MySQL - how do I write this Query

MySQL - how do I write this Query

I am very new to SQL and I wanted some help in writing this SQL query.
I have a movie table like this:
Movie_id Actor_name Director_name
1 a AA
1 b AA
2 b BB
2 d BB
Now I want to print out all the pairs of actors and directors who have not
worked with each other - for eg in this case it will print out (a,BB) and
(d,AA)