LG OLED C9: PC audio via ARC (not eARC) Stereo Only?

VincentHanna · 18 Nov 2019 at 14:02

So for years I've been using my Denon AVR to do video pass-through to the TV from my PC GPU. This allowed me to listen to high quality audio, such as movies supporting True HD/DTS-HD Master and more recently, Dolby Atmos.

The OLED C9 has now been updated to support Nvidia G-SYNC over HDMI, so I've now plugged the HDMI output from my 2080ti - directly in to the TV, bypassing the receiver completely.

G-SYNC is working fine, but now to get sound I am forced to use the audio return channel (arc) and the only option under Windows sound is 'Stereo'

Is that the best I can hope for? I assumed it would do 5.1 surround sound at least.

I know I can hook up an optical cable, but that will still only give me lossy 5.1

AVR is a DENON X3200W so it only supports HDMI 2.0 and came out before eARC was a thing. Upgrading the AVR isn't currently an option as I am waiting for 2020, when Denon will likely support HDMI 2.1

james.miller · 18 Nov 2019 at 14:12

is a 2nd hdmi from the gpu an option? one to the tv and one to the amp?

VincentHanna · 18 Nov 2019 at 14:21

Sadly not, the 2080Ti I have only has 1 HDMI.

The rest are Display Port.

james.miller · 18 Nov 2019 at 14:22

Display port to hdmi should work though, im sure sound still works over DP. Somebody else will need to confirm that but i'm sure that's the case.

200sols · 18 Nov 2019 at 14:26

ARC should be better than optical. For ARC to work you need to enable CEC on TV and AVR.

Radox-0 · 18 Nov 2019 at 14:28

Sound does indeed work over DP, but not sure how an adaptor would play out. Could be worth a try with a DP to HDMI cable as if it does work, would be a solution and one that I use (One cable to TV / Monitor and another to AV receiver)

200sols said:
ARC should be better than optical. For ARC to work you need to enable CEC on TV and AVR.

Yes but problem is he will not get 5.1 etc or higher format's if going from GPU to TV then TV to AV receiver via ARC.

VincentHanna · 18 Nov 2019 at 14:31

Radox-0 said:
Yes but problem is he will not get 5.1 etc or higher format's if going from GPU to TV then TV to AV receiver via ARC.

Exactly this

Yes, ARC works - Sound comes out through my speakers. But Windows only lets me select Stereo sound and though I'm sure I can use some trickery to make a 5.1 surround sound from a stereo signal, it's not the same as proper surround sound.

sHo0sH · 18 Nov 2019 at 14:36

Have you got the latest sound drivers for your motherboard? https://appuals.com/channel-surround-sound-not-working-in-windows-10/
Seems that there is an issue in general with this by the looks of it.

VincentHanna · 18 Nov 2019 at 14:48

Radox-0 said:
Sound does indeed work over DP, but not sure how an adaptor would play out. Could be worth a try with a DP to HDMI cable as if it does work, would be a solution and one that I use (One cable to TV / Monitor and another to AV receiver)

I wonder if this might work - bit pricey though:
https://www.belkin.com/uk/p/P-F2CU038bt/

sHo0sH said:
Have you got the latest sound drivers for your motherboard? https://appuals.com/channel-surround-sound-not-working-in-windows-10/
Seems that there is an issue in general with this by the looks of it.

I'm not using the soundcard for this, this is pure audio from the GPU

Radox-0 · 18 Nov 2019 at 15:00

VincentHanna said:
I wonder if this might work - bit pricey though:
https://www.belkin.com/uk/p/P-F2CU038bt/

I'm not using the soundcard for this, this is pure audio from the GPU

Not too sure to be honest in regards to Type C. I have used a Active Displayport to HDMI connector before (R9 Nano to 4k TV as it only had HDMI 1.4) which did pass both audio and Video perfectly. Could possibly try one of those from the rainforest which is much cheaper (and nice return policy) and would do the same thing I would have thought for purpose of passing Audio.

VincentHanna · 18 Nov 2019 at 15:03

To be honest, I could do with USB-C to HDMI anyway for my Surface Pro X.

ElliorR · 18 Nov 2019 at 15:57

Now that’s strange. I upgraded to a C9 yesterday but before that I had an LG nanocell TV and I had the option for stereo, 5.1, 7.1 or Dolby Atmos when I right clicked on the speaker icon on the taskbar.. I just checked on the C9 and now 5.1/7.1 are greyed out. Some investigation is needed.

VincentHanna · 18 Nov 2019 at 16:13

Interesting...I wonder what's going on.

VincentHanna · 19 Nov 2019 at 19:07

Update - all I could get from the USB C -> HDMI was stereo

ElliorR · 21 Nov 2019 at 11:20

VincentHanna said:
Update - all I could get from the USB C -> HDMI was stereo

A development. On my old LG Nanocell TV I had my computer plugged into a HDMI on my Sony ZF9 soundbar but on the C9 I plugged it directly into the TV. I just plugged the computer back into the ZF9 and.....

No idea why though I'm sure people smarter than me will know the reason but that obviously won’t let you run g sync.

hyperseven · 21 Nov 2019 at 13:32

Might be an issue with the Nvidia hd audio driver? Have you tried rolling back to an older version, I know you will lose gsync, just to test if the driver is at fault.

soulstoner · 21 Nov 2019 at 23:54

Made an account just to reply with my findings on this.

The LG C9 has a bug where it will not process LPCM signals directly through eARC or ARC. The reason you're seeing those 5.1/7.1 options is because the receiver is capable of processing that signal, as it is bypassing the LG C9 entirely and just passing video.

LG has announced that it will be issuing a firmware update in the second quarter of 2020 to resolve this issue. It feels like a long distance away, but I guess it's better than nothing.

VincentHanna · 22 Nov 2019 at 11:31

soulstoner said:
Made an account just to reply with my findings on this.

The LG C9 has a bug where it will not process LPCM signals directly through eARC or ARC. The reason you're seeing those 5.1/7.1 options is because the receiver is capable of processing that signal, as it is bypassing the LG C9 entirely and just passing video.

LG has announced that it will be issuing a firmware update in the second quarter of 2020 to resolve this issue. It feels like a long distance away, but I guess it's better than nothing.

Thanks for registering, I really appreciate it and the feedback.

Yes Q2 2020 does seem miles away, but at least they are addressing it.

I'm down to my last throw of the dice now - I've ordered a 'Displayport to HDMI' active adaptor, hoping I can send that signal from the GPU to the AVR and get decent audio again, whilst still having the HDMI connection direct to the C9 with G-SYNC.

Kind Regards
Gary Ambrose

soulstoner · 22 Nov 2019 at 15:02

VincentHanna said:
Thanks for registering, I really appreciate it and the feedback.

Yes Q2 2020 does seem miles away, but at least they are addressing it.

I'm down to my last throw of the dice now - I've ordered a 'Displayport to HDMI' active adaptor, hoping I can send that signal from the GPU to the AVR and get decent audio again, whilst still having the HDMI connection direct to the C9 with G-SYNC.

Kind Regards
Gary Ambrose

I also tried that, along with a USB-C > HDMI adapter > AVR. For whatever reason, I was still unable to pick 5.1/7.1 when outputting via that connection, which I verified in sound options that the AVR was the default sound device. I am not sure why, but I'm curious if you have better luck.

VincentHanna · 23 Nov 2019 at 13:22

soulstoner said:
I also tried that, along with a USB-C > HDMI adapter > AVR. For whatever reason, I was still unable to pick 5.1/7.1 when outputting via that connection, which I verified in sound options that the AVR was the default sound device. I am not sure why, but I'm curious if you have better luck.

Same as you.

I'm going to hazard a guess that Nvidia will only output the full range of audio options via HDMI.

I notice ASUS do a Strix 2080Ti with 2x HDMI ports - Obviously i'm not going to go to those sorts of lengths to get decent audio back, but maybe somebody who has one can confirm that both HDMI outputs offer the full range of audio options?