Just bought 4K Apple TV streaming device. When using Plex, the device will not play or passthrough Dolby Atmos audio. My A/V receiver displays “PCM” and evidently is not getting any Dolby Atmos signal. Called Apple, no help - they claim it’s a Plex problem. I also have Nvidia Shield Pro and that device has no problem passing through Atmos from any of my .mkv movie files.
Anyone else having this problem?
The Apple TV box does pass through Atmos from other sources (Netflix, Max, etc.) - but not when using .mkv thru Plex.
What is the audio codec? There are two types of Atmos and most devices only support DD+ Atmos which is found on streaming services.
Shield is the notable exception which supports TrueHD Atmos which is found on Bluray.
AppleTV\Plex will convert TrueHD Atmos to PCM (I believe).
If you post your media info for the video you played that’ll probably help sort it out.
It doesn’t seem to matter what codec it is. Trying to play movies like “Sicario - Day of the Soldado”, “Zero Dark Thirty”, “Hacksaw Ridge”. Some have AAC 7.1, others have TRUEHD 7.1. Shield plays em all (in Atmos) - Apple TV doesn’t.
I’m trying to find a good video converter to convert these movies to mp4 to see if Apple will passthrough if it’s a different format. Haven’t found one yet that also brings over the Dolby Atmos.
And, why does Apple TV do anything to the audio signal? Not a true pass through.
It 100% has to do with the audio codecs in your files.
Atmos is available via Dolby Digital Plus (DD+ EAC3) or TrueHD. Atmos is a layer of information that provides for upfiring speakers as well as specific channel information for devices that support it. That latter is great for getting specific audio environments as well as for downmixing multiple audio channels to fewer speakers.
TrueHD is not supported on AppleTV so it can’t play that audio format so Plex has to transcode the audio to a different format otherwise you won’t hear anything. PCM is pretty close to full quality, just without the atmos info.
Because of the way these codecs are licensed, devices typically can’t passthrough TrueHD without supporting it. Since TrueHD is only found on Bluray discs there’s no reason for a device that doesn’t play Bluray discs to include support for it. That’s why they typically only support DD+Atmos because that’s what the streaming services use.
DTS-MA is also a Bluray only format but more devices seem to handle this a bit better because there’s a built in downmix to DTS. DTS-MA doesn’t have Atmos.
AAC 7.1 also doesn’t have Atmos.
Shield is essentially the only “plays everything” device, particularly audio codecs. If you really really want atmos then you need to use the Shield. If your audio equipment is saying it’s playing Atmos when you play AAC7.1 codecs then that’s the Shield doing something funny to fake it maybe?
You can use Infuse on AppleTV to get a bit more codec playback support - lots of folks like it over the native Plex app - but it still won’t give you TrueHD+Atmos or DTS-MA support. Unless something has changed recently anyways.
If you post media info for some different files and the transcoding\audio equipment info, folks can help out a bit more. I’m not an expert on any of these things - just been around them a REALLY long time and been trying to find my own TrueHD+Atmos w/Dolby Vision solutions.
First, want to thank you for your input. Really helps and I 'preciate that.
The Apple TV device can play movies/series with Dolby Atmos. I was watching “Masters of the Air” on Apple TV channel and my A/V receiver indeed displays and decodes the Atmos signal. So, Apple TV device must have a license then, correct? Otherwise, how is is able to pass the Dolby Atmos information thru to my receiver? And, if it does, why isn’t in passing thru Atmos when I play movie thru Plex?
FYI, I have a nice Yamaha Aventage A/V Receiver and it was not cheap.
Long story short Dolby Atmos for Plex even with the supported codecs is still hit and miss on tvOS at this juncture and is a known issue. Some work is going on in the beta channels to address some of the numerous shortcomings. Fingers crossed they’ll get to that soon.
Refer:
That statement suggests that something in what I’m trying to express is still missing the mark. Let me try again. 
Atmos is a data layer added to audio streams for devices to have advanced instructions for decoding and playing back the audio streams. There are 2 different versions of Atmos which means there are two different types of formatting for those instructions.
- Dolby Digital Plus w/Atmos (often listed as DD+Atmos or EAC3+Atmos when looking at the codec) - streaming services like Netflix, AppleTV+, and Amazon Prime use this.
- TrueHD w/Atmos (usually listed like that or just “TrueHD”) - only bluray discs use this.
As an analogy, think of version 1 as a CSV file and version 2 as an XLSX file. Or version 1 as a JPG and version 2 as a PNG. Or version 1 as a TXT file and version 2 as a DOCX file. They all output similarly - tabulated data, an image, a document - but how they are coded are different.
That AppleTV service\channel playing Masters of the Air is using DD+Atmos. That’s the streaming service version Atmos I’ve mentioned. The AppleTV supports that version of Atmos (almost all streaming devices support it).
An MKV file created from a Bluray rip with a TrueHD Atmos audio codec is using the native TrueHD Atmos pulled directly off that Bluray disc and is the version of Atmos that the AppleTV doesn’t support.
The term “Atmos” can be confusing because of those two different versions of it. That difference is what I’m trying to express in these explanations. AppleTV says “Atmos support” for it’s device but it means only the DD+Atmos for streaming services. It’s a streaming services device so only supports that version of Atmos.
To go back to your example, if someone ripped Masters of the Air from bluray then it’d have the TrueHD w/Atmos codec instead of the DD+Atmos codec.
It doesn’t help that marketing materials and tech specs don’t really differentiate this stuff when it’s listed for devices, but unless someone is managing a local digital file collection it doesn’t impact most people. Devices that playback streamed content get the DD+Atmos support for streamed content and devices that play Bluray discs get TrueHD Atmos support.
And then you also have to have the A\V equipment to support the different audio and video codecs as well (and codec passthrough is separate from that even). That’s usually easier to determine on AV equipment since they usually break that out better but not always so that’s MORE research and investigation into those marketing materials and tech specs.
When people like us who use Plex or Jellyfin or Emby or Kodi or Infuse to playback local files, that’s where it requires additional work sorting these things out. It usually means making some compromises or being particular about the codecs in the files based on the AV equipment being used. Plex and Jellyfin and such can transcode audio and video codecs so the files will still play the audio and video on a device that doesn’t support those particular codecs. That makes managing those codecs and playback scenarios easier; in the past it just wouldn’t play.
That is what you’re experiencing with the audio being converted to PCM. AppleTV doesn’t support TrueHD w/Atmos so when Plex plays back a file AppleTV doesn’t support it converts it to one as close to the quality it can. For the AppleTV that would be PCM. PCM is essentially the TrueHD audio quality but with the Atmos data stripped out.
The same thing would happen if you used Jellyfin - it’s not the app not supporting the codec, it’s the device.
Converting TrueHD w/Atmos to DD+Atmos is very restricted and not easy to do (requires very controlled tools). So that’s why that’s not an option - though that’d be nice.
The Shield does support both DD+Atmos and TrueHD+Atmos so that’s why people who want support for both types of Atmos, the Shield is the usual solution.
**insert Newt from Aliens saying "mostly"**
It’s a commonly confused situation really so hopefully by trying to explain it a bit differently that has helped it click a bit better.
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Once again, thx so much for your input. I get it 100% now as I’ve thought the whole thing through, so to speak (it clicked). Currently the neurons in me brain aren’t transmitting like they used to. Five years I probably wouldn’t have written my second comment.
Anyway, I now wonder if the lack of TrueHD w/Atmos audio support by Apple TV may have something to do with DMCA. MKV files are notorious as the preferred format of ripped blu-ray/4K discs. Perhaps Apple is playing the good guy by not supporting these thieving pirates… :-<
Or, perhaps they’re just too lazy to fix this discrepancy. Apple TV support is a joke. None of the people I talked to there even heard of MKV files or the Shield Pro device (moi, who used to be a tech support person, would know ALL of my competitor products).
As I mentioned, I do have the Shield Pro at every TV so I’m simply gonna use that when I know media source has the better Atmos (TrueHD) flavor. I’ll look into Infuse and keep up with blackzwe suggestion.
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Totally understand and glad it clicked for ya’.
Since the only people trying to play digital files with TrueHD audio are people who ripped discs… yeah, that’s definitely a big aspect of it even if having digital copies of bluray discs you own is legal (cracking the security software is the problem in those cases but… whole different topic). I avoided mentioning it to try not to put even more text in my post.
The WDTV - an early local file playback device - used to play EVERYTHING (at the time). It was like having VLC in a box. Even DVD ISO files off a simple network share. It didn’t last long after RIAA\MPAA started cracking down on them as a “pirating device”.
These days the Shield is the way to go but even that doesn’t work for everyone (didn’t work for me - just didn’t play well with my AV equipment).
Lots of people do this - they use Shield for the nice bluray rips with the nice TV and audio setup and then AppleTV for all the streaming services and the non-bluray rips. You’ve essentially got the top two streaming boxes now… should be as good as you can get.
AppleTV only has 2 output modes, dictated by Apple.
- LPCM
- EAC3+Atmos
That’s it, 2 modes. If the media file does not conform to lossy EAC3+Atmos, then it can convert to lossless LPCM.
TrueHD != EAC3, so it goes as lossless LPCM with no atmos.
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