For this year/model TV there is a firmware issue which Samsung has confirmed which is preventing the app from switching audio tracks on the client (which is required to do this and maintain DirectPlay). As a work around, when an audio track change is required, this is being confirmed on the server.  In most cases, no conversion is done to the audio or video tracks, the track order is just switched in a new container on the server and it is delivered via DirectStream instead of DirectPlay.