Understanding Plextools

I need help understanding the C1/C2 scan results I get from data or audio CD burns, using PlexTools Professional. I have gotten partial answers by studying this forum and by contacting Plextor, but I have some unanswered questions that are still bugging me.

As I understand it, the C1 stage of error checking normally counts up all the E11 + E21 + E31 and reports this sum. This would seem to be indicating the total block error rate. As I understand it, the E11 and E21 are corrected at this stage, and the E31 are passed along to the next stage.

After the interleaving shuffle, the C2 stage normally counts up all the E12 + E22 + E32. Again, as I understand it, the E12 and E22 are corrected at this stage and - - in most cases - - the E32 are not correctable at this stage and are registered as CU (uncorrectable).

The PlexTools “Help” file says that PlexTools reports E11 + E21 + E31 as C1. It further says that it reports only E22 as C2. This explanation leaves me puzzling over some of my results: In many cases of defective media, I have max C2 values that are bigger than my max C1 values. For example, I have one scan where C1max = 33 and C2max = 195.

So I am confused. If the C1 stage reports ALL the occurrences of read errors and corrects most of these, it should be passing a much smaller number to the second stage. Shouldn’t C2 therefore always be smaller than C1?

On top of that, PlexTools supposedly only reports the E22 portion of C2. This should make the reported C2 even smaller.

So how can I be getting results like C2max = 195 while C1max = 33???

And - - while we’re on the subject - - why does PlexTools only report E22 under C2? I can see the value in knowing E22, since it is the closest thing to the usually uncorrectable E32 without actually going there. But I’d like to know about E12 as well.

Now that I’m thinking about it - - does CD Speed report C2 differently from PlexTools? Would there be some advantage of using that instead?

First of all this is hardly Newbie territory, and this sort of discussion would fit perfectly in the Media Testing/Identifying Software forum. :slight_smile:

Due to interleaving, a single E31 error can result in as many as 28 E12 errors, so C2 can indeed be higher than C1.

And - - while we’re on the subject - - why does PlexTools only report E22 under C2? I can see the value in knowing E22, since it is the closest thing to the usually uncorrectable E32 without actually going there. But I’d like to know about E12 as well.
It’s true that PlexTools doesn’t include E12 in C2, but neither does any other consumer drive that I’m aware of. Some consumer drives don’t even include E22 but only E32 in the C2 count.

There’s an excellent essay on CD Writing Quality and C1/C2 errors here.
From that essay (the emphasis is mine):

Source: Writing Quality essay at CDRinfo

E12 count indicates the frequency of occurrence of a single symbol (correctable) error in the C2 decoder. A high E12 is not problematic because one E31 error can generate up to 28 E12 errors due to interleaving. Each C1 byte is sent in a different C2 frame, therefore never affecting more than one byte in any C2 frame
Perhaps that is why E12 is not included in the C2 error reporting in PlexTools nor is it included in disc quality scans in most (or all?) other drives.

Nero CD-DVD Speed can only report what is returned by the drive, although the data may need to be normalized in some way.

CDSpeed by default doesn’t support Disc Quality scans on Plextor drives, and if you try to circumvent this, you will get no C1 errors reported and only E32 will be reported as C2 and it will use a nonstandard unit of measurement.
See this post.

Thank you Dragemester :). Moving to appropriate forum…

Thank you for moving my question to the appropriate forum. I sure FEEL like a rookie in asking a question like this. But I should take into consideration the types of issues being discussed in various forums before choosing where to post. Thanks for waking me up on this.

Dragemester - - thanks you very much for the comprehensive answer. As soon as I read your reply, I felt enlightened. I had read about the effects of the interleaving process, but I wasn’t thoughtful enough to “put 2 and 2 together” and envision how C2 can balloon relative to C1. Your explanation is great!

Also, your thoughts on the relative usefulness of reporting E12 and E22 are very helpful to me.

Concerning the use of CD Speed - - - I did not write my idea very well. My idea is to use my BenQ DW1655 with CD Speed to do burn quality testing. (I do my PlexTools testing using my Plextor Premium.) I was wondering whether this BenQ/CD Speed combination might offer any advantages in assessing burn quality, when compared with the Plex Premium/PlexTools combination.

Again, thank you for the very comprehensive answer(s). It would have taken me considerable study to figure this out on my own, and I may still not have gotten the insights you have provided.

Using a BenQ DW1655 with CDSpeed for CD disc quality tests in addition to the tests you’re already doing with PlexTools will give you a second opinion abut the quality of a disc. The BenQ will also show you jitter as a percentage, which can be an interesting parameter to measure when you’re burning Audio CDs.

The BenQ DW1655 reports C2 errors in a way that is less useful than Plextor drives with PlexTools. As far as I can tell from experimenting, the BenQ only reports E32 errors as C2 - ignoring E22 errors entirely. I can’t be 100% certain about this, but the circumstantial evidence is compelling.

So I don’t recommend that you use the BenQ for scanning instead of your Plextor drive, because the Plextor drive reports C2 in a more useful way, but it is a good supplement to the Plextor/PlexTools scans.

Again, thank you for the very comprehensive answer(s).
You are welcome! :slight_smile:

Thanks again, DrageMester! Your observations will be very useful to me. In fact, our discussion here has put this whole subject of quality testing in a new light.

I am currently having problems with a batch of 100 MAM-A gold 80min discs that were apparently manufactured at the French plant. I’m getting C2 errors on perhaps 25% of these discs, as reported by my Plex Premium through PlexTools. I’ve also been getting - on average - about twice the level of C1 errors I have previously gotten on MAM-A. Interestingly, many forum participants - as well as the people at MAM-A - agree that the occurrence of C2 errors means you should use your disc as a “coaster” and burn another copy. Yet I am learning (with your help) that the C2 reported by various drives and software is not necessarily well defined. This is a huge bit of learning for me. I will need to reconsider my criteria for creating acceptable data archive discs. Do you have any personal “rules” for acceptable levels of C1max or “C2” on a disc used for long-term archiving? That is, how do you determine if a given burn will be a good, stable archive disc, based on either PlexTools or CD Speed quality checks?

Thanks for your comments on the BenQ. I have a stack of about 30 “coasters” from this batch of MAM-A. I will try to test some of these on the BenQ (with CD Speed) for comparison with the PlexTools results. Perhaps I will be able to help confirm your suspicions concerning what the BenQ reports as C2, relative to the Plextor.