user: Question: When was the dvd release directed by Billy O'Brien?
Columns: ['#', 'Title', 'Maneater', 'Television Premiere', 'DVD release', 'Writer', 'Director', 'Producer']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Blood Monkey', 'Chimpanzees', 'January 27, 2007', 'November 6, 2007', 'George LaVoo Gary Dauberman', 'Robert Young', 'Charles Salmon']
SQL:

assistant: SELECT "DVD release" FROM "Table" WHERE "Director" = 'Billy O''Brien';