I am wondering how come i missed this, anyway today i saw noticed that the v2.16 introduced a new measuring mode called "BURST" mode.






Below are two scans of the same disc, one with PISUM8 and one with BURST mode, as we can see the BURST mode reports additional, POE (Parity Outer Errors)





Plextools doesn't exactly indicate if BURST and PISUM8 modes measure the same way PIE errors, but from a first look the graphs at both modes look very similar , now if only PX-712A could also report PIF errors at the same test, we would had a perfect package

Do we even know that the POE errors being displayed are accurate to any degree? Perhaps another comparison to CATS is in order?

(in reply to emperor)

Ok lets see what CATS define as:

* POF: Parity Outer Fails. The decoder was unable to correct the data using the outer parity codes in the first pass. The wording the 'first pass' is of importance because the decoder may be designed to do several passes of error correction. There is a possibility that the error may be corrected in the following passes. POF is measured over 1 ECC block. The highest possible value for this parameter is 1, which indicates a probable uncorrectable error. NOTE! POF should never be present on a DVD! Compared to the CD, this can be related to the E32 parameter.

There doesn't seem to exist "POE" term at the CATS manual, my guess is that its something like E22 at CD, second stage correctable errors.

(in reply to Dolphinius_Rex)

Hm ... strange ... I thought that Parity Inner Failures would become Parity Outer Errors automatically ...

PIE: errors being corrected during the first stage
PIF: uncorrectable errors in the first stage being passed to the second stage
POF: second-stage error correction failure -> uncorrectable error

My assumption thus would be that POE = PIF and vice versa.

BTW: you cannot compare yellow book CD error correction with DVD error correction since data CD error correction uses a third stage (ECC) ... it would be better to see the analogy with red book audio CD IMO (see PIE as C1, PIF as C2 and POE as CU with CU being more than 2 C2 errors per block which seems to be uncorrectable by most chipsets - some can correct up to 4, though) ...

(in reply to emperor)

JeanLuc, maybe you are right, since the term POE doesn't exist at the standard methodology, only Plextor can explain it..

(in reply to JeanLuc)

Try scanning a disc with Sum8, Sum1, and Burst, and see what error types corraspond with each other... maybe POE does equal PIF

(in reply to emperor)

Yea nice idea

(in reply to Dolphinius_Rex)

POE is not equal to PIF.

The DVD specifications error correction works through the ECC blocks first through rows then through columns (a block is a 2D matrix of data).

So, one PIF (which is a failure of a parity inner ROW) may contain several COLUMNS worth of incorrect data, before the Parity Outer code correction is applied.

This means that one PIF can trigger several POE per ECC block, but only one POE per column. We measure and look at disc scans per 8 consecutive ECC blocks (POE) or 1 ECC block at a time (PIF). However, from the specification point of view, a single ECC block COLUMN is also important.

Look at this (simplified example):

0 and 1 = correct data
X = incorrect data
1 - 4 = rows
A - D = columns

  Parity outer columns
  A B C D
P 1 0 0 0  = PIE=0, PIF=0, POE=0
a 2 0 x 0  = PIE=1, PIF=0 (assuming that one PIE is correctable), POE = 0, POF = 0
r 3 0 x x  = PIE=2, PIF=1 (assuming that one PIE is NOT correctable), POE = 2, POF = 0
i 4 x x x  = PIE=3, PIF=1 (assuming PIE unc.), POE=3, POF=0 (assuming POE corr.)
t
y Inner Rows

The first row is clean.
The second row has one POE, but let's assume it's still correctable (=0 PIF)
The third row has 2 POE, let's assume that's too much to correct (=1 PIF) 
 and this results in 2 POE (two columns are erroneous after Parity Inner code has been applied)
The fourth row has 3 PIE (uncorrectable), this results in 1 PIF and 3 POE (because 3 columns are erroneus

Do note that I'm talking about number of errors per row and column, not per ECC block.

NB! This is a simplified example to illustrate rows and columns. 
ECC blocks on DVD are not comprised of 4x4 byte ECC blocks! 

I haven't seen a statistical simulation of correlation between PIF and POF and I'm too tired/scared/dumb to walk through the DVD correction circuit algorithm by hand.

However, there are some interesting tidbits in the spec itself.

On a dvd disc, there are 208 rows of Parity-Inner code fixable data in an ECC block. Each row has 172 columns for which there is Parity-Inner codes (there are actually 182 columns on each row, only the 172 payload data columns have PO codes for them).

So, assume that a PIF (which is a parity inner ROW failure after Parity Inner code has been applied) can result in 1 - (172-5) PO columns having an erroneus bytes. You notice I subtract 5 from the max of 172, becaue the PI code can fix up to 5 erroneus bytes per row. So, when a PIF occurs, lets assume that PI code has still fixed up to 5 erroneous bytes, so not all columns are erroneus (in reality it could be more than 5 in the worst case, depending on implementation).

So, 1 PIF may result in anything from 1 to 167 PO errors.

As for POF, up to 8 bytes (8 rows having an uncorrectable byte in the same column) can still be corrected by the Parity Outer code PER column. More than 8 bytes of erroneus data on any one column and a POF may ensue.

This is a simplified example from the spec. The actual chip level implementation might differ (due to several passes being applied).

Additionally...

According to CISD a DVD disc (conforming to original dvd spec) should have a maximum of 0 POE. Haven't seen too many scans like that yet... In fact, I suspect this figure could be wrong and they mean 0 POF. No wonder the DVD+R spec is then more relaxed (allows up to 4 PIF, which can mean anything from 4x(1-167) POE).

So, in fact, if we wanted to scan more diligently, we should have the following spec limits:

<280 PIE / 8 consecutive ECC blocks (to pass dvd specs)
<=0 POE / 1 ECC block (if CISD data is right) this equals 0 PIF, because each PIF is AT LEAST 1 POE (to pass a good disc)
<=4 rows that have max 5 PIE each / 1 ECC block (to ensure that likelihood of being <=PIF, thus within DVD+R spec)
<=4 PIF / 1 ECC block (to pass DVD+R spec)
<=8 POE / 1 ECC block COLUMN (to be still be readable, because after 8 POE a POF may ensue *depending on the implementation of the error correction)
<= 0 POF (to be theoretically readable)

regards,
halcyon

PS I cannot guarantee the above is 100% correct, as it is based on my limited understanding of DVD specs (DVD, DVD+R) and third party sources. I'm very tired now, this text may have a lot of typos, but I might as well post it now... Please shoot it down if I was too tired to notice my mistakes :)

(in reply to emperor)

As always Halc you gave a good explanation of the used DVD Error correction mechanism, to be frankly, we will change the way we make our writing quality tests, meaning the Plextools scans will include: PIE,POE and POF.

(in reply to Halcyon)