2-channel Linear PCM: 2-channel, 32 kHz – 192 kHz, 16/20/24 bit
Multi-channel Linear PCM : 7.1-channel, 32 kHz – 192 kHz, 16/20/24 bit
Bitstream: Dolby Digital / DTS / Dolby Atmos / Dolby TrueHD / Dolby Digital Plus / DTS:X / DTS-HD Master Audio / DTS-HD High Resolution Audio / DTS Express
I'd imagine whatever source is getting AAC is going to need to decode it and send as linear PCM, which should be fine.