Much requested Dolby Atmos "passthrough" finally coming to tvOS?

[JeffPerrin]

The ability to bypass Apple's spatial audio processing?? Or perhaps just the option to pass the Dolby signal through to the AVR and bypass Apple TV decoding? 🤔🤔🤔

"The Music app will also introduce support for a feature dubbed "Passthrough," which will only be available on supported hardware. What that supported hardware is, remains unclear at this time.

Although the details surrounding this feature are also unclear, it appears to be related to Spatial Audio with Dolby Atmos, with it possibly being a rebrand of the feature."

iOS 18 to include new audio features for gaming and music

Apple is internally testing improved versions of its built-in Music and QuickTime apps, which in iOS 18 and macOS 15 will gain support for smooth audio transitions and a new "Passthrough" feature.

appleinsider.com

 

[Jdhommert]

The issue with the Apple TV with local files is that Apple didn’t pay for the TrueHD Atmos license, right?

So based on what you said, that will be irrelevant and as long as your receiver supports it, you’re 100% golden?

God I can only hope. If I could play full ass Atmos with the height tracks and everything, I’d probably be persuaded to put an Atmos system in. I guess if not I could just get a Shield and it will still play all the DV/Atmos files as intended

 

[JeffPerrin]

There are two potential issues at play. One is that the Apple TV decodes all Dolby signal on it's own before sending the audio on to the AVR or sound bar as PCM audio. So you're hearing Apple TV's version of the decoded audio. And it never sounds quite the same or (arguably) as good as the original Dolby signal sent directly to the hardware decoder. Enabling this ability is commonly referred to as "passthrough," and has long been a requested feature by those with high-end audio equipment.

The other issue is how Apple's spatial audio can sound different from a Dolby Atmos binaural mix. Moreover, spatial audio processing can change with each OS release. "Passthrough" for iOS might mean customers can bypass spatial audio processing and hear Dolby Atmos binaural mixes exactly as they were mixed in the studio. (This seems unlikely, however...)

The most likely scenario, from my unique point of view as the developer of Surround Speaker Check, is that Apple may be allowing an Apple TV passthrough option in order to solve the issue of how some smart TVs degrade or fail to properly pass through the Atmos metadata sent from an Apple TV. (Currently, the most reliable way to play back Dolby Atmos from Apple TV is to bypass the TV and connect the ATV directly to the AVR or sound bar.)

 

[priitv8]

Why would Apple decoded Atmos sound different from Atmos decoded by AVR/PrePro?
I bet the code to do that comes from Dolby anyway.
Apple’s own spatial renderer only muddies the waters, but it should already be bypassed if I have my aTV directly connected to AVR. It ought only be relevant to users of headphones or HomePods.

 

[JeffPerrin]

Why would Apple decoded Atmos sound different from Atmos decoded by AVR/PrePro?
I bet the code to do that comes from Dolby anyway.
Apple’s own spatial renderer only muddies the waters, but it should already be bypassed if I have my aTV directly connected to AVR. It ought only be relevant to users of headphones or HomePods.

I couldn't tell you why. Apple's decoding/spatial audio processing has always been bit of a black box. I know for a fact there was a difference in early iterations of tvOS, but it's been years since I've gone back to compare between Dolby output on Apple TV gen 4+ (ie. tvOS) vs early Apple TV models 2 or 3 (the pre-tvOS models which had passthrough). Don't see the point as it is what it is...

Anyway, I'm not here to put down or debate audio quality on the Apple TV, just speculating on the rumor linked above. Anyone else have any guesses at what a "pass through" feature or setting might mean for the Music app? 🤨

 

[bozzykid]

Anyway, I'm not here to put down or debate audio quality on the Apple TV, just speculating on the rumor linked above. Anyone else have any guesses at what a "pass through" feature or setting might mean for the Music app? 🤨

The rumor in the link is specific to iOS and is referring to spatial audio. I don't see it having anything to do with tvOS.

 

[JeffPerrin]

The rumor in the link is specific to iOS and is referring to spatial audio. I don't see it having anything to do with tvOS.

No, tvOS is not mentioned specifically in the article, but as with many media-related APIs, it can safely be assumed this feature (whatever it will be) will likely makes it's way to tvOS as well. At least at some point. See the following quote, for example: "Passthrough is also set to make its way to QuickTime on macOS 15, indicating that Apple intends to make it available system-wide."

 

[bozzykid]

No, tvOS is not mentioned specifically in the article, but as with many media-related APIs, it can safely be assumed this feature (whatever it will be) will likely makes it's way to tvOS as well. At least at some point. See the following quote, for example: "Passthrough is also set to make its way to QuickTime on macOS 15, indicating that Apple intends to make it available system-wide."

Again, it is related to spatial audio. Just because it uses the word "passthrough" doesn't mean it is anything remotely what you are inferring.

 

[JeffPerrin]

Well, it's a vague rumor and we can't be sure exactly what it relates to for sure. I don't believe the author fully understands the topic though, seeing as they hypothesize this rumor signals a possible Apple rebranding of spatial audio to "Passthrough" 😅 My prediction is merely based on common audio industry usage of the term "passthrough." Nevertheless, it's all in good fun! Reading tea leaves and all...

 

[oneMadRssn]

Why would Apple decoded Atmos sound different from Atmos decoded by AVR/PrePro?
I bet the code to do that comes from Dolby anyway.
Apple’s own spatial renderer only muddies the waters, but it should already be bypassed if I have my aTV directly connected to AVR. It ought only be relevant to users of headphones or HomePods.

My understanding is that the problem isn't solely that Apple decodes the Atmos signal, rather it is that Apple mixes-in it's OS sounds on top and then re-encodes that signal into a different digital format (PCM) before sending it on. That latter process, mixing in Apple's UI bleeps and bloops (even when there are none) and re-encoding the signal necessarily messes with the levels and fidelity, and thus the output is different than the input.

Ideally you have the decoder right next to the analog amplifier, and there is no re-digitalization in between (as Apple does). And, ideally the signal is not altered in any way (as Apple does).

 

[priitv8]

My understanding is that the problem isn't solely that Apple decodes the Atmos signal, rather it is that Apple mixes-in it's OS sounds on top and then re-encodes that signal into a different digital format (PCM) before sending it on. That latter process, mixing in Apple's UI bleeps and bloops (even when there are none) and re-encoding the signal necessarily messes with the levels and fidelity, and thus the output is different than the input.

Ideally you have the decoder right next to the analog amplifier, and there is no re-digitalization in between (as Apple does). And, ideally the signal is not altered in any way (as Apple does).

Well, PCM is the ultimate final format of any digital audio. So it will not be re-encoded to that. Apple decodes Dolby Digital Plus packed audio into uncompressed PCM and adds its own sounds to the mix.
What is unclear to me, is how the Dolby Atmos objects and metadata are carried over in this scheme (Dolby MAT 2.0), but the DD+ decoded into PCM is the final sound, so should not matter, whether it is done in the appleTV or in the AVR. PCM goes straight into the DAC, as-is.
As I have said earlier, I am pretty confident, the code to do that comes from Dolby Labs anyway.
I am even more confident, that the Dolby Atmos Renderer code (that places Atmos objects into the listening space using available speakers), is Dolby Labs' proprietary code and comes from them in any Atmos-capable device.

 

[oneMadRssn]

As I have said earlier, I am pretty confident, the code to do that comes from Dolby Labs anyway.
I am even more confident, that the Dolby Atmos Renderer code (that places Atmos objects into the listening space using available speakers), is Dolby Labs' proprietary code and comes from them in any Atmos-capable device.

I think you're right about it being Dobly Labs code that decodes the signal to PCM. And I think you're right that Dolby probably provides the code (likely binary) for applying the object mapping. My understanding is that latter part happens in the ultimate audio device though, not in the ATV (ie., it happens in the AVR, TV, or soundbar).

But as we know Apple is at a minimum injecting their own sounds into the mix in between decoding the DD+ and sending the PCM to wherever next. Plenty of ears here and other forums tell us that Apple is also doing something more in that step. They're not just mixing in their sounds, they're also changing and adjusting the mix.

 

[priitv8]

What Apple does, is it confuses people with its own Spatial Audio renderer.
Which decodes Atmos and creates immersive effect just on 2 speakers.
More can be read here

Why Your Atmos Mix Will Sound Different On Apple Music | Production Expert

In this article Edgar Rothermich gives a detailed explanation of the differences between Dolby Atmos and Apple’s Spatial Audio and all the steps you have to take to audition a Spatial Audio rendering of your Atmos mix!

www.production-expert.com

And some more here

https://professionalsupport.dolby.com/s/question/0D54u00007vd4WJCAY/does-apple-do-extra-processing-to-atmos-mixes-once-theyre-on-apple-music?language=en_US

But to the best of my understanding (which may be wrong), if I have my appleTV connected via HDMI directly to my Atmos-decoding AVR, this Apple Spatial Renderer is not involved and I essentially hear the direct DD+ Atmos, only decoded by tvOS and Atmos-rendered in the AVR.

The only exception is when playing back Apple Music content on the AppleTV through the HDMI output connected to a Dolby Atmos capable AV receiver or soundbar. In that case, you are listening to the Dolby Renderer and not the Apple Renderer.

That can work, because (for backward compatibility reasons), the decoded from DD+ 5.1 or 7.1 PCM contains the whole audio (channels and objects alike). Now, the Atmos Renderer in the AVR uses the supplied metadata (and object essences?) to subtract object audio from the decoded channels and mix them into appropriate bed and height channels, according to their room coordinates and the given speaker layout.

 

[JimmerJabber]

Anyone been able to work out whether the latest announced updates confirm the passthrough rumour?

 

[JeffPerrin]

Nothing like that was mentioned. If anything, just the opposite. The new "Enhance Dialogue" feature appears to further reinforce Apple's intention to manage all audio processing strictly within tvOS/on-device. But perhaps the official release of tvOS18 will bring a pleasant surprise to us "power-users." Ya never know... 🤷‍♂️

 

[JimmerJabber]

Damn. But appreciate your response, thanks.

 

[errol]

Nothing like that was mentioned. If anything, just the opposite. The new "Enhance Dialogue" feature appears to further reinforce Apple's intention to manage all audio processing strictly within tvOS/on-device. But perhaps the official release of tvOS18 will bring a pleasant surprise to us "power-users." Ya never know... 🤷‍♂️

Such a shame really. Apple could leave it up to app developers to enable this at the application level. That way streamers could turn this on within app, rather than at the system. That way infuse, plex, etc. could use straight passthrough.

 

[bozzykid]

Anyone been able to work out whether the latest announced updates confirm the passthrough rumour?

There was never a rumor of passthrough on the Apple TV unless you count this thread that misinterpreted an article about iOS 18.

 

[JimmerJabber]

There was never a rumor of passthrough on the Apple TV unless you count this thread that misinterpreted an article about iOS 18.

I believe that is correct. You will see my comment does not refer to ATV. Whilst not explicit, I was asking about the original rumour first posted on Apple Insider and repeated here which I understand was about Apple Music on iOS and MacOS.

However, if passthrough were to be implemented in Apple Music on iOS and MacOS, I don't think it's too big a stretch that passthrough might be implemented in Apple Music on ATV. Passthrough for the entire tvOS might be a different story.

Let the people speculate!

 

[B/D]

Nothing like that was mentioned. If anything, just the opposite. The new "Enhance Dialogue" feature appears to further reinforce Apple's intention to manage all audio processing strictly within tvOS/on-device. But perhaps the official release of tvOS18 will bring a pleasant surprise to us "power-users." Ya never know... 🤷‍♂️

@JeffPerrin


The passtrough setting does indeed appear on the IOS 18 and Mac Os Sequoia betas, and it looks promising. BUT it's not system wide and only appears within the settings of the Music app. So I believe passtrough has indeed arrived, but only for the Music app (for now).

Here is how the setting looks like on Mac OS:

https://i.redd.it/6y44xo5r9z5d1.png

www.reddit.com

Someone with an Apple TV 4K and the tvOS 18 beta 1 installed could go to Settings/Apps/Music and check if a passthrough option is present there?. Thanks in advance.

 

[Alpha Centauri]

I can't remember when (4-5 yrs ago), I bought an Apple TV to bring into the fold of other devices and an AVR. I did return it just because it didn't allow passthrough, doing it own processing before the signal reached the AVR.

 

[mhmercer]

@JeffPerrin


The passtrough setting does indeed appear on the IOS 18 and Mac Os Sequoia betas, and it looks promising. BUT it's not system wide and only appears within the settings of the Music app. So I believe passtrough has indeed arrived, but only for the Music app (for now).

Here is how the setting looks like on Mac OS:

https://i.redd.it/6y44xo5r9z5d1.png

www.reddit.com

Someone with an Apple TV 4K and the tvOS 18 beta 1 installed could go to Settings/Apps/Music and check if a passthrough option is present there?. Thanks in advance.

I have the 2022 version of AppleTV4K, with tvOS Developer 18.0 Beta 1 installed. I don't see a reference to Pass Through under Settings/Apps/Music.

 

[B/D]

I have the 2022 version of AppleTV4K, with tvOS Developer 18.0 Beta 1 installed. I don't see a reference to Pass Through under Settings/Apps/Music.

Interesting, thank you very much.