I have the same problem...
i do assign a single channel to view in to my string:
vlc -vvv /root/channels.conf XXXXXXX --sout '#transcode{vcodec=DIV3,vb=1024,scale=1,acodec=mp3,ab=192,channels=2}:std{access=mmsh,mux=asfh,dst=:8080}}' --ttl 12
??!?!?!?!??!!??!