GRboss - 2007-02-04

I have downloaded and I'm trying to use it.
I cannot figure out what you expect as first argument.
I tried:
/mnt/cdrom
/mnt/cdrom/VIDEO_TS
/mnt/cdrom/VTS_01_0.IFO

The message i get all the time is:
No DVD structure found! at ./lxdvdshrink.pl line 33

Thank you in advance
Stefanos