ factorypressed DVDs — the ones with shiny,
silvery backs. We are not discussing those
recordable DVDs with backs of purple
or some other strange hue. So what’s going wrong with these discs that we all
thought were well-nigh indestructible?
Potentially catastrophic
Perhaps that’s an exaggeration in global
terms, but it could be bad news economically for the companies who produce and
sell DVDs, especially if they are forced
to compensate the customers who paid
good money for them. Recent rumblings
from movie buffs in the US complain
of pressed commercial discs failing to
play properly (or at all). Named most frequently are Warner Bros and Fox discs
of Hollywood movies manufactured before 2010. This covers thousands of films
released on DVD during that period.
My informant wites: ‘Since most of
the complaints do not originate in the
UK and these faults might conceivably
be the result of extreme heat or humidity, I ignored these stories as not relevant
to the UK. Yesterday, I deliberately took
a mint, unplayed DVD from a boxed set
from that period, which was noted by collectors as one of those affected. It stuck
halfway through. So I tried another disc
from a different boxed set, with a similar
result. I tried different drives and players. I also cleaned the discs, but they
were both still faulty. Each time irrecuperable read I/O errors were reported.
This raises several questions about the
longevity of optical discs, especially as
10
there is no apparent consistency of the
fault. However, the numerous 2006 to
2008-era DVDs that fail read-error tests
usually have one or more of the following
numbers etched on the underside inner
ring: IFPI L906, IFPI L907 or IFPI L908.’
This could generate reputational damage, as the general robustness of optical
discs has led to a false sense of purchaser security. If this new ‘DVD disease’
affects potentially every DVD ever produced, the DVD and Blu-Ray industry is
in deep trouble. The sincere hope currently is that the discs affected are only
those made at specific manufacturing
plants or else during a few years of production. It would indeed be disastrous
if we should now have to consider the
DVD format potentially unstable.
What to do now?
One American collector reports finding
around 200 affected in this way, and
many other users have discovered dodgy
discs. If you have any recording of great
importance or a DVD that you treasure
above everything, should you back these
up? If so, on which format? Hard drive?
Or use one of those hideously expensive
archival-grade DVDs that is claimed to
last for 100 years? The real horror of it
is we just don’t know.
At this stage there appears to be no concerted industry response to the problem,
with movie studios acting inconsistently.
Some companies have replaced defective DVDs, while others are refusing to
provide replacements outside of the
normal warranty period. It may be that
consumer associations will launch class
actions, forcing the producers to issue
replacements. There is a legal precedent
for this in Britain, as this is what happened when large quantities of faulty
CDs had to be replaced. Mind you, in
some cases the firm that released the
films originally may no longer have the
rights to re-press the DVDs if those rights
have changed hands.
Now for the techie stuff
So, what exactly is ‘disc rot’? It’s the
name given generically to a number
of mechanisms by which CDs, DVDs
laser discs and even Blu-Rays tend
to self-destruct. All of these discs are
optical media in which binary data is
recorded in the form of ‘pits’ (minute
depressions) and ‘lands’ (flat surfaces)
that represent the digital values of one
and zero. The rot occurs as a result
of physical or chemical deterioration
that causes the recorded data to become unreadable. Potential causes of
‘rot’ include oxidation of the reflective
layer, physical scuffing or abrasion,
reactions with contaminants (such as
spirit marker pens), fading caused by
exposure to ultraviolet light and debonding of the adhesive used to adhere
the layers of the disc together. The
marketing claim made originally that
optical discs were indestructible was
pure fantasy – or lies – take your pick!
The rot causing the current flood of
complaints is reportedly confined to
double-layer pressings of two companies’ releases from 2006 through to
2008, in which the double-layer transition point deteriorates. DVDs produced
prior or subsequent to this time period
do not (generally) show read errors. It
appears that a specific manufacturing
plant used faulty/defective double-layer
DVD materials. Single-layer pressings of
this era do not seem to be affected. Read
errors occur usually (and specifically)
at the double-layer transition break.
Sometimes, this renders the DVD unloadable from the very start. Other times,
the DVD will load and the film will play
fine all the way through. However, the
‘Special Features’ (which can be selected from the menu) will not play.
When the Special Features do decide to
play, then the film or main feature will
start fine and then freeze about 1 hour
40 minutes in. This may possibly depend upon the specific location of the
dual-layer defect (ie, whether it occurs
in the first layer or the second). Many
boxed sets are affected, particularly
those from 2006-2008 with slim cases,
though quite a few individual DVD releases are also problematic.
Sorry to be a gloomster again. I’ll try
to find something more cheerful to write
about next time.
Practical Electronics | July | 2021
