I installed the new TVOS just fine but I am baffled by what is going on with Dolby Atmos. Some of my purchased movies have been upgraded to Atmos, so I tried some of them out. My new NAD receiver has Atmos support. Some Atmos-labelled movies now play with the NAD showing "Apple TV - Dolby Atmos" whereas others show "Apple TV - PCM surround". So now I do not have a clue where the decoding is happening. If my amp shows Atmos I think it means the amp has received the raw signal and is decoding itself, but with PCM I think the Apple TV might be doing it? I rather expected the amp to get the Atmos info without interference from the Apple TV.
Can anyone clarify - apologies if this is a dumb question. I am an Atmos newbie and was rather surprised that Apple TV does not allow one to control whether the signal is decoded or not before going to the amp, and baffled by two different Atmos-labelled movies behaving differently.
When you play them, do you hear sounds coming from above speakers? (edit: if not, it may be that apple just updated the latter one and there needs to a "refresh" like with a web browser...try restarting your router, or try again tomorrow.)
FYI: tvOS 12 will take the DD+ Atmos stream, mix it with system sounds and convert and output it as LPCM...Dolby MAT 2.0, (LPCM + metadata, which I previously thought LPCM could not handle metadata, however, new AVRs with Atmos capability should have this capability). So, your AVR may show something different than when playing Atmos from other sources.
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Dolby Atmos in Dolby MAT
The Dolby Metadata-enhanced Audio Transmission (Dolby MAT) encoder resides in a Blu-ray player to pack the variable bit-rate Dolby TrueHD bitstreams for transmission over the fixed bit-rate HDMI connections. A MAT decoder is subsequently employed in an AVR to unpack the Dolby TrueHD bitstreams. With the introduction of Dolby Atmos, we have expanded this technology to support encoding of Dolby Atmos content as lossless pulse-code modulation (PCM) audio.
A key benefit of Dolby MAT 2.0 is that Dolby Atmos object-based audio can be live encoded and transmitted from a source device with limited latency and processing complexity.
Among the possible sources are broadcast set-top boxes, PCs, and game consoles. The Dolby MAT 2.0 decoder in an AVR outputs the object-based audio and its metadata for further processing. The Dolby MAT 2.0 container is scalable and leverages the full potential of the HDMI audio pipeline.
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from pg. 12 here: https://www.dolby.com/us/en/technologies/dolby-atmos/dolby-atmos-for-the-home-theater.pdf
ALSO: HDMI can be quirky, someone else tried this before I suggested it, but, try disconnecting your HDMI cables and hooking everything back up again. Doing this will make the devices communicate their EDID information, which tells other devices what it is capable of, something that may help after a software/firmware update.