Video input switcher for DVD and other sources

I own several pieces of video, including two VCRs, one DVD player and soon another DVD player. I have noticed that DVD players often show a very strange distortion, the picturing distording, going dark/light, which I suspect of being Macrovision or some sort of protective device connected to another input and then, from this other device(typically a VCR) to a direct video input. Any help with recommendations will be greatly appreciated.