What exactly does the -binary switch do when creating s/mime output?

[Bart W Jenkins]

Given:

openssl smime -binary -sign -passin "pass:SomePassword" -signer cert.pem -inkey 
key.pem -in Document.txt -out Document.txt.sig -outform DER

What *exactly* is done to the s/mime text to create a "binary" file?

I'm trying to do the equivalent in Java using BouncyCastle and just can't get 
from a text based PEM file to a binary/DER file.

(and no, issuing a call to 
SMIMESignedGenerator.setContentTransferEncoding("binary")) does NOT do the 
equivalent.

Any help would be appreciated.

Bart