All of the CDs in my old collection are fine, but I’ve had major problems with my DVD collection. I haven’t spent any time trying to figure it out, but it looks like some kind of unusual mold that I’ve never seen or some kind of deterioration of the substrate occurred inside some of the discs and they became completely unplayable. Attempts at cleaning completely failed to solve the problem. Is there really a major difference between DVD and CD manufacturing on a commercial level?