How comes that some drives report impossible PI levels?

vbimport

#1

I open this thread because of a discussion I had on another forum concerning DVD quality scanning.

It suddenly striked me that I’ve seen on this forum many scans performed with NEC or BENQ drives showing PI errors levels up to 3000+.

But theorically, from all available sources I could find, PI errors should max at 1664 when scanning @8ECC… which is the case for Benq and Nec.
So something’s wrong, either these drives are reporting very badly, or this 1664 calculation is flawed, anyway there’s a missing piece and I feel a bit lost.
I’ve re-read ECMA 338 and 337 but couldn’t find this missing piece.

Does anyone have some light to shed on the subject?


#2

http://www.cdfreaks.com/article/194/5

But what is a row and what is an ECC block? Again we refer to the ECMA standards. We do not copy and paste everything but if interested look in the ECMA standards. A row is 182 bytes long where the last 10 bytes contain PI (Parity Inner) information. An ECC block is 208 rows long where the last 16 rows contain the PO (Parity Outer) information. This gives us a maximum possible PI error amount of 208 errors per block and for 8 blocks after each other this sum is of course 8 times higher giving a maximum possible amount of 1664 PIE-8 errors. In practical use a disc with 1664 PIE-8 errors is unreadable.
in some review somewhere there was a comment made about this but i cannot remember what was said sorry


#3

http://www.cdfreaks.com/article/202/5
found it :

*: this value of 2360 PIE SUM8 is of course impossible, as there are only 1664 columns in 8 ECC blocks. It corresponds to one of the spikes on the blue PIE graph, which are not due to actual errors but to sampling problems in CDSpeed. This problem is specific to Philips drive and has been fixed in the latest CDSpeed version, but it illustrates the kind of problem which can occur with a consumer drive, which is not specifically designed to measure and report errors.


#4

So if it was fixed for benq still I see a awfull lot of scans still usseing the old version. (Seems I missed something !)

However what about the NEC drives and cdspeed ?


#5

Thanks CNelson for the input :slight_smile:

I’m curious if it has been confirmed that this problem has been fixed for the Benq in recent CD Speed versions… I’ll take a look at the scans in the Benq forums.

As Dakhaas (hi :)) writes, for NEC drives we’re still in the dark… :frowning:


#6

Well this scan might give you the answer, transfer test fails while spinning up. Amazingly, my Pioneer DVD-119 is able to rip it, albeit veeeeery slowly and a lot of retries.

Edit: This is v4.01, haven’t tried v4.04 yet.

Q.



#7

Thanks for the input :slight_smile:

So at least with 4.01 the problem hasn’t been fixed yet for Benq drives, it seems… (max PIE 2777 :eek: )


#8

Seeing the PIF shape and levels makes me wonder what’s going on with the benq 1640.


#9

If you’re referring to my drive, I can say that it reads less extremely bad discs fine. I’ve gotten quite a few QS 99% with it. This particular disc was recorded on a Pioneer A04, about 2 years ago.


#10

It’s might me the matrix sampleing (counting rows vs columns ) between 2.5gb and 3gb. Still it’s looks a little weird to see the PIF-8 reported higher as PI-8.


#11

Ah ok. I agree about that… I remember there was a discussion about that somewhere, unfortunately I can’t remember where.