Two newb questions

  1. What is the software everybody is using to scan for errors, and more importantly is there a way to properly interpret these in terms of what is an acceptable error rate and all that?

  2. I posted this elsewhere, but only had one response, and it didn’t really get at the heart of the issue:

I’ve seen scans of burned discs, be they DVD or CD, or whatever. In many/all cases it seems that burning inherently is accompanied by some errors. So, I take it to mean that if you have data that you’ve copied to a disc, that data is not being copied 100% perfectly. So, in some cases you have an 0110 in the source, and maybe an 0010 in the target disc.

If this is indeed the case, why don’t these errors cause more problems? I know that with application code, for instance, a single missed character can blow an entire program up, so why doesn’t this occur with information copied to a disk? If we burn an essay, how come when we pull it back it’s not. How is it really that error correcting can somehow “guess” what the original intent of the burn was, and how does it end up being correct enough that programs don’t blow?

The programs are called K-Probe (for Liteon only drives)
And NERO CD-DVD Speed (for Liteon, Benq and a few other drives)
Another program is Plextools (for Plextor drives only)

Disc Quality testing (scanning) will not work with NEC drives

The errors we are scanning for are correctable errors. CDs and DVDs use a two-layered Cyclic Redundancy Check (CRC) method to correct bit errors on the media. This can be done because “extra” bits are written to the media in such a way that errors can usually be detected and corrected, or when the media is really damaged it can only be detected but not corrected.

CDs use C1 and C2 checksums. There will always be C1 errors on a disc. Uncorrectable C1 errors can usually be corrected by the C2 check. A good disc shouldn’t have any C2 (correctable) errors on it, but even with C2 errors it will usually still be readable in a decent drive. Uncorrectable C2 errors are known as CU, and you definitely shouldn’t have any CU errors on a disc. Even with CU errors the drive might be able to read the correct data by automatically re-reading the problematic portion of the disc. When drives encounter large number of errors they will normally slow down the spinning of the disc so that reading becomes easier for the laser.

DVDs use PI (Parity Inner) and PO (Parity Outer) checksums, which are generally considered superior to the C1/C2 error correction of CDs. There will always be PI errors (PIE) on a disc. Uncorrectable PI errors (known as PIF - PI Failed) can usually be corrected by the PO check. A good disc should have few PO (correctable) errors (POE) on it. Uncorrectable PO errors are known as POF (PO Failed), and you definitely shouldn’t have any POFs on a disc. Even with POF the drive might be able to read the correct data by automatically re-reading the problematic portion of the disc. When drives encounter large number of errors they will normally slow down the spinning of the disc so that reading becomes easier for the laser.

Interpreting the scans is not an exact science, and it depends on which scanning program and drive you are using. When scanning you are not only testing the burner but also the reading capabilities of the drive you use for scanning.

DVD standards (I don’t recall the name right now) specify acceptable limits for a DVD; PIE rate should be no more than 280 and POE rate should be no more than 4. In PlexTools these limits are shown as a horizontal line in the Sum8 and Sum1 tests.

When comparing scans made with different scanning programs, you should be careful not to compare apples with oranges; PIE and PIF are very different, but are often both labeled as just “PI”, and POE and POF are also very different but usually just labeled “PO”.

Even without a proper scanning program (or without a drive that supports scanning) you can get a reasonable idea of the disc quality by doing a read transfer speed graph in e.g. Nero CD-DVD Speed; if you get a smooth graph it means that the drive didn’t have to slow down due to an excessive (correctable) error rate.

You don’t normally have to worry that data written to optical media becomes corrupted (0110 in the source, and maybe an 0010 in the target disc). Many CD/DVD burning programs, including Nero Burning ROM, provides you with the option to verify the data after it has been written to disc - usually by checking an appropriate “Verify” checkbox somewhere.

the basic rule of thumb for dvd error counts is pi errors 250 and below and pio errors under 6 should be readable by standalone dvd players and pc drives…although i have had errors up to 600 be read fine in dvd player…although the pi and pio errors give a good indication of burn qaulity i feel it just as if not more important in the nero speed test…this should be a steady curve with no dips in speed (i wouldnt rely on your nec to provide a steady curve though…either invest in a liteon reader or writer or use a dvdrom for the speed check).
i use nec 2500a@2510a to burn
liteon 812@832 for scanning in kprobe. (well basicaly i ise the liteon for everything except burning)

My NEC ND-3500AG reads almost anything with a smooth curve in Nero CD-DVD Speed.

The only notable exceptions I can think of are some 1 year old burnt CDs (of questionable quality) with a label attached - these instead failed totally, even though my notebook DVD-ROM could read them. I’m not going to attach any labels in the future after this experience!

In general if you use low quality media or write media at a higher speed than they were certified for, the results could be acceptable, poor or even horrible.

Don’t buy another drive just for scanning the quality of burns made by your current drive! :wink: