Random CEC/ARC issue

[Dougiebabe2003]

Evening,

So this is a really weird one that I can't figure out...

6 months ago I replaced our old plasma TV with a LG OLED, old plasma didn't have ARC so was never used but when the LG arrived I wanted to use that as I have no optical in the wall as I only planned to use ARC. Start trying to use ARC and getting no sound when using ARC, had to use optical much to my dismay.

Ended up unplugging my graphics card (RX470) from the input on the AVR and it starts working! Plug it back in and it stops again... Plug the HDMI cable into my 2nd gfx card (7950) and it starts working again, move back to 470 and it stops.

So with the above I thought the 470 is faulty and I've been swapping the cable over whenever I need to do something and leaving in the 7950 until I want to game on the TV.

Fast forward to today and I take ownership of an RX580, plug everything in expecting there to be sound via ARC from TV.... nope! Same issue again with a different card. What I have noticed tonight is that ARC stops working whenever the PC is plugged into the AVR, even if the PC has no power cable attached.

Things I have tried:

• Swapping PCI-E ports (only tried this due to the 7950 being in this slot
• Tried new cable between PC and AVR
• Tried new cable between TV and AVR
• About to test putting the 470 back in and using the 580 as the second card.

Everything I have tried leads to the same thing, if I plug the PC into the AVR the sound stops working via ARC about 5 seconds after plugging in. It's never instant which makes me think a setting or something is changing on the AVR.

Anyone have any ideas? This is going to drive me insane as I was relying on CEC/ARC for sound and control of the AVR and really don't want to have to keep unplugging the PC from the AVR just to use it!

 

[PiKe]

Rather than go direct into the AVR, go into it via a hdmi switch should strip out any hdmi CEC stuff the graphics card may be causing.

 

[Dougiebabe2003]

So I've plugged the 470 back in as the 1st card and 580 as the 2nd card, same as when the 7950 was in the PC but no joy. Even tried enabling and disabling crossfire but the same thing happens.

Have also tried plugging the AVR in via a DVI to HDMI adapter, this worked but only allowed me to use 1080p and not 4k.

I've tried my laptop as well and this works, 4K and everything and ARC continues to work. It's only the AMD cards in the PC that seem to be causing this and as the 7950 worked it seems to be limited to the 4xx/5xx range. If that's the case I'm sure more people would have noticed this...?

PiKe, I don't have a HDMI switch that I can test tonight but will see if my mate has one I can borrow. I'm not sure I understand though, if the GFX card is sending any CEC stuff surely the AVR can just ignore it due to it being on an input and not the output which accepts ARC? If the gfx card is sending CEC stuff can't I just stop it from doing this!?

EDIT: That also doesn't explain why it won't work when the PC power is unplugged from the wall but the HDMI is still in that it won't work