Do you have TV Autoplay enabled under the Arc’s settings in the Sonos app?

Yes TV autoplay is enabled.

Hi @riiiic 

Thanks for your post!

Then you’ve already done all that can be done from the Arc’s perspective.

Do you have other devices connected to the TV? If so, please test with them temporarily disconnected - does this help with the issue at all?

There are a lot of issues concerning CX and ARC and various devices:

• PS5 is fine
• PC not fine, I guess if I started without having a sound signal it won’t wake up the arc, then I have to pass through CX-app-Netflix and back to PC works).

On the other hand this arc behavior is good when I want to use BT headphones linked to the TV, as a matter of fact when arc is awake it is impossible to use CX BT audio, no matter what you do it will revert back to arc.

It would be just nice to have the chance to switch everything on/off.

Is disabling TV autoplay leading to this result? Can I manually select when to turn the arc on and off ?

Hi @riiiic 

Disabling Autoplay would prevent the Arc from automatically selecting the HDMI input as what to play. If it is already set to play TV audio (no music has been played to it since the last time TV audio was played) then I don’t think it would make a difference.

It’s possible that an external device is causing a HDMI-CEC conflict, resulting in the behaviour you see. Please try the following: turn on your PS5, then select the Settings cog from the top-right corner. From there, go to Settings > System > HDMI and disable HDMI Device Link.

Note that if you prevent the issue from happening, it's entirely possible you won’t then be able to use your headphones with your TV unless you disable the TV’s CEC functions too (which will stop audio from going to the Arc) - LG call their version of CEC “Simplink”. Also, if you were to leave Simplink off, that would prevent the Arc from playing until you turn Simplink on again, so that may be the answer you’re looking for - to be honest, I’m now a little confused over which result you actually want.

I hope this helps.

Hey thanks a lot, I am also confused cause these pieces of technologies in 2023 they should just work and do what you ask them.

I am guessing the main fault is due to LG, the arc simply received a signal whether or not the TV send the signal to it.

The problem is that the TV is set so send the audio signal to the ARC at all times, if I check which audio output is on it says “arc”.

• BT audio should be prioritized (by the tv)

• Youtube (TV) should turn on the arc, I am suspecting it is something related to the audio format (stereo vs multi channels).

• PC should turn on the arc, but this is also bugged, native atmos sounds work, other sounds that are remixed by windows 11 sometimes are not reproduced correctly,  hence you have to manually set the sound output to stereo (in win sound settings) and back to atmos to make it work (I know is dumb but it is the only way).
• Nintendo switch HDMI coding is amazing, it does turn on the arc and the TV
• PS5 also works ok.

I know you are not LG customer service, but I am doubting they will listen to me.

If sonos tells them “hey dummies at least disabled simply link when a BT device is connected” I think we have more chances to get something right out of this mess.

I am very sorry for the rant, but the ARC is outputting the sound, if no sound comes out, I’d think it is the first culprit.

Hi @riiiic 

You are not alone in this, unfortunately, but the Arc (or any other external audio device, for that matter) can only play if it is sent audio data in the first place.

I recommend you get in touch with our technical support team, who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports. The Arc will supply them with HDMI-CEC data and whether or not it was actually receiving audio data at the time.

I hope this helps.

Thank you so much Corry, I was wondering whether this sort of analytic software existed like a log file.

I really appreciate the fast and kind support, one more thing to like about Sonos.

Hi @riiiic 

You are most welcome. I hope the team find a fix for you!

Hi Corry, 

I checked the settings in the TV and found this out: 

Will there be an improvement, forcing one of those format instead of Auto?

Technically I chose “pass Through” but maybe if I force an audio format and then force

PCM letting the TV decoding, could there be an improvment ?

What do you think ?

Hi @riiiic 

Technically, there shouldn’t be a difference, at least in terms of the issue you initially described. However, technically, that shouldn’t be happening in the first place, so feel free to experiment.

I would not specify PCM, however, as that likely refers to PCM stereo, which is a downgrade from any other format. Passthrough is generally the best option - as long as other devices/apps are not configured to output a format that Arc does not support (DTS-HD, for example).

It may be worth trying things with eARC disabled. Standard ARC can still supply Dolby Digital + (Atmos), which is the best format you’re likely to get from streaming services. You would need to watch a BluRay to benefit from eARC being enabled at all.

I hope this helps.

Dear Corry, 

I found out something important.

I turned on the TV and the PC (PC was on but in sleep mode).

I started a game and checked the win audio output (dolby atmos).

Sonos app revealed that the sound was WMA not supported.

I check the LG and the setting was passthrough. So I changed it to PCM and the sound was stereo PCM, changed back to passthrough and “boom” the Arc recognized the sound as Dolby Atmos.

Now I am baffled:

1. PC must always transmit the same signal
2. TV must have interpreted as WMA and send it to the Arc which can’t reproduce?
3. Turning passthroughs to PCM and back to passthrough solved the issue

This is a f***cked up, I would say the fault is 100% the TV, but then how should I correct it?

Do the trick each time it doesn’t work and set itself to WMA for no reason ?

There is a lot of negotiation when an HDMI connection is established. Each end of each connection attempts to figure out what the other guy supports and they all attempt to find common ground. There’s no absolute standard regarding how this is done, Plus there can be timeouts where one device does not respond fast enough and another device makes a wrong assumption because of this. Restarting the negotiation might result in a different outcome. I know this can be an annoying mess, but this is the current state of the art.

A good plan of attack is to remove all HDMI connections from the TV, make sure that software is up to date, reboot everything, then connect only the TV and SONOS. Often the TV and SONOS will work out a good compromise at that time. Now, begin to connect other devices to the TV. Hopefully their negotiation will not corrupt the SONOS-TV compromise.

In some cases a device’s CEC is working against you. Unfortunately, turning OFF its CEC support might lock out certain audio formats on one or another device. There are HDMI inserts that will block CEC communication. This sometimes helps because it eliminates the negotiation and allows each device to assume that the other guy simply does not support CEC. This CEC blocker can have side effects, such as not allowing a remote control to adjust Volume because the Volume commands were being sent over the CEC bus. It is also common to send power and input selection data over CEC. When CEC works, CEC allows simply dropping a disc into a player and all appropriate devices switch ON and pass the disc through to the display.

Another dimension is EDID because it might influence the audio processing decision. This is another negotiation that occurs when the HDMI connection is established. There are also little ‘boxes’ that can fake the EDID data that is sent both ways.

Hi Buzz,

Thanks a lot.

I don’t think that would work, cause the PC randomly works immediately and randomly LG TV thinks is WMA audio. I would say the best would for the arc to support every format, ahahah

As other sound systems support almost everything, this might pass unnoticed.

For us that love the SONOS style, is a pain. But hey, at least now it would cost me only a couple of clicks, until LG figures it out.

Hi @riiiic 

That is most strange - I have never heard of a TV passing WMA before, so I can only presume that the TV was doing something incorrectly. Arc can play WMA files via the Music Library, but this format just isn’t used in Home Theatre and the Arc does not expect to see it coming via it’s HMDI socket. I suspect that the feed wasn’t actually WMA, but for some reason it was interpreted/labelled as such.

I recommend unplugging your TV from power for at least 2 minutes, if you haven’t already - this will make the TV’s software fully restart in a way that Standby just doesn’t achieve.

I hope this helps.

With respect to TV reboot, I’m not familiar with the LG detail, SAMSUNG TV’s need to be powered down for at least two minuets before they will reboot on power up.