Festivals evolve. That’s a fact I’ve realized watching South by Southwest grow up over the course of nearly a dozen years. In that span, SXSW has gone from a locally focused regional fest to one of North America’s most important sprocket operas, and the transformation couldn’t have been clearer than from where I stood as a juror at the 2010 edition.

When I first attended the fest in 1998, out-of-towners flew in because Austin was laid-back and served great BBQ, not to discover the next Lena Dunham or Gareth Edwards. I was an undergrad at the U. of Texas then, and “South by” (as we called it) was conveniently in my backyard, but nowhere near the level of Sundance or Telluride.

The films to get excited about that year? Richard Linklater (whose “Slacker” defines ’90s-era Austin) premiered lame period effort “The Newton Boys,” while Tim McCanlies unveiled his sweet, small-town directorial debut, “Dancer, Texas Pop. 81,” about four teens itching for some big-city excitement.

There were plenty more Texas-based entries, most of them lousy, and a handful of decent docs, but overall, not much to justify flying in from Gotham or Los Angeles to attend.

This year, fest head Janet Pierson expects buyers from Fox Searchlight, Lionsgate and Relativity, in addition to such repeat shoppers as IFC, which acquired “Cold Weather” and “Tiny Furniture” (the gem that earned our jury’s top prize), and Magnolia, whose Magnet division picked up “Monsters.”

In 2001, after moving to New York, I convinced Entertainment Weekly to let me cover the fest. (I wasn’t the only journalist moving up the ladder, either: Former Dallas critic Elvis Mitchell had joined the Gray Lady and was now reporting on SXSW for the New York Times.) But the fest itself hadn’t really advanced.

An outgrowth of Austin’s world-famous music confab, SXSW Film was still primarily a local-interest event. Unspooling two months after Sundance, SXSW has always wrestled with its identity in relation to that fest. Every indie filmmaker in America wants his pic to premiere in Park City, with all the press and industry attention that entails, leaving SXSW (and other U.S. fests) competing for the leftovers.

Attending off and on over the next decade, I saw the festival slowly change. A young, energetic movie buff named Matt Dentler, who had edited the Daily Texan entertainment section alongside me in school, became SXSW’s head of programming. Rather than chasing what Sundance rejected, Dentler turned his attention elsewhere. With a populist taste that wasn’t put off by lack of polish, Dentler embraced films like Joe Swanberg’s scrappy microbudget “Kissing on the Mouth” and invited them to screen in Austin.

The 2005 lineup was loaded with such DIY discoveries. Dentler was on to an emerging strain of talent that Sundance had more or less ignored, thanks in part to the exploding number of ultra-low-budget features being made. By introducing a number of these filmmakers to one another, he unwittingly sparked the so-called “Mumblecore” movement.

But the real watershed year for SXSW was 2007, when Swanberg’s “Hannah Takes the Stairs” (a film that cemented the Mumblecore connections made two years earlier in Austin) and Judd Apatow’s “Knocked Up” played the fest — two seemingly opposite films that each use comedy in pursuit of a certain truth about twentysomething relationships.

Dentler had seen an early cut of “Knocked Up” and lobbied Universal to debut the movie at SXSW. The Austin audience went crazy. Made up largely of college kids and young film fans, the SXSW crowd tends to be open-minded and enthusiastic, closer in spirit to the Comic-Con set than the more jaded auds that jam more industry-centric fests.

“Knocked Up” helped open the door to bigger studio premieres, establishing SXSW as more than just a word-of-mouth stop on the regional publicity train (the function most second-tier fests serve in Hollywood’s eyes). Last year, “Kick Ass” played to wild applause; films such as “The Beaver,” “Bridesmaids” and “Super” hope to capture that excitement this year.

In 2008, Dentler pulled his own Dancer, Texas, trading in his big-fish-small-pond status for a Gotham-based gig with Cinetic. Pierson (who had been attending at least as far back as 1998 with husband/producer’s rep John Pierson) took over, extending the fest’s status as a place to make important alt-Sundance discoveries, while adding new initiatives, like Tim League’s genre-focused “Fantastic Fest @ Midnight” selections.

“When Matt was handing the reins to me, he said, ‘SXSW is lucky, because it’s not really defined yet,’?” Pierson recalls. Backed by a small staff of programmers — tiny by comparison with Tribeca and other deep-pocketed fests — Pierson hand-picks the lineup according to gut feelings, rather than clear-cut artistic considerations, which makes for an idiosyncratic mix backed up by real passion.

“We’re looking for unique voices,” she says. “There are people who make ‘two people talking in a room’ films that they think are perfect for us, and I say, ‘No, there’s nothing new about that.’ And then there are all these films I accepted that are exactly that, but for some reason, they transcend all the other ones in terms of their intelligence, the performances or the emotional resonance.”

Predictably heavy on music docs (including closing-night Willie Nelson portrait “The King of Luck,” directed by Billy Bob Thornton), the premiere-heavy lineup also features favorites from Toronto (such as “In a Better World” and “Beginners”) and Sundance (Park City sleeper “Sound of My Voice” could be a real SXSW breakout).

Without a proper market, SXSW will never reach the level of a Sundance or Toronto, though discoveries such as “Mutual Appreciation” and “Marwencol” wouldn’t matter if the buyers didn’t take the festival seriously — and they do.

“It used to be that only the junior acquisitions people were sent to SXSW, but what happened over time was that all those junior acquisitions people became senior acquisitions people,” Dentler observes. “Whereas they couldn’t buy a film when they first attended, now they had the authority to buy something on the spot.”

SXSW is adapting to the added attention with mixed results. Attendance for film and interactive events now outnumbers the music component, resulting in a massive hotel crunch. True to its egalitarian origins, SXSW does not offer special treatment for press and industry, which means buyers and critics must line up early or risk being shut out of popular screenings.

But crowding is hardly unique at a major film festival. The world’s best BBQ, on the other hand, you can only find in Austin.

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