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Different drives, different quality test result - 1/24/2006 7:45:19 AM   
dkmb.peeters

 

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Joined: 1/2/2006
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Strange things. I have two discs +R here, that I recorded with my Philips dvd-recorder. One disk has mediacode Fuji/Taiyo Yuden (Yuden0002) and the other is a Arita/Ritek (Ritek R03). When I do the quality test in Nero CD/DVD Speed I got two totally different results whether I do the quality test with my BenQ DW1610 dvd-writer or newer NEC 3540A writer. You can see it in the encluded graphs and stats. What is wrong and whitch drive gives the most accurate test results?

Another question: I have many dvd's burned both with my dvd-writer and dvd-recorder. What is the best way of storing those discs: mini dvd-boxes, or nylon dvd-maps (40 or more discs)? The last is more convenient for series, but is it also a good solution in the long run?

PS: Only graph with BenQ quality test attached to this mail




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RE: Different drives, different quality test result - 1/24/2006 10:11:33 AM   
Antonio


Posts: 1320
Joined: 7/21/2005
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You could post all in one topic by using the Post Reply insted of the Fast Reply, this way would be much more convinient.


"...totally different results ..."
This is logical. According to CDRinfo's review they always mention this in their tests where they compare the drive's scanning ability to the SA300 system. For example:
"...Please note that the posted results are only valid for the specific tested LiteON SHW-1635S drive. Using other drives, even another SHW-1635S, can produce totally different results. Be aware..."
So, in your case the different drives will produce different results mostly due to the different hardware(chipset) they use. Moreover none of those results are 100% correct, proffecional equipment costs over $100000 so a simple drive and a software cannot compare to them, which are modified and calibrated just for a specific task.

Personaly I use only one drive, my Plextor, in order to compare my results. Don't try use different drives for the quality scan since you won't have any reference, as your results also confirmed.


_____________________________

salute proffessionista!

(in reply to dkmb.peeters)
Post #: 2
RE: Different drives, different quality test result - 1/26/2006 2:22:16 AM   
dkmb.peeters

 

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Joined: 1/2/2006
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Agreed that a simple tool can't be as accurate as professional tools up to 100.000 $, but the difference is so obvious that I suspected that something was wrong. And if the results of the Nero tool depends on the chipset of the drive, how can I control the quality of a disc after a period of time to see it is still good? And what is the value of all the postings, websites and other stuff on the web that mostly rely on tools as Nero CD/DVD Speed (or similar other) to qualify disc quality?

Greetings,

Dirk

(in reply to Antonio)
Post #: 3
RE: Different drives, different quality test result - 1/26/2006 2:46:20 AM   
Antonio


Posts: 1320
Joined: 7/21/2005
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"...how can I control the quality of a disc after a period of time ..."

Make sure you have the same drive as the this one you used for the first time. The software version doesn't seems to affect the result. As I told you if you want to compare your results, better use the same drive, otherwise there comparison will not be correct.


_____________________________

salute proffessionista!

(in reply to dkmb.peeters)
Post #: 4
RE: Different drives, different quality test result - 1/29/2006 11:08:52 AM   
Halcyon

 

Posts: 172
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dkmb.peeters,

What you are observing is perfectly normal.

PIE/PIF/POE/POF errors are not on the disk.

They are read errors, made by the drive, when it tries to read that data off the disk.

The errors themselves are not on the disk.

Consider the following analogy, to understand the situation:

DVD-disc = a piece of paper
dvd burner = a pen
dvd reader (scanning drive ) = a reader

When somebody writes on a really bad piece of paper, the text may be all there 100% error-free, but readers will make more errors when reading the text from really smudgy paper.

These are read errors.

Some readers are just much better at reading text written with bad quality or on really bad quality paper.

Those readers make much less errors, when reading back bad writing.

The same applies for dvd scanning.

Bad burner or bad disc will result in a bad burn quality.

However, this burn quality does not results in bit-level errors on the disc.

It results in (using the analogy again here) smudged out inscription, which is hard to read.

Now, reading this hard-to-read smudgy inscription results in read errors.

Those are errors that are made by the reader, because the inscription is fuzzy.

Do you understand the difference?

Burn quality = inaccurate, variable and out-of-spec modulation of dye-characteristics on the burned dvd disc

Read quality = number of errors made by the scanning drive, when reading back a disc with a certain level of burn quality

-----

Now, the second question:

Why are readers so different in reading back discs?

Why some drives make more errors than others, when reading back discs with marginal burn quality?

This is a difficult question to answer exhaustively (I'm not sure I even know all the variables).

However, the following properties determine the reader's ability to read back discs error free:

- amount of money used on parts (cheaper can often be worse, but not always)
- amount of time spent on optimizing read capabilities (instead of writing capabilities of drives)
- skill of the dvd design team, availalable testing resources & equipment
- luck
- etc

However, regardless of what causes it, it is a know fact that some DVD readers are better readers than others.

Hence, they report back lower number of read errors (PIE/PIF/POE/POF).

This is why consumer grade read errors should NEVER be used as a measure of GENERAL disc quality.

A consumer read error DVD scan is always a measure of disc compatibility with the drive doing the scanning.

One can generalize a bit further, by using several different readers (Plextor, LiteOn, BenQ, etc) to scan the same disc, statistically analyze the results and then deduce something from the results.

However, this requires much more scanning and the results are not self-evident.

That is, it is NOT safe to assuma that if PIE/8ECC<280 that the disc is "good" or that if PIF/1ECC > 4 that the disc is bad.

One must use these as a relative measures only.

The numbers reported by different drives are not comparable which each other, not only because the drives are of different reading quality, but because they report different units!

For example, LiteOns report:
- PIE as a sum of 8 consecutive ECC blocks (floating 8ECC window)
- PIF  from each 1 ECC block

BenQs report:
- PIE as a sum of 8 consecutive ECC blocks (adjacent non-floating 8ECC block groups)
- PIF from each 8 consecutive ECC blocks (adjacent non-floating 8ECC block groups)

AOpens report:
- PIE as a sum of 32 or 64 consecutive ECC blocks (adjacent, non-floating)
- PIF for each group of 32 or 64 consecutive ECC blocks (adjacent, non-floating)

As you can see, the type of reporting is different, so are the units. As such, they are not comparable.

I hope this explains some of the background why:

- dvd scan results vary depending on the drive used
- why there are differences
- why one should never compare results from two different drives
- why one should NOT read the results as absolute values (but as relative measures)
- who one should NOT trust any one single reader to provide accurate information about what kind of quality a certain disc is

The overall situation is a little bit more convoluted, but I hope I was able to summarise the situation above in a simplified form.

Best regards,
Halcyon






(in reply to Antonio)
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