Steven Spielberg takes the stage at the “Ready Player One” premiere at South by Southwest. (Getty Images)

AUSTIN — Just as a climactic battle scene was about to begin during the world-premiere screening of Steven Spielberg’s “Ready Player One” at the South by Southwest festival on Sunday night, disaster struck: The sound entirely cut out.

The glitch had the potential to turn a landmark gathering with a Hollywood icon into a high-profile embarrassment. But rather than boo, the audience did the unexpected: They started cheering and supplying their own dialogue and sound effects. The mishap turned the room into “The Room.”

“This is perhaps the greatest anxiety attack I’ve ever had,” Spielberg said as he took the stage after the screening, to roaring applause.

He has reason to be concerned. “Ready Player One” puts a lot on the line from a business standpoint, as one of the most lucrative directors in American history ($10 billion-plus in adjusted domestic box office) returns to terrain that helped earn him that status. Spielberg has spent much of this phase of his career making historical dramas such as “The Post” and “Bridge of Spies.” “Ready Player One,” which Warner Bros. opens March 29, brings him back to the childlike adventures of his earlier chapter — and tests whether he can still draw a crowd in doing so.

The stakes grow even higher. “Ready” is about a future in which virtual reality dominates; it and the 2011 Ernest Cline bestseller on which it’s based imagine an Earth on which people have given up on their real-life problems to escape to VR.

In the present, in fact, VR is desperately trying to establish a foothold, with a hodgepodge of headsets and platforms all struggling to get attention and a slate of rapidly growing content in search of a business model. While one movie certainly won’t make or break an industry, it will provide the widest advertisement yet for the medium, and its popularity could determine how and if the technology is adopted.

“We made this with a lot of ambition,” Spielberg told the audience before the screening, referring to the general undertaking.

The SXSW screening was meant to get that off on the right foot. The film festival, which mixes the commercial and indie, has a history of launching spring/summer studio hits — recent go-rounds include “Baby Driver” and “Furious 7” — often at secret screenings. Audience members did not know what they were buying admission to — a ticket merely said “TBA” — with “Ready Player One” identified as the mystery title one day before the screening.

To introduce the film, SXSW Director of Film Janet Pierson took the stage with a number of people in spacesuits and VR headsets and said she didn’t know whether to feel “protected or terrified.” Then she brought out Spielberg — a first-time SXSW attendee and a rare presence at a fan event — to a raucous crowd of 1,300 wearing T-shirts of Spielberg movies. Spielberg got especially loud cheers when he told the audience he was a gamer, cementing his status as a godfather of modern fanboy culture.

To head to the future, Spielberg mines the past. Although “Ready Player One” is set in a dystopian 2045, much of it looks back at and pays homage to pop culture, particularly the 1980s genre romps of contemporaries such as Robert Zemeckis and Stanley Kubrick. “Ready Player One” may be newsworthy because it’s about the defining storyteller of the present chronicling a medium of the coming age. But much of the film is designed as a nostalgia play about the movies with which many of its audience members grew up. (To say more about what these are would be to violate the filmmakers’ request against spoilers of the film’s references.)

“This is also a movie that has so many cultural windows,” Spielberg said. And although he urged people to look out the “side windows of reference,” he also advised that if you do that too much “you may miss the story … out the front windshield.”

He didn’t address the VR implications. But at this gathering, with a tech conference running concurrent with the film festival and debating all manner of future media, he may not have needed to. A separate VR installation that takes users inside the world of “Ready Player One” has been playing at a nearby venue.

The audience’s vocal enthusiasms throughout the screening, as well as the massive lines to get in, suggested Spielberg may have a hit on his hands. At the same time, the self-selected nature of the group — from the questions and signs, many appeared to be hardcore fans of the book — suggested that it would be wise not to make too many inferences.

Meanwhile, another recent Spielberg attempt to return to “E.T.” glory, the children’s adventure “The BFG,” demonstrates that this could be a rough proposition: The movie grossed $183 million worldwide two years ago and performed domestically well below “The Post,” “Bridge of Spies” and “Lincoln.”

Spielberg was aware of how he was breaking away from recent work. “This is not a film we’ve made. This is a movie,” he told the audience before the screening. Then he drew another distinction.

“When I make a movie [like ‘Bridge of Spies’], I direct from behind the camera,” he said. “But when I direct a film like this, I’m in the seat right next to you. It means I make it for you. And your reaction is everything.”