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question about CD-r error correction

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First post, by ncmark

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Hell all....

I have a question about CD-ROM error correction.

I have taken to scanning some old CD-R disks and re-burning those with higher error rates. I noticed a few of the original ROMs were scratched and scanned those as well. To my dismay, I found some C2 errors on the original disks.

So my question is this - do C2 errors automatically mean corrupted files? I have done some reading on this, and cannot really find a straight answer. Several sites say on a music CD-R the missing bits will be smoother over, but that computer CD-ROM drives have additional error correction and may be able to read the disk.

Can you assume that if you can drag all the files to your hard drive without an error message that the data is intact? Or will it "fix" some of the files without telling you?

Thanks!

Reply 1 of 6, by GL1zdA

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C2 are correctable, so no, files are not corrupted. Rip your CDs to ISO with ImgBurn, it will tell whether there are unrecoverable errors. Bear in mind, that if the disk is SafeDisk protected there will be read errors, because corrupt data is there on purpose - you will have to turn off error correction or you rips will take hours.

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Reply 2 of 6, by Leolo

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Mode 1 discs have additional error correction (which comes at the cost of less space available for data), and they will provide another layer of defense against corruption.

Unfortunately, Mode 2 discs don't have this extra protection and they were very popular among my friends (because they could squeeze more megabytes in each disc).

http://en.wikipedia.org/wiki/CD-ROM_XA

The data in Mode 2 is very easily damaged and corrupted with only a few scratches.

Reply 3 of 6, by TheMAN

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imgburn does not support raw disc reading, use nero, alcohol, clonecd, etc instead, which supports it

if you're able to copy files from the disc just fine, then the errors were correctable... you see, the disc already has checksums in it, and file copy operations will cause these checksums to be verified during copying... if it's an uncorrectable error, you would know

Reply 4 of 6, by GL1zdA

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TheMAN wrote:

imgburn does not support raw disc reading, use nero, alcohol, clonecd, etc instead, which supports it

Honestly, do you need it? It's only required for "perfect" backup copies and for copy protection to work, something that was important 10 years ago, but now? I simply play all my boxed games with no-cd cracks.

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Reply 5 of 6, by Leolo

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TheMAN wrote:

if you're able to copy files from the disc just fine, then the errors were correctable... you see, the disc already has checksums in it, and file copy operations will cause these checksums to be verified during copying... if it's an uncorrectable error, you would know

In an ideal world, you would be correct. Unfortunately, in our real (and crappy) world, that's not the case.

There are lots of drives that will read corrupt data in a Mode 2 cdrom without warning the user. Windows won't notice anything and you won't get any kind of error. Just data that is slightly corrupted (you won't even know WHERE exactly is the corruption).

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