If I’m understanding you correctly, you can’t get 5.1 OR 7.1 OR any HD audio steam to your AVR when connecting your setup like this:
RPi -> via HDMI -> TV -> via HDMI -> AVR
This was never possible and will not even be possible with eARC for this reason: For this to work, the TV would have to passthrough the audio signal coming from the RPi via HDMI back to the AVR via the audio return channel of the HDMI connection between TV and AVR. This doesn’t work for several reasons…
- TVs take the incoming HDMI audio signal and decode it. They are not built to passthrough any audio streams. It’s the same, if you connect your TV to your AVR via Toslink (RPi -> via HDMI -> TV -> via Toslink -> AVR) the TV will not passthrough the 5.1 DTS or Dolby signal to the AVR, but just a 2.0 PCM signal. It’s only passing on the decoded signal, if any.
- The TV would have to know from where to TAKE the audio stream and where to passthrough it TO. So, assuming you RPi is connected to HDMI1 of your TV and the AVR is connected to HDMI2 of your TV, the TV would have to know that it’s supposed to passthrough the audio signal from HDMI1 over to HDMI2. No TV does that or can even do that. And the ARC (and eARC) is not meant to do this.
ARC the same as eARC is JUST to take audio from INTERNAL TV apps (Netflix, Amazon, internal TV tuners) back to the AVR. It can’t and will never do anything else.
So, you should connect you RPi directly to the AVR via HDMI. The RPi can stream Dolby (including Dolby Digital+), DTS and PCM signals as high as 7.1 24bit 48kHz to your AVR. It can’t do more. And no ARC/eARC connection can change that.
Only the Vero 4k can stream all HD audio signals via HDMI. And the same as I worte before (1. and 2.) applies to a setup with the Vero 4k.
BTW: This is going completely off-topic. So, if you have any more question regarding your setup and how ARC/eARC works, you’re welcome to PM me or post this question in a new thread…