LG C1 (OLED48C16) Issues with 5.1 LPCM over eARC

tamber

Novice Member
Hello everybody,

as my last TV died a few days ago, i got the LG C1 48" on a bargain.
I already read about some glitches with LG TVs (Choosing Bitstream instead of PCM, etc.), but discovered an issue maybe some of you can comfirm and have a solution for - i think it's some kind of bug in the LG TV firmware:
My problem is that the LG TV is not able to reliably pass through 5.1 LPCM from a PS5 to my AVR, i.e. I can easily reproduce a scenario where passthrough of uncompressed PCM does not work anymore - when changing input sources.

My Setup:

TV Streaming Box is connected to HDMI 1 on the LG.
My eARC capable AVR (Canton SmartAmp 5.1 Gen2) is connected to HDMI 2 (ARC) on the LG.
My Playstation 5 is connected to HDMI 3 on the LG.

Settings LG TV: Audio output via HDMI(ARC), Bitstream, Passthrough, eARC activated.
Settings TV Streaming Box: Audio Output Bitstream Dolby Digital (as it's the only option besides Stereo)
Settings PS5: HDMI Device Type set to AV Amplifier, Number of Channels set to 5.1., Audio Format (Priority) set to Linear PCM.

Problem/Scenario:
Setting everything up from Scratch in the above configuration with the PS5, everything works as expected: the AV amps Display is showing "Multichannel PCM Direct", all 5 Speakers play the intended Surround Sound (verified by Turning the Camera around a camp fire in a game).
When changing the input source to the TV Box watching TV, at first everythings normal - "Dolby Digital" is shown in the display of the AV amp - as configured in the settings. But changing back to the PS5 is where the Problem kicks in:
LG C1 is not able to switch back from the TV Box's Dolby Digital to the PS5's LPCM and passing it through via eARC to the Amp anymore: all speakers remain silent, as the amp does not get an audio signal at all. Switching to Dolby Digital 5.1 in the PS5's settings i can get surround sound back, switch back to LPCM in the PS5 the speakers remain silent again.
I can reproduce this.

To reset this, disconnecting HDMI and power plugs from the TV is sufficient, Multichannel PCM is working again after reconnecting - as long as i don't switch to an input with an compressed audio source.


????
Can anybody confirm this scenario? Is this a bug in the TV? All devices have their actual firmware updates.
????


My Workaround at the moment is setting the PS5 to Dolby Digital, as there is no problem after switching input sources with this. This is absolutely not ideal, but works. But there must be a way to output uncompressed multichannel PCM in a reliable manner, somehow, as the HDMI specs of all connected devices are supporting eARC.
Please excuse my language, as i am not a native english speaker.
 

next010

Distinguished Member
eARC is not a strict standard so differences in implementations can produce issues.

I would contact canton and see if they can investigate the problem as it might be down to how their eARC interfaces with LG's eARC.

It is possible to replace the eARC system if your sound system has a free HDMI input by using the Sharc but its not cheap nor is it a 100% guarantee that it solves your problem, though the Sharc was originally developed for use on LG TV's with eARC.
 

tamber

Novice Member
I will contact Canton about this issue too, sure. But what makes me think this is a thing on the TV side is when i switch from Passthrough to Automatic in the TV's Menu, it works again for LPCM, but downmixed to 2.0 Stereo. Switching back to Passthrough runs in the same error. For compressed material in Dolby Digital there is absolutely no Problem as it works flawlessly.
It starts working again once you disconnect all devices and reconnect them, though.
So my hope was that somebody here has run in the exact same issue and may has a solution based on TV/AVR/PS5 settings.

I thought about using the Shark or the FineTech VAX01202 already, but that is not a good option either, as my receiver will act as a "dumb" amp in this case and i can't use the other devices directly connected to it without occupying an additional HDMI Slot on the TV.

But thanks for the suggestion.
 

Recall

Active Member
I have had an issue where I could be listening to Youtube, then click another video and no sound. Youtube uses PCM, so I then changed to SD TV channel and no sound, however HD channels in Dolby Digital work fine.

Switching to TV speakers still has no sound for PCM. Only fix is a power cycle. There is a new engineer firmware floating about, so this may resolve the issue.
 

tamber

Novice Member
I have had an issue where I could be listening to Youtube, then click another video and no sound. Youtube uses PCM, so I then changed to SD TV channel and no sound, however HD channels in Dolby Digital work fine.

Switching to TV speakers still has no sound for PCM. Only fix is a power cycle. There is a new engineer firmware floating about, so this may resolve the issue.
This hardens my suspicion that there is something wrong on TV's side with changing codecs. But in your case with only TV speakers, there is nothing configured regarding eARC, passthrough and the like, right?
 

Recall

Active Member
I had the issue happen again last night. This seems to be linked to Alexa as only happened after I used.

Out of curiosity have you linked Alexa to TV? If so try and disable.
 

tamber

Novice Member
I had the issue happen again last night. This seems to be linked to Alexa as only happened after I used.

Out of curiosity have you linked Alexa to TV? If so try and disable.
No, i don‘t have Alexa. Siri on Apple TV on HDMI 4 is disabled.
 

andy1249

Distinguished Member
Hello everybody,

as my last TV died a few days ago, i got the LG C1 48" on a bargain.
I already read about some glitches with LG TVs (Choosing Bitstream instead of PCM, etc.), but discovered an issue maybe some of you can comfirm and have a solution for - i think it's some kind of bug in the LG TV firmware:
My problem is that the LG TV is not able to reliably pass through 5.1 LPCM from a PS5 to my AVR, i.e. I can easily reproduce a scenario where passthrough of uncompressed PCM does not work anymore - when changing input sources.

My Setup:

TV Streaming Box is connected to HDMI 1 on the LG.
My eARC capable AVR (Canton SmartAmp 5.1 Gen2) is connected to HDMI 2 (ARC) on the LG.
My Playstation 5 is connected to HDMI 3 on the LG.

Settings LG TV: Audio output via HDMI(ARC), Bitstream, Passthrough, eARC activated.
Settings TV Streaming Box: Audio Output Bitstream Dolby Digital (as it's the only option besides Stereo)
Settings PS5: HDMI Device Type set to AV Amplifier, Number of Channels set to 5.1., Audio Format (Priority) set to Linear PCM.

Problem/Scenario:
Setting everything up from Scratch in the above configuration with the PS5, everything works as expected: the AV amps Display is showing "Multichannel PCM Direct", all 5 Speakers play the intended Surround Sound (verified by Turning the Camera around a camp fire in a game).
When changing the input source to the TV Box watching TV, at first everythings normal - "Dolby Digital" is shown in the display of the AV amp - as configured in the settings. But changing back to the PS5 is where the Problem kicks in:
LG C1 is not able to switch back from the TV Box's Dolby Digital to the PS5's LPCM and passing it through via eARC to the Amp anymore: all speakers remain silent, as the amp does not get an audio signal at all. Switching to Dolby Digital 5.1 in the PS5's settings i can get surround sound back, switch back to LPCM in the PS5 the speakers remain silent again.
I can reproduce this.

To reset this, disconnecting HDMI and power plugs from the TV is sufficient, Multichannel PCM is working again after reconnecting - as long as i don't switch to an input with an compressed audio source.


????
Can anybody confirm this scenario? Is this a bug in the TV? All devices have their actual firmware updates.
????


My Workaround at the moment is setting the PS5 to Dolby Digital, as there is no problem after switching input sources with this. This is absolutely not ideal, but works. But there must be a way to output uncompressed multichannel PCM in a reliable manner, somehow, as the HDMI specs of all connected devices are supporting eARC.
Please excuse my language, as i am not a native english speaker.

What about your cables ?
Are they certified Ultra Cables or Certified Hgh Speed/Premium "with Ethernet" ?

The reason I ask is because in your list , the PS5 is the only item actually using the higher bandwidth that eARC requires , and for eARC to be stable those wires ( pins 14 and 17 ) must be a twisted pair.

On certified High Speed /Premium without ethernet they are not a twisted pair , standard dolby digital and 2 channel PCM will still work , but multichannel PCM will be unstable at best. You would get intermittent operation.
 

andy1249

Distinguished Member
Don‘t know if they are really „certified“, but as there are 2.1 Ultra 8k capable with Ethernet, i think they‘ll do. when i‘m not switching to compressed source inputs, these cables work forever when switching PS5 on and off.

Cables: https://www.amazon.de/gp/aw/d/B084BQ9GHR
The Cable linked is definitely not certified , and there is no mention of eARC , just ARC , meaning the relevant pair of wires may not be twisted and may be the cause of your issue.

HDMI numbers and all the blurb in that link is not relevant to cables.

hdmi.org is the sole official source for cable information , here is all you need to know about cables.


Note the logo , and how to verify the cable with a free app.
Ultra certified cables with the logo are available off amazon for cheaper than the cable you linked.
With no certification , you don't know what you are getting.
 

tamber

Novice Member
The Cable linked is definitely not certified , and there is no mention of eARC , just ARC , meaning the relevant pair of wires may not be twisted and may be the cause of your issue.

HDMI numbers and all the blurb in that link is not relevant to cables.

hdmi.org is the sole official source for cable information , here is all you need to know about cables.


Note the logo , and how to verify the cable with a free app.
Ultra certified cables with the logo are available off amazon for cheaper than the cable you linked.
With no certification , you don't know what you are getting.
I will try another „certified“ cable for the connection between PS5 and TV, as between TV and Amp the cable is that what was delivered with the PS5. Thank you so far, i will get back when i tried it out.
 

Sage2050

Novice Member
It is 100% the tvs fault, no hdmi cable you buy will fix it. I've been working this problem for months. A quick Google search will yield dozens of conversations about the issue - these TVs just can't handle LPCM properly over eARC. Sometimes it will work for no obvious reason only to stop working again next time it turns on.

I registered here solely to try to find help with solving this issue.

Edit:I'm at my wits end so I went ahead and ordered a highly recommended certified cable. I will gladly humble myself in shame if I was wrong, I just want this to work.
 
Last edited:

Sage2050

Novice Member
Got the cable, still no 5.1 LPCM. still convinced it's the TV.

Zeskit Maya 8K 48Gbps Certified Ultra High Speed HDMI Cable 6.5ft, 4K120 8K60 144Hz eARC HDR HDCP 2.2 2.3 Compatible with Dolby Vision Apple TV 4K Roku Sony LG Samsung Xbox Series X RTX 3080 PS4 PS5 https://a.co/d/jgY8qYC


Fwiw the edid data coming from the TV says that it supports only 2 channel lpcm
 

tamber

Novice Member
The Cable linked is definitely not certified , and there is no mention of eARC , just ARC , meaning the relevant pair of wires may not be twisted and may be the cause of your issue.

HDMI numbers and all the blurb in that link is not relevant to cables.

hdmi.org is the sole official source for cable information , here is all you need to know about cables.


Note the logo , and how to verify the cable with a free app.
Ultra certified cables with the logo are available off amazon for cheaper than the cable you linked.
With no certification , you don't know what you are getting.
Tried a certified cable. Same outcome than before. Works once, then silence. So there must be something wrong with the TV, as i tried the same configuration on a philips TV and there it works.
 

Sage2050

Novice Member
To elaborate on the problem a bit, it also drops to 2 channels when switching to another uncompressed source, a Nintendo Switch in my case. Changing sources at all seems like rolling the dice on whether it will work when I go back to the PS5, and sometimes when it stops working I can't get it working again.
 

tamber

Novice Member
To elaborate on the problem a bit, it also drops to 2 channels when switching to another uncompressed source, a Nintendo Switch in my case. Changing sources at all seems like rolling the dice on whether it will work when I go back to the PS5, and sometimes when it stops working I can't get it working again.
I cannot try this, as the Nintendo is connected directly to the Amp. When i will have some free time the next days, i will elaborate on enforcing the problem and trying to reconnect the HDMI cable from PS5 to TV, and another in reconnecting the HDMI cable between TV and Amp.
With luck, one of those two will do the trick so my next step will be connecting an HDMI switch in between so i can enforce a new Handshake and solve the problem with the press of a button.
 
Last edited:

Recall

Active Member
Sure, but take note this will void your warranty. Also try turning off HDMI CEC on everything and enable one by one. It may be one of them is causing a gremlin in system.

 

tamber

Novice Member
Sure, but take note this will void your warranty. Also try turning off HDMI CEC on everything and enable one by one. It may be one of them is causing a gremlin in system.


Ok, as there are no public release notes available i won‘t try my luck with this.
I‘d rather keep on working out a solition where mainly a switch -may it be HDMI, may it be power - will solve/reset the issue… brave new digital world o_O
 

Sage2050

Novice Member
I haven't had any success with unplugging/replugging hdmi. My go to is to switch audio output to Auto and then back to pass through. It works maybe a third of the time
 

tamber

Novice Member
I haven't had any success with unplugging/replugging hdmi. My go to is to switch audio output to Auto and then back to pass through. It works maybe a third of the time
Tried the same with a HDMI switch, no luck. My workaround now is a power extension cord with a switch for the TV. Switching the TV completeley off and on makes the broken mc lpcm work again. At least the TV remembers the last input source.
It's a shame that such a lousy bug is still an issue in a TV made in 2021. You'll need WiFi for each and every b$$$$$$t, but LG is incapable of sorting this stuff out which can be healed with a simple restart of the device.
WTH are they doing?
 

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