I have written a tvOS app which receives AAC 5.1 audio stream over the network and I am using AudioToolbox to decode (mFormatID = kAudioFormatMPEGAAC) to 5.1 channels. But I only hear 2 channels (Stereo) outputs on my 5.1 surround system (which is connected to the TV using an Audio Optical cable). I am not sure why PCM multi-channel is not outputting from AppleTV. Am I missing anything? Decoder parameters:     AudioStreamBasicDescription asbd = {0};     asbd.mFormatID = kAudioFormatMPEG4AAC;     asbd.mFormatFlags = kMPEG4Object_AAC_Main;     asbd.mSampleRate = samplingRate;     asbd.mBitsPerChannel = 0;     asbd.mBytesPerPacket = 0;     asbd.mFramesPerPacket = 1024;     asbd.mBytesPerFrame = 0;。     asbd.mChannelsPerFrame = numOfChannels; // 6     asbd.mBitsPerChannel = 0;     asbd.mReserved = 0; Additionally, when I query the total number of audio channels on AppleTV, it is always 2 (even though it is connected to the surround system). This is just for me to know audio capabilities. AVAudioSession.sharedInstance().currentRoute.outputs[0].channels