For all the broken-hearted Joaquin Phoenix fans, Casey Affleck has news that will cheer them up.

Affleck, Ben Affleck's younger brother will direct a documentary on close pal and brother-in-law Joaquin Bye! Good Phoenix.

The documentary will chronicle Phoenix's abrupt decision to leave his Oscar-nominated acting career for a musical one as a rapper.

Phoenix's first album will be produced by Sean Diddy Combs and he will make his first public performance this Friday at a Las Vegas club, which will officially kick off Affleck's shoot.

Affleck has directed a range of shorts for the Sundance Channel. He has also appeared in Gone Baby Gone, The Assassination of Jesse James by the Coward Robert Ford and the Ocean's Eleven series.

Joaquin Phoenix has been credited for his contribution behind production desk in the soundtrack album of Walk the Line. The theme song LP won a prize at 2005 Grammy Awards for Best Compilation Soundtrack Album for a Motion Picture, Television or Other Visual Media.