Hello, and welcome to the forum.
As you likely know, DVDs have fixed resolution: 720x480 NTSC, 720x576 PAL. Yes, there are smaller sizes in the standard, but commercial DVDs will use this largest size.
Upscaling resolution, via hardware or via software, will likely not improve the image quality. If you look at resizing methods ... there's no section in any algorithm I know of that says, "add detail where none now exists. "
That doesn't necessarily mean you won't *perceive* improved quality, just that it won't actually be there. And you may want to perceive it, if you consider all the time and computing resource it will take to "make an HD video" out of standard DVD content.