The encode/decode tool (from the LDAP menu) gives "aGVydsOp" for BASE-64 encoding from the ISO-8859-1 string "hervé".
while the website http://www.base64decode.org/ gives the same results from the same string but in UTF-8.
Also UTF-8 BASE 64 encoding of Apache Directory Studio match with ISO-8859-1 BASE64 encoding of the previous website.
The result from my own java code match with that website.
I think there is a confusion between ISO-8859-1 and UTF-8 in the encode/decode LDAP gui tool of Apache Directory Studio.
It will be easy to fix.