[toast0]

> it's not that hard to run an audio cable back from the TV to an audio receiver and you'll be hiding the cable anyway so it matters not the slightest what it looks like.

That's fine for regular ARC which is basically the same capability as spdif, ATSC audio and DVD audio. But there's no consumer audio cable that has the capacity for lossless surround except for HDMI, and then you really want eARC because otherwise you have one HDMI running from the receiver to the TV for video (and maybe audio) for sources that can go through the receiver, and a second HDMI that runs from the TV to the receiver for audio only for sources that can't go through the receiver (built into the tv like the tuner, network streaming, and playback from USB; and also devices that exceed the HDMI bandwidth of the receiver or don't negotiate to an appropriate video and audio format unless going direct --- I have a 4k Roku and a 1080p BluRay player that need different settings on the TV to work through my receiver, or I can wire one source direct to the TV and use eARC)

[Kerbonut]

Does eARC support AAC audio for surround sound or is it only DTS or AC3?

[toast0]

I'd guess AAC is technically possible, but not actually supported. A list of formats from a random current receiver is:

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.

[piperswe]

In my experience multi-channel AAC gets sent as multi-channel LPCM over HDMI, whether that be eARC or not. That's fine though, I don't really care what part of the chain does the AAC decoding because it has to be turned into LPCM _somewhere_.