Best way to backup a Video DVD

Hi can anyone tell me the best way (in terms of best quality) to backup a video dvd? should i use dvd decryper 1st then dvd shrink it or shrink 1st then decrype?

You will always need to decrypt either before or during. DVD Decrypter removes protections while ripping leaving you with unprotected files ready to transcode. Any DVD works in the background making the disc seem unprotected allowing a transcoding application to do its work. Whether you use DVD Decrypter to rip, or run Any DVD in the background it will have no bearing on quality. As far as the best transcoding application look here:

if you main concern is quality, you’ll want to use DVD Rebuilder along with CCE Basic (Cinema Craft Encoder).