i referred to the third parameter in the call
attributes - a bit array specifying any optional attributes describing this value. These attributes are a hint to the about the value's characteristics and some or all may be ignored by this method due to platform restrictions. Attributes that are invalid or not applicable are also ignored.
public void setBinary(int field,
As for base64 encoding that is only way how it accepts binary -- so you do it correctly
Have you checked this "How to add a video clip to a contact in Java ME"