I think the term "sample" is causing some confusion here, because scanning is not a question of taking only some (random) samples on the tested disc, but an attempt at checking *all* the blocks/sectors on a disc.
Ideally, DVD scanning will process all ECC blocks on a disc and the number of errors are retrieved from the drive for each interval, which can be 1 ECC blocks, 8 ECC blocks or something else. Regardless of what the scanning interval is, all ECC blocks on the disc will be tested for errors and reported by the drive to the scanning software. The data in those blocks are not sent from the drive to the software, however.
When performing an actual scan, the theoretically ideal situation will not be present, and for some drives this will mean that some of the samples are dropped because the software cannot process the reported info fast enough, or because the drive cannot send the info fast enough or some other bottleneck is preventing all samples from being processed.
Depending on the drive and perhaps the software, dropped samples are simply gone (e.g. LiteOn drives) while the drive keeps on scanning, or they are redone causing the effective scanning speed (but not the drive speed) to drop (e.g. Plextor drives).
Nero CD-DVD Speed will calculate how many samples were actually collected out of the the available samples, and present this as the scanning interval at the end of the scan. For a 1 ECC scan in a LiteOn drive this should ideally be 1.00 but I've never seen it close to that - 1.15 or higher is more common and depends on scanning speed and system speed. For an 8 ECC scan this should ideally be 8.00 and that's quite common when scanning in a BenQ drive, which means that samples are rarely dropped.
AFAIK the PIE/PIF averages calculated by CDSpeed takes the actual scanning interval into account, so that the average isn't artificially low because a lot of samples were dropped.
I hope that was clear. If not then I will try to do better. 
__________________
Do not meddle in the affairs of dragons, for you are crunchy and taste good with ketchup. |
Posted:
30-03-2007
Simple and clear enough, even for me.Quote:
