I'm not sure of the exact rules and regulations, I would imagine that you wouldn't get away with it on film as that would be distributed and viewed a number of times.
There is provision in the various copyright laws which all use of insubstantial parts of a work...
The Copyright Act (s.3) protects substantial parts of works as well as whole works.
"Since "substantial" is not defined in the Act, the quantity and importance of what is being copied must be evaluated. In deciding whether a part of a work is considered substantial, the whole work must be taken into account. A few sentences from a novel would probably be considered insubstantial but a single line from a poem might be essential to the work and be considered substantial."
http://library.concordia.ca/help/copyright/?gu id=substantial
Not sure if it's a written rule but I think with music on radio if it's a short bit of music less than 20 seconds or so that wouldn't incur a fee to be paid.