Nero DVD disc quality vs speed test, no sense indication err

[Ronaldus]

I found some interesting things having run more Nero "disc quality" error scans (with Nero CD-DVD Speed 3.80). I often get "no sense indication (000)" errors on certain discs burned with and scanned on my BenQ DW1620, but not on my Pioneer A06 or A07 burns. Sometimes the Nero error scan will show 4489 MB as the end for a disc that is not that full. Whenever I scan it, it fails with the "no sense indication" error near the end. If I eject and reinsert the same disc (sometimes multiple times), sometimes it will show the correct size and the scan no longer fails with the error message. Is there a way to make Nero disc quality consistently detect the correct end so that I don't have to keep ejecting/reinserting or restarting the program to avoid the "no sense indication" error?

I retried some discs that got this error before (including several pressed originals). I found the size was always correctly detected on pressed originals, but these originals often failed with the "no sense indication" near the layer change if I scanned at 6x or faster. The scans worked 100% of the time through the layer change if I scanned at 4x. I don't know if this is a firmware issue, the pressed media is flaky, or the BenQ just doesn't do a good error scanning job near the end of a layer. Does anyone know why?

Also, I observed that pressed dual-layer originals I error scanned at 6x or 8x sometimes showed an odd speed graph where the BenQ drive would periodically slow down to 4x across both layers, but burned media has no problem doing a straight speed line up to 8x (except for a single blip near the start on the BenQ).

My understanding is a drive slows down when it's having trouble reading (too many PIFs or POs), so this tells me that some pressed dual layer media must have a lot of PIFs or POs. Either that or maybe it's not physically possible to error scan the harder-to-read layer (I assume that would be the semi-transparent top layer) faster than 4x. Does the first half of the error scan always correspond to the semi-transparent top layer? I have noticed that the PIE and PIF is always worse on the first half of the scan of a dual-layer disc.

At least I now have a workaround for my failed scans... scan at 4x or eject/re-insert the disc until the size is right. Apparently there is now a Nero Toolkit 4.0 which I need to try to see if it does better detecting the end size.

Steve2713, I read one of your posts in an old thread saying not only do you usually error scan your burned media, but you also run a speed test. The Nero (or DVD Info Pro) speed test is something I've never understood. Most of the time when I run speed tests on a BTC 16x or the BenQ 1620 drive, I see a straight line from 4x to 8x so it doesn't seem too helpful. What am I supposed to see if I have a flaky disc? Periodic dips in speed like I see when I error scan at 8x on dual layer pressed media?

If the speed test reflects the drive slowing down due to errors, shouldn't those errors be reflected by the PIFs/POs of the error scan? If so, wouldn't that make the speed test redundant to the disc quality error scan?

[Hawseman]

I haven't scanned too many pressed disks so I'm not much help there.

About the "Sense" error.....I get those quite a bit when burning with my NEC and scanning on my BenQ....it's a wacky thing, but no harm done. I've noticed that it doesn't skew the results.


On your last question:
There usually is that correlation between transfer and quality tests....but if the transfer test is good, what test do you do to see how good? Quality scanning can look deeper into disk.

The difference between a transfer test and quality scan is one tests raw data, the other tests correction data. A transfer test reads real data and reports on how easy that data is moved. It will utilize correction data when needed. It's a little more "real world" of a test....cept' that it reads faster than normal dvd players.

Quality scanning reads only corrective data (Parity) and reports on how well the disk can correct bad raw data. The theory behind quality scanning is that if a disk has excellent corrective properties, it should last longer and be more resilient to everyday handling. Also, if a standalone player needs to work too hard to correct raw data, it will be prone to skipping or pixelation.

Quality scanning is rarely done at "max" speed. There aren't any drives I know of that report parity errors correctly at max. Speed lock to 4x or 5x (NEC's) or 8x(BenQ) for a consistent test.

IMHO, a good transfer test trumps a bad quality test. The way different drives report parity errors on a quality test is a bit inconsistent....so it's still considered a "black magic" test......especially here.