Why no POF on an unreadable disc?

Why is there no POF on the disc quality test if there are unreadable sectors on the disc?

Not all scanning drives report POF.
BenQ and Plextor do this, but LiteOn, Samsung, NEC, Pioneer… for example do not.

Here are the Disc Quality/Transfer Rate/ScanDisc pictures of the disc




It seems to me my BenQ drive is not reliable on reporting POFs, i mean just by looking at the Disc Quality test one couldn’t know the disc is unreadable :confused:

Apparently the BenQ DW1640 has a problem similar to what I reported for the BenQ DW1655 here in another thread.

This unfortunately means that you cannot use the Disc Quality scan on your BenQ DW1640 to determine readability, and you must perform a real readin test by e.g. performing a Transfer Rate Test as you have done.

Thanks on the response DrageMester, i see you have had the same problem in the thread you linked to.

This is the first time i have gotten an unreadable disc burnt on the BenQ drive and i’m frankly surprised at the drive not reporting it as POFs in the Disc Quality test…

I guess i’ll stop using the Disc Quality test as it doesn’t show me if the disc is readable or not (I’m not saying it’s useless though as it can still be used to gauge disc degradation or burn quality)

Thanks :clap:

Let this be another reminder to all those who mistakenly think that PIE/PIF scan is a one-fits-all method of testing burnt discs… :disagree:

User data is NOT read/retrieved during PIE/PIf scanning. The drive only parses the ECC blocks, retrieves “raw data” at this level only, and merely reports the error correction it has to apply when retrieving this “raw data”. (I’m oversimplifying). Sidenote: (once again :bigsmile: ) the errors reported are not “errors on the disk”, the errors reported are [I]reading errors caused by a given disc/drive combination at a given speed.[/I]

Reading actual [I]user data[/I] is a whole different matter and only a TRT, a scandisc or or copying all files to HD can tell you for sure that user data is fully retrievable (with the drive used - a different drive may still have reading issues with the same disc :doh: )

PIE/PIF scanning is [I]not[/I] a way to tell you that the disc is “good for use” or “bad for use” (keeper/coaster). Even when using 16X scanning, that is IMO far more reliable to report potential reading problems than @4X or 8X scanning, there is still room for doubt: in the example you show here, a 16X scan would probably have been just as unable to detect the problem as your 8X scan. :frowning:

@[B]the original poster[/B]: would you be so nice to mention de burner and burning speed used? :slight_smile:

Sure the disc was burnt on the BenQ DW1640 with BSRB firmware, as for the speed i’m not sure but it was either 12X or 16X :slight_smile:

Let me know if you’d like a 16X scan or any other test you deem helpful :slight_smile:

Actually, if you’re willing to perform additional tests, I’d be very interested in :

  1. A scan @1X of the 0950 -> 1200 MB area (select the area in CDSpeed, NO NEED to scan the full disc @1X, it would take ages! ;))

  2. A full scan @16X

No problem i’ll get to it but first let me show you this

As can be seen even POFs seem to be unrelated to disc readability :rolleyes:



Nothing strange i notice on the 1X scan.

The 16X scan on the other hand shows a steep increase in PIE and a steep decrease in jitter on the unreadable area of the disc :stuck_out_tongue:



When you say it’s unreadable - did you try to recover the data? Did you try to recover the data from another drive? Did you try a read test in another drive? :slight_smile:

Well, the drive slows down then.
If you forced the drive to continue reading at high speed it would give L-EC UNCORRECTABLE ERROR or something like that.

Actually the 8X scan showed the same thing if you take a closer look :wink: - what you call “decrease” is actually a jump: Benq jitter graphs are not all that precise, and very sudden variation can show as either decrease or increase. It’s a limitation of the Benq/CDSpeed combination.

As [B]kg_evilboy[/B] mentions, in TRTs the drive is allowed to slow down to read a difficult area. In PIE/PIF scans, it’s not allowed to, so a problematic area may show as POF though in real-world the sector can still be retrieved (not in all cases though). And vice-versa, actually. Which is what (more or less) I tried to explain in my post above: there is no fully trustable correlation between PIE/PIF scans and actual readability. That’s simply not the way it goes.

You also have to know that [B]DrageMester[/B] found quite some time ago that there is a quirk with Benq drives having trouble reading sectors on discs that can be perfectly read in other drives. Since then I’ve encountered a couple of such burns. That’s not much, but these things happen.

This sort of quirks are more frequent than expected with [I]burners[/I] used as readers. For example, [B]DrageMester[/B] also found that PIF peaks created by re-linking points in NEC burners induce readability issues in LiteOn drives, but not in other drives (at least the ones he tested, or so I guess).

Media testing is not an exact science, you can look for trends but you can’t expect things to be 100% consistent. That’s the way it goes… :rolleyes:

Thanks for the additional scans :slight_smile:

In this particular case, my guess is that the blank itself was kinda defective. Have you experienced something similar with other MCC03RG20 burnt in your Benq?

Your guess is right :slight_smile: -> i checked the underside side of the disc under a strong light and noticed a splotch on the dye where the 1GB mark would be located.

MCC03RG20 has been very reliable media (much more than the equivalent TYG03 in my case) combined with my BenQ 1640, i’ve burned around 35 discs prior to this faulty one :slight_smile:

Yes, the problem exists with both my BenQ DW1655 drives with all the firmware versions I have tried. My dad’s BenQ DW1620 didn’t have any problem reading the same discs and neither do most other drives.

For example, DrageMester also found that PIF peaks created by re-linking points in NEC burners induce readability issues in LiteOn drives, but not in other drives (at least the ones he tested, or so I guess).
The LiteOn drives had Read Transfer slowdowns or failures at those relinking points, but the disc could still be read in the LiteOn drives (with slowdown and re-reading of sectors), my BenQ DW1655 likes these relinking point even less (see above).

I have found that the relinking point problem can occur with burns at higher than 4x speed in my NEC ND-4551A and higher than 6x speed in my Optiarc AD-7173A - in other words for burnspeeds that are faster than the drive’s maximum CLV burnspeed. My NEC ND-3500AG doesn’t seem to have the same problem, although it also creates relinking points with PIF spikes, but these relinking points don’t upset other drives as much.

They are not exactly unrelated, but just like you I have had some Disc Quality Scans on my BenQ 1655 drives that showed a lot of POF where the same disc in the same drive had a flawless TRT.

So I think the BenQ DW1655 and DW1640 drives have broken POF reporting with both false negative and false positive results.

:wink:

A last comment, about your G04 above, showing an awful scan but still readable.

It’s not the first time that I write about this in the forum, as G04 has been one of my worst headaches maker, and a MID that I’ve extensively tested and researched.

Ritek G04 has a great compatibility with readers due to an excellent reflectivity. It’s also, sadly, a MID that has been infamous for fast degradation since mid-2004 (previous production seem fine).

Here’s the problem: even when degradation is very advanced and PIE/PIF errors skyrocket (like above), the disc can still be readable (many MIDs couldn’t be read with such PIE/PIF figures). But then when it reaches some point of no return, it fails [I]totally[/I] and [I]irremediably[/I], meaning the difficult sectors get totally unretrievable in almost [I]any[/I] drive. In other words: many G04 discs are time bombs. :a

So beware: if you have anything important on G04 (or G05, that has even worse stability issues), re-burn the discs as fast as possible on trustable discs (almost anything is less risky than Ritek -R these days, but for peace of mind of course you want something stable like Verbatim -R or +R, Taiyo Yuden +R, or CMCMAG E01 under good brands like HP or Imation).

I just tried to copy back the affected file and indeed it gives me a crc error.

Regarding tests using another drive, i’m too lazy to find/install my other drives :o

That is correct, i hadn’t noticed it as it looks less pronounced :doh:

This is something every cdfreak should know :iagree:

:a

:iagree:

I’ll have to get to it soon enough but for the moment i’m out of discs.

So far i have used up 4 50pc cakeboxes of MCC 03RG20/TYG02/TYG03/T02 (1 of each) and jugding by my scanning results i would say MCC 03RG30 and TYG02 give the best burns with my BenQ 1640 (TYG03 give much lower quality burns and i have noticed quick degradation on T02). I am leaning towards trying out the Maxell Plus discs (Dolphinius_Rex says they are the best)

Thanks on the advice :cool: