How to base64 encode /dev/random or /dev/urandom?

cat /dev/urandom is always a fun way to create scrolling characters on your display, but produces too many non-printable characters.

Is there an easy way to encode it on the command-line in such a way that all of its output are readable characters, base64 or uuencode for example.

Note that I prefer solutions that require no additional files to be created.