He was the subject of the 2002 documentary Sweet Old Song .
Zwigoff 's interest in Armstrong eventually blossomed into a one - hour documentary , Louie Bluie , released in 1985 .
Armstrong was the subject of the 2002 documentary Sweet Old Song .
Zwigoff 's interest in Armstrong eventually blossomed into a one - hour documentary , Louie Bluie , released in 1985 .