Re: [Bug-ddrescue] C2 error correction for CDs

[Antonio Diaz Diaz]

Hello Kay,

For some reason, the mailing list ate your message twice. I quote it below.

Kay Diederichs wrote:
> Dear Antonio,
>
> I have been trying to recover, using ddrescue 1.21-rc2, data from a CD
> burnt in 2002. After trying 6 different CD drives, I got 99.9% of data
> back, but ended up with 32 remaining errors (65536 lost bytes, affecting
> several files). This was using the -d -r3 -b2048 options, and the
> process took several hours. In the last hours there was little reduction
> of errors so I thought that the affected files were lost.
>
> However, I could quickly and painlessly recover this same CD after
> trying (in dispair) the dvdisaster 0.79.5 tool, by enabling the "Read
> and analyze raw sectors" under "Preferences"/"Read attempts". The
> visualization that dvdisaster provides showed up to a few hundred
> recovered C2 errors in the damaged range of the CD, but not even the
> read speed decreased much. I have now all my files back.
>
> So, do you think it would be possible to enable, in ddrescue, the
> correction of C2 errors if the drive supports it? Or is there a
> workaround using, say, hdparm to issue a ATA-passthrough command or the
> like?
>
> My CD drive is a "HL-DT-ST DVDRAM GH22NS50", and I don't think this is a 
> special nor expensive drive.
>
> thank you,
>
> Kay

First of all, I am glad that you recovered all your files. :-)

I think that there is no need to add correction of C2 errors to ddrescue 
because there is already a specialized free tool that corrects them; 
dvdisaster.

I think the best thing I can do is to document in the manual that 
dvdisaster may be a better option than ddrescue for recovering data from 
CDs because dvdisaster can read and analyze raw CD sectors, which 
ddrescue can't.


Best regards,
Antonio.