LG C9 + Arc + UB820 / Multichannel PCM for DTS Blu-Ray discs

@Hebassaurus  I believe there are issues with the way Sonos Arc handles lpcm 7.1. On top of that there may also be issues with LG TVs converting everything to 7.1 lpcm even if the input is 5.1 and set to pass through. At this point I’m fairly resigned to the fact that this will never be perfect, and if it ever is, it’ll only be one update away from breaking again. 

Yep, the 7.1 issue for everything , i’m pretty sure is LGs end, I have the LG CX and I have had enough responses from various forums to suggest its LG issue, but unfortunately LG are to lazy to acknowledge the problem and fix it.

If anyone from LG reads this, don’t expect me to buy another LG tv in the future, I’m going to be looking at other brands in the future, LG may be good at releasing firmware but actually fixing issues that are widely reported across AV forums, they never seem to be bothered about fixing.

Interesting, thanks all. I have read that the Sonos crew was potentially working on a fix to downmix the 7.1 to 5.1, so I’m hopeful something will come from that in the future, though it has no indicated timeline. I do hear you on the potential, future updates breaking things...it can happen in today’s world...especially with such young technology and all of the vendors not testing against one another’s equipment. The matrix of possibilities might be too large to tackle that.

Few things in a few attempts I made this today using the DR HDMI 4K device:

1. Dolby Vision is staying active today sometimes, even when I re-sink. Good news, maybe...but a cautious good news as I believe it has to do with the order of powering on things (possibly even the DR HDMI 4K device). I got a message from the Panasonic mentioning the device it was connected to was not HDCP 2.2 compliant until going back to the Home screen on the Panasonic.
2. For the 7.1 thing, I made a new custom bank that only has FC, FL, FR, RL, RR channels as available in the Speaker layout portion of the EDID stuff. It still outputs as 7.1. 
3. When I switch to Auto (and PCM) instead of Pass Through on the LG, it outputs as Stereo PCM, so I stuck with Pass Through. I also tried combinations with the DTS settings on the Panasonic as Bitstream or PCM...seemed to make no difference, I still get 7.1 in Pass Through whether it’s in Bitstream or PCM.

I’ll find some time to play around again later, but my ideas are not many at the moment.

@Hebassaurus Thanks for sharing your situation. The more we point out these issues, the better. Not sure we’ll get the fixes we want, but at least we’ll have workarounds. I suspect that LG is putting its development into the soundbars they make. I just added a C1 model to my lineup (attached to an Arc), and I see a number of new settings related to their products. (I have my Oppo 4k plugged into this, and happily DTS and Dolby Atmos all played fine with my settings.)

My experimentation (which I have not changed in months) was on a C9 model. I did not see the Dolby Vision issues you describe. So, could be a G1 issue or something else wrong in the pathway. Have you changed out all cables as a test? I used 8K cables to be sure there was enough bandwidth. 

Also, my Dolby Vision testing is probably limited. While I do have a number of UHD discs, my main disc viewing is older Criterion and Kino Lober released films - most with DTS tracks which caused me to find the issue with the Panasonic-LG-Arc set up.

Finally, definitely do not turn on PCM or have the LG modify the audio signal. That will for sure create issues with the Arc.

Sonos has made progress with the 7.1 to 5.1 down mixing issue. All four of the surround channels of a 7.1 mix from a DTS-encoded disc now plays audio. The two rear surround channels from a 7.1 mix used to not play at all, only the two side surround channels. I tested this using DTS 7.1 Sound Check on a DTS demo disc.

That’s good news @GuitarSuperstar , I did see that they were working on it, but that they haven’t technically marked it resolved just yet. I haven’t had a chance to do a proper test when receiving 7.1 at this point. Do you know what DTS demo disc you’re using? I found one for 2020, but it only seemed to have movie clips...not a sound check that you mentioned.

And thanks for the tips @Laird M Malamed . Good to hear that it all works great on your Oppo! Wish I could find one of those...maybe I’ll look into acquiring one used, but we’ll see...kind of expensive..and used haha. So does the Oppo convert it to Multichannel PCM 5.1 correctly from DTS-HD Master 5.1, or is that still incorrectly coming through as Multichannel PCM 7.1?

As for the cables, I have not switched them out, but I have tried them all (they’re capable for 48Gbps) with the Xbox Series X and PS5 and can confirm that I get HDR no problem @120Hz in games, so it shouldn’t be a transfer rate issue as the Panasonic can’t output more than 60Hz. I use these same cables from the Panasonic → HDMI 4K → LG G1 → Sonos Arc (not needed for this last step, but still am using it).

For the Dolby Vision issue, I’ll play around with ordering, but I have been able to consistently get Dolby Vision in my few runs so far since that first post. Just gets a little finicky at times...so I can’t complain too much. But I really would like the Multichannel downmixing thing to be resolved on the Arc. That will make me super happy!

@Hebassaurus I am using the 2015 DTS Demo Disc Blu-ray:

Still producing 7.1 for DTS discs but correctly sending out Dolby channels (including Atmos all the way to the Arc with True HD). I have not done a lot of sampling to be accurate - just a few discs so far. Will test more next weekend.

Anything passed through as LPCM will output in 7.1, its an issue on the LG, Im surprised it’s still an issue on the C1, clearly LG have not had enough reports of this problem.

Not helped by the clueless LG first line of support who just dismiss the issue.

I have tried many times reporting it for my CX without success. 

Understood @ledzep1, I’ll look into submitting a bug report to LG with my setup.