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New Apple TV - audio passthrough?
- Thread starter marcel500
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I did too and finally gave up. I now use a Windows 10 HTPC to play my files. No Dolby Vision but I'm fine with HDR and bitstreaming.
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The lack of Atmos over uncompressed PCM could have something to do with the amount of processing power required to decode decode and re-encode the lossless signal with the Atmos meta which is the current process with the Apple TV box. I also believe that decoding a lossless signal to uncompressed PCM requires a protected audio path (PAP) which is a combination of hardware and software, similar to the PAP provided by the nVidia Shield, nVidia, Intel, and AMD GPUs.
It doesn’t need that much processing power to bitstream the data though and pass it through which is all we’re asking for, I have a 2016 Xiaomi Mi Box, which has a little Arm Cortex-A53 in it and is nowhere near as powerful as an A10 or A12, and it passes full uncompressed Atmos TrueHD no problem. The current version of Android breaks this capability, but that’s only an issue of software not hardware-it’s the same for the TV
I know it doesn't take a lot of CPU power to bitstream but this is not how the Apple TV works and partially explains the reason it it outputs lossy PCM Atmos vs streaming box the out DD+ Atmos.
If the Apple TV does not have a hardware protected audio path, it will never bitstream.
Currently, the Apple TV takes the DD+ Atmos stream, decodes it to PCM, folds in the Atmos metadata, and then sends the signal out as Dolby MAT 2.0.
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Here's the plex support thread with more info
That’s not how it works now, but again I think that’s simply a choice not a hardware limitation. It used to passthrough Dolby Digital and DTS (never Atmos though but the ATV didn’t do Atmos at all then) up to tvOS 11.25, but it has been removed since tvOS 11.3.
So how does it work now if the ATV is not converting DD+ Atmos to Mat 2.0? I see non-Apple streaming devices are outputting DD+ Atmos to receiver without converting to PCM and re-encoding the PCM signal with Atmos metadata.
From Nakamichi( the-ultimate-dolby-atmos-guide):
Certain content devices, such as Xbox One X/S and Apple TV 4K, come with a Dolby Atmos MAT encoder, which is designed to encode, decode and incorporate Dolby Atmos metadata into lossless pulse-code modulation (PCM) audio, allowing listeners to experience Dolby Atmos even in PCM audio.
With the MixBox, the protected audio path was removed from the Android OS.
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Thanks for the link.
Which DV profile was used to encode the videos? AFAIK, there is no system that will play straight rips of UHDs with profile 7 DV dual-layer rips in anything other than HDR. Apparently, remuxing to MP4 may work but this means removing the lossless audio tracks.
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Looking at some DV 4K titles, they seem to play in HDR10 rather than Dolby Vision. Look fine. Videos were MakeMKV rips from UHD disk.
I have no problem playing my UHD rips in HDR with bitsreaming. Like others, I sometimes prefer DV over HDR. I was commenting because someone had mentioned DV issues on the Apple TV with Plex.
I’m not entirely sure which profile was used but all of the DV files I tried in Plex on ATV were playing with green/purple. All of those same files play just fine in the Plex client for Android TV which is built into my Sony X900H.
My TV flips into DV mode when playing the files in Plex for ATV but the colours are all off and match the issues in the thread I linked above. The Plex employee acknowledged that there is an issue and they are working on it but no fix in sight yet.
Looks like the Plex employee responded to the thread with the following:
Plex Support said:
So it looks like I’ll be returning my ATV and go back to using my Android TV experience for the next while.
So read more about in the plex channels, doesn’t look good. I believe Apple wants to push through e-AC3 Atmos since streaming is the future for them and not Blu-ray. Wondering if there is a converter available from trueHD atmos to e-AC3 Atmos?
I wish we had something like that available. Unfortunately at this moment there is nothing. Especially in the public domain. Dolby's tools may be able to cope with said task, I am not sure.
PS It is the same with Dolby Vision: I know of no way to convert the Bluray DoVi into a streaming DoVi that appleTV could render.
I wonder how can @Jus711 get Dolby Vision from bluray rips from the Infuse. It does definitely not work for me.
Unless we are talking about the base-layer HDR10 that Infuse can render.
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Understood but I thought he said he was having an issue with webrips that have DV playing properly in Plex on the new TV and that’s what I was responding to
Nope. It is just that the amount of Profile 5 content is almost nonexistent compared to profile 7 Bluray-rips.
Oh, and I have not followed the latest developments in the DVDFab Downloader arena. I see the number of services is steadily increasing but this is something I have no interest in.