CHONGQING, China — A self-taught filmmaker who spent five months interviewing Tibetans about their hopes and frustrations living under Chinese rule is facing charges of state subversion after the footage was smuggled abroad and distributed on the Internet and at film festivals around the world.

The filmmaker, Dhondup Wangchen, who has been detained since March 2008, just weeks after deadly rioting broke out in Tibet, managed to sneak a letter out of jail last month saying that his trial had begun.

“There is no good news I can share with you,” he wrote in the letter, which was provided by a cousin in Switzerland. “It is unclear what the sentence will be.”

As President Obama prepares for his first trip to China next month, rights advocates are clamoring for his attention in hopes that he will raise the plight of individuals like Mr. Wangchen or broach such thorny topics as free speech, democracy and greater religious freedom.

With hundreds of lawyers, dissidents and journalists serving time in Chinese prisons, human rights organizations are busy lobbying the White House, members of Congress and the news media. In some ways, the pressure has only intensified since Mr. Obama won the Nobel Peace Prize, raising expectations for him to carry the torch of human rights.

Lhadon Tethong, executive director of Students for a Free Tibet, said Mr. Obama had an obligation to press Mr. Wangchen’s case and the cause of Tibetan autonomy in general, given his decision not to meet the Dalai Lama in Washington this month.

That move, which some viewed as a concession to China, angered critics already displeased with what they say was Secretary of State Hillary Rodham Clinton’s failure to press human rights during a visit to China in February.

“Beijing is emboldened by such moves,” Ms. Tethong said. “They see a weakness in the U.S. government, and they’re going to exploit it. This idea that you’ll gain more through some backroom secret strategy does not work.”

Until now, the case of Mr. Wangchen, 35, has received little attention abroad. Uneducated and plainspoken, he was an itinerant businessman until October 2007, when he bought a small video camera and began traveling the Tibetan plateau interviewing monks, yak herders and students about their lives.

Tsetring Gyaljong, a cousin who helped him make the documentary, said that Mr. Wangchen’s political awareness was sharpened nearly a decade ago, when he witnessed a demonstration in Lhasa, the Tibetan capital, that was quickly broken up by public security officers.

“He saw how it was dissolved in two or three minutes and how everyone was taken away,” said Mr. Gyaljong, speaking from Switzerland, where he has lived in exile since escaping from Tibet. “There were no pictures, no testimonies, and he felt like the world should know that Tibetans, despite the Chinese portrayals, are not a happy people.”

Out of 40 hours of footage and 108 interviews came “Leaving Fear Behind,” a 25-minute documentary that is an unadorned indictment of the Chinese government. Although given the choice to conceal their identities, most of his subjects spoke uncloaked and freely expressed their disdain for the Han Chinese migrants who are flooding the region and their love for the Dalai Lama, who has lived in exile since 1959.

In his own comments at the start of the film, Mr. Wangchen said the approach of the 2008 Olympics had compelled him to record the feelings of Tibetans, many of whom were less than enthusiastic about the decision to hold the Games in Beijing.

“We have no independence or freedom, so Tibetans have no reason to celebrate,” said one young woman standing by a road. “The Chinese have independence and freedom, so this is something they can celebrate.”

On March 10, 2008, Mr. Wangchen traveled to Xi’an in central China to hand over the tapes to Dechen Pemba, a British citizen who ferried them out of the country. That same day, a protest in Lhasa turned into a rampage that left at least 18 people dead, most of them Han Chinese.

On March 26, Mr. Wangchen and Golog Jigme, a Buddhist monk who helped him make the film, were arrested. Mr. Jigme was subsequently released.

“It really is a remarkable coincidence,” Ms. Pemba said.

Mr. Wangchen’s family hired a lawyer, but the authorities barred him from court last July, leaving Mr. Wangchen with a public defender.

Before he was forced to drop the case, the lawyer, Li Dunyong, said Mr. Wangchen had told him that he was tortured and that he had contracted hepatitis B while in custody. Since then, he has been held incommunicado. Officials at the Xining Intermediate Court in Qinghai Province, where Mr. Wangchen is being held, would not comment on his case.

Mr. Wangchen seemed acutely aware that his project could get him in trouble. Just before he began filming, he sent his wife and their four children to India, where they live along with his elderly parents.

In an interview from Dharamsala, where she works as a baker, Mr. Wangchen’s wife, Lhamo Tso, said she feared she might not see him again for many, many years.