Re: [Bug-ddrescue] Reference to dvdisaster in manual

[Bob Proulx]

Robert Mittendorf wrote:
> Gadgetmind wrote:
> > address@hidden wrote:
> > > dvdisaster can only recover discs that generated ECC data for and not
> > > generic disks with read errors?!
> >
> > That is also my reading.

I also was confused by the reference to dvdisaster in the ddrescue
manual.  Because I similarly went to dvdisaster hoping to be able to
read data from a dvd and found that dvdisaster was useless unless ECC
data was previously generated.  It was a very frustrating redirection
to a dead end.

> Minor amendment: dvdisaster can read RAW form CDS, but only from CDs.
> For DVDs drives do not allow a RAW data access. Maybe in order to
> prevent 1:1 copies of protected disks (afaik Error Correction Code of
> CDs is placed in the subchannels that were often used by copy protection
> techniques)
> 
> So I think that is the only condition under which dvdisaster can help
> without pre-calculated external disk-redundancy: A CD that is accesses
> RAW instead of logical.

Ah!  That is a very nice summary and clarification.  It explains
everything.  Thank you.

Perhaps the ddrescue manual could be improved in the reference to
dvdisaster that it only works for CDs and not for DVDs?  I know it is
already very explicit that it works for CDs.  Perhaps I should have
made that connection that it *only* works for CDs.  But the name was
"dvd"isaster and so I assumed it would work for DVDs.  The manual says:

       In some cases, a specialized tool like dvdisaster may be a
    better option than ddrescue for recovering data from CD-ROMs
    because dvdisaster can read and analyze raw CD sectors, which
    ddrescue can't.

Perhaps if that said:

       In the special case of reading CD-ROMs (but not DVDs), a
    specialized tool like dvdisaster may be a better option than
    ddrescue for recovering data because dvdisaster can read and
    analyze raw CD sectors, which ddrescue can't.

Bob