Question regarding image files

[porigromus]

I attempted to search the net to find this information but never found what I was looking for. This question mainly stems from curiosity.

I recently was fiddling around with a neat little tool I downloaded (CDMage) to test the integrity of some image files I have and noticed some tested positive for errors. These files are a copy of games I archived so I could store the originals. I assumed that after creating an image file if any type of file corruption occurs it would make the image file unreadable. These games are still readable, they mount fine and install fine. So I will quit rambling and get to my question.

If a program such as CDMage finds an error in an image yet the image in this case a game still is mountable and burnable does this signify the error was produced during the creation of the image rather than the image becoming corrupt post creation. I assume the error was produced during the creation of the game rather than post because of the assumption a post corruption would make the image unreadable.


I apologize if this isn't completely coherant I tend to ramble. I am just curious that is all and hoping one of you are a computer whiz with such knowledge. Thanks ahead of time curiosity was killing this cat.

[guns1inger]

Might also be a false positive - detection of an error that doesn't exist.

The assumption that error was created during creation is erroneous as whether or not is was created corrupt, or became corrupt afterward, it would still be corrupt, and fail to function.

So I suspect one of the following is true

1. It is not corrupt, and CDMage is wrong
2. It is corrupt, but in some manner that makes it technically corrupt, but still functional. This could be some low level image setting, rather than data corruption.
3. It is corrupt but you haven't reached a point in the game where it affects play - perhaps it is level graphics data or something else.

What does CDMage actually have to say about these errors ?

[porigromus]

Thank you for the quick response. CDMage states that these errors are low to mid level and yet unidentified. I atttempted to browse the sectors that have errors and CDMage states that this area is not within the image.

I find this info interesting as I never thought about checking images for errors. Second note is this is on a disk that isn't required to be in the drive to play the game. So this may mean it that it isn't intentional to fool copy protection.

Thanks again!

CDMages error log below:

------------------------------------------------------------------------------

CDmage 1.01.5 error report for image "Microsoft Train Simulator cd.2.ccd"

Track #| Sector|Sync|Header|Subheader|EDC|Intermediate|ECC P|ECC Q|Severity|Content of sector
1| 956 | No | No | N/A |Yes| Yes | Yes | Yes |Medium |Yet not identified
1| 976 | No | No | N/A |Yes| Yes | Yes | Yes |Medium |Yet not identified
1| 992 | No | No | N/A |Yes| Yes | Yes | Yes |Medium |Yet not identified
1| 1,005 | No | No | N/A |Yes| Yes | Yes | Yes |Medium |Yet not identified

[Cornucopia]

I have had a number of times where a particular drive will show errors where another drive won't. I these cases, it's not the media, it's the drive.

In your case, the ripping of the disc to discimage may have been done with a drive that produced (non-existent) errors--hopefully in the EDC/ECC portion of the RAW sector. Then, at least the UserData is OK. That's my guess for now.

Try ripping one of your discs using different drives, then do a binary file compare and see if there's any difference in the outcome...

Scott

[porigromus]

Thank to both of you for the information. I will attempt to burn a copy with another drive and examine the outcome. Worse comes to worse I just have to pull out the original disk if the game freezes and reinstall. :P