CDFreaks Presents: Home PI/PIF scanning article

**Dee** · 23-09-2006

CDFreaks Presents: Home PI/PIF scanning article - Who to believe?

You can read the article here
Please feel free to comment on this article in this forum thread.

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Last edited by DrageMester; 09-02-2007 at 23:55. Reason: updated link

Zachzi · 23-09-2006

Nice one! Could be really handy!

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*kg_evilboy* · 23-09-2006

Cool! Finally an official article!

Thanks guys!

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**geno888** · 23-09-2006

I'm reading it now

Thanks Dee

**MegaDETH** · 23-09-2006

Just read the whole Article.

Very well done and informative.

*Quema34* · 23-09-2006

It is quite nice to see an article amassing all the respective burners commonly used for PIE/PIF scanning (BenQ, NEC, Plextor, LiteOn). So far, here's some observations of my own:

With burning in the 1640, for yuden000t02-00: all burners except the 760 show the 4.0 gb PIF spike; the LiteOn reports the least PIE and PIF (but only 2 less PIF than the 760). The 760 also reports a smoother beta graph for the 1640 burn than the H10 burn

Burning the T02 in the H10 and scanned on the 1640 made the H10 burn look like crap; the PIE spike is reported at the same spot on the 1640 and NEC4570A, but is reflected as a PIF spike on the LiteOn 16H5s; the 4570 and 16H5s report about the same occurences of PIF clumping from 3.7gb to end, whereas it appears not to be reflected in the Plextor 760; interestingly the 760 reports the least PIF here. While the PIE spike above isn't reflected in the 760, if the scale is accurate and I read it correctly, it is accounted for on the Beta/Jitter graph; the LiteOn 16H5s still reports the lowest PIE, however...

Burning with the LiteOn 16H5s: 1640 reports a PIE mountain, leveling off at ~ 1GB (as do the 16H5s and 760), and also reports PIF clumping up to .5 gb of the burn; no such report from 4570A nor 16H5s. Again, the 16H5s under KProbe shows least PIF total.

With NEC-4570A: The jitter shift downward in the 760 is more or less represented by PIF spike on 1640; only possibly indicated by PIE spike on 760 and 16H5s. The 760 shows highest PIF total, with 16H5s still lowest, but the 4570A and 1640 are within 4 of each other.

With Pioneer DVR-111: 4570A and 1640 PIF totals are within 12 of each other; only the 760 and 16H5s seem to report PIF clump nearly at the end of the burn. The LiteOn again reports lowest PIE/PIF under Kprobe.

760A: PIF reported within 6 on 1640 and 4570A; the only curiosity is the 1640 reports a small PIF clump at the end of the burn, but no other drive shows this. 16h5s again shows lowest PIE/PIF totals.

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Last edited by Quema34; 23-09-2006 at 02:20.

BeardedKirklander · 23-09-2006

I really, really like articles like this.

I especially like how you help explain what the graphs mean and what specs folks should look towards when trying to determine what actually constitutes a quality scan.

Thanks very much.

BeardedKirklander · 23-09-2006

Here is a bit from the front page that I like in particular:

Easier explanation on how to read the test results.
--------------------------------------------------------------------------------

Maybe this has got too technical, and you are wondering what to look for in KProbe reports?

Use this as a guideline for good discs:

PI (Parity Inner): No larger areas on the disc should exceed 280 PI-8 errors, do not worry too much about high single spikes that exceed 280.

PIF (Parity Inner Failures): No larger areas on the disc should exceed 4 PIF-1 errors, do not worry too much about high single spikes that exceed 4.

And as always; lower is better

*pchilson* · 23-09-2006

Quote:

There is also the matter of scanning drives following the criteria for Disc Quality Scanning according to the ECMA standard. One of the requirements of this standard is for the scan to be done using a CLV reading method. The NEC drive is not able to perform this task at a reasonable scanning speed, (by reasonable we mean 2x – 4x scanning speed).

Your results are clear. Problem is, I can't really take this as an objective test.

Here you are quoting a requirement from the ECMA but you fail to adhere to this requirement on drives that are clearly capable of doing so.
You also fail to mention that that same standards require 1x CLV as the scanning speed.

Forum standards for scanning speeds should have had no part of this test, this shouldn't be a popularity contest.

If you want to give an objective comparison, you should scan at the lowest common CLV speed of the drives, even if that means 1x.

I realize this takes time but none of us are going anywhere...

*DrageMester* · 23-09-2006

Quote:

Originally Posted by pchilson

If you want to give an objective comparison, you should scan at the lowest common CLV speed of the drives, even if that means 1x.

The only thing that is special about 1x CLV scanning is that it's the original reading speed for DVD media and the one mentioned in the ECMA standards.

There's nothing about 1x scanning that makes it more "correct" than other scanning speeds. Just because CATS scanners scan at 1x doesn't mean that they somehow see the "true" quality of a disc or that scanners scanning at higher than 1x show a "false" view of the quality of a disc. It only means that CATS scanners are following certain standards defined years ago.

There is no single "true" view of the PIE/PIF on a disc, because the PIE/PIF are not actually "on the disc" but occur only as the result of a drive reading the disc and having trouble reading everything correctly. So PIE/PIF not only reflect what's on the disc but also how the drive reading the disc is performing. Reading/scanning speed also influences the PIE/PIF occurring.

CATS scanners are of course more consistent than the consumer drives used in this article and on our forums, and they can also measure many characteristics that the consumer drives cannot measure.

Some of our users have found that high-speed PIE/PIF scanning (12x or faster) can sometimes show problems that are not seen in the low-medium scanning speeds. This doesn't mean that high-speed scanning is somehow more "correct" than low-speed scanning, but performing scans at different speeds may show a more complete picture of how a disc behaves.

Scanning a disc in multiple drives may provide an even more complete understanding of how the disc behaves.

But it all takes time of course.

It is my current opinion that 1x scanning is not only too slow to be practical for everyday use, it may also be the least useful scanning speed for some drives because it shows a "best case" scenario for many drives - not all drives however, because some modern drives may actually perform worse at the lowest speed compared to when reading at medium or high speeds.

The article shows different drives scanning at different speeds, and those speeds are in common use on our forums which makes the comparison both valid and useful. Using a 1x scanning speed would have been counter-productive in the sense that almost no home user would bother using such a slow scanning speed.

This subject is much more complex than just scanning a disc at 1x in one drive and then knowing "everything" about the quality of that disc!

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*pchilson* · 23-09-2006

I think you missed my point. I'm not saying it should have been 1x but if that is the only speed in common then so be it.

Analogy would be in Government automotive crash tests, some cars are run into the wall at 80 mph while others are run into the wall at 10 mph and then trying to give an objective review of their crash worthiness...

*scoobiedoobie* · 23-09-2006

Good review overall. One question though, why not use 4x or 6x CLV with the Benq? As you even say in the conclusion of the Liteon, you say that you consider CLV as a must for reliable scanning, only to use 8x CAV anyway with the Benq. 6x CLV is all I use since it was introduced, as not only does it give the consistency advantage of using a constant linear velocity across the entire disc, it is also faster than 8x CAV (the faster test time is from memory and was compared awhile ago but I believe it to be correct). For the same reason of consistency, I usually use 4x (CLV) on my Liteon 160P6S, and additionally my 4x Liteon scans are in closer agreement to my Benq drives and their scans vs. 8x Liteon scans, which further supports the logic in using CLV when available.

It could also be pointed out that Benq and NEC drives have a greater sensitivity to high jitter levels and that is often the source of their occasionally erratic error reporting, whether the jitter levels are accurate or only perceived is somewhat debatable though and opens up a whole new discussion that would not be entirely fit to the article. For some, the 'why's' of a drive's scanning performance and why the results can become skewed are not of their interest, only how accurate they ultimately are. The main reason for the article is to simply test and compare results between drives, not necessarily to go into what causes differences. High jitter levels can sometimes effect a disc's readback performance even with low reported error levels though so it's something worth considering when testing your own discs.

*Wesociety* · 23-09-2006

Quote:

Originally Posted by BeardedKirklander

Here is a bit from the front page that I like in particular:

And that explanation is in every one of our burner review articles!

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theEye · 23-09-2006

Why did you only use 'good accuracy' in Plextools instead of 'high accuracy' ?

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ScorpioSoft · 23-09-2006

Great article Dee! Maybe I should buy me a LiteOn 16H5s drive also.

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*DrageMester* · 23-09-2006

Quote:

Originally Posted by theEye

Why did you only use 'good accuracy' in Plextools instead of 'high accuracy' ?

To save scanning time probably.

Using Good Accuracy instead of High Accuracy saves 1/4 hour per scan x 2 scans per DVD x 4 media x 6 burners = 12 hours of scanning time saved.

theEye · 23-09-2006

any difference in the result using good instead of high?

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*DrageMester* · 23-09-2006

Quote:

Originally Posted by theEye

any difference in the result using good instead of high?

High Accuracy scanning has uh... higher accuracy?!

Good Accuracy samples only half the ECC blocks on the disc, so in theory you can miss some very brief PIE/PIF spikes or POF.

If you're going to use a Plextor drive for scanning I would recommend that you run at least the Sum1 (PIF and POF) test at High Accuracy, and then you can run the Sum8 test at Good or even Medium Accuracy to save time. That way every ECC block will be sampled and checked for POF, you won't miss any single PIF spikes, and you still get a PIE graph that is very close to the High Accuracy graph.

BTW when PlexTools performs sampling in e.g. Good or Medium Accuracy, and thus checks only half or one-quarter of the ECC blocks, you might think that it reports too few PIE/PIF. But fortunately PlexTools compensates by scaling the total PIE/PIF by a factor of 2 or 4 etc. so that total scores are comparable even if you don't use the same accuracy setting.

Personally I use PxScan/PxView instead on my PX-712A because the tests are more automated, and the tests data is saved in such a way that the graph can be scaled and manipulated at will afterwards.

Here's an example of such a scan:

Attached Images

TYG03 8x 826 PxScan @2x (1st burn).png (19.7 KB, 1822 views)

*zebadee* · 23-09-2006

Hi

An intersting "spin" of this topic.
As such excellent for forum members. A "definitive" guide, probably.
Well done Dee.

However, as a truly definitive guide. It merely scratches the surface. (Not surprising as this is a monumentual task to take on comprehensively. The results of which would probably go over my head).
pchilson's post is one of the only to (possibly the only one thus far) offer a constructive criticism & should been seen as such. So as to encourage enlightening/informative debate & not tit for tat posting.
Once again many thanks to Dee in even attempting such a topic. To present it in a clear well thought out manner. Making for an excellent reference point for this forum's (no doubt other's too) use.

**Dee** · 23-09-2006

Thanks everyone for the comments. I will do my best to answer the questions asked so far.

Regarding using 1x scan speed for all drives.
This was a no win, no win situation. Had i used 1x for all drives, members would have asked why the tests weren’t conducted using the scanning speed standards on the forum. And i would never ask members to conduct 1x scans so they could compare their own results with the ones in the article.

Regarding “good accuracy” with the Plextor tests.
As DrageMester has already stated. It was simply a matter of saving time. As a working mother with a family to look after, time is a very precious commodity. I also wanted to make sure that when a disc was burned, i had time to scan the disc on all the drives within a reasonable amount of time. I feel this was important to make the test fair for all the scanning drives.

Lastly i want to state.
This article is not a bible and the last word on Disc Quality Scanning. It’s only meant to be a guide. Each member will take what they want from the article and use which information they feel is relevant to their own needs.

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*pchilson* · 23-09-2006

Hi,
I can appreciate the time it takes to do this testing and also the fact that you have to formulate a plan for the testing and layout of the article before the testing begins. I am in no way criticizing your methods, just trying to point out there are different views, opinions and results if the methodology is changed.

That said, I would like to show what I see as "scanning consistency" from my side of the fence...

My take on consistency is the drive should spot the same relative charchteristics (good areas vs. bad areas) of the burn quality of the disc regardless of the speed in which it is being scanned. We all should note that changes in scan speed have no bearing on the physical burn charchteristics of the disc (a bad section is a bad section is a bad section...).

I would also like to state for the record that "neutral scans" are somewhat of a misnomer, PI/PIF/POF/Jitter reporting by any given chipset is by "programmed instruction", ie the developers programmed the instructions into the chip and the software is simply displaying the retrieved values. The chipset is reacting to what it is "instructed" to react to. Different chipsets, different instructions.

Following are my results of scanning the same disc in a BenQ DW-1640 and a LiteOn SHM-165H6S at three different scan speeds, 1x CLV, 4x CLV and 16x CAV in each drive. Remember, the only variable is the selected scan speed.

First up: BenQ DW-1640 (LiteOn SHM-165H6S in following post).

Attached Images

	quality_1x_1640.png (63.9 KB, 1771 views)
	quality_4x_1640.png (63.0 KB, 1767 views)
	quality_16x_1640.png (63.8 KB, 1765 views)

*pchilson* · 23-09-2006

Second up: LiteOn SHM-165H6S

Attached Images

	quality_1x_165H6S.png (61.3 KB, 1760 views)
	quality_4x_165H6S.png (61.7 KB, 1764 views)
	quality_16x_165H6S.png (61.6 KB, 1745 views)

*Chuck44* · 23-09-2006

Quote:

Originally Posted by Dee-27

...Lastly i want to state.
This article is not a bible and the last word on Disc Quality Scanning. It’s only meant to be a guide. Each member will take what they want from the article and use which information they feel is relevant to their own needs.

Thanks Dee-27 for your hard work and useful info.

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MediumRare · 23-09-2006

Very interesting comparison, thank you! I have a question and a comment though.

You keep stressing that the Plextor drive is a CLV drive. Yet in every image from Plextools, the read speed shown in the test setting is "5-12x CAV". Is this a bug in Plextools or am I missing something?

Since you use averages to draw a lot of conclusions you should be aware of some bugs or "idiosynchracies" in the way that CDSpeed and KProbe calculate averages:
- CDSpeed determines the maximum PI/PIF in each display sample (which I suspect to be ~1 MiB) and determines its averages from this display buffer (see here). This value will always be greater than the true average (because it uses the maximum in the display interval).
- KProbe uses the number of PI samples to determine the PIF average (see here). Therefore this value is generally ca. 7x too large. This has the somewhat absurd consequence that for problematic discs (or a partial scan of a bad region) the reported average can be greater than the maximum value.

For the most part, these averaging idiosynchracies have no bearing on your conclusions- but there are a couple of cases where it becomes evident:
- If you look at the scans of the Pioneer burn of the Verbatim 16x DVD+R (MCC004), you'll see that the PI total reported by BenQ and LiteOn are almost identical (18736 and 17562). The reported average values differ by more than a factor of 2: 2.12 vs. 0.99. This is CDSpeed's "subsampled averaging" at work. You can check this behaviour directly by scanning a disc in a LiteOn drive using CD-Speed and KPobe to eliminate the scanning dirve as a variable. Both tools report the total number of samples so that the disc coverage can be checked as well.
- If you look at the BenQ-burned CMCMAG AE1, you'll see that KProbe reports PIF total/average as 274/0.02. The Plextor scan shows PIF total = 576 (twice as much) but the (correct) average is 0.00.

Another observation: the Plextor Jitter curves seem to have no similarity at all to what BenQ reports (even if you only look at jumps in the traces).

Anyway, thank you again for this informative article!

G

*dakhaas* · 23-09-2006

Quote:

Originally Posted by pchilson

Hi,

My take on consistency is the drive should spot the same relative charchteristics (good areas vs. bad areas) of the burn quality of the disc regardless of the speed in which it is being scanned. We all should note that changes in scan speed have no bearing on the physical burn charchteristics of the disc (a bad section is a bad section is a bad section...).

There is something as shape issues at higher speed. IF you have a disc which is badly shaped. Then it can have problems with spinning at higher rotating speeds generating much more errors. So a bad section is not allways a bad section. (Low level measurements done at profesional drives at 1x can give some hint about the behaviour but still not all reason for Datarius and AUdiodev to come with higher speed testing options.)

Quote:

I would also like to state for the record that "neutral scans" are somewhat of a misnomer, PI/PIF/POF/Jitter reporting by any given chipset is by "programmed instruction", ie the developers programmed the instructions into the chip and the software is simply displaying the retrieved values. The chipset is reacting to what it is "instructed" to react to. Different chipsets, different instructions.

I agree with this one.Also even if errors were to be exact measured there still is the part that the majority is not allways right.

Also this is were there is a difference between the pro stuff and the home stuff.
THe pro stuff has low level calibrated measurements of parameters which can give you more info about disc's performing out of
standards and defacto standards. (some parameters invented by Datarius/ Audiodev which were not specified in the ECMA standards but can have mayor read back influence !). Which should be able to give a better idea about the performance. These parameters are supposed to be measured exactly because they do exist on the disc unlike the reported errors.

Let me add more comments on the article below

Accuracy
About the Accuracy part since error levels are not absolute even CATS or DATARIUS or SONY profesional analyzers also can't say a thing.

Plextor
Seeing that you take the most used testing conditions on this board. I wonder if anybody could say if the used "Good" accuracy is this boards standard. If not then rerunning it with the boards- standard would be better.
On most other boards I see high accuracy is being used that's the reason why I ask.

While the test data again gives one part of the puzzle and is quite nice. I still have to say the puzzle is not finished.
Like some of pchilson scans in this topic allready show.
Also the question is how do they compare to Audiodev's defacto standards CATS system. Since the largest part of the industry uses that one for thoroughly testing how will the scanners compare and how will parameters influence things. And are the scans of Benq and NEC not really neutral.
Not Neutral for me means that if it reads a disc for which the low level parameters are inside the standards but the drive seems to find someway that it's burned by another drive and gives it for that reason a lower score.
And which drive reports most close to the real life situations.
Some folks might say that there was a earlier report which compared CATS scans and home testers. However that report didn't take into account the influence of low level behaviour and it also has not looked in some weird stuff like benq supposdley hating NEC and LG scans because it didn't existed at that time.

So while we are one step closer, we still have mayor work to do.

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CDFreaks Presents: Home PI/PIF scanning article

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