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by dataflow 1855 days ago
> 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?
3 comments
userbinator 1855 days 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.)

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dataflow 1855 days ago
Wow! It does sound extremely painful haha. Thanks for sharing, that's pretty useful info.
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account42 1855 days 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

[1] http://wiki.redump.org/index.php?title=Dumping_Guides

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vardump 1855 days 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.
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philpem 1855 days ago
Sounds like "READ RAW". From memory it only works on certain drives - I want to say LiteOn but my memory is hazy.
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azalemeth 1855 days 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

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