Apple TV lip sync issues

OldSkoO1

Active Member
Delighted to have just upgraded my home cinema after about 14 years. I now have a denon x3700h, to also play ATMOS content as I have those speakers. Tv is an LG cx and I use Apple TV 4k for all my content.

I set frame rate matching (to prevent judder and to run the content as intended), this it seems is a common reason for lip sync issues. Syncs are different between atv apps and frames rates, ie dv 24hz is at a different sync to dv 50hz etc. Standard tv program 50hz requires no delay.

ATV is plugged into the AVR and I’ve tried to set a delay of 140ms on the AVR which is a rough average for most content but I still notice slight sync issues. Not really what I want after spending all this money to upgrade.

In my efforts to try and fix this, to no avail (aydessey re-calibration, atv wireless audio sync, different ports on the de on, different delay ms testing), I’m about to revert to how I had things with my old setup, the Apple TV into the tv and sound out via arc.

Now I have eARC. I would like to understand what the downside of using eARC is vs plugging the Apple TV into the AVR first. Do I loose some sound quality or processing options? I won’t use internal apps, all via Apple TV. On the flip side, why is it generally preferred to plug the ATV into the AVR first. I’m so out of touch with all the modern sound formats and config options, id like to understand them and how to solve this issue and what my compromises will be.

What should I do here?
 

next010

Distinguished Member
There is no loss of audio formats.

AppleTV 4K supports
PCM 2.0 (stereo)
PCM 5.1 and 7.1
Dolby Digital 5.1 with Atmos
Dolby MAT (PCM 7.1 + Atmos)

eARC on the LG CX supports all of the above.

LG is known for lag/sync issues especially with Dolby audio and 24Hz, it depends on the hardware if your affected or not.

eARC does have some automatic audio lag correction feature built in though its my understanding is everything must be HDMI 2.1 in the chain to use it, I could be wrong on that maybe TV/AVR is good enough.

In WebOS settings to enable eARC adjust the settings to below.
Sound/Sound Out = HDMI ARC
Sound/Additional settings/HDMI Input Audio Format = bitstream
Sound/Additional settings/Digital Sound Out = pass-through
Sound/Additional settings/eARC = enabled
 

OldSkoO1

Active Member
Thank you for confirming there are no differences in audio formats with both setups. Reassures me I'm not loosing anything by using ARC.

I've switched to eARC now

Although I had to choose Auto vs pass-through as some content ended up being multi-channel (PCM) with pass through. Using Auto I got DD-Surround on the AVR for the same content. No annoying "no signal" messages when it renegotiates at the correct frame rate. Just some quiet pops in the sound as the sound switches between DD/ATMOS/Stereo.

Atmos and DD is working great now. And most importantly, no lip sync issues anymore, across all content.

I assume that going via the AVR first is a must for UHD content that is delivered by a player or local media server, so that you can use other formats like TrueHD / DTS etc? Not so much of an issue with something like Apple TV because it decodes and only sends out DD/+ which is fine over eARC?
 

next010

Distinguished Member
I assume that going via the AVR first is a must for UHD content that is delivered by a player or local media server, so that you can use other formats like TrueHD / DTS etc? Not so much of an issue with something like Apple TV because it decodes and only sends out DD/+ which is fine over eARC?

Audio decoded as PCM is the same as the source, PCM is uncompressed digital audio.

AppleTV does not support DTS but if you use media player like InFuse with a NAS then it will decode DTS/DTS-HD and other unsupported formats as PCM audio up to 7.1
 

OldSkoO1

Active Member
Thank you again, I misunderstood the status of the signal.

I read it as Multi In > Format: 4/3/.1 - I didn't think this was what I wanted, but I realise now its a 7.1 soundtrack and the amp is handling it just fine.

I assume its better to have the original uncompressed digital audio vs the Apple TV decoding it and sending it out as DD+
 

next010

Distinguished Member
I assume its better to have the original uncompressed digital audio vs the Apple TV decoding it and sending it out as DD+

Yes if the source content has a PCM 7.1 audio track otherwise the ATV will convert the output to compressed DD 5.1
 

OldSkoO1

Active Member
I did notice that by using passthrough the lip sync returned. I made sure to test multiple apps, content and frame rates to make sure I wasn't imagined it.

Definitively, using passthrough I had lip sync issues again.
 

Coolbob

Novice Member
We have three 4K Apple TV streaming devices in our home and we were having sync problems on all streaming services with one of them. I tried resetting, updating and using the iPhone/Apple TV sync, but the problem persisted. We got faster internet service and I installed an ethernet backhaul to the WiFi mesh unit closest to the problem Apple TV device. I even ran a dedicated ethernet cable directly from our fiber internet modem to the back of the Apple TV and still programs slipped out of sync. I swapped other Apple TV devices from elsewhere in the home into the problem room and the sync problem persisted.



As an act of desperation, I replaced the 10' HDMI cable that ran through the wall from the Apple TV to the television and the sync problem went away! The 'old' cable was only a few years old and looks fine, but I guess it degraded somehow and was causing the problem.



In addition to sharing my experience here, I made a YouTube video in the hopes of helping others who are having Apple TV sync problems. Please feel free to share with others or in any forums.
 

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