Const
This value is the index field of the OutputInfoStruct from the OutputList attribute (from the AudioOutput cluster) and indicates which audio output the Audio Track should be played on. This field is absent for Text Tracks and only present for Audio Tracks. A value of null shall indicate that the server can choose the audio output(s) to play the Audio Track on.
This field shall indicate the Audio Track to activate.
Input to the MediaPlayback activateAudioTrack command