Ccd/dvd data integrity

vbimport

#1

I have been going a bunch of my old cds and dvds. Does anyone know how much the data read from cds and dvds can be trusted to be accurate? Does it depend on the file system that was use? Or what program or drive you use?

I know or think i know cds and dvds have crc checking and stuff. But there have been quite a few cds that i have copied ~600 movie files off of and sometimes they match the hash check on torrents 100% but many times they also match about 98% with the different hashes being in the middle of the files and not at the ends. Alot of times the data differences i am finding from old files are minor deterrences like a one or zero changed. Its really hard to tell which one is what the data was supposed to be because i am comparing the files in a hex editor. So this leads me to wonder where the inconsistencies come from.

My main concern is if they could be caused by scratches on my disks even when the files copy fine. Or is it more likely it may have been caused by something else like bad hard drive sectors, bad ram somewhere, or possibly stray gamma rays from the sun hitting a bit. If all cds have crc checking and stuff, I am also wondering how much it can be trusted to be correct. Is it crc16 or crc32, and are the calculated per file on cd or per sector or track or what?

I have also been using Iso Buster to make copies and images of many of my old cds. Iv been using the default SPTI interface that it uses. I have only been going by weather Iso buster gets read errors or not for my of my disks for determining weather the data is go. How do i know that the copied data is correct before i throw out the cds? I want to know for sure that i can get rid of the old cds and that some polishing or using a different drive might have not made a difference in the data copied.


#2

[QUOTE=cbcdr;2000773]I have been going a bunch of my old cds and dvds. Does anyone know how much the data read from cds and dvds can be trusted to be accurate? Does it depend on the file system that was use? Or what program or drive you use?

I know or think i know cds and dvds have crc checking and stuff. But there have been quite a few cds [B]that i have copied ~600 movie files off of and sometimes they match the hash check on torrents[/B] 100% but many times they also match about 98% with the different hashes being in the middle of the files and not at the ends. Alot of times the data differences i am finding from old files are minor deterrences like a one or zero changed. Its really hard to tell which one is what the data was supposed to be because i am comparing the files in a hex editor. So this leads me to wonder where the inconsistencies come from.[/QUOTE]

That are your own legal movie backups? Because you mentioned torrents, Its doubtful.