Re: [Videolib] Exploding dvds

Walt_Crawford@notes.rlg.org
Thu, 7 Aug 2003 12:08:25 -0700

Becky,

There have been reported cases of DVDs and CDs "exploding" in very high
speed drives, e.g. 52x CD-ROM drives (I'm not sure what the DVD equivalent
would be: 8x, maybe?). At that speed, the outer rim is moving at something
like 100MPH, and if the disc is flawed already, yes, it can break into
pieces that then fly off at high speeds.

(More likely to happen with a CD-ROM, or when ripping an audio CD, because
the computer's reading the disc at full potential speed. But DVDs are
always computer files, and some drives may do very fast readaheads...)

As I've heard it, the usual flaw is cracks in the hub.

Actually, even some visible cracks would not make most CD-ROMs or DVDs
unplayable. (A good audio CD player can handle a gap of 1cm. or 1/25th of
an inch without error, and that's a pretty wide crack...) There's a *lot*
of error-correction/redundancy in the encoding methods used for CDs, even
more for DVDs.

I suspect the board is overreacting, and as you say it's an awfully tough
mandate to carry out, but the phenomenon has been reported in the
literature. (No, I've never seen it happen, but then I have a "mere" 48x
drive.)

-walt crawford-

Yesterday, at a system meeting, a library reported having both dvds and
cd-roms explode in the players and computers. Apparently, it is believed
that this was caused by hairline cracks in the discs. Why the discs
explode, who knows. One theory on the cd-roms is that they are older
programs, being asked to run in newer computers, so the drives operate
faster. Several staff members saw this happen - on a dvd player, or
computer, I don't know. Also, it has happened to 2 patrons. This
library's
board has directed their staff to pull all dvds and cd-roms that have
hairline cracks. My question is - has anyone ever heard of this happening?
I can't believe that if this is true, someone on this list wouldn't have
mentioned it. Also, if it is a hairline crack - how can you see it anyway.
You would practically have to use a magnifying glass on each disc. If the
crack was any bigger, you would be able to see it, and it wouldn't run
anyway. Thanks for any info.

Becky Tatar
Unit Head, Periodicals, Audiovisual
Aurora Public Library
1 E. Benton Street
Aurora, IL 60505
PHONE: 630-264-4100
FAX: 630-896-3209
www.aurora.lib.il.us
E-mail: bltata@aurora.lib.il.us

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