Sanjay Dutt's biopic, which will be directed by Rajkumar Hirani, is all set go on floors on January 14. Ranbir Kapoor, who will be slipping into Sanju Baba's shoes, has already begun with preparations for his role. The shooting will commence in Mumbai, covering the crucial scenes first, followed by schedules in other parts of the country. The filmmaker, last year, had captured Dutt's exit from Yerwada Jail in Pune, with the thought of including it in the biopic. The 'Rockstar' actor and the 'PK' director have already started with the pre-production and were spotted in the latter's office many a times, reading the script. However, the film is still looking for its perfect title. The untitled biopic seems very intriguing, as it will be the first biopic, made on a Bollywood star. The film is set to have a Christmas release.