"It (biopic) will be a very emotional film and equally funny like most of my films. I like to tell human interest stories and I think Sanjay's is one too," Hirani said here on the sidelines of the 17th Jio MAMI Mumbai Film Festival.
Speaking at the Movie Mela, a one-day film event held on Saturday, Hirani and co-writer Abhijat Joshi spoke on 'How to make a blockbuster'.
According to Hirani narrating someone's life on the silver screen is not a cake walk.
"It's really difficult to the tell the whole life of a person in less than three hours," he said, adding that it took hours of meeting with the "Munna Bhai M.B.B.S." star to finalize the first draft of the script.
"Abhijat and I met Sanjay for 25 days straight. Each day would give us an engaging story and it was so difficult to compress all of it into the final script," he said.
The "PK" maker also shared that during one of the several meetings they even spoke about Sanjay's drinking habit.
Bollywood heartthrob Ranbir Kapoor will be playing role of Sanjay Dutt in the biopic. Hirani will begin working on the biopic next year.
The son of late actors Sunil and Nargis Dutt - Sanjay, who rose to fame in showbiz with films like "Rocky", "Vaastav: The Reality", "Agneepath" and "Khalnayak", is in jail for illegal possession of arms during the 1993 Mumbai bomb blasts and riots.
