(new) codec to play stereo with HDMI connection

It would be a lot easier if you said what would not play.  I am guessing its DTS-HD.

Read post 2 in this thread.

http://community.wd.com/t5/WD-TV-Play-Discussions/WD-solves-bitstream-of-DTS-HDMA-on-WD-TV-Play/td-p/543176