A total of 15 films, most of them European, will compete for the Golden Conch award at the 56th edition of the fete - a gathering proud of its product, even if it lacks the crowds of the film festivals in Venice and Cannes.
The chairman of the jury is American director Jonathan Demme, known for such films as "The Silence of the Lambs" and "Philadelphia."
Streep, a two-time Oscar winner, and Spanish actor Antonio Banderas will receive lifetime achievement awards, while Allen and Javier Bardem have come to plug the new Allen movie, "Vicky Cristina Barcelona."
Festival director Mikel Olaciregui said San Sebastian feels somewhat of a rivalry with the Venice Film Festival, in part because they are close together on the calendar, but does not seek only to draw big crowds of fans as do the Italian event or the Cannes Film Festival.
"The festival is not for everyday citizens, but rather for the industry and the media. The public is important, but the ones who validate the event are the performers themselves," Olaciregui said in an interview.
He said that since movie attendance is down these days, the nine-day festival reflects this by catering mainly to insiders.
"The festival is adapting to the changes and I think our formula is perfectly valid," he said.
The festival features the world opening of "The Boy in the Striped Pyjamas," based on the book by Irish novelist John Boyne about the Holocaust as seen through the eyes of a child. The film is being presented outside the main competition.
John Malkovich will be in San Sebastian to represent the latest movie by the Cohen brothers, "Burn After Reading."
"It is clear that a lot of the movies come with their teams, and that is always an important ingredient," Olaciregui said.
Korean director Kim Ki-duk will present a film called "Dream," about a person whose nightmares become reality the very next morning.
Most of the films will be screened at the city's elegant Palacio Kursaal convention center. The festival's traditional 100-meter red carpet will switch to fuchsia, the shade chosen to represent this year's event.