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

My setup is the UB820-LG CX-Sonos Arc and I got tired of waiting for a solution from Panasonic or LG for the multichannel LPCM problem so I purchased DR HDMI 4k and tried it a few days ago.

I was hoping to just set the unit to the 4K max mode EDID. “Green 1 – 4k60-444-600M-HDR-BT2020-3D-FULLAUDIO” and have it all work, but for me it wasn’t quite that simple. Using this mode did allow me to get 7.1 channel LPCM from the UB820, but I noticed 2 problems:

1. I wasn’t getting Dolby Vision indicatations by the LG CX. Only HDR indications even for disks that supported Dolby Vision (and that I had seen Dolby Vision indicated when I wasn’t using the DR HDMI).
2. For certain disks, I would get no audio when the playback first switched to multichannel LPCM (decoding DTS). For example the UHD Bluray menu may have started in DD 5.1 and only switched to LPCM for DTS when starting the actual movie. The UB820 indicated 7.1 LPCM being sent out, but the Sonos app would indicate no audio being received. Forcing the DR HDMI to restart a handshake fixed the problem each time.

I ended up fixing this by copying the LG EDID that was being sent out into the special bank for this in the DR HDMI. Then I used the DR HDMI utility on my PC to copy the EDID to a binary file, and then used an EDID editor (with GUI) on my PC to find the Dolby Vision “Vendor Specific Data Block“ EDID that was being provided by the LG and copied that info into a side file. Then I copied the “Green 1 – 4k60-444-600M-HDR-BT2020-3D-FULLAUDIO” bank to a binary file, and I used the EDID editor to start with that as a base and then added the Dolby Vision support info that I saved off in a side file. Then I saved off the resulting modified EDID into a binary file and then used the DR HDMI EDID utility to save that to bank “Custom 1”.
(I’m a little surprised the utility provided by DR HDMI doesn’t have more support to actually “decode” the binary into a GUI that figures out each field and includes a description)

When I used Custom 1 from the DR HDMI 4k, now I could see the LG confirming that it was getting Dolby Vision and not just HDR. But I was still getting the problem of not hearing the LPCM 7.1 for some disks unless I restarted the handshake of the DR HDMI.

So then I went back and looked at what the LG was sending for supported audio and modified the EDID I was using in Custom 1 to have matching audio support (this involved things like removing audio support for things like DTS/DTS-HD/1-bit SACD audio as well as 192k and 96k support for LPCM). After I saved these changes to the Custom 1 bank of the DR HDMI and used this, now my audio worked right away all the time for LPCM 7.1 coming out of the UB820 (no need to force the DR HDMI to reinitialize a new handshake). I wonder if the UB820 was trying to send out 96k LPCM for DTS-HD on some disks initially and only redoing the handshake somehow got it to send LPCM in a format supported by the LG and/or Sonos Arc.

I also mention that when I examined the EDID being sent by the LG CX, when I looked at the audio data block section of the EDID, I couldn’t find anything wrong. So its not obvious why the UB820 couldn’t figure out that it could send multichannel LPCM based on the EDID from the LG. There must have been something else wrong or different about the EDID being sent by the LG compared to the DR HDMI 4k max mode that is messing up the UB820. Oh well, now that I have something that works, I don’t think I’m going to bother investigating that any more.

I hope this helps anyone else with this setup that doesn’t get things to work exactly right when using the built-in modes of the DR HDMI.

@AaronT Thanks for sharing. I wonder if I was mistaken on Dolby Vision on my end and need to do the same thing for the C9. I will check when I can.

In the meantime, can you share which editor you are using? (Do you recommend it?) I was going to try to get the RS232 connection to work to inspect the TV one.

Also, I am curious if your 820 is limiting downsampling to 48kHz in the settings of the 820 or allows up to 192kHz which might explain why you had to change the EDID. (The Sonos can only accept up to 48kHz I think.) I have my 820 with this limit in place (which I am not sure even applies to the HDMI output).

So, my unit arrived and I’ve done a quick test. 
 

LG GX

ub820ebk

SONOS ARC

I can confirm Aaron T’s observations with the GX on

Green 1 – 4k60-444-HDR-2020-3D-Q9FN ALLM VRR HDR10+. (That’s the description on my unit, seems a little different from what others have?)
 

Dolby Atmos pass through works fine. 
DTS is presenting as 7.1 PCM

Unfortunately, DOLBY Vision no longer works. Laird, is it the same for you?

I tried a few of the other presets but none of them worked either. 
 

I guess we’ll have to use Aaron’s workaround. Aaron, any further details on your method/ software would be greatly appreciated! 

Curious if anybody has raised this with HDFury direct on their Discord server - their customer service is supposed to be excellent.

I have a unit ordered from TMF but not sure how long it takes to arrive. Hopefully quick for £11 postage :)

I got mine from TMF as well. Took a couple of working days. 
 

Good idea regarding HDFury. Will give it a try. 

I just want to thank you guys for doing so much to figure this issue out. It can be very demoralizing and frustrating when buying new tech and it doesn’t work correctly out of the box. It seems pretty complicating just to get the HD FURY 4K to work correctly so hopefully there is an easier fix.

Hey guys, can anyone confirm that the Arcana doesn’t have the Dolby Vision issue?

HDfury have pointed me to

https://hdfury.com/tools/HDfury_EDID_collection.zip

and suggested trying some of the EDIDS. 

I’m wondering whether the easiest route, if we have to muck about editing EDIDS,  might be to modify the LG one to allow MLPCM and leave everything else intact. 

I can 100% confirm that the Arcana works - you just need to set the device to pass the audio to the HDMI Out port and you do not use the eARC output port at all. You use the device just as a passthrough, similar to the intent of the DR HDMI 4K. This is my set up now and has been stable for weeks.

I can also confirm I am running into the Dolby Vision issue with the HDMI DR 4K. So, in my rushed eval on Monday, I missed this was not working with the built in EDID. I see now that the HDFury site has different EDIDs listed for the banks than what is on the sticker on the physical device. I have more to check on this and to get an EDID editor going for my personal interest.

And finally, I have chatted briefly on the HDFury Discord server with them. They are very fast and you can scroll through a ton of old chats too which can be helpful.

M wife wanted to watch All About Eve (which has a DTS-HDMA 5.1 track) so on a whim I decided to unplug my CX for a few seconds. Guess what, the Sonos app says Multichannel PCM 7.1!!

I’m not sure All About Eve is known for its spectacular surround sound, so next, I’ll try it with Die Hard or another DTS disc.

Stay tuned...

What type of UHD Blu Ray player are you running?