A few members have recently brought this topic up. It’s not a new topic, but I thought it might be interesting to have a thread devoted to this.
Issue: Scanning PI/PO at higher speed produces lower error rates.
This seems to contradict common sense, but it’s not a new thing, nor is it specific to any particular drive. Some drives will exhibit a “preference” for reading at a particular speed, sometimes a particular discs will do this while others will not.
My best opinion on this is that you usually do not see this on “well-burned” discs, or at least the differences are much less pronounced. If a disc has “acceptable” error rates at a higher speed, but “unaccaptable” rates at a lower speed, you should assume that it’s not a good disc. Although it may play/read well enough in the short term, it probably should not be relied on to do so in the long term.
In the past, some folks have noted that 4x CLV scanning seems particularly prone to showing higher error rates, but again this is almost always on discs that are “marginal” in burn quality.
Any way, I made a small page with 2x, 4x, and 8x scans on both my 401@811 and my 1213(TDK) drives so you can compare the results.
Here’s the page All 6 scans are done on the same disc.
Everyone will not agree on the reasons for this phenomanon, but it’s interesting to explore I think. The 1213 drive seems to be especially fond of reading at 8x CAV.
So, should you opt for the scanning speed that produces the lowest error rates, or the one that produces the highest? Food for thought.
What quality is it in a disc that makes it exhibit this behaviour in a drive? Maybe jitter or tracking issues? Who knows, we don’t really have a way to measure these issues, nor is there any way to correct it short of replacing the drive or the media. Is it a “problem”? No, not really. Just something to be aware of, and one more good reason to avoid comparing scans from different drives, different read speeds, etc.