"I've never read a novel so I don't know why I'm here," US film director David Petrarca joked at Perth's Writers Festival at the weekend.

But the man who has directed episodes of Game of Thrones, Hung and True Blood had a lot to say as a member of a panel discussing the rise of premium cable TV channels and its challenge to novels as a format of storytelling.

The filmmaker said while novels were presented as a finished product, it was not known how long a television show might last, and so, it was constantly evolving.

Panel mediator Rosemary Neill noted Game of Thrones was the most pirated show of 2012 and that 10 per cent of the downloads came from Australia.