Look up "DVD ripping". You don't really need to "capture"
the video as you can access the VOB, etc. files on a DVD
video disk directly from your computer. Then you need to
convert them to a file type that you can use for whatever
further processing (editing etc.?) you want to do.
Note that commercial DVDs are encrypted as the owners
of the content don't want you to make unauthorized copies.
OTOH, the ones from (for example) mini-DVD camcorders
are not encrypted.