How to verify the written data on the written disk?
 

Hello.

I started having problems with my DVD-R RIDATA G04. I was thinking my encoded movies using HC,QUENC etc were being someway incompatible with some standalone players around there.

I decided so, to check the option "verify written data" on nero. And then, I found that many read errors were occurring at the end of the disk! Nevertheless I got really surprised when I found read error on 12 continuous media :!: . In other words: I got a "bad 50 DVD-R pack". Fortunately I have another 50 DVD-R pack of ridata G04 that is burning pretty fine.

Anyway, I read somewhere (anyone to confirm this :!: :?: ) that the nero "verify written data" is NOT good at all :!: Or does NOT have accuracy.

I performed a search and found a nice tool: FSUM (freeware)
http://www.slavasoft.com/fsum/

It is a comand-line tool that generates many file integrity verification methods. Including the SHA-512 :!: (If I Recall Correctly, SHA-XXX is used by bittorrent to verify the file integrity). You can use it this way (assuming your DVD-Drive is E:\ and the data that were burnt is on D:\KDVD\):

1- You choose one (or many :!: ) checksum algorithm(s): MD2, MD4, MD5, SHA-1, SHA-2( 256, 384, 512), RIPEMD-160, PANAMA, TIGER, ADLER32, CRC32.

Lets say MD5 and SHA-512:

the >checksum.txt writes the results to the txt file "checksum.txt"

2- You verify the burnt data against the HD data:

and await it finishes (be patient :!: )

3- if you only want to display the errors (if they occur) use the -jf option:

that is it :!: Probably it will take time, but is highly recommended to do so :!: :!:

Nevertheless I found another very nice tool: CDCHECK
http://www.elpros.si/CDCheck/news.php

http://www.digitalfaq.com/archives/error.gif

Basically, it does the same as fsum: generates checksums and verify the data against the original one. But it has very handy features :D Give it a try :wink:

Thanks for the tips sparskter :D
I would like to add that I almost exclusively use QuickPar http://www.quickpar.org.uk/ for all of my long term storage backups.
That includes Loseless audio collection, MP3s, and video files.
I'm currently storing on DVD+RW many movies, and I add PAR2 files to the collection.
If something goes wrong with the media in the future, I can reconstruct the original files.
If there are no PAR2 files, then you basically loose your backups :!:

-kwag

@kwag
I though that programs like your quickpar you suggested did not exist! That is funny because I was thinking: "If I have a CRC file, can I restore if it gets corrupted"?

I think that (recover using CRC) is not possible.

Anyway, could you give some details about the process of quickpar ? I mean:

1- How big are the recovery files created using Quick Par ?
2- Where do you store them ? HD or media or Both ?

They are Parity files. Not CRC files :) Usually 5% of your total files is good enough, but if you are really paranoid, go for 10% :D
You store them together with your backup files.
This way, you can recover (reconstruct) any damaged/missing parts.

-kwag

Where you store it, in DVD media?

Yes.
Or whatever media you do your backups.

-kwag

Please could you say me how to backup a DVD with this protection.
Where you put the restore data.

@Prodater64:

I think I got your idea/doubt . If I got the correct idea, kwag before burn the data on his DVD, uses the quickpar tool. It will generate a "recovery file" of 5% of each file (I did not install the application yet). And then you burn everything on the dvd. If something goes wrong, you can restore the files that were in the recovery info.

The big question is:

Why to store the "recovery file" on the SAME dvd with the data which can be corrupted later ? If you store everything on the same DVD and then later, the data AND the recovery file gets corrupted, you probably won´t be able to restore anything :!:

@Prodater64: is that your doubt also ?

@kwag: could you please confirm/correct/suggest this last statement ?

It's a piece of cake :D
After you encode your movie and you make all your VOBs, IFOs, etc., simply run QuickPar and select all files that will go on the VIDEO_TS folder, and that will create a set of PAR2 files for every file on the directory.
Then you can use NERO to put these files on your DVD media, maybe on a folder called PAR2_FILES :idea:
Then, if anything happens to the disk in the future, you can copy that DVD to a hard disk and run QuickPar, selecting any one of the the PAR files, and the corrupted parts of your data/video files will be reconstructed to original form.

-kwag

Even if several PAR2 files get corrupted, another PAR2 file can actually reconstruct ALL data and reconstruct the bad PAR2 files :!: :D
So yes, it's a good idea to store them on the same media, and if you wish, store the PAR files on another DVD+-RW (a PAR2 library DVD :idea: ), so you have some extra redundancy ;)

-kwag

This statement is simply...unbelievable 8O I will download it now :D :D


kwag, many times I got the CRC error on copying my dvd files to HD. That "Cyclic Redundancy" error. And then windows explorer does NOT copy the file :cry: . Is there a way I can copy them (together with the par2 files) and then, restore the original data (considering that I burnt the par2 in the way you suggested)?

Please note I said "several", but I didn't say "all" :lol:
For example, if there's too much corrupt data on PAR2 files, then probably you won't be able to reconstruct. But most likely, if only several scarse bits/blocks are damaged, then you won't have any problems reconstructing all your data files.http://www.isobuster.com/ ;)

-kwag