DTS and DD+ sound issue (possibly Xbox One app only)

General Discussions
1

I’ve installed the Plex app on my Xbox One and imported my digital library, and there’s a couple of niggling problems I’ve noticed.
I should first explain how my system is set up:

  • Xbox visuals are connected to my HD projector via HDMI.
  • Xbox audio is connected to 5.1 blu ray home theatre via toslink optical cable.
  • Blu ray home theatre visuals are also connected to the HD projector via HDMI (I use a switch box to select the visual source)

This means if I’m watching a blu ray disc I get the blu ray player’s 5.1 sound, and then if I’m using the Xbox I turn on the blu ray player’s Optical input and I can play games using the 5.1 sound also. And I can use both on the projector.

My first problem I’ve noticed is the image quality of movies on Flex isn’t quite as good as they are when played on the blu ray player. I’m not talking about BDs, I mean the same .mkv video file appears sharper when played on the blu ray player than on the Plex app. It’s not a huge difference, but when projected on a screen ~80" it is noticeable.

The second problem I’ve found is the sound quality of certain audio types. Namely DTS and Dolby Digital Plus.
The volume levels become really unbalanced at certain points, for example when there’s a lot of instruments playing at once. It’s difficult to explain.
At first i thought it was due to the Optical cable not being as good as HDMI, but having tried another media player on Xbox it appears to be a Plex Issue.
I have an mkv file of the movie Spectre which has DTS 5.1 sound. When played on the Xbox Plex app, the music during the opening studio logos sounds fine, as it has a few bars of creeping subdued strings. But once the gun barrel part starts (when the trumpets blast out) the sound levels get really uneven, like the player can’t quite handle the volume levels. Almost like it’s clipping, and reducing the overall volume to compensate for the bigger sound.

If I load the exact same Spectre.mkv file on the Xbox VLC app, the music sounds absolutely fine.

Just to be sure, I downloaded a copy of Spectre with Dolby Digital sound, played it on Plex, and the sound was perfect.
I had a similar issue with an episode of Fargo which had Dolby Digital Plus sound. When played through Plex the levels went nuts. The same episode but with regular Dolby Digital sound was fine when played on Plex.

So from what I can gather, the Xbox Plex app doesn’t seem to be able to cope with DTS and DD+ sound too well (at least, not through an Optical cable anyway).

Can someone suggest if there’s any way of me getting around this issue? I really love the GUI of Plex, and desperately want to keep using it, but the sound issues I’m experiencing really puts me off. The only thing I can think of is to replace any DD+/DTS files I have with DD versions, but that would take months.

2

I hope this doesn’t muddy the waters, but I may have a related problem. When playing some DTS .mkv files results in extremely low audio volumes.

Most files work great for me on Plex. However, some of my DTS files are almost unwatchable right now because of this. Usually I watch all my sources (Tivo, consoles, etc) with the TV volume set to “14”; I watch these at “45”. The dialogue is almost unintelligible, and seems to get too easily drowned out in background noise. It’s almost as if a center channel is getting dropped in transcoding.

This happens with Plex on Fire TV, Xbox One, and PS4.

Audio is fine when playing the same file served via the Plex DLNA server, played on Xbox One VLC.

I’m happy to provide any debug info from screenshots to tcpdump and mediainfo.

3

Having looked a little further into it, I think the issue is that, as you mentioned, Plex transcodes the DTS sound, rather than playing it direct. The Xbox apparently can’t take DTS without transcoding (or it couldn’t originally).

However the VLC guys seem to have solved the issue, as their player apparently doesn’t transcode the DTS sound. It plays the DTS sound direct. This explains why the same DTS sound I tested works fine on VLC, but choppy and unbalanced on Plex.
Like you, I played the file on VLC-for-Xbox via the Plex DLNA server (and also directly from the NAS where it’s located) and there were no sound issues at all

I’m just hoping there’s a Plex-for-Xbox update on the way, which allows direct play of DTS with transcoding. If VLC can do it then surely Plex can too?

4

I’m just hoping there’s a Plex-for-Xbox update on the way, which allows direct play of DTS with transcoding. If VLC can do it then surely Plex can too?

I of course meant to say “direct play of DTS without transcoding”.

5

On the Fire TV stick, Plex tells me the reason for audio transcoding is, “DTS audio is not supported by the device”. Video is “Direct”. I believe that is correct, since the Fire TV stick doesn’t list DTS support (just various DD, AC-3…). I think it’ll have to transcode to work on the Fire TV stick, but there’s some sort of bug.

Video files with AC-3 audio tracks play “Direct” on the same device.

6

@parkieg said:
I’m just hoping there’s a Plex-for-Xbox update on the way, which allows direct play of DTS with transcoding. If VLC can do it then surely Plex can too?

Two completely different apps. The Plex app uses the Xbox One’s media player which means it is limited to the codecs Microsoft has allowed access to on 3rd party applications. VLC typically uses additional software decoders to fill in the gaps for a devices non compatible audio streams. What this means is that until Microsoft adds a DTS decoder that is available for the Plex App the app currently needs to have the server transcode the audio before sending it to the app.

Recently, Microsoft started testing (And I believe released) the initial phase of their pass through support. This would allowed the app to receive the DTS audio and then allow the device connected to the Xbox box do the decoding of the audio. But with that this functionality hasn’t been released to third party apps where the Plex app could take advantage of it yet.

For transcoding I was just starting investigating the audio cutting off myself before I left for vacation. Unfortunately, I am still away so I haven’t been able to do more testing since I started that yet. My current belief was that the server was using a type of audio normalization, but that it was struggling with really loud noises being mixed in. For me and another user I was working with this manifested itself as the audio sound like it was shutting off temporarily (what seemed like less than a second). The other user was still running a pre- 1.7.x version of the server and server 1.7.3(I believe it was .3) had a new version of the transcoder released (which was why I still have additional investigation to look into).

7

Any updates or an ETA? I’m trying to re-watch the MCU in timeline order! :smile:

8

The quickest solution is to simply change DTS to AC3 (5.1 or 2.0 - whatever you need).
Done in a few minutes with:
http://www.xmedia-recode.de/en/download.html
Pick your Container
Copy Video
Convert Audio

Battling the ‘low voices’ issue the above program is also useful in that it can ‘normalize’ audio levels to 89db (the industry standard - or any level you find appropriate) at the same time you’re doing the above. DTS is especially annoying in this regard. For some reason, some times, the voices refuse to cooperate at 89db. I have had to go as high as 95db, but I’ll admit that is rare.

Some 5.1 conversions require 84db - proving beyond any doubt DTS is a PITA just about any way you look at it. As such I’m involved in a life-long fight with DTS (dedicated to silence), so before anything with DTS hits the library it’s converted to AC3 5.1/2.0 as required. I don’t have the hearing of the Greater Wax Moth so I can’t notice any difference, but when I actually hear the audio and/or voices that’s a big plus in my book and I can notice that right away.

:slight_smile:

I also prefer a Direct Play over any transcoding. AC3 Direct Plays on all, but one, of my devices so that too makes me a happy camper.

9

Unless I’m mistaken, the new Xbox app update (Oct 2017) has now fixed the DTS issue. I just tested the opening of Spectre again and it sounds fine :slight_smile:

10

@parkieg said:
Unless I’m mistaken, the new Xbox app update (Oct 2017) has now fixed the DTS issue. I just tested the opening of Spectre again and it sounds fine :slight_smile:

Should have been a server update that fixed the issue as the Xbox One has no DTS audio decoder available to the app so DTS streams get transcoded before being sent to the Xbox.

It definitely should be fixed at this point in time, but if you notice it again, the first thing I would check would be if you have recently upgraded the server.