Hot Docs filmmaker Pawel Kloc bristles at using the word documentary to describe his gritty look at Cambodian street life, preferring instead to label his cinematic ambitions in "Phnom Penh Lullaby" as "epic."

And although writer/director Oliver Kochta-Kalleinen turned his lens on real-life mental health patients for the portrait "People in White," he likes to think of the endeavour as a "participatory art project."

Meanwhile, Boris Gerrets' film, "People I Could Have Been And Maybe Am," is touted as "docu-fiction" in film festival material, but Gerrets himself finds it difficult to categorize what he's made.

"These terms are very, very difficult -- no one knows exactly what it is," Gerrets admits as he gears up for the Hot Docs film festival, which kicks off Thursday.

Programming director Sean Farnel says several films bound for the annual non-fiction showcase push the definition of documentary by incorporating taboo elements including actors and scripts, creating entirely new forms that he expects will both invigorate and challenge audiences.

"What you're seeing is an incredible blurring of the lines between documentary and fiction," says Farnel.

"We've been seeing that over the last few years now and even traditional documentaries are becoming so seamlessly good at telling stories and feeling like fiction films. Those walls are coming right down."

An avid film fan, Farnel admits to wrestling with some ethical questions before allowing such avant garde works into the festival, but notes their unorthodox approach nevertheless strives towards a universal documentary ideal -- the search for authenticity.

Farnel notes that Kloc's fly-on-the-wall "Phnom Penh Lullaby," about an Israeli man, Ilan, struggling to build a life with his Cambodian girlfriend, Saran, had him wondering what was real and what was not. It features no obvious interviews and a surprise emotional wallop at the end.

"I was watching this thing thinking, 'Well this feels like a small character-based art film, in a way. And I was thinking well, that's fine but then some serious things happen so it's like, 'Well, how did this come to be? And if this is faked I might have a problem with it.' "

Kloc insists nothing was staged in his sometimes disturbing film --which includes footage of a street hustler haggling over the price of a child -- but admits to changing the chronology of events to fit a larger narrative, suggesting conversation topics to his stars and getting them to repeat things for the camera that were previously said.

From the very beginning, he strove to make something grander than a traditional documentary.

"I said to myself, 'This is my first feature length film and it's my first documentary but I will make it as I was making a feature film,"' Pawel says by phone from Poland.

"Because for me this was the opportunity for his story -- for Ilan's life, for Saran's life, for those children -- to make it more universal and to give it some space that is not there if you just ask them to sit and talk and film them like you would do a TV approach."

"We have to try to do it almost in a kind of epic way."

The Hot Docs festival (formally known as The Canadian International Documentary Festival) kicks off Thursday with a much more mainstream opener -- Morgan Spurlock's sponsorship spoof, "POM Wonderful Presents: The Greatest Movie Ever Sold," and features a slew of celebrity-driven titles that Farnel says he expects will appeal to a broad audience.

They include the comic road movie "Conan O'Brien Can't Stop"; actor Michael Rapaport's hip hop directorial debut, "Beats, Rhymes & Life: The Travels Of A Tribe Called Quest"; a look at Chaz (formerly Chastity) Bono's journey through gender reassignment in "Becoming Chaz"; the "Sesame Street" behind-the-scenes peek, "Being Elmo: A Puppeteer's Journey"; and the performer's portrait, "Carol Channing: Larger Than Life."

But many other films in this year's slate are much more difficult to define. Farnel points to genre-pushing fare including the sci-fi tinged "Empire North," the embed war film "Hell and Back Again," the performance art film "Marija's Own," and the actor-driven, "The Future Is Now."

Each of these films challenge the idea of what constitutes documentary, while reminding viewers to question for themselves what's up on the screen.

"I'm starting to think of it more as this notion of the reality arts," Farnel says of the genre.

"After all, documentary has always been heavily constructed -- you look back to 'Nanook of the North' and the earliest films -- they were heavily constructed."

"The fact is, as soon as you turn on a camera you're manipulating real events in some way -- you're choosing what to shoot, when to shoot, so I think filmmakers are just coming up with new strategies to work in this way."

Kochta-Kalleinen, co-writer and co-director of "People in White," says his scripted documentary is based on hours of interviews conducted with real-life patients talking about their doctors. When it came time to shoot, four refused to go on camera, sending him on a casting call to find actors to give voice to their story.

"I think (audiences) will understand that actually this adds another layer," he says by phone from Helsinki. "It gives the film a strange tension."

Gerrets, whose cellphone-shot film, "People I Could have Been" weaves together the stories of three people in London, says he had no qualms about changing the chronology and condensing their stories to fit a larger goal.

"I'm not necessarily convinced that making a difference between fiction and documentary is very useful because in both cases we're talking about film and the requirements of storytelling," he says.

"I'm responsible for my subjects, they gave me a lot of trust, I'm responsible for not breaching that trust. But it's a very slippery sliding scale and it's up to me to decide what is too far and what is OK. It meant I would also show the people I was working with the finished product."

Farnel says the genre-pushing works generally come from younger filmmakers reluctant to be pigeon-holed as documentarians rather than storytellers. And the choices they make are often not necessarily commercially driven.

"These are tougher, more difficult works, frankly," says Farnel, who attributes the movement in part to an explosion of reality-based television.

"But I think there's been other examples, like 'Exit Through the Gift Shop,' for example and 'Catfish' from the past year that have shown how a certain kind of blurring of the lines can be very engaging and accessible."

Still, Farnel wonders whether it's fair to expect audiences to distinguish between real and scripted material in something that purposefully blurs the line.

"This is where I wonder about our role as kind of being filters," he says. "I think audiences certainly don't want to be lied to, so I think there's got to be some transparency in the filmmaking."

Writer/director Jerzy Sladkowski, who is bringing "Vodka Factory" to the festival, says he's more concerned with capturing emotion than anything else.

"I don't feel any obligation to deliver the truth but I feel obligation to be honest with myself and with the audience and with my heroes, of course," says Sladkowski, whose film follows a 22-year-old single mother who works in a vodka factory in a backwoods Russian town and dreams of becoming an actress in Moscow.

Sladkowski derides most traditional documentarians as self-serving, particularly disaster films that capture the devastation of a war or environmental catastrophe.

"A certain number of filmmakers, they love to feel sorry about the people -- they run with the hand cameras among unhappy people and then feel sorry about them. This is not filmmaking to me," he says.

"For every five filmmakers who are saving the world you have 15 who don't but who try to use the cover that 'I'm saving the world, I'm trying to make people happy' but he's trying to actually to save himself from troubles because he's too oriented on himself. It's self-therapy, it's not filmmaking."

The Canadian International Documentary Festival launches Thursday in Toronto.