4K120hz hdmi 2.1 setup + sound bar question

pressslav

Standard Member
Heya quick question - I'll be connecting the LG C1 OLED tv to my 3080ti pc in the next room via HDMI 2.1. In order to use an Atmos capable soundbar I would need to plug the HDMI into one of the TVs eARC ports and then another HDMI cable between a second eARC port and the soundbar's eARC port? Is that correct? In that case, I don't need a soundbar with a 4K120hz passthrough, right? Sorry for my dumb explanation :D

Cheers!
 

outoftheknow

Moderator
Heya quick question - I'll be connecting the LG C1 OLED tv to my 3080ti pc in the next room via HDMI 2.1. In order to use an Atmos capable soundbar I would need to plug the HDMI into one of the TVs eARC ports and then another HDMI cable between a second eARC port and the soundbar's eARC port? Is that correct? In that case, I don't need a soundbar with a 4K120hz passthrough, right? Sorry for my dumb explanation :D

Cheers!
A TV only has one eARC port. The TV HDMI sockets are all audio/video inputs. eARC is a seperate audio channel where the audio travels the opposite way.

So if you want to plug the PC into the TV hear audio from the soundbar, plug the PC into any TV HDMI except the one marked eARC. That delivers audio and video to the TV. Connect another cable from the TV eARC socket to the soundbar HDMI output. That is also marked eARC. That gives you an audio connection from the TV to the soundbar.

in TV settings turn on eARC and set the audio to “passthrough” from the TV HDMI input (PC) to the soundbar. On the soundbar set the audio input to Din (on most) which is usually the eARC and optical (if it has that).

Now the audio from the TV passes through the TV.
4K/120Hz passthrough is a different thing. That is video passthrough. If you plug an audio/video device into a soundbar HDMI input, the soundbar can take the audio and process it without interference from an intermediate device (like the TV). The video then passes through to the soundbar HDMI output - the one marked eARC for audio return. Only only soundbar has the ability to pass 4k/120Hz video as far as I know so for those wishing by to see that video feature, they need to connect to the TV.

Some TVs don’t deal with audio passthrough very well and there can be issues with lip synch that can’t be fixed (without a third party expensive device - the audio is behind the video and needs a negative delay), or some audio codecs simply don’t passthrough properly or at all.

Basically if you want the soundbar to get audio as intended, connect the A/V device to a soundbar input and a cable from the soundbar output (marked eARC) to the TV input also marked eARC. That connection delivers the video to the TV and audio from the TV channels and built in apps to the soundbar. HDMI switches are fine if you don’t have enough soundbar inputs.

if you must have 4K/120Hz video, you need to connect to the TB and see what audio passes through to the soundbar. If you are lucky you may get the expected audio from the soundbar without issues.
 

pressslav

Standard Member
Hey,

Thank you so much for the exhaustive answer, really appreciate it! I'm looking at the Sony A7000 that was launched recently and has 4K/120hz passthrough. So is using the 4k/120hz passthrough of that soundbar the 'technically more appropriate' way to connect since you eliminate the TV as a middle man? Would that help with this part:
If you are lucky you may get the expected audio from the soundbar without issues.
Thank you once again.
 

chopples

Distinguished Member
Hey,

Thank you so much for the exhaustive answer, really appreciate it! I'm looking at the Sony A7000 that was launched recently and has 4K/120hz passthrough. So is using the 4k/120hz passthrough of that soundbar the 'technically more appropriate' way to connect since you eliminate the TV as a middle man? Would that help with this part:

Thank you once again.

Hi mate I don’t believe any Sony kit currently supports VRR, I am a massive fan of VRR and personally I think it offers more in terms of a consistent gaming experience than high framerate, on that basis, in this scenario I would still be inclined to connect the PC to the TV, that way you will have 4k120,vrr and ALLM (which I believe that Sony bar also doesn’t support at the moment)
 

pressslav

Standard Member
Hi mate I don’t believe any Sony kit currently supports VRR, I am a massive fan of VRR and personally I think it offers more in terms of a consistent gaming experience than high framerate, on that basis, in this scenario I would still be inclined to connect the PC to the TV, that way you will have 4k120,vrr and ALLM (which I believe that Sony bar also doesn’t support at the moment)
Oh yes, that does make sense, I missed the fact it has no VRR and ALLM. VRR will definitely be useful at 4K even with the 3080ti. Ok then, that leaves room to go for a less pricey soundbar without 4K/120hz passthrough. Thank you.
 
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outoftheknow

Moderator
Indeed Sony has left out VRR and ALLM passthrough in the soundbar - I left that out as you didn't mention it as a "must". Is it implemented in the PS5 yet? If so why would they leave it out of the soundbar I wonder.....
 

outoftheknow

Moderator
Ok then, that leaves room to go for a less pricey soundbar without 4K/120hz passthrough.
That is every other soundbar at any price at the moment (except Sony's four speaker soundbar the HT-9 I think it is - which is even more expensive).

Yes plugging into the TV will allow all 2.1 video features and you may be lucky with audio passing perfectly.
 

pressslav

Standard Member
Indeed Sony has left out VRR and ALLM passthrough in the soundbar - I left that out as you didn't mention it as a "must". Is it implemented in the PS5 yet? If so why would they leave it out of the soundbar I wonder.....
I don't think it has it yet but it's definitely coming soon. it's a shame, especially at that price point. I just found out that the Bose 900 is out for pre-order and coming very soon, that looks like a good option I guess, I remember the 700 had good reviews with the only real flaw being the lack of eARC and Atmos which is now present and it's almost £400/$550 cheaper than the Sony.
 

Joe Fernand

Distinguished Member
AVForums Sponsor
With the arrival of eARC the system designers envisage Source > TV > Sound system as being the norm to allow for optimum video capabilities of the Source and TV.

eARC is not reliant on CEC so should hopefully be more reliable than ARC.

How long are the various HDMI cable runs you will require?

Joe
 

pressslav

Standard Member
With the arrival of eARC the system designers envisage Source > TV > Sound system as being the norm to allow for optimum video capabilities of the Source and TV.

eARC is not reliant on CEC so should hopefully be more reliable than ARC.

How long are the various HDMI cable runs you will require?

Joe
Hey Joe thank you for your reply!

Since I last posted in the thread I've at least decided on one thing - I'm going full Sonos Arc + sub + surrounds.

As to the question of HOW to actually connect the PC to the TV I still don't have an elegant solution and I literally researched online for days. My cable run would have to be around 20m and that in itself is not a problem because there are plenty of high-end active optical HDMI cables that can do it easily. However, I have two doors that it needs to go under (on of the 2nd bedroom where the PC is and one of the living room where the TV is) and there really is not much clearance underneath them.

I've also found this solution from fibre command-> fibre command optical but I'm not sure I can even fit this one under the doors and also I've heard that fibre cables are pretty delicate so no idea if that's appropriate for my setup.

The budget is not a problem for this project, I really want that connection but we are renting so in-wall is not an option unfortunately.

If you do have any ideas of how to achieve that connection I'd be really grateful!

Best
 

Joe Fernand

Distinguished Member
AVForums Sponsor
What are you viewing via the PC?

Could you use a Networked streamer attached to the TV instead?

Cables are not ideal if you cannot easily install the cable.

Joe
 

pressslav

Standard Member
What are you viewing via the PC?

Could you use a Networked streamer attached to the TV instead?

Cables are not ideal if you cannot easily install the cable.

Joe
My ultimate goal for the setup is to solve both 4K120hz streamings from the PC to the LG OLED AND also solve any Atmos (lossless) and Dolby Vision restrictions for movie watching.

If I was only doing it for movies I'd just buy an Nvidia Shield Pro which supports the lossless Atmos but streaming games to it would be a mere h.264 4k60 stream which renders the purchase of a 120hz oled unnecessary.
 

Joe Fernand

Distinguished Member
AVForums Sponsor
I tend to not focus on just one metric when purchasing a TV - ideally I want one which produces a decent image no matter what the specs say, I’ve seen plenty of kit which hit specs but looked terrible.

Source > TV then TV eARC > Audio system eARC is likely your best option - how you get the signal across is, as you highlight, the big issue.

Multi part optical HDMI cables work well in Commercial applications but less well in Residential systems in my experience.

I would look at how to get a one piece Hybrid Fibre HDMI cable from the PC to the TV - can we assume moving the PC closer to the TV and maybe use the long HDMI cable ‘back’ to your gaming room is not an option?

Joe
 

outoftheknow

Moderator
high-end active optical HDMI cables
I've heard that fibre cables are pretty delicate so no idea if that's appropriate for my setup.
Bearing in mind optical HDMI is a type of fibre, the delicacy issue is there with those too. Neither is ideal where the cables can’t be run either physically protected or hidden.
 

pressslav

Standard Member
can we assume moving the PC closer to the TV and maybe use the long HDMI cable ‘back’ to your gaming room is not an option?
I though about that option as well, but the thing is that's mostly my work from home office and I have dual 1440P 165hz monitors over DP so a single hdmi can't work I think + I'll need all the usb cables for peripherals etc.

I was even thinking of running a thunderbolt 3/4 with a docking station but the support staff at all the docking station manufacturers adivsed me strongly not to use them with long thunderbolt cables soo...yeah

Neither is ideal where the cables can’t be run either physically protected or hidden
On a scale of one to Khaln Drogo, how barbaric would it be if I just have an HDMI 20m optical cable, have it always connected on one end to the tv and tucked behind the tv cabinet and then ..wait for it.. manually connecting to the pc every time I need to play at 4k120 😃😃 I can still have a shield pro or other for atmos playback over the local network and just occasionally pull the long boy out.
 

outoftheknow

Moderator
how barbaric would it be if I just have an HDMI 20m optical cable, have it always connected on one end to the tv and tucked behind the tv cabinet and then ..wait for it.. manually connecting to the pc every time I need to play at 4k120
That would work but every time you move it to connect it is a time it “could” be damaged. Small risk though with reasonable care when handling the cable…
 

pressslav

Standard Member
Well yes I'll have to try anyway I've got nothing to lose it's either that or 100mbps Moonlight streaming at 60fps for life. Thank you for your advice guys!
 

Joe Fernand

Distinguished Member
AVForums Sponsor
Swapping in/out is an option (assuming you prefer to not use a powered Distribution Amp).

I would tend to try with a short, very flexible HDMI Male to Female adapter at the end where you will be plugging/unplugging to avoid wear and tear on the PC graphics card.

I would also avoid hot swapping and aim to power kit down any time you are plugging/unplugging a cable.

We have had great reliability with the HDFury Hybrid Fibre at 10m and 20m - HDFury Fiber HDMI cable - The Media Factory

Joe
 

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