I have been able to use AVFoundation to enable my AVAudioSession to use the max number of outputs available of 8 (7.1 audio).
It will then show on my receiver the PCM 3/4/.1 output, but is still not getting any sound on the rear speakers since VLC is outputting 2.0 audio.
Reading around the forums I think VLCKit is downsampling all audio to 2.0.
Is there a way to output the encoded multichannel audio to the apple tv 4?
Thanks!