Jimi Bani stars in a new film about Eddie Mabo and directed by Rachel Perkins. photo taken on the 8th of may 2012.Photo: Jacky Ghossein

''I knew what it meant to struggle'' … Mabo director Rachel Perkins, with the film's star Jimi Bani, says the achievement of Eddie Mabo has not been fully appreciated by the wider population. Photo: Jacky Ghossein

THE 20th anniversary of the historic Mabo decision will be commemorated with an emotional screening at the Sydney Film Festival next month.

A film on the life of Eddie Mabo, whose campaign for indigenous land rights led the High Court to overturn the doctrine - terra nullius - that Australia was unoccupied before European settlement, will have its world premiere at the State Theatre.

Mabo's widow, Bonita, and other identities from the landmark case are expected to be in the audience.

Shows Jimi Bani as Eddie Mabo and Deborah Mailman as his wife Bonita in the film Mabo, part of the 2012 Sydney Film Festival. Pic supplied.mabo large image.jpg

Great love ... Jimi Bani and Deborah Mailman play Eddie and Bonita Mabo in Mabo, a film Perkins believes will be cathartic for the late activist's family.

The director Rachel Perkins, best known for the hit musical Bran Nue Dae and the TV series First Australians, describes Mabo as a classic David v Goliath story. It tells the story of his life from growing up on Murray Island in the Torres Strait to the court decision five months after his death in 1992.

''A man for all intents and purposes from nowhere takes on the might of the country and succeeds because of this injustice that he had to right,'' Perkins said. ''I'd grown up in an activist family so I knew what it meant to sacrifice for the struggle.''

Perkins believes the screening will be cathartic for the Mabo family, who were closely involved in making the film but still believe Eddie's achievement has not been fully appreciated by the wider population.

''There is a Mabo day but it's only celebrated by indigenous people,'' she said.

''There just hasn't really been the recognition.''

Jimi Bani (The Straits) and Deborah Mailman (Offspring, The Secret Life Of Us) play Eddie and Bonita in a cast that also includes Colin Friels, Miranda Otto, Ewen Leslie and Rob Carlton.

In an innovative collaboration between the festival and Blackfella Films, Mabo will have a gala premiere on June 7 - three days before its ABC TV screening.

''Historically, the story is so important,'' said the festival's director, Nashen Moodley, who will announce his first program in Sydney today.

''What the film does extremely well is convey the importance of the case and the key issues while looking at the man and his life,'' he said. ''And the performances are just phenomenal.''

Bani described Mabo as a strong family man who shared a great love with Bonita.

''It's a proud moment, especially being a Torres Strait Islander, to tell a story about someone who's from where I'm from,'' he said. ''He's an icon.''