I have been studying the results displayed in the image I posted earlier and after reading your post about the layer break the image makes more sense to me now.
When you say the disc is not so good mostly "in" the layer transition would it be more accurate to say the disc quality is not so good mostly "after" the layer transition? The difference in the amount of errors before and after the layer break is like night and day. I am a complete noob with these types of scans and what not but the way you worded your message would lead a noob, like myself, to think that there is only bad quality in the disc for a moment, during the layer break, and then all is well again. But from just looking at the image, and the amount of PI errors after the layer break, it all looks pretty much downhill to me after the layer break.
And if you agree with the wording I have suggested of your comment, could I assume that the second-layer of a DVD is located on the outer sectors of the DVD?(Edit:Im pretty sure this isn't the case now that I think about it). If this is the case, that the second layer is the outermost sectors of the disc, and they are mostly bad, what would cause this to be the case? Isn't the DVD more unstable at the outer edges of the disc versus the smaller concentric sectors located near the center of the disc just because of the physical circumference of the outer sectors being bigger? Maybe the DVD is more wobbly at the outer edges than the inner edges, which could possibly be a fault of the drive itself and not the media?
The only problem with the theory I just stated is that I don't have problems with 99% of other DVDs that I have burned using this same DVD-drive.
So, maybe my stated theory is somewhat correct, but obviously the fault cannot be dropped entirely on the DVD-drive. In the end, as you stated, the media must not be of the highest quality and only at the outer edges versus the inner part of the DVD. Odd.
Of course if I am completely wrong about the second-layer being on the outer edges of the disc then it must be that (Edit:This is what I believe is the case). both the first and second-layers of a DVD occupy the same flat area of a disc just at different heights on the DVD. This could mean that the second layer of the disc is of a lesser quality needing a more powerful laser wattage to read the second layer. Or maybe the second-layer of the DVD is of the same quality as the first layer but the DVD-drive laser isn't putting out enough laser power to reach the second layer appropriately. Maybe my DVD drive just doesn't read DVD-DL discs very well. When I said 99% of my other DVDs work in the drive thats true. But the majority of my DVD collection consists of regular single layer DVD discs and just a few, a single 15-disc box, of Memorex DVD+DL discs. And if I recall correctly, I've had more than a few unsuccessful burn attempts out of the 15-pack Memorex DVD+R DL discs I bought over 3 years ago.
*** EDIT: Follow-up question for anyone who might know
When the laser in the DVD alters it's power and focuses on the second-layer of data does it return to the inner part of the DVD to read the data or does it read it backwards by simply staying where it's at, the outer edges, and increasing its power? The way the image results of the scan disc are shown leads me to believe it does the latter but I am just guessing now.