What does PI/PIF error mean exactly...?

vbimport

#1

Hi

I have read about interpreting PI/PIF(PO) error scans in the DVD-media forum and got some questions.

PI errors can be corrected but when they can’t be corrected it means that you got a PIF, right ?

But the ECMA-paper says that you can have PIF errors as long as they stay under 4, so what does that mean in reality if PIFs are uncorrectable ?

The really important is that you got no POF, which at the moment only can be reported by some Plextor drives and PlexTools ?!


#2

PIF are corrected, POF are not. Also, the DVD spec is for 1x reading. And, the specs are just that, they are not a true reflection of how drives actually perform. Most drives can correct much higher error rates, but some will struggle with even high-quality discs. Movie players in particular are very unpredictable with recordable media, whereas PC drives tend to be very good with them.

Not all drives report errors in the same way, so you can’t compare error scans from different brands of burner. POF in a scan is misleading because during scanning the drive is locked at the scan speed and is unable to re-read and slow to correct, so it does not really mean the block is unreadable - just that it’s pretty bad. A better measure of whether a disc can be fully read is the transfer rate test, or Scandisc in CDSpeed.


#3

What rdgrimes said. I would only add that PIFs are correctable as long as you got fewer than 4 of them per ECC block. A block with 5 PIFs or more produces a POF.
Of course, you have to keep in mind that these errors only refer to read errors, not some defects physically present on the disk. Thus they are not absolute values.


#4

No that’s not true…


#5

PIFs are correctable as long as you got fewer than 4 of them per ECC block. A block with 5 PIFs or more produces a POF.

Actually, the reading drive itself decides what is a POF and what is not. POF simply means that the drive has failed to correct. Some drives can correct extremely high PIF levels, and others can barely correct any. (on a given disc or media type). The reading speed is also a critical factor. Therein lies the trouble with error measurements, it’s all relative.

The specs, (280PI/4PIF) are just standards for the maximum “allowable” errors. Each drive decides for itself what the error levels are and how to deal with them, and when to fail. DVD players are notoriously inept at error correction, and do not really adhere to any known “standards”. Where the error happens to fall in the datastream is also a factor.

To summarize in a simple way, there are several levels of error correction. The first level is called PI. IF an error is not corrected at the first level, it becomes PIF and a new (second) correction scheme is applied. If that fails, you have an unreadable sector referred to as POF.

Also note that read speeds plays a huge role. In scanning tests, a drive is locked at a set speed. In real life, the drive can slow and re-read a block to correct an error where in a scan it cannot. So, a failure in a scan does not always represent a truly “unreadable” block. Confused yet? :confused:


#6

Thanks for the answears. Now I can sleep at night. :slight_smile:


#7

Last question; what will actually happen if you have a single PIF error at 6-7 assuming it cannot be corrected on the DVD player? Will it cause a skip or a freeze, and if a freeze will a hit on the fast forward button clear it?

Thanks


#8

Depends on the player and where the error falls in the datastream. Could do either.