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. On 12/07/2017 12:54 PM, Gadgetmind wrote: > On 2017-11-20 15:29, mittend...@digitrace.de wrote: >> dvdisaster can only recover discs that generated ECC data for and not >> generic disks with read errors?! > > That is also my reading. > > A few years ago, I created a tool that used what's called a > "CatWeasel" card in a PC to read raw MFM sectors off some damaged > floppies, recover what it could of data (ignoring if required damaged > sector headers), and then create an output file of what it had got > along with "goodness" flags. I could then do multiple runs with > different drivers and settings and merge the results of a few passes. > > This didn't get all the data so I wrote a new tool that used the > quality of the MFM interleaved clock bits to suggest which areas where > bad and I could then use bad raw sectors from multiple runs, and if > required brute force, to try and get a good CRC32. > > I ended up getting every scrap of data off 15+ floppies that had been > in my loft for 30 years but it did take three months of part-time coding! > > A tool *could* use similar techniques for DVDs and perhaps merge good > data after C2 from multiple runs to try and get good data to feed into > C3 but dvdisaster doesn't seem to do this, so the good results story > seems to be more good luck. > > _______________________________________________ Bug-ddrescue mailing list Bug-ddrescue@gnu.org https://lists.gnu.org/mailman/listinfo/bug-ddrescue
