Do lower PI/PO errors real mean something?

Well, I tried this in another forum and got no response; I guess I should have been here first.

I would like to hear some feedback from those of you who are more technical and have more experience. I have noticed that no matter what the Kprobe and CDSpeed scans show on any of my DVDs, they are all playable with no problems or errors. I have noted scans that are near perfect for TY02 (as expected), in the 30s and 60s form Ritek R03 (also as expected), and scans with errors on the 80s to 120s on Prodisc S03 (right where it should be given the price. Since all of these are the same playback my question is this:

What benefits, if any, are gained with lower Kprobe errors when you get below 100 or so? Maybe long term quality will show up here? It certainly appears as though you get what you pay for, at least in the mid and upper range, but is this increase in quality going to show up some where. I can hazard lots of guesses but I am curious as to any facts out there I might have missed.

I would say, to put it simplified, that those PI/PO errors are a cumulative result of your burner’s quality and the media’s quality, where the media’s quality plays the major part in having more or less errors. However, when the error rate stays within the permitable margins all should be well. Nothing really to do with the expected lifespan of your device - that’s majorly the brands reputation :slight_smile:

here are all your answers and more…and welcome to CDFreaks Forums…

and anything below 280 pis and 4 pos at 8/1 ecc will play on just about any dvd player.

Let me try and simplify it a bit…(but it’s not a one paragraph dealio).

Optical media, by nature, is error prone. A spec of dust, finger prints, scratches, etc., all lead to the laser having issues reading the original data (video, file info, etc.). Burners too, have to fight bad dye, dust, finger prints, small substrate faults, etc.

Parity (PI/PO) is the built-in correction algorithm used to check and correct these errors. What you have is an array of data that is verified by parity data. Here’s an over-simplification of how this works:


 10      1
 00      1

PI 11

Here we have 4 data bits in a 2x2 array. We also have parity bits that we can use to test if the data bits are correct.
If you read the data bits across the top row, you’ll see we have a ‘1’ and a ‘0’, and the PO bit is 1, meaning that one data bit should be high…and the first bit is. If you read across the second row, you’ll see we have 2 data bits set to ‘0’ and the PO is 1…but this is wrong…one of those bits should be a 1. Now, if we do the same reading the columns (up & down) and using the PI error checking, we’ll see that the second column is also wrong. By this array of testing, we can deduce that the data bit in row 2, column 2 is incorrect, and we know what it should be:


 10      1
 0[I]1[/I]      1

PI 11

This is an oversimplified example, and true PI/PO correction is quite extravegant (complex arrays of self correcting parity). This just shows you how optical media readers can correct bad data.

There is a finite amount of parity errors before the data is lost forever. (See Jamo’s post above)

To answer your original question:

Media with low PI/PO error means that most data is written and read correctly. Media with high PI/PO error means that much of the data has not been written correctly and needs to depend on correction to figure out what it should be.

The lower your virgin-burn PI/PO correction error, the less the reader has to work to correct bad data. The media with the lower PI/PO correction will be more tolerant of scratches, dirt, dust, etc.
Nature itself, over time, will degrade the quality of media. High parity errors to start with, will have less tolerance for additional PI/PO errors. You might just exceed the correctable amount of error.

WHEW…good finger workout…hope this helps.

one more thing
po is a bit of a misnomer the correct term is PIF (parity inner Failures) as corrected in kprobe. :wink:

Much thanks for all your input. I had already read this link a while ago, and I really wanted to get feedback as to the value of lower errors over time. These answers do help.

“over time” is a very important qualification.

We know from experience with CDR’s that lower errors means long-term reliability. We have every reason to think that this is even more true with DVD, as the data density is 6x higher.

As to readability, any disc with PI under 300 should be equally readable, as long as PIF is under 4. There are situations where PI is under 300 but PIF is high, so this is why both PI and PIF should be watched.