Sonos Arc: Plex / Sound Formats / Transcoding?

  • 9 June 2020
  • 7 replies
  • 3494 views
H
Userlevel 6
Badge +7

Short Version: Can anyone out there who has their movie collections ripped to a Plex server and using Apple TV 4K speak to the experience they’ve had with Arc (or Beam / Playbar if connected via HDMI ARC)? I’m concerned / curious about how this combination works with differing audio formats / codecs. 

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Really Long Version: 99.9% of my viewing these days comes from an Apple TV 4K. Mostly via the usual streaming apps, but also in large part via my movie collection ripped, stored, and played via a local Plex server. While I keep a BD player hooked up to the TV, I honestly don’t remember the last time we used it (it’s there more as a backup / just in case).

Current audio setup is an older Onkyo THX receiver and a 3.1 speaker setup (L/C/R/Sub) simply because I haven’t been able to figure out a decent way to run surrounds that my wife would be happy with in the 12 years we’ve lived in this house. 

I’ve got a Sonos Arc on order and, if I can get Atmos out of it through the Apple TV 4K and Vizio E-Series TV (a big if at the moment), then I plan on replacing the receiver and current speaker setup with the Arc, the Sub, and a pair of One SLs as surrounds (which I can get power to easier than I could run speaker wires to regular surrounds). 

While quality is still very important to me (hence the desire for 4K, Dolby Vision, and Dolby Atmos), simplicity and convenience have become huge drivers for me these days, especially with a wife and two kids who don’t care how things work - they just want to watch what they want to watch when they want to watch without having to have a master’s degree to do it. Which is why we ditched the TiVo, moved to streaming apps, sold off the DVD collection, and put everything into the cloud and NAS servers. There’s something very, very compelling about having every single song, photo, movie, and TV show I own or have access to available to me on any device wherever I am. 

Which is also why the Sonos Arc has been a compelling idea. High quality, simplicity, integration with our existing music systems (Apple Music and HomePods via AirPlay 2), attractiveness, etc. However, since Sonos systems in general seem to have significant built-in limitations in order to obtain that simplicity (single HDMI port on Arc, lack of DTS support, etc.), I’m left with questions I can’t quite find the answers to. 

Primarily, I find myself wondering how Arc will deal with different audio formats / codecs via Plex over Apple TV. For example:  

  • What happens if the source is AAC Stereo? Will Arc simply play the audio in L/R stereo, or is there an option to do a type of “Dolby Pro Logic” steering of matrixed stereo surround? 
  • What happens if the source is AAC 5.1? Will the Arc (currently) see that simply as LPCM and down convert to stereo?
  • What happens if the source is DTS? Will something in the chain (either the Apple TV or the TV itself) convert it to an Arc-compatible Dolby Digital bitstream? Will it get passed along as incompatible LPCM? Will there just be silence? 

Maybe there's just no way of knowing this right now until more Arcs get into the wild. Maybe these questions will have different answers for the Arc because of the way both Apple TV and Arc handle Atmos and multi-channel audio. Or maybe the answers will be different once Sonos rolls out the multi-channel LPCM update for the Arc. But I’d love to hear any feedback anyone out there may have.

Thanks!

Arc + Sub 3 + One SLs = Awesome and Loving It!
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7 replies

T
Badge +1

Hey man,

I was wondering how you got on with this. I have the same setup as you (ARC, Sub, 2x OneSL) although won’t be able to set it up properly until January owing to house move, but I’ve been doing some research to see if I need to do anything else to do to get the max out of it.

I have PMS setup on a dedicated server and the Android Plex App running on a Sony Android 4K TV with ARC (not eARC and doesn’t look like the firmware upgrade will be heading my way to make this possible). I may upgrade to a 900H to take advantage of eARC which opens the door to Atmos and TrueHD.

Like you, a lot of my movie files are DTS (or DTS-MA) and having read about transcoding audio on the Plex website, it seems that PMS transcodes each DTS channel to Dolby which are then sent out to the ARC. I was interested in whether you’d tried enabling passthrough to allow to ARC to do this transcode itself, or even whether it’s capable? And also what kind of results you get playing DTS?

Cheers!

Timmeh

SONOS ARC | SONOS Sub | SONOS One SL x 2 | SONY XG809 |
H
Userlevel 6
Badge +7

Hey, @timmeh. 

A LOT has changed since I wrote that and I’ve learned a lot, so happy to give my thoughts and insight FWIW. 

The Arc / Sub / One SL system continues to be an awesome combo and I haven’t had a moment’s regret. Since getting everything hooked up I’ve since moved my Plex server from my daily driver iMac to an Nvidia Shield Pro (which is working really, really beautifully) and I’ve added the HD Fury Arcana to bypass my Vizio TV and get full quality audio from every source. 

For Plex, I still do most of my watching via Apple TV 4K but do also also use the Shield Pro as a Plex client from time to time. The Apple TV will happily transcode all DTS encoded material to what the Arc sees as “Dolby Digital 5.1” so have had no issues there at all. However, Plex on the Apple TV also transcodes Dolby TrueHD down to “Dolby Digital 5.1” so in those instances I switch over to the Shield Pro which will happily pass along the TrueHD audio track (and Atmos if so encoded) to the Arc. 

(Note: There are some who seem to think that Infuse Pro on the Apple TV will pass Dolby TrueHD (though not Atmos) but 1) it costs more money for a subscription, 2) the interface is sh*t compared to Plex’s IMO, and 3) I could never figure out how to make it work. YMMV, of course.) 

The Shield Pro has turned out to be a capable little streaming device with its own little quirks. Its Hulu app supports Dolby Digital which the Apple TV version doesn’t, stupidly, so it’s become the go-to for Hulu for us. On the flip side (with the Arcana at least), Plex on Shield Pro doesn’t seem to be able to transcode DTS to anything other than “Stereo 2.0” without changing an obscurely named setting - which then also makes all Dolby audio transcode to “Stereo 2.0.” Not ideal, which is why I always use the Apple TV for DTS encoded material on Plex and the Shield Pro for Dolby TrueHD/Atmos encoded material. 

And as for your comment about the Arc transcoding, it doesn’t do that at all. It supports just about every Dolby codec known to man, but if you try to feed it a straight DTS signal it won’t know what to do with it and you’ll just get silence. You can see many angry threads about this from Blu-ray owners and I can verify that’s correct. Since I’ve ripped all of my BDs to Plex, however, this doesn’t bother me as I have the dual benefits of having my entire movie collection always available wherever I am AND I’m not bitten by the lack of DTS in the Arc since the Apple TV transcodes nicely. 

I hope this answers your questions. If you’ve got any others, I’m happy to help. I learned a lot of this through trial and error so happy to help pass some knowledge along if it’s helpful. 

Arc + Sub 3 + One SLs = Awesome and Loving It!
T
Badge +1

That’s so helpful, thanks for taking the time to write such a detailed reply. The Arcana looks like a great bet. I have read a few mixed reviews so will weigh up buying that to add onto my current TV, or selling my TV (it’s only 1 year old) to upgrade to a 900H and get eARC that way.

But, that problem aside still doesn’t get me around the DTS issue and an Apple TV may be a good bet, however most of my video files are mkv and I know Apple TV doesn’t like them… and transcoding 4K is a big no no for my server. So that still leaves me with DTS being converted to Dolby stereo. However, I read somewhere that Sonos are releasing a multi-channel update which would mean Plex could convert from DTS to Dolby 5.1 and arc would accept this?

SONOS ARC | SONOS Sub | SONOS One SL x 2 | SONY XG809 |
H
Userlevel 6
Badge +7

That’s so helpful, thanks for taking the time to write such a detailed reply.

 

You’re quite welcome! Anything to avoid work and responsibility on this chilly Monday. ;-)

 

The Arcana looks like a great bet. I have read a few mixed reviews so will weigh up buying that to add onto my current TV, or selling my TV (it’s only 1 year old) to upgrade to a 900H and get eARC that way.

 

I was a beta tester for the Arcana so was deeply involved for quite a while but have since moved on to the “happy user” phase of use. What reviews did you read that expressed concerns? Pretty much everyone I’m aware of (myself included) has had a very positive experience with the Arcana. Plus, there’s something to be said for just taking the TV completely out of the equation where audio is concerned. The Arcana does what it does and does it very, very well. 

 

But, that problem aside still doesn’t get me around the DTS issue and an Apple TV may be a good bet, however most of my video files are mkv and I know Apple TV doesn’t like them… 

 

Plex on Apple TV has no problem with MKV files. Every Blu-ray Disc I own was ripped using MakeMKV and fed directly to my Plex server with no further conversion or compression in order to maintain all soundtracks and subtitles. It all works great. 

 

 

and transcoding 4K is a big no no for my server.

 

Yeah, transcoding is generally something to be avoided in my experience. Especially when 4K is involved. While very off topic for this particular thread, what I’ve found works best is to maintain two libraries: a 4K movie library for local streams and an HD movie library for everything else. That way I can direct stream / direct play 4K files from my Plex server to the Apple TV / Nvidia Shield over Ethernet for highest quality when in the house with no transcoding, then use the HD versions for external access or mobile devices (also, generally, with no transcoding). It takes up a little more hard drive space, but drives are cheap these days and HD is incredibly easy to sling around. 

 

So that still leaves me with DTS being converted to Dolby stereo. However, I read somewhere that Sonos are releasing a multi-channel update which would mean Plex could convert from DTS to Dolby 5.1 and arc would accept this?

As I mentioned above, Plex on Apple TV ALREADY converts DTS to Dolby Digital which the Arc is perfectly happy with. It’s all about where in the chain the audio decoding is taking place. Most people with AV Receivers are used to the receiver itself taking the audio bitstream (DTS or Dolby Digital) and decoding it there. Apple TV does something a little different in that it decodes the bitstream internally, then RE-encodes it (along with the Apple TV system sounds and Siri) into another format (container, actually) called Dolby MAT.

Plex on Apple TV is actively decoding any DTS-encoded material being played through it then re-encoding it as multichannel LPCM audio in a Dolby MAT container that the Arc understands and supports. The upshot here is that DTS gets automatically converted through Plex/Apple TV into full 5.1 channel surround sound that the Arc can happily (and beautifully) play without having to wait for the multichannel LPCM update from Sonos that is supposedly coming down the pike before the end of the year. 

Arc + Sub 3 + One SLs = Awesome and Loving It!
T
Badge +1

That’s really useful. Thanks again.

Seeing as how the TV is still reasonably new and I can’t really justify spending $400 more on a whole new TV just for an eARC port, so I’ll get myself an Arcana and be done with it. That way any other TV I might buy is futureproofed…

Maybe an Apple 4K TV is the way forward. It would certainly put an end to any issues with DTS which would be a relief, although by the sounds of things when Sonos update their firmware to incorporate LPCM, then I may not have to go down this route :fingers_crossed: and everything will just work… I guess I’ll take a view on this in January when we finally move in and get this all setup.

Cheers for your help man :sunglasses:

SONOS ARC | SONOS Sub | SONOS One SL x 2 | SONY XG809 |
A
Userlevel 1

Hi Folks, I’m in a similar situation but I can’t seem to get 5.1 through the Apple TV (4k) with Plex.

I can get Dolby ATMOS with Apple content fine (e.g. Film from iTunes or TV+), but anything through Plex comes as just stereo, most of which is saved as E-AC3 5.1, some is 7.1

I can get 5.1 with Plex going through the Xbox or Panasonic TV clients, so that’s mostly what I do, but it would be good to get the Apple TV version working.

In the Apple TV settings it is set to ATMOS, if I start changing that option it warns about degraded audio quality.

Does anyone know if it’s an Apple TV/Plex client limitation, or is there something I can tweak?

Thanks,

-Alastair

 

Morgano4u
Badge +1

I have a similar issue where I want DTS streams transcoded to multi-channel LPCM to leverage the lossless DTS-MA content on the Arc. I got a TCL Roku TV, a Shield Pro and an ATV4K. Also got the Arcana but since the Arc update with multi-channel LPCM I haven’t used it, also it causes sync issues that I’m too lazy to troubleshoot. I think we need a custom Plex profile to force PMS to transcode audio to multi-channel LPCM. Also when I play 7.1 DTS streams I only get 5.1 Dolby streams. I hope updates on the Plex clients will fix this or someone cooks up an XML for PMS for our devices.

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