What’s a “diffuser” and why would an image format like 4K have any relation to a sound format like DTS?

You need a dvd player that converts dts into PCM multichannel. 
 

UB820 does this. However multichannel PCM sounds really bad on the arc system. Inconsistent volume levels and overall not very good. Sonos has never tried aiding this. 

I'm still using a 50" FHD Plasma as a diffuser, I thought it was related.

I'm sorry to hear that so it doesn't help my case if it's not optimal as the DTS Master HD originally is. I don't have a 4K player just a Shield TV Pro. So basically if I made backup copies of my DVDs or Blu Rays to prevent my discs from deteriorating I wouldn't be able to play them if they have DTS Master HD via the Shield TV Pro is that right? I'll definitely need a 4K player like the one you're telling me about?

Ah, right. You meen the screen. I never heard the word “diffuser” used for it - but English is not my native language. I also own a Shield and use the last 19 version of Kodi to play DVD/BD .iso’s (I can’t get the newer 20 version to play .iso’s). Kodi can translate DTS to Dolby Digital. See the “Passthrough output device” settings, mentioned on https://kodi.wiki/view/Settings/System/Audio

It's not my native language either, I'm French. And clearly your nickname is the first thing to which it is to the great Sebastien Loeb. But to return to what interests us here. I thought that all the settings were still good on my Kodi that I had adjusted before with my amp. But maybe I need to see other settings thanks to your link. Because if it can transform the DTS into Dolby that would be good, that it passes me the DTS Master HD into Dolby TrueHD. On the other hand, I think that my Television will pose a problem because when I launch a 4K file, the image lags like crazy when it is a DTS Master HD as a soundtrack. If it is Atmos or DD+ it goes well.

There’s a French connection to my nickname, yes (although I’m Dutch). It alludes to my first cars. And my avatar picture was shot on vacation in Normandy…..

The TV could be busy trying to decode DTS (to PCM 2.0 normally) . If you could get the Shield to do the decoding to DD your TV would not have to.

Oh yes I really like your country even if I haven't had the opportunity to go there yet. I like this freedom that we don't have in France on many points. Not having the EARC on my TV, I go through the HD FURY Arcana system and it is it that decodes the sounds. And great as a first car, my little brother had a tuned 205 and my father had a DS3 Sebastien Loeb.

I have upgraded from the ARC to the Ultra and find it disappointing that there’s no DTSX support for the Ultra. I buy 4K UHD discs for films that are my favourites, simply for the superior quality in Audio and Visuals. I buy digital format on Apple Store only if it’s a title I’m not that bothered about buying and paying the extra for the disc; for example a title like Bad Santa. Otherwise, a title like Interstellar i buy on 4K disc. The annoying part is that all Christopher Nolan films are mastered in DTS, as are a lot of my 4k UHD discs. 

I have the Lord of the Rings trilogy on Apple (digital) and the 4k UHD discs. When playing the Dolby Atmos tracks for these films through the Arc or Ultra, you can clearly hear the quality difference on between the formats. As other people have pointed out, it amazes me how Sonos hasn’t included support for DTS formats, especially for a flagship product such as the ultra. In edition as some others have pointed out, some other brands of soundbars and TV’s support DTS formats, even on their lower end products. 
 

For me, i would have scrapped the touchbar controls on the Arc Ultra for an extra HDMI pass through and DTS support. Who uses their touch controls on the Arc? If i want to control to sound levels, pause or skip, i use a remote. I think the touchbar spoils the sleek design of the Arc and for me, it serves no purpose. 

Please Sonos, as DTS support at least. 

Hi, so there I agree with you on all the points that you have just mentioned because clearly there I see with the series, and films that I have ordered or that I am going to buy the DTS Master HD for example is majority and clearly the touch controls for a sound bar that is either anchored in the wall, or placed on a television cabinet, I do not see its usefulness. Where the usefulness on a Five in all directions on certain occasions. So clearly I also campaign for this future addition. Because we agree that it is not at the hardware level that it is played out but just a license to acquire. Otherwise clearly I contact the CEO of DTS Corporation. The guy is like all of us, and I give him the serial number of my Ultra and I ask him to ask one of his engineers to send me the license that I will have acquired to decode the DTS Master HD at least. The DTS:X would be great. But already a step before reaching the summit. We do not reach Everest in one go.

Bummer I am in the market for a new soundbar setup the Arc ultra looked promising. I can’t purchase if it doesn't support DTS. This puts a limit on a LOT of 4k content. I have a vizio elevate and even it supports DTSX and Atmos.

I was looking to replace it with something nicer and play the swap game. It would have gone to the bedroom and the sonos the living room. Looks like I will be waiting probably another year for someone to hopefully come out with something for folks who like audio beyond what comes out of a firestick.

I blame this on folks general lack of understanding of audio codecs. 2 channel audio is likely good enough for 85% of the people who buy soundbars. Although I’d argue those paying more then $1k for a setup expect a little more out of the equipment.

As some of the others have stated, touch controls seem like a feature majority of folks never use. Heck I dont even use my soundbar remotes. Plug it in and let CEC take care of the controls.

It probably does not help that two of the biggest players in the TV market (Samsung and LG) do not dor DTS on their TV's, not even to pass through to a soundbar.

Asd a work around, do BD-players not decode DTS to DD? My NVidia Shield does this.

LG is doing DTS pass through on my LG G4. Perhaps not all models? Or older models?

Having DTS support is a nice bump up from whatever dolby pro logic support they added at some stage. If I get the Arc ultra as a replacement for my Playbase at some point I guess I can use LPCM from my bluray player for the DTS-HD and X formats.

I have the LG G4 as well and it allows pass through of all DTS formats. It’s a shame the Ultra doesn’t allow this; In fact it’s ridiculous. I have to make do with LPCM. I so wish Sonos had ditched the stupid touch controls and given us an extra HDMI port and all DTS formats. Or at least just the DTS support and no extra HDMI port. 

not sure where you got that info I have LG OLED and pass through DTS just fine.

You are right for newer LG devices: https://www.reddit.com/r/LGOLED/s/enq7sRHdsO