Casey Affleck directing documentary on Joaquin Phoenix

Actors Casey Affleck (L) and Joaquin Phoenix pose for photographers as they arrive for a staged reading of ''The World of Nick Adams,'' at Davies Symphony Hall in San Francisco, California October 27, 2008

LOS ANGELES (Hollywood Reporter) - Casey Affleck will get behind a camera lens to track the musical career of fellow actor Joaquin Phoenix, who portrayed Johnny Cash in "Walk the Line."

Affleck is directing a documentary feature on his friend and brother-in-law Phoenix, who in the fall announced his retirement from the thespian business in order to focus on a music career.

Phoenix is embarking on a new path as a rapper, with an album to be produced by Sean Combs. He is scheduled to make his first public performance Friday at a Las Vegas club, which will officially kick off Affleck's shoot.

Affleck is known for his work in front of the camera with movies like "Gone Baby Gone," "The Assassination of Jesse James by the Coward Robert Ford" and the "Ocean's Eleven" series. He directed a series of shorts for Sundance Channel in the late 1990s. He is married to Summer Phoenix, sister of his new film subject.

Reuters/Hollywood Reporter