Steven Spielberg says Robin Williams got him through the ''trauma'' of filming 'Schindler's List'.

The legendary director credits the 'Mrs. Doubtfire' star - who passed away in August 2014 - for helping him through the tough filming for the period drama, which documents the persecution of Jewish people by the Nazis.

Speaking at the Tribeca Film Festival's special 25th anniversary screening of the film, Steven revealed: ''Robin called me. Robin knew what I was going through. Once a week he called me on schedule. He knew exactly what time it was in Poland, what time it was in San Francisco ... and he would do 15 minutes of stand-up on the phone, and I would laugh hysterically because I had to release so much. The way Robin is on the telephone, he'd always hang up on the loudest, best laugh you'd give him. He'd never say goodbye, just hang up on the biggest laugh.''

Spielberg - who took the helm of the movie - picked up the Best Picture and Best Director at the Oscars the following year but didn't feel like he could celebrate their win because of its harrowing subject matter.

He shared: ''That night wasn't really a celebration at all. I don't feel this movie is a celebration. The subject matter and the impact the film had on all of us ... took sort of the celebration out of that. It was wonderful to win, but at the same time I just remember how moved I was when Branko Lustig, our co-producer, showed the world that he was in Auschwitz, too, and had numbers on his arms.''