5.1 Audio output on iPad

Hi,

I have an iPad 2 along with the official Apple Digital AV Adaptor. I have it connected to my AV receiver using one of its HDMI sockets. The video is fine (although it does not entirely fill the screen which is a totally different issue and I'm told this is normal). The main problem I have is that I cannot get 5.1 audio from my iPad. I have several other sources connected to my AV receiver all of which allow 5.1 audio, but when my iPad is connected I can only receive a stereo signal. I have used AV Player HD as well as films off iTunes but I just can't get any surround sound. Can anyone please give me some suggestions?

Many thanks,

stewyd