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Magic!? Verify says drive corrected faulty image file


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I used ImgBurn today to make a backup copy of the software CD that came with some new hardware. The process was a simple 'Read' stage, followed by a 'Write' stage with 'Verify' checked.


During the 'Verify' process a single-sector miscompare was reported :



But impressively, ImgBurn seems to report that the drive detected the faulty sector within the ISO file, and auto-corrected it !


I 14:41:51 Verifying Sectors... (LBA: 0 - 277043)
W 14:42:37 Miscompare at LBA: 3807, Offset: 2334, File: directx\dx90b_redist.exe
W 14:42:37 Device: 0x15
W 14:42:37 Image File: 0x53
W 14:42:37 Total Errors in Sector: 1
W 14:42:37 Note: The drive probably corrected the L-EC Area because it's wrong in the image file.


Can this really be true ?

Also: what's the "L-EC Area" ?

[in case it's relevant, the CDRW is the standard fitting on a Dell GX620 desktop, and identifies as "HL-DT-ST CD-RW GCE-8487B F109"]


I'm not clear whether IB is saying the drive corrected the error when burning the image to the disk, or when reading it back during the verify. I've checked, and the affected file (the MS DirectX 9.0B redistribution package) reads ok off the backup CD, unpacks ok, and can be executed (it's an installer).


Whatever the magic is, I like the result :thumbup:

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Being a Mode 1 file (which I suspect this is), the actual user data is only 2048 bytes in that 2352 byte sector. All the rest is error correction stuff etc.


Drives tend to perform sanity checks on that data sent to them and will correct it if need be. It's just something they do.


Read the MMC specs at www.t10.org if you really want to know about the L-EC area and what it contains.

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Read the MMC specs at www.t10.org if you really want to know about the L-EC area and what it contains.

=)) =))

Hope you got lotsa time scuzzy :)

hmm ... I ran out of time :coffee:

www.t10.org may contain a wealth of information, but for some reason best known to its owners it lacks any kind of useful search engine. Praise the lord for Google : "Layered Error Correction (L-EC) is an error correction technique used with CD-ROM sectors". I guess it's the checksum/parity/Hamming thing LUK mentioned, in the last 304 bytes of each sector, and Imgburn was saying the drive reconstructed it for the faulty sector. I still don't know whether that was when burning the ISO, or reading it back again later, but that's enough study for one day - I'll just settle for the good result :drinks:

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