Club CDFreaks - Knowledge is Power - View Single Post - CDFreaks Presents: Home PI/PIF scanning article

muchin · 05-12-2006

Quote:

Originally Posted by scoobiedoobie

Looking briefly at that thread, it looks as though you claim the Benq is under-reporting PIE/PIF error rates by comparing its scan to a failed TRT. Comparing the two tests is irrelevant if you are comparing tests at different speeds. It would only be reasonable to make a conclusion by comparing tests performed at equal speeds.

If that disc Mciahel tested is completely readable, most drives will slow down in TRT when encountering difficult sectors rather than abort the test, and even reread in read test. I am not aware of any disc with aborted TRT at high speed to finish that test at lower speed in repetitive scanning. Can you give such an example (please do each kind of test at least three times)? I myself have always conducted such comparisons at the same settings to avoid disputes.

Quote:

I am not suggesting it doesn't happen and I know that it can and does happen on rare occasions (and as I said in my post it is likely that ANY drive is capable of these situations).

Not every drive does so AFAIK.

Quote:

Discs can sometimes test with significantly worse PIE/PIF at maximum speed, and conversely a disc that fails a TRT at maximum speed can often read back perfectly fine at a lowered speed. Drives that report PIE/PIF levels, likely ALL of them, can sometimes report acceptable PIE/PIF error levels when the disc is actually unreadable particularly at maximum reading speeds, it's just the nature of testing media and that it's not a perfect science.

It is well known that many drives tend to report higher error rates at higher speed, if that speed can be maintained. However, in actual reading of files, the drive will slow down and even reread the bad blocks. So if a drive reports acceptable PI/PO error levels when the disc is actually unreadable, then that drive under-reports PI/PO errors IMO.

Optical discs are based on hi-tech, and disk quality test is well within the scope of science; you need to know how the binary information is processed, which is very complicated, to understand that though. PI/PO errors vary in part with many parameters pertaining to the testing device, so we cannot say that the error rates measured at only a particular speed is correct, but it also does not follow that PI/PO errors given by each drive is correct.