LG C1 audio sync issue

Sotiris

Novice Member
Hi everyone

I'm hoping somebody can point me in the right direction. I recently upgraded my whole AV setup to 4K and Dolby Atmos. The equipment I have is

LG C1 65"
Denon X3700H
Apple TV 4K (2021 model)
Panasonic Blu Ray player

I have all my sources going into the Denon using high speed HDMI cables, and then the AV Receiver is connected to the TV. I have tried both input 1 and input 2(ARC) on the TV but I get audio sync issues. The audio is always before the picture, but it's not a constant delay. iTunes movies (4K) is very noticeable, and Prime video is completely unwatchable. There are no issues playing HD movies through the blu ray player.

If I play audio through the TV speakers, it is synchronized perfectly, so it's just AV Receiver sound that is out.

This morning I connected the Apple TV directly to the TV and then using ARC sent the audio back to the receiver and it is perfect. However, it is my understanding that using the AV Receiver as the entertainment hub is usually preferred? Happy to hear opinions about this, and if AV Receiver is preferred then how can I sort the audio out.

Thanks in advance

Sotiris.
 

Clem_Dye

Distinguished Member
Have you checked the receiver’s settings to see if there are any audio settings that might be relevant? Is the firmware on all devices up to date? Lip sync issues where LG TVs are involved are legion, and I speak from personal experience. Check things like TruMotion on the TV, PassThru and so forth.
 

Sotiris

Novice Member
Thanks for your reply. Yes, all receiver and LG TV and apple TV have the latest firmwares (i'm always checking!)

The LG TV has the filmmaker picture settings (as suggested by Phil from AVForums, all settings match his) so there should be very minimal picture processing on. TruMotion is off definitely.

Ideally I'd like to keep the apple TV connected directly to the receiver so I'll keep trying out suggestions until we solve it.

Thanks
 

Sotiris

Novice Member
So...I've been playing with a lot of settings, and have come across something very interesting...

On the Denon AVR, I've set video to 'bypass' but that still had the video delayed after the audio. However, I found a setting called 4K/8K Signal Format which by default is set to 'Enhanced'. When switching it to 'Standard' the video and audio are in sync correctly. Switching it back to Enhanced has the issue again. So, I've narrowed it down to this one setting. From the description it's to do with the chroma of the signal. Is Enhanced sending too much data down my cables and they can't keep up? Obviously I'd like to be able to use 4:4:4 chroma for more accurate colours, currenty I'm having to limit it to 4:2:0 for the picture and audio to be in sync.

I own the amazon basics High-Speed HDMI 2.0 cables and one is connected from my apple TV to the AVR and the other is from the AVR to the HDMI2(ARC) input of the LG C1.

Hopefully we are close to solving this.
 

next010

Distinguished Member
The enhanced setting is basically the toggle for higher bandwidth video and 4K HDR support.

Chroma setting compresses video signal to save on bandwidth, it doesn't make that much of a difference for movie video so its not a deal breaker.

Leave it on enhanced and in ATV video settings select
Format = 4K SDR 60hz
Chroma = 420
Match Content = Dynamic Range & Frame rate both on.

See how that fairs as the ATV will auto switch to 24Hz HDR output for playback of video.

If problem persists changing cables may help, get "certified premium high speed" HDMI cables.
 

Sotiris

Novice Member
Thanks for your reply.

Problem persists if I leave the AVR on enhanced and use the above apple TV settings.

I phoned Denon technical support and they said it's probably the LG as they're infamous for audio lag. I will order new cables if I can't find anything on the TV that fixes this, as I would have run out of things to change.

Thanks
 

Sotiris

Novice Member
So, so here’s an update on what I’ve changed and my findings:

I bought ultra high speed certified HDMI 2.1 cables, one to connect the apple TV to the Denon and one from the Denon to the LG TV. The audio is unfortunately still out of sync with the picture.
Denon’s second bit of advice was to factory reset the AVR (using the engineer reset sequence), and straight after the initial setup I still had audio sync issues.

But what I have found is if I connect the Apple TV directly to the LG into HDMI 1 and then enable eArc from HDMI 2 to the AVR, the audio is magically in sync with the picture!! So what is going on here? What piece of equipment is causing the issue? I do not want the Apple TV connected this way because it looks untidy with 2 thick cables up the wall (the LG is wall mounted). Also by going via the TV first, when playing non Dolby Atmos movies through iTunes, the AVR displays DD+D Surround whereas when connected directly to the AVR it displays Multi Ch In, not sure if that’s correct.

Hopefully something I’ve mentioned here will help pinpoint where the issue is.

Thanks in advance
 

next010

Distinguished Member
I do not want the Apple TV connected this way because it looks untidy with 2 thick cables up the wall (the LG is wall mounted). Also by going via the TV first, when playing non Dolby Atmos movies through iTunes, the AVR displays DD+D Surround whereas when connected directly to the AVR it displays Multi Ch In, not sure if that’s correct.

DD+ Atmos is what's used by streaming services on ATV4k and its supported over ARC.

Dolby-MAT (PCM + Atmos) will be used by ATV4K if it detects it, the DD+ audio is decoded as Dolby-MAT, this may be why your AVR reports it as multi channel (PCM).

PCM is a lower latency audio format, perhaps that might be part of the issue in using Dolby-MAT with the AVR which has its own latency issues or cant keep in sync with it.

In ATV settings go to audio format
  • change format = on
  • new format = dolby digital 5.1

This should auto disable Atmos and just push out regular Dolby 5.1 audio, see if that's any better when connected to the AVR.
 
Last edited:

Sotiris

Novice Member
Yes, changing those two settings has the audio perfectly in sync. But…I have downgraded the audio in doing so if I’m understanding you correctly?

On viewing an Atmos film like The Two Towers, it now only displays DD+D Surround, so I’m not getting Atmos.

From all the info I’ve provided, is the issue with any particular device (AppleTV, Denon 3700 or LG C1), or are all to blame? It might make it easier for me to browse device specific forums to see if others get the same thing and the solution.

Thanks again
 

next010

Distinguished Member
Yes, changing those two settings has the audio perfectly in sync. But…I have downgraded the audio in doing so if I’m understanding you correctly?

On viewing an Atmos film like The Two Towers, it now only displays DD+D Surround, so I’m not getting Atmos.

From all the info I’ve provided, is the issue with any particular device (AppleTV, Denon 3700 or LG C1), or are all to blame? It might make it easier for me to browse device specific forums to see if others get the same thing and the solution.

Thanks again

If you cant hear the difference then I wouldn't worry about it, yes your losing the spatial audio but if your still getting DD+ then there isn't anything higher quality than that on the ATV.

The problem is the Denon 3700 and how it handles Dolby-MAT which is an alternative way of decoding DD+ Atmos, the ATV detects the Denon supports it and uses it (via HDMI-ARC the ATV is limited to DD+ Atmos only it cannot use Dolby-MAT).

The Denon is losing audio sync when it receives Dolby-MAT from the AppleTV. I would suggest checking for a firmware update to the Denon and contacting their support letting them know you've isolated the problem.
 

Sotiris

Novice Member
Ok, so after speaking with LG technical support today, they said that I should plug my devices directly to the TV to avoid audio sync issues, as AVR’s just can’t passthrough video fast enough, even when set to Passthrough. Shame, not sure if it’s completely true though, I’m sure Denon would have tested this. It must be something more complicated than that. Anyway…

…they ensured me that connecting my Apple TV directly into the TV, and then using eARC, I would not lose audio quality (as long as I set digital audio to Passthrough on the TV). As I was on the phone with them, the audio synced up perfectly this way, however when i turned the system back on after a few hours, the TV said it should enable HDMI Deep Color for that input, so I did, and then audio is out again! So I’m back to square one.

I thought I would try a different source device, so I plugged in my Panasonic Blu Ray player (1080p)…and I’ve found that if I have a film where there is both Dolby Digital, the audio is in sync, but if I choose Dolby TrueHD then the audio is out of sync. What the?? So, a devide I have used for years on my old setup now also has the same issue.

So my finding are this.

On the Apple TV, if I set picture to 4:2:0, i don’t have audio sync issues

On the AVR, if I set 4K/8K Signal Format to Standard (instead of Enhanced), I don’t have audio issues.

On the TV, if I disable HDMI Deep Color, I do not have audio sync issues.

On the Blu Ray player, if I choose Dolby Digital (not TrueHD or DTS:Master) then I have no audio sync issues.

Considering I’ve spent £2000 on the LG C1 and £1000 on the Denon, I’m very annoyed that I cannot enjoy a movie with audio in sync with the picture when the best video settings are used.

Any further ideas or suggestions would be greatly welcomed









sync issues.
 

EA666

Active Member
Did you get this sorted? I will also have the same setup from Monday onwards so will be able to experiment with various things.
 

Sotiris

Novice Member
Hi

Glad to hear you’re going to have the same setup. That will be super useful for both of us I think.

No, I didn’t get this sorted unfortunately. LG say it’s Denon’s fault, and Denon say it’s an LG issue. However, due to the HDMI 2.1 bug that plagued 2020 receivers (including mine), the store I bought the Denon from have agreed to send it back to Denon and he’s put another X3700H on order for me with the corrected HDMI chipset. It could be a while before I get the replacement, but once I do I will be ready to experiment as well.

The other thing which rules out it being an Apple TV issue is I tried the Apple TV app on the actual LG TV, and this still has issues when outputting to the AVR.

The only satisfactory result I have had is to manually delay the audio by 120ms on the AVR. It’s not perfect (as each type of stream has a different offset).

Looking forward to hearing your findings.
 

EA666

Active Member
Hi

Glad to hear you’re going to have the same setup. That will be super useful for both of us I think.

No, I didn’t get this sorted unfortunately. LG say it’s Denon’s fault, and Denon say it’s an LG issue. However, due to the HDMI 2.1 bug that plagued 2020 receivers (including mine), the store I bought the Denon from have agreed to send it back to Denon and he’s put another X3700H on order for me with the corrected HDMI chipset. It could be a while before I get the replacement, but once I do I will be ready to experiment as well.

The other thing which rules out it being an Apple TV issue is I tried the Apple TV app on the actual LG TV, and this still has issues when outputting to the AVR.

The only satisfactory result I have had is to manually delay the audio by 120ms on the AVR. It’s not perfect (as each type of stream has a different offset).

Looking forward to hearing your findings.
My C1 was manufactured in August 2021 and the Denon 3700 amp is the revised model which I've been waiting for since July.

The amp is due to be delivered tomorrow so will have a play around and see if the newer chip set amp does the trick.

Fingers crossed.
 

EA666

Active Member
One thing I do recall about the ATV 4K is that even though it has a HDMI 2.1 port it is not enable at present. 2.1 functions could be something that apple pushes out in a future update. So for the present using a standard 4k 2.0 HDMI input would be fine on the 3700.
 

EA666

Active Member
My issuse is just with a sonos sound bar, but its still there. Mines connected with optical out, as hdmi arc wont turn the sound bar on...
When you have connected the Sonos sound bar have you tried to switch of the HDMI CEC function?
 

EA666

Active Member
Hi

Glad to hear you’re going to have the same setup. That will be super useful for both of us I think.

No, I didn’t get this sorted unfortunately. LG say it’s Denon’s fault, and Denon say it’s an LG issue. However, due to the HDMI 2.1 bug that plagued 2020 receivers (including mine), the store I bought the Denon from have agreed to send it back to Denon and he’s put another X3700H on order for me with the corrected HDMI chipset. It could be a while before I get the replacement, but once I do I will be ready to experiment as well.

The other thing which rules out it being an Apple TV issue is I tried the Apple TV app on the actual LG TV, and this still has issues when outputting to the AVR.

The only satisfactory result I have had is to manually delay the audio by 120ms on the AVR. It’s not perfect (as each type of stream has a different offset).

Looking forward to hearing your findings.
Amp arrived today and connected ATV and Panasonic 820 Blu-ray player to the amp and then eARC into C1. Happy to report everything is working fine.

Only slight issue is that when playing something it display no signal for a few seconds.
 

Sotiris

Novice Member
That’s great news! Gives me hope. So hopefully when I receive my replacement Denon I won’t have any issues either. If you changed any settings would you be able to share?

I ran my LG C1 through the AVForums picture calibration settings that Phil Hinton did a month or so ago. Also enabled Deep Colour on the LG so that HDR works from an external device. And on the Apple TV I enabled 4:4:4 chroma.
I will be interested to hear what you’ve set everything to.

Thanks in advanced
 

EA666

Active Member
That’s great news! Gives me hope. So hopefully when I receive my replacement Denon I won’t have any issues either. If you changed any settings would you be able to share?

I ran my LG C1 through the AVForums picture calibration settings that Phil Hinton did a month or so ago. Also enabled Deep Colour on the LG so that HDR works from an external device. And on the Apple TV I enabled 4:4:4 chroma.
I will be interested to hear what you’ve set everything to.

Thanks in advanced
I am using the same settings. With the Denon I have plugged the ATV in CBL hdmi port and Bluray in the Bluray HDMI port. The eARC monitor to HDMI 2 on the C1.

I have left the HDMI function as enhanced on the app. and the C1 automatically brings up the Deep Colour message which I have enabled.

In the sound setting of the C1 you can go into the advanced section and select bypass.
 

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