What is Direct Data Extraction from a non-commercial DVD?
DVDs that play in DVD Players have a coded file that cannot simply be opened for editing. It must be extracted and changed to a file type usable by editing software. Only non-commercial DVDs can have data extracted.
Make sure you are extracting data from a non-commercial DVD: it should be blueish-purple on the bottom. Extracting anything more than very short clips from a commercial DVD is illegal as they are protected by copyright laws.
NOTE: if you are making an exact duplicate of a non-commercial DVD, with no changes at all, see the Duplicating a Non-commercial DVD guide.