I’m not using my smart TV functionality at all since I started using Arcana, but it should work.  First thing I would check is make sure The HDMI-ARC port on the TV is connected to Arcana, as that’s the only port where the TV will send out audio.  If still not working, make sure your TVs audio settings has the ARC connection turned on.  I don’t recall what LG calls their version of this, you may have to refer to your user manual for that.  If it’s still not working after that, I would connect your Sonos Arc directly to the TVs HDMI-ARC port, temporarily bypassing Arcana.  Assuming your setting are correct, it should work.  Then set it up as normal with Sonos Arc connected to Arcana, and Arcana connected to TV, and everything should still work.

Thanks for your suggestion. I have tried the ARC HDMI TV socket connected direct to the Arcana input (ie not through the Matrix switch first) but the Arcana does not recognise a signal. The TV Sound out was set to ARC by the way for this test.

I had already been told by EZCoo that their matrix switch will not support an ARC TV signal so I imagine (I’ve no technical idea on this!) that an ARC TV output is only providing a subset of what a normal HDMI AV source would.

I seem to need a way to take the ARC Sound signal and turn it into a full AV signal before it reaches the matrix so that then the matrix will pass it through to its output port and the Arcana can receive it and extract the audio to pass to the Sonos Arc. 

Isn’t iPlayer on the Apple TV 4K?  I know that’s not a complete solution.

Yes, but sometimes the BBC make available UHD versions that the ATV BBC App can’t process but the LG TV can because they support the relevant AV protocols.

Also , the LG can play video files of old movies from my NAS which I don’t have any other way of playing.

It is a bit of a 1st world problem though!

For Clarity.  The TV HDMI-ARC (which is technically an input) connects to the Arcana’s HDMI out (ARC/CEC/UP).  It’s important to remember that ARC stands for Audio Return Channel...audio flows in the opposite direction of normal audio.  Arcan is not going to recognize that there is audio coming through the ARC channels at it’s HDMI input port, only at it’s HDMI out part.  It’s counter-intuitive, but that is how ARC audio works.

Close, but it’s not really a subset, but an entirely different flow of data as I described above.  Your switch shouldn’t need to deal with any ARC audio data though, as in the correct setup, your TV smart apps will generate the audio, sending in through the TV’s HDM-ARC port to Arcana (thorough the HDMI out port) which then sends it on via it’s eARC Out port to the Sonos Arc.

Nah, you don’t actually involve the matrix .  However, you could use a SHARC to do as you described.   For better clarification look at https://www.hdfury.com/product/4k-arcana-18gbps/ on the Getting Started Tab.  The setup you are looking for is titled “Multi sources + ARC”.  The alternative setup with the SHARC is “Multi sources + eARC”.

Ah lightbulb moment! I hadn’t seen that Getting Started section and the “Multi sources + ARC” but then who reads the manuals!?

Perfect - problem solved and all seems to be working perfectly.

I had updated the Arcana firmware over the weekend, I wonder when that functionality I needed was introduced as it is marked as “New” in the product description Key Features.

Many  thanks for switching on the lights for me!

That features was not part of the original product design, and was not there when preorders began.  However, they did add it about a month before the first product was shipped.  Rather trivial I guess I this point.