CD-ROM archiving

[Jan-Benedict Glaw]

On Thu, 2006-10-26 17:33:51 +0100, arcarlini at iee.org <arcarlini at iee.org> wrote:
> Jan-Benedict Glaw wrote:
> > For a pure data CD, an ISO image is probably good enough. (Though you
> > may want to additionally get hold of all the TOC/ATIP information
> > that's not inside the ISO image.)
> 
> OpenVMS CDs and Ultrix CDs are not ISO9660 just for starters so I
> think you really do need a dump of the entire CD (via dd or any
> of the CD/DVD-writing programs out there). Even if it looks like
> an ISO9660 CD that's not enough. I've written CDs that have both
> an ODS-2 filesystem and an ISO9660 filesystem (in my case the data
> was shared between the two but there could easily have been data
> that existed in only one or the other).

Are they multi-session?

> > For anything else (CD+G, CDI, ...) you need to understand how a CD
> > works and at which layer this type of CD is operating.
> > 
> > Especially for "copy-protected" CDs, which may contain premastered
> > broken sectors, you probably also want to get hold of the C2 level
> > error bits.
> 
> Ideally you would want a dump of the raw CD "bitstream" (I think it
> has a proper name but I don't know it) but for most CDs that's far more
> than is needed. If the CD device for the target system never made that

Unfortunately, you cannot access it at the lowest level with regular
CD drives. (Well, at least not with the documented MMC-5 commands...)

> much info available you probably don't need it. Even having all that
> info won't necessarily be enough to recreate a CD (the PS copy
> protection
> scheme you mention relies on deliberate error data and I think even
> modern
> writers don't give you enough control to reproduce such a disc).

These are two distinct problems: Preserving all information and
recreating a new disk from it.

Even while we might not be able to reproduce an errorneous disk with
today's CD burners, we really might want to preserve the information.
Just in case the original CD gets lost.  Or think about emulators.
They could be taught to emulate errors. I didn't understand all of the
CD formats (information about these is quite sparse and I don't have
some free money to buy the standards) and I know even less about the
burning process.  But I remember that there are some (Windows based)
tools around to burn CDs with errors, so I guess it's possible to some
extent...

MfG, JBG

-- 
      Jan-Benedict Glaw      jbglaw at lug-owl.de              +49-172-7608481
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