Verify written data (Nero) vs Q-check C1/C2 errors (Plextools)



When I started making archival copies of my music CDs as CDROMS, I
always checked the “verify written data” option on Nero. However,
when I got my Plexwriter Premium drive, I relied on a Q-check for
C1/C2 errors (via Plextools) after making the backup.

I am wondering now if there is any difference between the two options
and whether I should be using both of them. I rather not, as that
adds even more time to the CD burning process.

Obviously, though, as I am making archive copies of my CDs, I want an
excellent copy. Is it sufficient to simply run a C1/C error check or
do I also need to check the verify written data option in Nero? What’s
the difference between the two? I appreciate your help.


I assume Nero’s verify process will report only uncorrectable errors, while with Plextools you can check both C1/C2 errors. Plus, i am not really sure how much Nero is reliable while doing this.


PlexTools checks at physical level: it will report if the “surface”/data is easily readable.

Nero checks at logical level: it will report if the source file on your hard disk is different from the burned file.

You can actually have different files because of data corruption while burning, and the disc will be perfectly fine with no C2/error reported (of course, that file won’t be readable because “checksums” will fail).


Thanx for clearing that up Minix :slight_smile:
So Nero will only do a file comparison?


So Nero will only do a file comparison?

well, I don’t know… I thought it was well known…
I’ve never cared to check what it exactly does.

But it seems like it’s making a comparision. That’s why the verifying option can’t be used with audio discs. Audio discs were not created to be bit perfect, and some drives wouldn’t be able to read audio discs correctly.

I’ve always thought that it’s a comparision, but I might be wrong…


So, how uncommon would it be that my data would not match up when backing up my audio CDs on a Plextor Premium drive? I really don’t want to verify my data AND run a Q-check for C1/C2 errors.

It would seem more likely I would end up with some C2 errors then my data wouldn’t verify. I guess I am leaning towards only running the Q check unless I hear good evidence to the contrary.


Well, after some digging, it seems like Nero’s verification will only involve an MD5 or CRC checksum calculation of some sort, and not a surface scan. As Minix already mentioned, that would take care of the random data corruption while burning, but will not check the disk for C errors.

The safest way would be therefore to do both checks, as they refer to different potential problems. You can of course do the surface scan once for each type of media you use or every now and then, as it is likely that disks from the same batch will exhibit the same behaviour.


I have contacted someone i know from Nero’s Tech support. Hope he has the time to share some more info on this


Most C2 errors are correctable.
If C2 errors cause reading errors, then it means that the burning quality has been really poor, or a defect on the disc.
I’ve never seen that with my drives and quality CDR discs. I don’t know about DVD media, but it seems more problematic.
I had some discs with a couple of C2 errors after burning, but they were perfectly readable.

The verifying option in Nero is only useful if your computer is “broken”.
Data corruption should never occur unless your system has problems.
I would only use it after setting up a new PC / new O.S. / new busmaster drivers / DMA modes, etc., to check that everything’s OK. After some good burnings without errors, I would disabled it.



I knew C2 errors are correctable, it’s just that as an archival copy, I don’t want any C2 errors present. If I see any, I make another copy until I get none. Thus, I was assuming it is more likely I will get some C2 errors from time to time than my data getting corrupted. That’s why I was leaning toward running a Q-check. From your comments, it seems like that is the better choice as data corruption is a somewhat mute point on a stable system.


[LEFT]The Nero Data verify feature runs a Bit comparison. Bit comparison is a very basic test of the model computation. It checks that the results are exactly the same, down to the last bit. But if like to double check your disc, you can by using a feature we offer call, “CD Quality Check. The CD Quality Check will run the C1/C2 Error check. This feature will not correct any errors.

Path to Program: Start>All Program>Nero>Nero Toolkit>CD-DVD Speed

Path in Program: Extra>CD Quality



From your comments, it seems like that is the better choice as data corruption is a somewhat mute point on a stable system.

I completely agree.

how uncommon would it be that my data would not match up when backing up my audio CDs on a Plextor Premium drive?

For audio CDs, this is a different matter because reading audio is not reliable and errors are allowed while reading.
With drive like yours, the data will be usually the same, but different data is read if there are scratches.

With Nero you can’t verify anything when ripping audio.
With Feurio you can know if there were C2 errors while ripping.
And PlexTools and EAC will make a data comparision, at least when C2 errors are detected.


Hmm, using Nero, and the supplied CDSpeed / DVDSpeed (which is a seperate util), it allows a surface scan and quality check - CDSpeed recommends a surface scan is BETTER than the CD quality check for testing how good the written cd is - this is in their own manual !!

I wonder about this, can anyone explain why?