No sound from assigned inputs on STR-DN1010

[FosterJa]

Hi,

I get sound through my STR-DN1010 fine if I select the HDMI inputs directly. I'd like to assign the BD remote button to an HDMI channel, when I do this I get picture fine but no sound? Input assign does not give me the option to select HDMI as an audio source. It does this no matter what source type (BD470 or my Humax Freeview box). What am I doing wrong?