i) mount the disk as UDF
ii) copy encrypted movie
iii) dump volume id using specialized software, such as dumpvid (not available on ps3 linux) or aacskeys (again, not on ps3 linux).
iv) search google for MKB of the movie
v) provide dumphd with these volume id & MKB
after all these steps you will obtain unencrypted film.
there is also possibility that your film is BD+-infected. in this case try the last version of dumphd (it may work or not).
it is impossible to "mount a bluray movie". you can only do the following: