The film provides a record of a day in the life of India - midnight to midnight - to bring alive a nation overflowing with human stories of both beauty and pain.
"India in a Day", powered by Google and executive produced by Ridley Scott and Anurag Kashyap, is an 86-minute documentary composed of videos shot on a single day - October 10, 2015 - by thousands of people across the country.
"The story of evolving India is the story of the evolving world," says Mehta, who was born and raised in Canada but is now based in London.
Mehta has shot two features in India - "Amal" (2007) and "Siddharth" (2013) - and is currently filming a television series on Delhi Police. He has spent enough time in the country to grasp its social and cultural nuances.
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"We (Mehta and film editor Beverley Mills) spent three months just watching the videos before embarking on the process of cutting," he says.
The first indication that the Toronto audience is getting
the film, says Mehta, is that they chuckle at the right points.
"Like when, in the opening, a young man talks about five families sharing a single Wi-Fi router or when a boy in a car says his age is 25 and his sister in the backseat says 26."
"Within ten seconds," says Mehta, "you realise that this is real, that there is no artifice in what is on the screen. So people get caught up in the momentum of the film."
As one contributor says in the film, it might seem insignificant at present but in 50 to 60 years from now every bit of "India in a Day" will acquire importance.
Asked if he had to leave out any footage that he really loved, Mehta says: "There were lots of beautiful videos that did not get into the film, but nothing that we did not use is better than what is in the final cut."
"The wealthy are perfectly fine with the status quo and are not looking to change anything. The rest of the country has a wide range of issues to highlight and has a stake in how the future pans out," he says.