ATMOS on Nvidia Shield Pro

Plex Players Streaming Devices
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I’m trying to figure out if I’m “really” getting ATMOS from my PLEX movie on my Nvidia Shield Pro.

The movie file I’m playing shows up on my PLEX server as English (TRUEHD 7.1), but it’s an ATMOS file. On the Nvidia Shield Pro and the AppleTV it shows as TRUEHD 7.1 and if I play both sources I hear sound from the speaker… the same sound on both, which gives me the impression that I’m not getting true ATMOS.

From what I understand, ATMOS is not really a sound channel, but more of a metadata channel. How do I tell its playing correct on the Nvidia Shield? Should it say ATMOS?

Server Version#: 4.33.1
Player Version#: Nvidia Shield (latest update)

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Short Answer: Look at your audio gear during playback. Most Atmos capable audio equipment has a display or other indicator to let you know it is receiving Atmos enabled audio.

Long Answer:

There are two types of Atmos audio in the home theater market: TrueHD + Atmos is what is found on Blu-ray discs. It is commonly referred to as “Lossless Atmos.” EAC3 + Atmos is what is used by streaming services such as Netflix, Amazon, Apple, etc. It is commonly referred to as “Streaming Atmos” (EAC3 is also known as Dolby Digital Plus).

The Shield will pass TrueHD + Atmos and EAC3 + Atmos to attached soundbar/receiver/etc. It is the only off the shelf streaming box that passes TrueHD with the Plex app.

The AppleTV decodes TrueHD to PCM before passing the audio to the attached device. Atmos information is lost during this conversion. Note this is an Apple restriction. Apple does not permit any app to pass TrueHD audio. EAC3 + Atmos will passthrough.

Plex apps do not show if the Atmos data is present. TrueHD + Atmos audio is displayed as TrueHD. EAC3 + Atmos audio is displayed as EAC3. This is a display issue only. It does not affect how Plex actually handles the audio. FYI, the same thing happens with dts:X audio. It is displayed as dts or dts-HD.

You can tell if the audio stream contains Atmos information by analyzing the video with MediaInfo. It will show if Atmos data is present.

Many receivers/soundbars/etc that support Atmos have an indicator if they are receiving Atmos data during playback. For example, the front panel on a Denon receiver displays “Atmos.”

How equipment is connected also matters. Ideally, the Shield is connected directly to your audio equipment. Traditional HDMI-ARC cannot pass TrueHD due to bandwidth limitations. The new HDMI-eARC can pass TrueHD. However, both the TV and audio equipment must support HDMI-eARC. Both HDMI-ARC and HDMI-eARC can pass EAC3 5.1, including EAC3 + Atmos.

For TrueHD + Atmos:
Good:
Shield <–HDMI–> Audio Gear <–HDMI–> Display

Good:
Shield <–HDMI–> Display <–HDMI-eARC–> Audio Gear

Bad:
Shield <–HDMI–> Display <–HDMI-ARC–> Audio Gear

MediaInfo output for TrueHD + Atmos audio

Format                                   : MLP FBA 16-ch
Format/Info                              : Meridian Lossless Packing FBA with 16-channel presentation
Commercial name                          : Dolby TrueHD with Dolby Atmos
Codec ID                                 : A_TRUEHD
Duration                                 : 1 h 58 min
Bit rate mode                            : Variable
Bit rate                                 : 3 810 kb/s
Maximum bit rate                         : 7 158 kb/s
Channel(s)                               : 8 channels
Channel layout                           : L R C LFE Ls Rs Lb Rb
Sampling rate                            : 48.0 kHz
Frame rate                               : 1 200.000 FPS (40 SPF)
Compression mode                         : Lossless
Stream size                              : 3.17 GiB (10%)
Title                                    : TrueHD 7.1 + Atmos
Language                                 : English
Default                                  : Yes
Forced                                   : No
Number of dynamic objects                : 11
Bed channel count                        : 1 channel
Bed channel configuration                : LFE
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Thanks for the answer, lots of great information and I learned a lot reading your reply. Hopefully you can answer this one last question. Why is it that when I play a movie that is ATMOS on my AppleTV 4K, I do actually hear select sounds from the ATMOS speakers?

And to address the configuration question earlier. I’m running a Yamaha Aventage A3080 receiver, the Nvidia is connected via HDMI. Display is a Sony 295es 4k projector out of HDMI out 1 on my Yamaha.

From what I understand, ATMOS is not really a sound channel, but instead metadata that detects what sounds to direct to the ATMOS speakers. Is that correct? Just trying to figure how it is that the ATMOS speakers do actually pass sound through the AppleTV that sounds strikingly similar to my Nvidia Shield Pro.

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Clarification: There is another form of Dolby Atmos which uses Dolby MAT 2.0 and PCM audio. It is referenced in the PDF document below (pg 12). I’m not sure how the Shield, AppleTV, etc handles this type of audio. AFAIK, all my movies are TrueHD + Atmos and I don’t have any Dolby MAT + Atmos audio in my library.

Possibly your Yamaha is altering things based on the sound mode in use.

I’ve a Denon AVR-X4300H and a 5.1.2 speaker setup. Depending on the sound mode I use, I hear sounds from the “.2” speakers even when playing non-Atmos audio.

That is my understanding as well, based mostly on Wikipedia (below) and other info I’ve found by searching the web. The PDF file from Dolby (below) has more detail (and I freely admit I haven’t read/understand all of it).

As far as the AppleTV goes, you’re still hearing 7.1 lossless audio (PCM is lossless, so converting from TrueHD to PCM should have no loss in quality).

I’ve never tested playing TrueHD vs TrueHD + Atmos for the same soundtrack, so can’t really say how different it would sound.

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