DGMPGDec is an MPEG decoder suite with a Frame Server, based on DVD2AVI and MPEG2Dec. It is used to decode MPEG1 or MPEG2 streams from such sources as DVD VOBs, captured transport streams, *.mpg/*.m2v/*.pva files, etc. Most commonly it's used when decoding VOBs from DVDs.
You will most probably need theAvisynth as well and alsoVirtualDub will be a great for viewing the decoded video.