ANSWER:

it seems to be impossible, cause multiparted rar archive contents metadata about all the files inside all the parts of an archive.

and even if you tries to unrar a single file (movie) not from the beginning, it will fail, cause file contains metadata of itself in the beginning, and even video stream is a container with a special format ant it’s headers and so on… (mp4, mkv…).

Even if you’ll try to chop the file, it’s a bad idea. Just find a full source of the file you want ))

by remort from http://unix.stackexchange.com/questions/37190