The Walk The Line star announced plans to quit acting last year (09) and concentrate on making music. He grew a straggly beard and waded through a string of bizarre public appearances which led many to believe his career-change was little more than a practical joke.
Phoenix's brother-in-law Affleck subsequently announced he would be filming his friend's burgeoning hip-hop career for a documentary, which further fuelled rumours of an elaborate hoax - even though the Oscar-nominated actor insisted he was serious about becoming a rapper.
Affleck has now completed his film, titled I'm Still Here: The Lost Year of Joaquin Phoenix, and has previewed the footage in a bid to find a distributor. Reports suggest the picture features shocking scenes of the star apparently snorting cocaine, ordering call girls and having oral sex with a publicist - fuelling gossip the film is in fact a 'mockumentary'.
But Affleck is adamant the footage is real. He tells America's ABC News, "I wanted to explore what I thought would be an interesting period in his life. He said he didn't want to act anymore, he wanted to try doing music, and that, right there, says something's going to happen...
"I had no idea what exactly was going to happen and all that would unfold and every day I spent with him on this journey. It ended up being more and more fascinating, more and more things happened that were both in the public spectacle and a very private internal implosion that I got to witness. It made for this unbelievable, one-of-a-kind movie. You'll find out what was happening in his life in that period - what was going on before he went on (sic), what was going on afterwards."