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> I once wrote some code to recover degraded CD/DVD(+/-R) sectors by disabling the ECC of the drive How did you do this? Is there some SCSI/ATAPI command for t

> I once wrote some code to recover degraded CD/DVD(+/-R) sectors by disabling the ECC of the drive How did you do this? Is there some SCSI/ATAPI command for this?

vardump 5y ago
I'd also like to know. I tried to send those commands (SCSI I think?) to the drive, but it seemed to just ignore them. Heck, it seemed to ignore a huge portion of the different commands I tried to send it.
- philpem 5y ago
  Sounds like "READ RAW". From memory it only works on certain drives - I want to say LiteOn but my memory is hazy.
  - azalemeth 5y ago
    That matches with my recollection too. I remember getting a specific model of a LiteOn drive specifically to ensure that I had the ability to do this, both for data recovery and because some forms of copy protection abused disc read errors and made reading your own CDs a (kernel blocking) pain under linux. I think the source of `cdparanoia` [1] has some good examples. [1] https://xiph.org/paranoia/faq.html https://xiph.org/paranoia/faq.html
account42 5y ago
What data you can get depends on the disc drive. DiscImageCreator [0] or the redump.org wiki [1] are good starting points. [0] https://github.com/saramibreak/DiscImageCreator https://github.com/saramibreak/DiscImageCreator [1] http://wiki.redump.org/index.php?title=Dumping_Guides http://wiki.redump.org/index.php?title=Dumping_Guides
userbinator 5y ago
I found out how to use a vendor-specific command to read the raw data from the buffer of the drive before descrambling and ECC. Look up the "FriiDump" project for some more background information. I then patched the firmware in memory (that took a lot of work...) to cause regular read commands to return the raw data. (Contrary to some of the other comments in this thread, the drive was actually an LG.)
- dataflow 5y ago
  Wow! It does sound extremely painful haha. Thanks for sharing, that's pretty useful info.

> I once wrote some code to recover degraded CD/DVD(+/-R) sectors by disabling the ECC of the drive How did you do this? Is there some SCSI/ATAPI command for this?

vardump 5y ago

I'd also like to know. I tried to send those commands (SCSI I think?) to the drive, but it seemed to just ignore them. Heck, it seemed to ignore a huge portion of the different commands I tried to send it.

philpem 5y ago
Sounds like "READ RAW". From memory it only works on certain drives - I want to say LiteOn but my memory is hazy.
- azalemeth 5y ago
  That matches with my recollection too. I remember getting a specific model of a LiteOn drive specifically to ensure that I had the ability to do this, both for data recovery and because some forms of copy protection abused disc read errors and made reading your own CDs a (kernel blocking) pain under linux. I think the source of `cdparanoia` [1] has some good examples. [1] https://xiph.org/paranoia/faq.html https://xiph.org/paranoia/faq.html

account42 5y ago

What data you can get depends on the disc drive. DiscImageCreator [0] or the redump.org wiki [1] are good starting points. [0] https://github.com/saramibreak/DiscImageCreator https://github.com/saramibreak/DiscImageCreator [1] http://wiki.redump.org/index.php?title=Dumping_Guides http://wiki.redump.org/index.php?title=Dumping_Guides

userbinator 5y ago

I found out how to use a vendor-specific command to read the raw data from the buffer of the drive before descrambling and ECC. Look up the "FriiDump" project for some more background information. I then patched the firmware in memory (that took a lot of work...) to cause regular read commands to return the raw data. (Contrary to some of the other comments in this thread, the drive was actually an LG.)

dataflow 5y ago
Wow! It does sound extremely painful haha. Thanks for sharing, that's pretty useful info.