EDC/ECC, can someone help me with a problem that I'm having?

Newbie Forum
#1

well here is the thing, I use CDmage to scan my backup copies of games (in this case PSX) after I back them up, and most of the time I am able to correct any errors that I may find with this tool… But now after backing up Chrono Trigger, 3 errors appeared, I tried fixing the errors with CDmage as usual, but to no avail… I checked up with some other people that I know and they all had the same errors on the disk, in the same place, on the same files, these were all copies of Originals… My question is, is it possible for the algorithm used in CDmage for scanning images for errors be wrong? I know that the only way to find errors in a CD or image of the same would have to be with EDC and to correct them would have to be with ECC… Is it possible that these errors were placed on purpose (this is assuming that CDmage’s scanning function does not work as it should)?

please respond, I’m really stumped with this one…

#2

I forgot to mention, the errors are located in the sub-header of the error filled sectors (there are three error filled sectors). Another curiosity is that the data looked as if it was shifted, in relation to the data in the sectors before and after the error filled sectors. And there is a pattern, this pattern is as follows, 5 exact lookalike copies (that only vary in the frame identification byte of the header), one completely different sector after those five similiar sectors, another sector that is the same as the first five the only difference is the edc and the frame identification byte in the header, then yet another completely different looking sector and finally another series of 5 exact copy sectors, one different, another same, another different etc… The pattern, if we say that those lookalike sectors equals 1 and the completely different looking sector equals 0, is as follows: 11111010 11111010 11111010 etc… So what we have here is a nice little bit pattern, so all of the errors were found in the second “bit” of the sequence, and the “bit” before this one was different from the sequence as well, and this is only found where those errors were found…