I have tried playing VCDs and DVDs but I always get this type of error:
File reading failed:
VLC could not read the file (Input/output error).
You probably just miss some libraries for reading DVD. Ensure you have libdvdcss2, libdvdread4 and libdvdnav4 installed:
sudo apt-get install ubuntu-restricted-extras libdvdread4 libdvdnav4
Then run:
sudo /usr/share/doc/libdvdread4/install-css.sh
Reference: https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs
vlc -vvv /media/[PATH_TO_MAIN_VOB_FILE]
from terminal and post the result