LG C9 eARC Info Thread - Page 26 - AVS Forum | Home Theater Discussions And Reviews
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post #751 of 869 Old 10-15-2019, 08:23 AM
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Originally Posted by mazymus View Post
So if I connect all my HDMI sources to normal HDMIs on the C9, and route from C9 eARC HDMI to eARC HDMI on soundbar, then I’m getting all the benefits of eARC?
No!
Stick with the previous setup - route everything trough the soundbar - you will have far fewer audio problems.

Connect a source to the C9 only if that source requires a feature that the soundbar does not support - such as VRR, HFR, ALLM, etc.
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post #752 of 869 Old 10-15-2019, 08:36 AM
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Originally Posted by jmpage2 View Post
Ah, but I'm pretty sure that audio sync correction is now a mandatory part of the HDMI specification in HDMI 2.1 with eARC so if it's not working properly it should be viewed as bug/breakage and not just "this manufacturer is not following the standard".
Yes, let's hope that ALL manufacturers implement the mandatory Lip-Sync so eARC does not become a crippled feature, ridden with delays.

If this new HDMI 2.1 strategy does not pay, we will go back to the classic solution - AVR/soundbar in the middle of everything, not at the end of the HDMI chain.

And this means that ALL of the HDMI devices have to be HDMI 2.1 or if not, to respect/report the Lip-Sync delay over older versions of HDMI... And we already know the situation of Lip-Sync over HDMI 2.0... It's a mess!
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post #753 of 869 Old 10-15-2019, 08:53 AM - Thread Starter
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Originally Posted by dfa973 View Post
Yes, let's hope that ALL manufacturers implement the mandatory Lip-Sync so eARC does not become a crippled feature, ridden with delays.

If this new HDMI 2.1 strategy does not pay, we will go back to the classic solution - AVR/soundbar in the middle of everything, not at the end of the HDMI chain.

And this means that ALL of the HDMI devices have to be HDMI 2.1 or if not, to respect/report the Lip-Sync delay over older versions of HDMI... And we already know the situation of Lip-Sync over HDMI 2.0... It's a mess!
Well, I imagine that it's to the advantage of display makers and sound equipment makers to completely conform to the specification. Not doing so means that prospective owners learn what the "bad" combinations are and avoid those devices.

Also not all sound formats are compatible with the timing scheme used. I believe that PCM audio is not timing adjusted for example.

A hybrid solution is possible where some devices are connected directly to the display and then on to the AVR and other devices with more limited capabilities are connected to the AVR directly.

People have focused on the HD audio component of eARC as being the selling point but for me and probably some other people it's maxing out the video capabilities of our displays that is the real selling point of eARC.
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post #754 of 869 Old 10-15-2019, 10:03 AM
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Originally Posted by dfa973 View Post
No!
Stick with the previous setup - route everything trough the soundbar - you will have far fewer audio problems.

Connect a source to the C9 only if that source requires a feature that the soundbar does not support - such as VRR, HFR, ALLM, etc.
Yes, but I've also used up all the HDMI ports on my Denon so I'm using a few connected directly to TV (Xbox, Fire TV and Chromecast Ultra). It's mostly the devices I don't use as often.

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post #755 of 869 Old 10-15-2019, 12:09 PM
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Originally Posted by dfa973 View Post
Yes, let's hope that ALL manufacturers implement the mandatory Lip-Sync so eARC does not become a crippled feature, ridden with delays.

If this new HDMI 2.1 strategy does not pay, we will go back to the classic solution - AVR/soundbar in the middle of everything, not at the end of the HDMI chain.

And this means that ALL of the HDMI devices have to be HDMI 2.1 or if not, to respect/report the Lip-Sync delay over older versions of HDMI... And we already know the situation of Lip-Sync over HDMI 2.0... It's a mess!

So wait, I wont get the benefits of eARC if source is coming from any old HDMI? I thought once the source is given off to TV, and TV and soundbar are connected via eARC, then thats all needed to sync the video/audio. Is this wrong?!
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post #756 of 869 Old 10-16-2019, 12:24 AM
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Originally Posted by mazymus View Post
So wait, I wont get the benefits of eARC if source is coming from any old HDMI?
If the source does not report the Lip-Sync delay, eARC does not resolve anything.

And all or most non-HDMI 2.1 sources do not report anything - leaving to the sink the management of delays.

That's why:
1. - sources originating inside the TV (cable, antenna, streaming apps, USB) that are played to the internal speakers do not have Lip-Sync problems (there are exceptions...) - because of minimal and local processing (low lag), but immediately as you use ARC or eARC to send the audio to an external device you may end up with delays in some cases (because some audio formats go through further processing, and that adds delays, the TV does not report the Lip-Sync and the audio sink must cope with that);

2. - sources that are connected to the TV and go via ARC or eARC to an AVR/soundbar experience audio delays - because you have 2 devices (source + TV) that each introduces delays and all the delays end up at the audio sink (AVR/soundbar);

3. - sources that are connected to the AVR/soundbar experience lower delays or no delays at all - because you have only 1 device (the source) that adds delay to the signal and the AVR/soundbar can correct the delays - if there are still delays in this scenario it means that the accumulated delays are bigger than what the AVR/soundbar can correct (sometimes in this cases adjusting the Lip-Sync at the AVR/soundbar level does not resolve the problem or exacerbates the problem);


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Originally Posted by mazymus View Post
I thought once the source is given off to TV, and TV and soundbar are connected via eARC, then thats all needed to sync the video/audio. Is this wrong?!
No, it's true, but the Lip-Sync works only if the TV is a good boy and reports to the downstream device the delay, and the downstream device uses the Lip-Sync.

When all of our devices will be HDMI 2.1 devices and all of those devices will be forced to report the Lip-Sync delay - in that moment this mess of audio delays will be resolved. eARC by itself will not cure the world of audio delays.
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post #757 of 869 Old 10-16-2019, 09:48 AM
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Originally Posted by dfa973 View Post
If the source does not report the Lip-Sync delay, eARC does not resolve anything.

And all or most non-HDMI 2.1 sources do not report anything - leaving to the sink the management of delays.

That's why:
1. - sources originating inside the TV (cable, antenna, streaming apps, USB) that are played to the internal speakers do not have Lip-Sync problems (there are exceptions...) - because of minimal and local processing (low lag), but immediately as you use ARC or eARC to send the audio to an external device you may end up with delays in some cases (because some audio formats go through further processing, and that adds delays, the TV does not report the Lip-Sync and the audio sink must cope with that);

2. - sources that are connected to the TV and go via ARC or eARC to an AVR/soundbar experience audio delays - because you have 2 devices (source + TV) that each introduces delays and all the delays end up at the audio sink (AVR/soundbar);

3. - sources that are connected to the AVR/soundbar experience lower delays or no delays at all - because you have only 1 device (the source) that adds delay to the signal and the AVR/soundbar can correct the delays - if there are still delays in this scenario it means that the accumulated delays are bigger than what the AVR/soundbar can correct (sometimes in this cases adjusting the Lip-Sync at the AVR/soundbar level does not resolve the problem or exacerbates the problem);



No, it's true, but the Lip-Sync works only if the TV is a good boy and reports to the downstream device the delay, and the downstream device uses the Lip-Sync.

When all of our devices will be HDMI 2.1 devices and all of those devices will be forced to report the Lip-Sync delay - in that moment this mess of audio delays will be resolved. eARC by itself will not cure the world of audio delays.
Thanks for this. I was hoping that all I needed was an AVR/Processor that supported eARC and I could connect some of my sources to the TV and all would be fine. But if all sources need to be HDMI 2.1 that could be quite a while coming. I haven't heard anything re cable boxes, UHD players, Apple TV supporting HDMI 2.1. In some respects good news as I don't have to worry about changing AVR/Processor just for eARC support and just worry about more substantial features for an AVR/Processor swap out - George

Spoiler!
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post #758 of 869 Old 10-16-2019, 11:17 AM
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Originally Posted by ggrossen View Post
But if all sources need to be HDMI 2.1 that could be quite a while coming. I haven't heard anything re cable boxes, UHD players, Apple TV supporting HDMI 2.1.
Implementing HDMI 2.1 to the myriad of devices will be a nightmare, that will take a lot of time and of course, the HDMI 2.1 ports, switches and repeaters are not cheap. And when the device does not actually use any major HDMI 2.1 feature, the case for upgrading to HDMI 2.1 just to resolve some "minor" glitches is going to be very hard.

Anyway, HDMI 2.1 receivers are due in 2020+2021.
Next-gen consoles also in 2020.
Graphics cards? Probably next year.
Blu-ray players... god knows when...
Streamers..., STBs...
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post #759 of 869 Old 10-16-2019, 11:51 AM
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Originally Posted by ggrossen View Post
Thanks for this. I was hoping that all I needed was an AVR/Processor that supported eARC and I could connect some of my sources to the TV and all would be fine. But if all sources need to be HDMI 2.1 that could be quite a while coming. I haven't heard anything re cable boxes, UHD players, Apple TV supporting HDMI 2.1. In some respects good news as I don't have to worry about changing AVR/Processor just for eARC support and just worry about more substantial features for an AVR/Processor swap out - George
Well my understanding is that only the display and the audio processor have any reason to get involved since they are the two output devices (one for audio, one for video) that add delays to the output due to processing the signal. The source device should be sending the audio and video in sync in the signal and any switches and other devices along the way should be passing it together (the audio is interleaved with the video in the signal as far as I know anyhow). So really there should not be any reason for lip sync to be involved in anything other than the display and avr and hence nothing else should need to be HDMI 2.1 nor have any clue about ARC, eARC or lip sync at all. The only way a source device ought to have anything to do with lip sync issues would be if it generates the audio and video separately and combines them and isn't combining them in sync, which would just be broken by design and not what lip sync is meant to fix.

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post #760 of 869 Old 10-16-2019, 12:47 PM
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Originally Posted by lsorensen View Post
Well my understanding is that only the display and the audio processor have any reason to get involved since they are the two output devices (one for audio, one for video) that add delays to the output due to processing the signal. The source device should be sending the audio and video in sync in the signal and any switches and other devices along the way should be passing it together (the audio is interleaved with the video in the signal as far as I know anyhow). So really there should not be any reason for lip sync to be involved in anything other than the display and avr and hence nothing else should need to be HDMI 2.1 nor have any clue about ARC, eARC or lip sync at all. The only way a source device ought to have anything to do with lip sync issues would be if it generates the audio and video separately and combines them and isn't combining them in sync, which would just be broken by design and not what lip sync is meant to fix.
Nope. This is NOT how it works!

Decoding audio and video in devices requires some processing time, and each process introduces different time delays, or latencies, in each device. When multiple devices are connected together in a chain, with each device decoding or processing audio and video, this latency can build up. Additionally, while each device can account for its own audio/video sync, it’s a much harder problem when the audio and video are played from different devices - e.g. video out of a television, audio out of a soundbar connected over HDMI-ARC or eARC.

The HDMI specification includes an Auto-Lip-Sync parameter that is intended to address this problem. In an ideal world, each device in an HDMI chain is supposed to report its latency and effective Lip-Sync delay (the difference between audio and video caused by these processing latencies), and the first device (the source) in the HDMI chain should compensate for all of the latency values reported by all of the downstream devices (sinks, TV, AVR, etc). For example, if I had a set-top box connected to a TV, and then a soundbar connected to that TV over HDMI ARC, the set-top box should compensate for the video latency of the TV, and the audio delay of BOTH the TV and the soundbar. This would guarantee that both the picture and sound were reproduced at the same time on both of the sinks, video (TV) and audio (soundbar).

But sink devices don’t typically include the HDMI Auto-Lip-Sync parameter, and even if this parameter is made available, source devices don’t use that parameter when calculating audio/video sync.

So the source must use the Lip-Sync parameters reported from every device in the HDMI chain and sync both video and audio to be matched at the sinks. And most devices do not report! So there is no calculation made to sync the A/V!

Since Lip-Sync has been made mandatory in HDMI 2.1 (but not in HDMI 2.0 or lower) and the job of syncing is done at the source-level it means that you must use a complete HDMI 2.1 chain, from source to all of the sinks or intermediary devices.

An eARC TV and an eARC receiver or soundbar is not enough (except when audio is originating at the eARC TV)
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post #761 of 869 Old 10-16-2019, 01:16 PM
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Originally Posted by dfa973 View Post
Nope. This is NOT how it works!

Decoding audio and video in devices requires some processing time, and each process introduces different time delays, or latencies, in each device. When multiple devices are connected together in a chain, with each device decoding or processing audio and video, this latency can build up. Additionally, while each device can account for its own audio/video sync, it’s a much harder problem when the audio and video are played from different devices - e.g. video out of a television, audio out of a soundbar connected over HDMI-ARC or eARC.

The HDMI specification includes an Auto-Lip-Sync parameter that is intended to address this problem. In an ideal world, each device in an HDMI chain is supposed to report its latency and effective Lip-Sync delay (the difference between audio and video caused by these processing latencies), and the first device (the source) in the HDMI chain should compensate for all of the latency values reported by all of the downstream devices (sinks, TV, AVR, etc). For example, if I had a set-top box connected to a TV, and then a soundbar connected to that TV over HDMI ARC, the set-top box should compensate for the video latency of the TV, and the audio delay of BOTH the TV and the soundbar. This would guarantee that both the picture and sound were reproduced at the same time on both of the sinks, video (TV) and audio (soundbar).

But sink devices don’t typically include the HDMI Auto-Lip-Sync parameter, and even if this parameter is made available, source devices don’t use that parameter when calculating audio/video sync.

So the source must use the Lip-Sync parameters reported from every device in the HDMI chain and sync both video and audio to be matched at the sinks. And most devices do not report! So there is no calculation made to sync the A/V!

Since Lip-Sync has been made mandatory in HDMI 2.1 (but not in HDMI 2.0 or lower) and the job of syncing is done at the source-level it means that you must use a complete HDMI 2.1 chain, from source to all of the sinks or intermediary devices.

An eARC TV and an eARC receiver or soundbar is not enough (except when audio is originating at the eARC TV)
Then the HDMI designers were idiots. I don't think they would have done something that stupid.

Simple design: TV tells AVR what its processing delay is. AVR delays audio for that amount of time minus it's own processing time by buffering it (this does not require that much ram). All source devices send audio and video in sync. Problem solved. Only two devices have any reason to deal with synchronization at all. Making the source device responsible for delaying audio vs video would be idiotic.

If HDMI did it any differently, then no wonder this never works.

Also my reading of the HDMI 2.1 info is that lip sync is a mandatory part of eARC and an optional part of ARC. It has nothing to do with any other HDMI link. Only ARC and eARC. That too makes me think my idea is in fact how it works. It's the simplest and it would work and avoids complicating every other device in the setup.

Of course the hdmi specs aren't public so I can't check to be sure.

The discussions here however agree with me and the audio delay is added by the AVR based on the processing delay reported by the display:
https://www.avsforum.com/forum/90-re...sync-work.html

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post #762 of 869 Old 10-16-2019, 07:03 PM
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Originally Posted by dfa973 View Post
Since Lip-Sync has been made mandatory in HDMI 2.1 (but not in HDMI 2.0 or lower) and the job of syncing is done at the source-level it means that you must use a complete HDMI 2.1 chain, from source to all of the sinks or intermediary devices.
HDMI Lip-Sync has been around since HDMI 3.1, although optional, and the only thing I've seen about HDMI 2.1 is that they've made it mandatory for eARC. Do you have some other source info?
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post #763 of 869 Old 10-17-2019, 02:37 AM
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Originally Posted by lsorensen View Post
Then the HDMI designers were idiots. I don't think they would have done something that stupid.
That is the official way that HDMI deals with delays in the transmission chain - at the source - and all devices must collaborate for that to work. Stupid or not.
We already know that this mechanism does not work - because manufacturers did not properly implement this feature.
This is why today we still have manual delay controls at the sink level (TV, receiver, soundbar, etc) - and no automatic delay control at the source level.


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Also my reading of the HDMI 2.1 info is that lip sync is a mandatory part of eARC and an optional part of ARC. It has nothing to do with any other HDMI link. Only ARC and eARC. That too makes me think my idea is in fact how it works. It's the simplest and it would work and avoids complicating every other device in the setup.
True, but tell that to all of eARC users that have experienced delays when using eARC TVs and eARC AVRs - that combination should NOT have any delay problems, no?
Why there are still Lip-Sync issues when the link is eARC?
If you search on this forum you can see a pattern:
  • If the source-TV-AVR sends PCM or DTS soundtracks = no delay.
  • If the source is connected directly to the AVR/soundbar = no delay.
  • Audio originating from internal apps (ex. Netflix) = no delay.
  • Atmos Blu-ray on Xbox to eARC TV then to eARC AVR/soundbar = delay
  • Atmos Blu-ray on Xbox direct to AVR/soundbar = no delay
and so on, and on, and on...

Why this variation if eARC should take care of the TV-AVR link delay?

What is different in all of those scenarios?
1. - the source (local or upstream);
2. - audio format (complexity, processing, etc.);

So, we go back to the delay that is originating (or not) at the source level.


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Originally Posted by lsorensen View Post
The discussions here however agree with me and the audio delay is added by the AVR based on the processing delay reported by the display:
https://www.avsforum.com/forum/90-re...sync-work.html
To me, that discussion only confirms that the Lip-Sync mechanism is broken/unfunctional and that's is why there are MANUAL delay controls at the video and audio sink level.
Note1: regarding your "delay reported by the display" - in that discussion, you can even read that Samsung and Vizio TVs do NOT report any delays, ever...
Note2: also regarding your "delay reported by the display" - devices should report de delay to the upstream device (source), not to the downstream device (audio sink, AVR, soundbar);

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HDMI Lip-Sync has been around since HDMI 3.1, although optional, and the only thing I've seen about HDMI 2.1 is that they've made it mandatory for eARC.
True, but the Lip-Sync mechanism works at the source level and I think that the mandatory Lip-Sync for eARC is there mostly for audio originating at the TV level (for future lossless/HD audio streaming via internal/local apps) and not as a cure for all of the Lip-Sync delays that accumulate when the source is upstream.
My hope is that the HDMI Forum will require that all HDMI 2.1 devices (including sources) report and account for Lip-Sync delays, forcing manufacturers to do their job in syncing the audio across the whole HDMI chain, not only across the eARC link.
It will be unfortunate and a lost opportunity that the Lip-Sync mechanism still is left optional at the source level.
4K, 8K, HDR, VRR, HFR will only increase the video processing time inside a device - increasing the delay of video versus audio, making the Lip-Sync feature a critical one and most importantly the Lip-Sync error is and it will be very dynamic at the source level - just think what will happen at a game console level, changing the game or its settings may change the resolution, maybe is WCG, maybe is HDR, maybe is VRR, maybe is Dolby Vision, maybe not, all of that variation will also vary the Lip-Sync error.
If the HDMI 1.3a introduced fixed Lip-Sync delay, the HDMI 2.0 introduced dynamic Lip-Sync (perfect for content changing on the fly). Both are still optional... Not mentioning that the fixed Lip-Sync delay in HDMI 1.3 is unrealistic... Lip-Sync error is very rarely fixed!
In 2008, two years after the introduction of HDMI 1.3a the effects of the optional Lip-Sync feature was clear:
Quote:
There are no HDMI-ATC system level Lip Sync performance compliance specifications, or test tools designed to ensure accurate Lip Sync delivery. There is no "timing conformance" specification that must be demonstrated to any authority in order to build a compliant product.
There is an increasing awareness in both broadcast engineering and the CE industry that audio-video synchronization errors, usually seen as problems with lip sync, are occurring more frequently and often with greater magnitude. With the advent of digital processing in CE devices, the issue has become critical. Some CE manufacturers deny there is a problem, believing the audio/video asynchronies in their units to be imperceptible. Knowing how to measure audio/video delays and compensate for them is become increasingly important.

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Do you have some other source info?
No.
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Given all of these implementation issues, can LG resolve these problems through a firmware update at some point in the future? Or was the "2.1" label pre-mature and nothing more than a technicality to please the marketing department?
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post #765 of 869 Old 10-17-2019, 03:07 PM
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Given all of these implementation issues, can LG resolve these problems through a firmware update at some point in the future? Or was the "2.1" label pre-mature and nothing more than a technicality to please the marketing department?
Only LG would know. There are certainly claims that some update is coming soon that should improve eARC and HDMI 2.1. I guess we will know when it happens.

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post #766 of 869 Old 10-18-2019, 01:52 PM
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Hi there,

I have a C9 and an old DENON AVR-E400, connected by HDMI (ARC).

I also have problem when I use my Shield with Plex, DTS-MA is played in stereo (even if the receiver tell me "DTS").
I'd like to use WebOs Plex player instead of the shield, but I also have trouble with DTS-MA files.

I' thinking about buying a new receiver, so I don't have to use ARC with the Shield. I just have a 5.1 sound system, and I don't plan to move (no place for more speakers).
We use our receiver for movies with Plex, Amazon prime, Netflix / TV / internet radio.

I'm looking for a cheap receiver.

Any advice for the receiver? (of course, I'm also listening if you have another way).
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post #767 of 869 Old 10-18-2019, 02:06 PM
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Originally Posted by VerbatimMtl View Post
Hi there,

I have a C9 and an old DENON AVR-E400, connected by HDMI (ARC).

I also have problem when I use my Shield with Plex, DTS-MA is played in stereo (even if the receiver tell me "DTS").
I'd like to use WebOs Plex player instead of the shield, but I also have trouble with DTS-MA files.

I' thinking about buying a new receiver, so I don't have to use ARC with the Shield. I just have a 5.1 sound system, and I don't plan to move (no place for more speakers).
We use our receiver for movies with Plex, Amazon prime, Netflix / TV / internet radio.

I'm looking for a cheap receiver.

Any advice for the receiver? (of course, I'm also listening if you have another way).
... Solved, I haven't checked the "Passtrough" option.... and it works! Finally can use my shield with DTS-MA without problem.
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post #768 of 869 Old 10-19-2019, 01:08 AM
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Hi,
I have two questions regarding the LG C9 and Denon X4400H:

1. How die you manage to enable eARC without CEC? I followed the hints in the first post, but as soon as I enable ARC, the LG enables „Simplink“ as well... (and when I disable Simplink, ARC is disabled).

2. Is there a was to get Dolby Atmos work with the X4400H in the meantime? Although I can enable eARC (with passthrough), the Atmos Checkbox is greyed out... :-(
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post #769 of 869 Old 10-19-2019, 01:14 AM
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Originally Posted by martiko View Post
Hi,
I have two questions regarding the LG C9 and Denon X4400H:

1. How die you manage to enable eARC without CEC? I followed the hints in the first post, but as soon as I enable ARC, the LG enables „Simplink“ as well... (and when I disable Simplink, ARC is disabled).

2. Is there a was to get Dolby Atmos work with the X4400H in the meantime? Although I can enable eARC (with passthrough), the Atmos Checkbox is greyed out... :-(
Denon X4400H is a 2017 generation AVR and it does not work with LGs C9 eARC, read the first posts of this thread and there are more details here.
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post #770 of 869 Old 10-19-2019, 02:00 AM
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Originally Posted by dfa973 View Post
Denon X4400H is a 2017 generation AVR and it does not work with LGs C9 eARC, read the first posts of this thread and there are more details...
I am a bit suprised, as I can enable eARC and get correct sound... So obvoiusly „standard“ ARC is used, although eARC is enabled...

Do you see a chance, that eARC could be get to work with firmware updates for either X4400H or the LG C9?
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post #771 of 869 Old 10-20-2019, 06:21 AM
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Originally Posted by martiko View Post
I am a bit suprised, as I can enable eARC and get correct sound... So obvoiusly „standard“ ARC is used, although eARC is enabled...

Do you see a chance, that eARC could be get to work with firmware updates for either X4400H or the LG C9?

Just for information: the latest SW 4.70.05 (now officially available in Germany) does not solve the ATMOS problem.


I still get Dolby 5.1 (etc.) sound via eARC to my X4400H, but Atmos is not working (checked with Amazon Video and local playback files, which are play with ATMOS when only internal Speaker is enabled).
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post #772 of 869 Old 10-20-2019, 11:59 AM
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Originally Posted by martiko View Post
Do you see a chance, that eARC could be get to work with firmware updates for either X4400H or the LG C9?
There is a chance that the expected winter2019/spring2020 big eARC firmware update for the C9 might resolve some compatibility problems but nothing is known right now. You just have to wait.
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post #773 of 869 Old 10-21-2019, 01:14 AM
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Quote:
Originally Posted by martiko View Post
Just for information: the latest SW 4.70.05 (now officially available in Germany) does not solve the ATMOS problem.


I still get Dolby 5.1 (etc.) sound via eARC to my X4400H, but Atmos is not working (checked with Amazon Video and local playback files, which are play with ATMOS when only internal Speaker is enabled).
According to the list here https://www.avsforum.com/forum/40-ol...l#post58227638 your Denon AVR-X4400H is listed as not work with C9s eARC.
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post #774 of 869 Old 10-22-2019, 11:20 AM
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Stolen from the C9 thread:


https://lgcommunity.us.com/discussio...#Comment_13639


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Good Morning,
LG will be introducing PCM Multi-channel support when using eARC in the 2 quarter of 2020. This will be possible via a software update for 2019 & 2020 TV that support eARC.
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post #775 of 869 Old 10-22-2019, 09:08 PM
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@dfa973 - Thanks for the detailed explanation on the HDMI lip-sync issue. However, I can't help but notice an obvious flaw in this design so hopefully this is something you may be able to elaborate on.

One of the biggest selling points of the recent LG OLED's is their minimal input lag, which is important for gaming use-cases (less so for movies). I would imagine that video processing is far more intensive than audio processing (speculation), so why is it that in LG's case the video leads the audio when utilising ARC or eARC to passthrough audio from externally connected HDMI source devices? Shouldn't setting audio to bypass passthrough theoretically be faster (processing wise) than to process and display a video signal?

From what you've said, I understand this as the source device should be responsible for delaying the faster of the two audio-visual options in order to get them both in sync, however, wouldn't this type of design limit input lag to the slowest of the two audio-visual options, which in this case theoretically shouldn't exist (on the assumption that video is more processor intensive than audio passthrough)? The way I see things, LG have prioritised video processing and left audio processing toward the back of the queue, which has introduced the lip-sync issues - this is evident because lip-sync issues disappear when you go Source > Soundbar/AVR > TV (video and audio in sync), but appear when you go Source > TV > Soundbar/AVR (video leads audio, but only for Dolby related content).

Could you please share your thoughts on this aspect? I'm just trying to understand from a technical perspective as to why LPCM and DTS can operate perfectly in sync via Source > TV > Soundbar/AVR setup, whereas Dolby audio will cause the video to lead the audio by around 1sec via the same connection setup. Surely this is an LG coding problem rather than a HDMI standard problem, seeing as LPCM and DTS work perfectly fine? Appreciate your input on the matter.
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post #776 of 869 Old 10-23-2019, 07:15 AM
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Quote:
Originally Posted by DJ_GLiTCH View Post
One of the biggest selling points of the recent LG OLED's is their minimal input lag, which is important for gaming use-cases (less so for movies). I would imagine that video processing is far more intensive than audio processing (speculation)
No speculation needed! It is true that most of the time video is behind the audio, because of various filters, scalers, decoders, etc. that are employed in the video path and less processing in the audio path.
Without a mechanism to ensure lip sync, audio often plays ahead of video, because the latencies involved in processing and sending video frames are greater than the latencies for audio.


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, so why is it that in LG's case the video leads the audio when utilising ARC or eARC to passthrough audio from externally connected HDMI source devices?
This problem surfaced on the LG TV sets when LG introduced Dolby Atmos compatibility (the 2016 B6/C6 were the first if I remember correctly). If you scour the net, B6/C6, B7/C7, B8/C8 and C9 models are mentioned every time there is a delayed audio issue and most of the issues are with Dolby encoded audio.
But the Lip-Sync problem is older than that and is present on every TV (not only LG) that can send audio to an external audio device, via Optical, Coaxial or HDMI-ARC/eARC.
On the LG side, the Lip-Sync problem is exacerbated by the integrated transcoder that acts almost exclusively for Dolby content and it seems to be active even when Passthrough is active.
We can skip the transcoder by:
  • 1. Using another audio format that is not processed by the transcoder (MPEG, LPCM, DTS, etc.)
  • 2. Connect source to an audio sink (AVR/soundbar) instead of the video sink (TV) but the audio sink must be able to correct Lip-Sync. There are lots of soundbars that do not have any kind of Lip-Sync correction! Most AVRs have an integrated Lip-Sync correction mechanism that should be able to be set per source and/or content type.
  • 3. Letting the TV to be also the audio sink - by using only the integrated speakers - not a real solution...


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Originally Posted by DJ_GLiTCH View Post
Shouldn't setting audio to bypass passthrough theoretically be faster (processing wise) than to process and display a video signal?
Not if the transcoder is active...

Quote:
Originally Posted by DJ_GLiTCH View Post
From what you've said, I understand this as the source device should be responsible for delaying the faster of the two audio-visual options in order to get them both in sync, however, wouldn't this type of design limit input lag to the slowest of the two audio-visual options, which in this case theoretically shouldn't exist (on the assumption that video is more processor intensive than audio passthrough)?
The Lip-Sync correction (automatic or manual) acts only on the audio path. So the video lag is not influenced. And the built-in correction can only delay the audio, not speed up the audio - if the audio is behind the video. There are external synchronizers that can do delay and speed up. But sadly, most CE devices only can delay the audio. Most of the time, if the audio is behind video the consumer has no way to correct that.

Quote:
Originally Posted by DJ_GLiTCH View Post
The way I see things, LG have prioritised video processing and left audio processing toward the back of the queue, which has introduced the lip-sync issues - this is evident because lip-sync issues disappear when you go Source > Soundbar/AVR > TV (video and audio in sync), but appear when you go Source > TV > Soundbar/AVR (video leads audio, but only for Dolby related content).
This is why the classic scenario of using a receiver as an A/V hub is the only solution for a lot of problems. And the advent of VRR, HFR, G-SYNC features will make the use of an HDMI 2.1 receiver almost mandatory in the future because eARC by itself does not solve the Lip-Sync problem if the Lip-Sync mechanism is not implemented at the source level.
Choosing a soundbar instead of a receiver will be not a wise move if the soundbar has no integrated Lip-Sync correction mechanism!

Quote:
Originally Posted by DJ_GLiTCH View Post
Could you please share your thoughts on this aspect? I'm just trying to understand from a technical perspective as to why LPCM and DTS can operate perfectly in sync via Source > TV > Soundbar/AVR setup, whereas Dolby audio will cause the video to lead the audio by around 1sec via the same connection setup. Surely this is an LG coding problem rather than a HDMI standard problem, seeing as LPCM and DTS work perfectly fine? Appreciate your input on the matter.
Yes, it is an LG generated problem - by using the transcoder for Dolby Atmos compatibility - but if you look at other brands you will see the same problem - Dolby audio is delayed - even when the TV has no Atmos support (and most brands and models do not support Atmos).
Why?
I can only speculate that all the Dolby encoded audio requires more time/power to be unpacked from the source and then repacked and sent to the destination and the lag is more evident when the destination is external (via Optical/Coaxial or ARC/eARC). Even when there is no transcoding, the unpacking and repacking are mandatory when audio is moved (passed) from the source (external or internal) to the destination (external or internal).
In one bedroom I have a 2013 gen. TV that is not Atmos compatible (only DD/DD+ compatible) and I must add at least 40ms of audio delay by using the AVR to correct the Lip-Sync with DD/DD+ content - but when I switch to the TV speakers the delay is very small (but perceptible) and that delay disappears completely when I switch to PCM or other codecs than Dolby.
Maybe the DTS processing is not that intensive or is more efficient - as for PCM, the complexity is zero...

As I have said before, this Dolby lag is present on every brand and the problem is very old, older than the LG OLED TVs and it does not seem to be a solution other than inserting an AVR between the source and the TV.
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post #777 of 869 Old 10-23-2019, 03:00 PM
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Quote:
Originally Posted by dfa973 View Post
This problem surfaced on the LG TV sets when LG introduced Dolby Atmos compatibility (the 2016 B6/C6 were the first if I remember correctly). If you scour the net, B6/C6, B7/C7, B8/C8 and C9 models are mentioned every time there is a delayed audio issue and most of the issues are with Dolby encoded audio.
Does this mean that DD and DD+ audio was in sync prior to the B6/C6 when support for Dolby Atmos was introduced? Whilst Atmos content is different, I thought it would take a very similar amount of processing effort since it utilises pre-existing standardised containers (DD+ and TrueHD).

Quote:
Originally Posted by dfa973 View Post
On the LG side, the Lip-Sync problem is exacerbated by the integrated transcoder that acts almost exclusively for Dolby content and it seems to be active even when Passthrough is active.
I understand this as being an LG problem rather than an industry standard or Dolby problem - do you feel that this is something LG are responsible for fixing? To me, this would imply that they have not programmed the proper utilisation or efficient use of their Dolby transcoding process.

Quote:
Originally Posted by dfa973 View Post
The Lip-Sync correction (automatic or manual) acts only on the audio path. So the video lag is not influenced. And the built-in correction can only delay the audio, not speed up the audio - if the audio is behind the video. There are external synchronizers that can do delay and speed up. But sadly, most CE devices only can delay the audio. Most of the time, if the audio is behind video the consumer has no way to correct that.
Thanks for the clarification on this - that's great to know. I was worried that our single-digit input lag might get bumped up due to any audio sync issues, so this is a relief.


Quote:
Originally Posted by dfa973 View Post
This is why the classic scenario of using a receiver as an A/V hub is the only solution for a lot of problems. And the advent of VRR, HFR, G-SYNC features will make the use of an HDMI 2.1 receiver almost mandatory in the future because eARC by itself does not solve the Lip-Sync problem if the Lip-Sync mechanism is not implemented at the source level.
Choosing a soundbar instead of a receiver will be not a wise move if the soundbar has no integrated Lip-Sync correction mechanism!
I purchased a LG SL8YG soundbar with my LG C9, which does offer lip-sync correction for the HDMI input on the soundbar. The problem is that almost all soundbars are limited to 1 or 2 x HDMI inputs, which is not enough for most people.

However, this really shouldn't be an issue as the vast majority of TVs have 4 x HDMI inputs, which would permit 3 x direct HDMI inputs and 1 x indirect HDMI input that passes through a soundbar or AVR (which is the ARC or eARC input). I would expect, like many others, that this second type of setup would work perfectly, but in reality it doesn't if you wish to use any kind of Dolby audio. Even the same brand and generation of products doesn't seem to help.

The only time this kind of setup will work is when you use the internal TV apps (e.g. Netflix can playback Dolby Atmos over ARC or eARC perfectly in sync) or you use LPCM or DTS audio from external sources. Can you please elaborate on why internal TV apps don't experience any kind of audio lip-sync issues, whereas external HDMI connected sources do?

I might be wrong about this, but I would have thought from a technical perspective that audio being received from either internal or external sources wouldn't matter as it still needs to be passed on via ARC or eARC - doesn't seem to matter whether it's lossless or lossy Dolby content on external devices either, for what it's worth.
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post #778 of 869 Old 10-24-2019, 05:59 AM
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Quote:
Originally Posted by DJ_GLiTCH View Post
Does this mean that DD and DD+ audio was in sync prior to the B6/C6 when support for Dolby Atmos was introduced?
Depends.
As I have said, most TVs insert some audio delay when they send audio to an external device. Most of the time, that audio delay is small or very small.
When the audio is Dolby encoded that delay gets bigger, even when the TV has no transcoder.

Quote:
Originally Posted by DJ_GLiTCH View Post
Whilst Atmos content is different, I thought it would take a very similar amount of processing effort since it utilises pre-existing standardised containers (DD+ and TrueHD).
It seems that is not the case, as Atmos compatible TVs do exhibit a fairly good amount of Lip-Sync issues.


Quote:
Originally Posted by DJ_GLiTCH View Post
I understand this as being an LG problem rather than an industry standard or Dolby problem
It is a shared problem between manufacturers and Dolby. All TVs have Lip-Sync issues when the source is external and the audio is sent away and it seems that the Dolby codecs are the most affected by the internal processing - transcoding or not.

Quote:
Originally Posted by DJ_GLiTCH View Post
- do you feel that this is something LG are responsible for fixing? To me, this would imply that they have not programmed the proper utilisation or efficient use of their Dolby transcoding process.
Surely, LG can speed up the transcoding to improve the audio lag. But otherwise, the Dolby lag is a universal thing that has not been resolved for many years.


Quote:
Originally Posted by DJ_GLiTCH View Post
Can you please elaborate on why internal TV apps don't experience any kind of audio lip-sync issues, whereas external HDMI connected sources do?
Because the audio path is shorter, with less unpacking and re-packing.
The shortest path is an internal app that plays audio via internal speakers.
When you add the soundbar I am sure that there is some delay, but it is imperceptible by you.
When you add an external source to the TV-soundbar chain you further increase the audio path - at this stage, you have 3 devices that process audio and each of them inserts audio sync issues, that accumulate at the soundbar level (audio sink).
That is why inserting an AVR/soundbar between the source and the TV improves the Lip-Sync issues - that way, the audio path becomes shorter (2 devices, instead of 3) and the AVR has the meaning to correct the delay.

Quote:
Originally Posted by DJ_GLiTCH View Post
I might be wrong about this, but I would have thought from a technical perspective that audio being received from either internal or external sources wouldn't matter
For the TV it matters, because the source already may send delayed video vs audio, the TV adds its delay, the Optical/ARC/eARC re-packing adds its delay, the AVR/soundbar adds a further delay.
All those delays accumulate - and at one point it will be perceptible - beyond the tolerable level.
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post #779 of 869 Old 10-24-2019, 12:07 PM
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Just got Firmware 4.70.05 and it seems to have fixed the eARC issues I was having on the last firmware.
The Netflix App is now giving me Atmos again back to my Denon 3700.
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post #780 of 869 Old 10-25-2019, 10:00 AM
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update may have also fixed the hdmi handshake with the xfinity 4k STB for me, working okay after three days of no reboot required

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Originally Posted by tony_reilly View Post
Just got Firmware 4.70.05 and it seems to have fixed the eARC issues I was having on the last firmware.
The Netflix App is now giving me Atmos again back to my Denon 3700.
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