How can I find out if a read error on a optical disk is due to corrupted file system or physical damage?

I have a video DVD that I'm trying to extract but that is very hard to read (takes several days and not finished). **Is there any way to find out if the problem is a physical damage of the surface of the optical disc, or some corruption in the file system?** I'm asking because the disc has no visible physical damages, and I want to take proper action in the continued tries to extract it data. E g need to know if a polishing of the surface of the disc might help.