I have a BT home hub 3 plus infinity. Casting from a chrome browser on a windows 8.1 laptop works fine.
From my phone (A Nexus 5) the picture works but no sound comes through the home cinema amp.
The sound does come through the TV speakers if a turn them up and mute the Amp. Can't be bothered to tweak my home cinema connections to get the phone to work so am happy with it as it is