Hobs wrote:so it would check and change it, say, every 400mb? this would explain why the spikes are evenly spaced
to this means the discs are 100% fine?
I don't remember how Pioneer's OPC works but with some drives, it is pretty evenly spaced. If you post a screenshot, I can give you a better idea.
Even with OPC, the writing quality can still be bad with some media. If you have a drive that can do write quality testing, you can check the error rates. Otherwise, just do a transfer rate test. If the graph is fairly smooth, there probably aren't any major issues.