avoid intentional bad blocks
Report from Don Mahurin:
I modified dvdbackup to avoid unused blocks according to pgc traversal.
For the source of the change and for details see:
It uses libdvdvm from libdvdnav. While libdvdvm is not exactly prepared to function as a stand alone library, it is sufficient for most cases.
I don't know the specific details of ARccOS, but this modification can avoid such intentional bad sectors.
By default, the behavior does not change.
Using '-r u' will calculate and skip unused blocks.