I have the same problem....don no much about 20 bit....
I decoded SONY protocol with picBasic.....
My algo can detect 12bit , 15bit & 20bit codes searately....
12bit :7 bit (Command) + 5bit (Address) 15bit :7 bit (Command) + 8bit (Address) 20bit :7 bit (Command) + 5bit (Address) + 8bit(Unknown)