Why complains transcode about a missing VIDEO_TS.IFO file?
That’s Ok. The corresponding messages are printed by libdvdread if you transcode files on harddisk (which is the default case with dvd::rip). You see something like this: libdvdread: Couldn’t find device name. libdvdread: Can’t open file VIDEO_TS.IFO. but these are only (very confusing) warning messages of libdvdread, which naturally can’t find any DVD device or VIDEO_TS.IFO file if started from a directory with only VOB files in it. Just ignore these messages, and please don’t report this as a bug.