apSetFunc(id, AP_Set_Input , 0, 0, '&iFilename' , 0) &&input file. apSetFunc(id, AP_Set_Output, 0, 0, '&oFilename', 0) &&output format and file.This probably should be:
apSetFunc(id, AP_Set_Input , 0, 0, iFilename , 0) &&input file. apSetFunc(id, AP_Set_Output, 0, 0, oFilename, 0) &&output format and file.You were passing a string value instead of the variable value.