Which PI/PO Scan to Believe

I observed on few of my DVDs huge error report contradiction; below are the scans as they appear on three drives used for testing, and the read curves… I am simply amazed to such variations. The disc is faulty - or Plextor and LG think so? Which one indicates the reality? The read curves also follows.

First: BENQ 1640

Second: QSI SDW 082

(see next post for continue due to max 5 images per post)

(continuing from above one):

Third: PLEXTOR 712

Fourth: LG 4163

So … I used to believe Plextor but nowadays Benq seems the scanner of the day ( even Plextor produces 740 that is a rebadged Benq 1640), but don’t you think it is too optimistic and beside a very good reader…

I am frankly puzzled - I do not know what drive’s scan to trust… is my data endangered or is a simply an error of error reporting ?

Believe them all, the drive is just reporting the number of errors THAT THAT DRIVE finds, with all the drives there is an obvious trend that it is a poor burn. It’s ‘less bad’ with the Benq, but I wouldn’t be pleased with the results based off of any of those tests.

Yep, that is a horrid burn.

It has not yet become unreadable on the BenQ (BTW, update from the N firmware to the O firmware as N is bug’d and O is the fix) but it will do very very soon.

For the BenQ I usually bin any disc that has a group of errors over 10 PIF (single peaks are fine as long as no POF errors) and that has a total PIF count over 2000.

Well I agree it is a horrid burn, though I do not understand why such discrepancy between those scans and read-speeds?

There’s absolutely nothing to gain from comparing scans from different drives. Variations are normal, and will be greatly accentuated with crappy or even marginal discs. Pick one drive for scanning and stick with it, you’ll only drive yourself nuts like this. And yes, all these scans are “correct”.

It is not unusual to see scans by different drives varying greatly when the disc is neither the best nor the worst. If your Plextor 712 still works in a proper way, it remains wise to rely on it for testing disc quality, as it is one of the most sensitive PC drives, closer than most others to AudioDev CATS device. And yes, I concur that Benq 1640 is too optimistic. You may consult:

  1. Plextor 712 vs. CATS

  2. Benq 1640 vs. CATS

I used to believe that view also. However, I have not seen any evidence for it, not to mention proof, after very extensive reading at several major websites. So it is better to regard it as merely an assumption to be tested, IMO, unless someone can provide strong evidence for it.

What a curious way to see this. :confused:

If you ask a hundred different people about, how easy it is to read Shakespeare’s Othello in English, they may all give you different answers.

In your view it is mereley a theory that they their views are valid, and unless that theory can be proven, you will accept the alternate theory that they are all wrong except for one person (and anyone who agrees with him/her)?

I’m going to accept the theory that all drives scan the discs how they see it, and it is completely meaningless to say that just one of those drives provide the accurate scan.

There will of course be some drives who scan in a way that better predicts how the disc will be readable in other drives, but that doesn’t mean that those drives tell the One Single Truth.

There are still many, many people - some of them so-called experts - who simply do not understand what an error scan is and what is being displayed. Be that as it may, it is true that there’s no such thing as an “accurate” or “inaccurate” scan. Drives all have different error reporting schemes, no 2 are alike and thus should not be compared. Furthermore, all the posted scans do in fact agree on the fact that the disc is crap or at best questionable.


Try forced 16x burning on some of the worst DVD media made by Princo or some Chinese makers and scan them in Lite-On, LG, Plextor, BenQ, NEC, Toshiba, Samsung…

You have stretched my words too much.

To my knowledge, people in the optical storage industry would not bother looking at scans done by non-professional machines. Since there is no evidence to support that every drive is correct in error testing (I did not say that viewpoint is wrong), I would rather trust industrial standard at present. I did not say that Plextor 712 is the only one that is accurate, but rather that it is one of the most sensitive PC drives. Several Lite-On DVD-ROM/Combo drives (but not its more recent DVD writers) are also very sensitive. There may be others, but less information is available. The scans by Plextor 712 and by Lite-On DVD-ROM drives do not differ greatly in many if not most cases, but there are exceptions, so I favor using scans by more than one drives to search for the best combinations of discs/writers. For routine uses, any single drive may be OK.

It is highly unlikely that a person can figure out the underlining basis of PI/PO error scanning by oneself with no experience with any professional testing device. I understand it only after studying the manual of Pulstec’s analyzer and performing some tests with the help of a senior expert in the industry’s R&D sector. As I have said in another thread, I am not a professional in this field and do not consider myself to be an expert.<O:p</O:p

To my knowledge, no one at any forum in the internet has correctly described DVD jitter. If one can not fully explain how DVD specifications define jitter and the way to measure it, it is not possible for him to be an expert. A link is provided below for those interested: <O:p</O:p



…it is true that there’s no such thing as an “accurate” or “inaccurate” scan. Drives all have different error reporting schemes, no 2 are alike and thus should not be compared.
You are still saying that without providing supporting evidence.

There will of course be some drives who scan in a way that better predicts how the disc will be readable in other drives, but that doesn’t mean that those drives tell the One Single Truth.

the Zen of scanning, we are all on seperate paths to digital enlightnment.

ive found them scans to be a fun thing to try but i dont trust em i have disc who got a score of 0 yest they play great in my standalone dvd player.id imagine the higher the score the more it will play in though

Answers to that repetitive opinion have been offered before, a very recent one is:


After waiting several days in vain for some one to provide evidence for that statement, I shall present some evidence against it. Please read the graphs in:<O:p</O:p


Pay attention to those scans with jitter way, way off specs, surprisingly PIF may be as low as 5 in some of them. The two numbers cannot be correct at the same time.<O:p</O:p

I’m not sure I understand your point at all: You cannot have very high jitter and low PIF values at the same time? Is that your point?

You can if the scanning drive is very resistant to high jitter. But the same disc may be difficult or impossible to read on another drive that is not resistant to high jitter, with resulting high PIF and POF numbers.

If I misunderstood your point, then please clarify.

So muchin, you say jitter is the most important sign of quality recording? It could be so and I tend to think so too, though PIF are wide-spread as the best quality indicator and then PIE. What is obvious is that a good burning is marked as so by all readers but a bad one can trouble scans with great variation from manufacturer to manufacturer. If you see my first posts the thing that troubled me was that on the disc studied around 250M point the Benq reported PIF of around 4 and Plextor around 60 (!) knowing that 4 is the limit for a good burn; moreover Plextor reported POFs, so incorrectable errors and finally gave up the scan while Benq seems to have no trouble in that are… now the big question is: from the lots of scans we can see here spreaded around this forum, with high scores and good scans how many are so indeed and how many, if tested with plextor or another drive (see QSI) can lead to complete different results… The people who observe good scan on Benq are sure their burns are ok, but what happens if in a matter of weeks the data became unreadable… ? They will blame the quality of media for sure as a rapidly degrading one and they can lose data; so my question is: can we have confidence in Benq scans? even if lots of other scans seems to follow the Plextors way of reporting errors, this seems not to be true for all media. So, the question remains: whose scan de believe? who may tell data is at risk? benq does not, especially in the initial portion, QSI and Plextor strongly suggest the opposite. If this is an isolated problem should be ok but what if lots of so-called good scans on Benq tends to be unreadable or hardly readable on other drives… that is what worries me :confused:

Let me elaborate by using the graph in the post below as an example:


According to research done by Pioneer, 15 % is about the highest jitter level that can be effectively handled by the error correction mechanism. Accordingly, that disc must be unreadable by that drive. On the other hand, PIF max of 9 @ Sum 8 is very good according to DVD specifications. If the disc can still be read flawlessly, then the jitter level reported is wrong. So either jitter or PIF or both is incorrect. <O:p</O:p

To my knowledge, no reader is capable of correctly reading a disc with jitter >20%. At such high jitter, PIE/PIF max and POF similar to the following data should have been obtained:


About two years ago, C’t estimated levels of jitter tolerance for several writers; but I don’t know how they performed the tests, as I have only seen a summary of it in English translation. Do you have some more information?<O:p</O:p