YouTube says its paid the music industry $1bn (£794m) in royalties this year. But that's still not enough according to record companies. They say YouTube does not pay a fair rate to musicians and record labels, and is slow to police illegal and pirated material uploaded by its users. Nine of the 10 most-watched clips on YouTube are music videos, topped by Psy's "Gangnam Style." James Brydges has been finding out more from music law expert Elliot Chalmers, of Music Law Advice.