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dBPowerAmp CD ripper does this process, too. It ends up with blank spots for the unrecoverable data, 
so the track lengths stay intact. I think it relies on freedb and accurip data to determine what the 
final track length/size needs to be. I had it grinding for over 3 hours on one scratched disc. It 
recovered about 90% of the fatally-damaged track, which was the same as useless to me. But it tried 
...

-- Tom Fine

----- Original Message ----- 
From: "Carl Pultz" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 07, 2013 8:21 AM
Subject: [ARSCLIST] Save the Unicorns


> Hey, here’s a way to get your geek on! Thanks Aaron. I'll try this on the one commercial disc I 
> have that suffers from fatal bit-rot - disc 2 of Mahler 3rd Horenstein on Unicorn-Kanchana. Disc 
> 1, and the disc of Sym 1, are also badly tarnished, but I could rip those successfully. Disc 2 
> wouldn't rip via EAC or Media Center. A real-time transfer from a CD player didn't work without a 
> few dropouts, although this has been successful on severely scratched up library discs when 
> ripping wouldn't work. Apparently the gaps are too big. This is a pity, because these issues are 
> hard to find and usually very expensive. Given their cult-like following, I'm surprised they 
> didn't have a second round of reissue. They are UK PDO pressings.
>
> Any other catalog series that are typically vulnerable to wasting? We should be proactive toward 
> preserving such items. This Mahler went from okay to not okay in just a couple years. OTOH, the 
> big kerfuffle over bit-rot predicted years ago seems to have been overstated. For USA collections, 
> the vast majority of CDs remain playable, at least based on the collections I know. Are others 
> finding more rotten beer coasters?
>
> -----Original Message-----
> From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf 
> Of Aaron Bittel
> Sent: Tuesday, August 06, 2013 7:17 PM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] CD-R help request
>
> I have had some luck recovering data from burned discs using the command-line tool ddrescue:
> https://www.gnu.org/software/ddrescue/ddrescue.html
>
> A version for Mac (OS X 10.5+) is available here:
> http://tinyapps.org/blog/mac/200808220700_ddrescue_for_leopard.html
>
> ddrescue doesn't itself do any error correction, but rather extracts the readable data bit by 
> bit -- 
> often at many times slower than real-time, depending on the number of errors -- to a disc image
> file representing a complete read of the disc minus any bits that are missing.  You can then mount
> this disc image (OS X will do this natively) as if it were a CD-R and use the CD ripper/audio
> extractor/error correction software of your choice on it, which may be more successful than on-
> the-fly correction from the optical disc itself.
>
> Another feature of ddrescue is that you can run it multiple times on the same disc, and each time 
> it
> will go back and try to fill in the bits that are missing.  That obviously won't work with data 
> that's
> completely gone, but sometimes can recover data that didn't read correctly for some other reason.
> And these subsequent reads are faster because the program is only addressing the missing data,
> and skipping over the parts it has already successfully captured.
>
> But the best case will be if you have two copies of the degraded disc.  In this case ddrescue can
> scan both copies, merging them into one image that will probably be error-free, since it's 
> unlikely
> both discs have degraded in exactly the same places.  And again, only the missing bits are read
> from the second disc in an attempt to fill in the gaps.  [Disclaimer: I haven't used this 
> particular
> feature of ddrescue myself yet, but am describing it based on information on the project's web
> page.]
>
> It's a bit more involved than popping a disc in, firing up iTunes and clicking "extract," but it's
> worked for me when nothing else would.
>
> - Aaron
>
> --
> Aaron M. Bittel
> Archivist-Librarian/Digital Projects
> UCLA Ethnomusicology Archive
>
>