Dolby Atmos with headphones, not that simple...

[LionIT]

So, I'm analyzing the options available to enjoy the Dolby Atmos tracks on headphones connected to a DAC / AMP with USB input.
Actually the streaming platforms that offer Atmos are Amazon Music, Apple Music and Tidal.
However, the matter is not that simple...
For the ideal listening of Dolby Atmos on headphones, a render that uses binaural metadata should be used.
But actually only the Dolby AC4 IMS format constitutes a 2-channel flow encoded in binaural with proper distance metadata.
Here an excerpt from a thread on Dolby Professional Support forum:

Apple uses the DDP JOC (EAC3) codec which doesn't use the binaural render mode distance metadata. Instead it decodes and renders the audio to 7.1.4 ahead of Apple's proprietary Spatial Audio binauralization process. Amazon Music uses the AC4-IMS codec which does use the binaural renderer mode distance metadata. Depending on the content and the distance settings used this can indeed lead to discrepancies in how content sounds on headphones on the two platforms. Conversely sometimes the differences are minimal. I'm not aware of instances of different masters submitted.

Avid also provides an excellent explanation of the Dolby format on the various platforms.
In this discussion on Reddit, several users confirm that Apple Spatial Renderer sounds different from the Dolby Binaural one (when headphones are used) probably due to the lack of use of distance metadata.
In fact, Audiomovers sells this add-on for manufacturers to monitor in real time how the track sounds on Apple Renderer.
Here is a couple of YouTube videos of Atmos mixing engineers illustrating the different options: video #1, video #2

Other online sources however seem to clarify that Tidal also offers AC4 IMS like Amazon.
Here a very very exhaustive article that summarise everything.

Leaving aside the customization of HRTF offered by Apple with its pods, from this information one would think that the ideal option for Dolby Atmos in headphones is Amazon Music and Tidal.
But there is one aspect that I cannot clarify.
These apps certainly provide the stream in AC4 IMS when used on mobile devices, as they are 99.9% connected to a headset.
But if I use a DAC / AMP for USB headset connected to a PC, for example, what happens?

It is known that Dolby Access app must be installed from MS Store to use Dolby Atmos on Windows. Since 24H2 version, however, Microsoft has removed the AC3 / EAC3 codecs. This is not a big problem because if ask ChatGPT how to install them it seems feasible (and also for AC4).
However, this should point out that Dolby Access on Windows has a renderer for EAC3, which as explained initially does not use metadata for binaural and therefore is not the best option for headphones.

So it would seem that the best option to listen to Dolby Atmos on a DAC / AMP with USB is to connect it to a mobile device, but it is still not clear how the streaming app detects that device and what Dolby format it streams consequently.
And it should be added that the audio engine of the devices may not be Bit Perfect and may have non-optimal performance in the Sample Rate Conversion or Limiter (possibly present / used).

It is really boring for a user to have to dig so deeply ... Obviously we are still in a phase of development and transition where standards have not established themselves, And where, however, large companies do not want to pay licenses and therefore develop proprietary solutions, favoring the heterogenization of the market (see the recent announcement by Samsung / Google)

What are your experiences?
Does anyone have newer or more in-depth information?
Are there state-of-the-art solutions that escape me?

 

[olieb]

From this information one would think that the ideal option for Dolby Atmos in headphones is Amazon Music and Tidal.

I am totally confused by this Atmos format jungle, but I would not think that. I do not know what to think.
Just from reading your text and quotes it seems that " (EAC3) codec [which[ doesn't use the binaural render mode distance metadata". It is not clear to me what that means. Binaural render yes, but distance information no? That is how is seems to me, but maybe I do not get it.

In any case you need HRTF information for binauralisation. AFAIK Apple does this from pictures of your ears, but I do not know how well that works. How do the other binaural renderers (Dolby) do this?
Without the use of your personal HRTF the result can only be based on a generic head-ear combo and the results for different persons might vary considerably. And then there is the question of head tracking (which plays quite a big role in binauralisation).

Looking forward to someone who can clear things up a bit.

 

[LionIT]

In any case you need HRTF information for binauralisation. AFAIK Apple does this from pictures of your ears, but I do not know how well that works. How do the other binaural renderers (Dolby) do this?
Without the use of your personal HRTF the result can only be based on a generic head-ear combo and the results for different persons might vary considerably.

Dolby also supports the PHRTF (Personalized HRTF) for its renderer.
Then that the OEMs offer the function to their customers is another matter.
In any case, mixing is rarely done with engineer's PHRTF, so the master's spatial validity is always questionable.
The fact remains that the distance parameter is particularly relevant.

Create and Deliver Transformative Experiences in Dolby

Dolby Professional is our answer to content creators looking for resources specifically for them. From music and cinema to gaming, learn what Dolby can offer you.

professional.dolby.com

 

[LionIT]

Just from reading your text and quotes it seems that " (EAC3) codec [which[ doesn't use the binaural render mode distance metadata". It is not clear to me what that means. Binaural render yes, but distance information no? That is how is seems to me, but maybe I do not get it.

Here is the AC4 whitepaper that illustrates the technical details better.
Dolby AC4 decoder uses distance metadata (near, mid, far) for headphones virtualization.
EAC3 looks like can render in binaural for headphones or 2 channels downmix for speakers, but without using distance metadata in first case. So technically not perfectly accurate to the master.

However, yes, it's like a jungle

 

[olieb]

The fact remains that the distance parameter is particularly relevant.

Why? If that were so important, I would expect more than three values and it would not be the first thing to be deleted from a stream. And for music I suppose, the "near" option will not even come into play. That is more for effects in movies and gaming when someone whispers in your ear or a fly is circling your head.
So at best there is "medium" and "far" (whatever that exactly might signify, maybe it is "medium" all the way for music?) and the differences for the HRTF are not that big. The ear cannot differentiate (longer) distances very good by HRTF, that happens by (room) reflections and maybe attenuation of HF.
In any case the personal HRTF is essential and if your app does not ask for it or has an input for it, this generic binauralisation is more of a gimmick.
The Dolby PHRTF so far seems to be rather exclusive (licence and content creators status) and more of a beta. I would not hold my breath for this to reach mortal customers.
And who is mastering Atmos for binaural listening? 7.1.4 will probably be several orders of magnitude more popular for that. Considering this maybe Apple's approach is more robust.

 

[LionIT]

Why? If that were so important, I would expect more than three values and it would not be the first thing to be deleted from a stream. And for music I suppose, the "near" option will not even come into play. That is more for effects in movies and gaming when someone whispers in your ear or a fly is circling your head.
So at best there is "medium" and "far" (whatever that exactly might signify, maybe it is "medium" all the way for music?) and the differences for the HRTF are not that big. The ear cannot differentiate (longer) distances very good by HRTF, that happens by (room) reflections and maybe attenuation of HF.
In any case the personal HRTF is essential and if your app does not ask for it or has an input for it, this generic binauralisation is more of a gimmick.
The Dolby PHRTF so far seems to be rather exclusive (licence and content creators status) and more of a beta. I would not hold my breath for this to reach mortal customers.
And who is mastering Atmos for binaural listening? 7.1.4 will probably be several orders of magnitude more popular for that. Considering this maybe Apple's approach is more robust.

About Dolby binaural rendering:

https://professionalsupport.dolby.com/s/article/What-is-Binaural-Render-Mode-and-how-do-the-settings-affect-my-mix?language=en_US

I believe that most devices on which spatial audio is listened are headphones, so the binaural is important.
Professional mixing engineers take into account all available rendering options, and pose the problem of how to do the mix where the rendering is not standardized between various platforms and hardware.
Audiomovers started to sell the Apple renderer for this very reason, that is to allow engineers to compare realtime the rendering on the Apple system and on the remaining platforms with Dolby renderer.
Online comments, even by professionals, still confirm that the difference between renderers is sometimes very perceptible (sometimes not). It is not known whether due to the use of distance metadata or not.
In any case, if the distance has been chosen by the mixing engineer, it should be decoded by the playback device. It is still an artistic choice.

This official guide illustrates the mixing in Dolby for headphones. it doesn't seem to me to be niche honestly...

As for the custom HRTF, I agree that it is more accurate for each individual, but a binaural with generic HRTF is always better than nothing or than stereo downmix of Atmos.
Surely Apple with its customization of the HRTF in AirPods offers an excellent solution to users, but not game changer to me.
However, it must be said that its spatial renderer has been changed since the beginning and it is not excluded that it will change again to use AC4 metadata.

 

[LionIT]

As a corollary, I would like to add that to bypass Apple's binaural renderer, of which there is no control or possibility of using PHRTF and head tracking without AirPods, there is a not very practical alternative but very powerful.
It involves using a Mac with Apple Music* and the 16-channel BlackHole loopback device configured in 7.1.4, with which you send audio to a DAW and after which you can use Binauralizer Studio 2 to create your binaural stream with custom HRTF created with MESH2HRTF and with which you can use professional head trackers.
I have tested it personally and it is a great sounding solution, but the complication of this setup is not worth it compared to the Apple AirPods.

* Apple Music must be set with "Automatic" on the Dolby Atmos setting, otherwise it will only play 2 ch binaural (at least with streamed tracks, with downloaded it seems to have different behaviour).
In any case, to see the format that you are playing just see the logs on Console app (type "mediaformat" in the filter).

 

[LionIT]

I am looking for more information on the Amazon Music on PC with Dolby Access app, but I can hardly find confirmation on the decoding that is practiced in the case of headphones.
Even in the following guide it is not clear whether the Dolby Access decoder is compatible with AC4.

Dolby Atmos Documentation

Dolby Atmos is an immersive audio format that provides a compelling listener experience by surrounding the listener with sound. In addition to the traditional 5.1 or 7.1 surround setups, Atmos introduces height channels to enable sound from above to increase aural envelopment. These are...

professional.dolby.com

 

[LionIT]

As a corollary, I would like to add that to bypass Apple's binaural renderer, of which there is no control or possibility of using PHRTF and head tracking without AirPods, there is a not very practical alternative but very powerful.
It involves using a Mac with Apple Music* and the 16-channel BlackHole loopback device configured in 7.1.4, with which you send audio to a DAW and after which you can use Binauralizer Studio 2 to create your binaural stream with custom HRTF created with MESH2HRTF and with which you can use professional head trackers.
I have tested it personally and it is a great sounding solution, but the complication of this setup is not worth it compared to the Apple AirPods.

* Apple Music must be set with "Automatic" on the Dolby Atmos setting, otherwise it will only play 2 ch binaural (at least with streamed tracks, with downloaded it seems to have different behaviour).
In any case, to see the format that you are playing just see the logs on Console app (type "mediaformat" in the filter).

I just found out that Virtuoso also exists and Allows you to binauralize with personal HRTF and Head Tracking.
Note that Virtuoso received the highest ratings in overall preference and fidelity.

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aes2.org

 

[Madlop26]

Dolby ATMOS with headphones does not exist, it is a lie, physically impossible, the day you show me a system with only 2 speaker that can do ATMOS as my 7.2.4 system I would stand corrected.

 

[Biblob]

This video explains how and why Atmos often doesn't deliver it's promises. A producer explains the concept and tries it out, from a consumer perspective. To me, it made clear Atmos can only work in a very optimised system. IF it even works is sometimes a mystery in itself.

 

[LionIT]

It is clear that effectiveness and preferability cannot be generalized because, unfortunately, there is no unique standard, neither of mixing nor of rendering and nor of hardware.
Furthermore, even when everything is perfectly tuned, there is the Room Divergence Effect that comes into play.
Therefore debating in principle if Atmos is good, bad, meh, not existing, etc, it is completely devoid of usefulness.
Currently it looks like a jungle, indisputably, but this does not mean that the Atmos should be set aside.
As far as I'm concerned, when the factors involved are correctly managed, the headphone experience is always more engaging and exciting than the classic stereo mix.
I opened the thread to discuss a specific aspect of these factors in play, that is the binaural rendering options currently possible / available with USB headphones (DAC/AMP to analog headphones).

 

[LionIT]

Still on the subject of binauralizing by oneself, I found that through script you can set BlackHole 16ch to 9.1.6 configuration, with Apple Music that uses all of them.
From Audio MIDI actually only 7.1.4 is allowed unfortunately (inexplicably).

Edit. I have checked better and from MacOS Sonoma (contrary to Ventura) the CoreAudio framework does not render anymore the 9.1.6 format, despite the setup forced with the script. Apple only left 7.1.4, probably for licensing issues.

 

[LionIT]

I was further inquiring about the distance rendering in the binaural, possible with AC4 IMS, and I think I have found an Applied Acoustic article that explains the complexity to reproduce nearby acoustic events in headphones, problem for which perhaps (I guess) Dolby developed AC4 binaural renderer that change the convolution algorithm based on distance metadata.

https://www.sciencedirect.com/science/article/abs/pii/S0003682X16302407

 

[Human1]

I went through this whole rigamarole this weekend as well! Powernode and wiim don't support it. Paid for dolby access and noticed dolby wasn't working on tidal on pc.

Finally plugged in my ka11 dac into my phone using uspapp. It finally worked. Then plugged my phone into my smsl c200 via usb and it worked as well. Would love a streamer that supported it so I could lose one cable (or charge my phone if needed).

 

[Ongii]

How to listen to the stereo downmix of an ATMOS album with headphones? I ask because of the superiority of ATMOS releases compared to the stereo releases (e.g. The Cure's last album).
I don't need binaural effects, but just to enjoy music in best quality and avoid loudness war.
Thanks!

 

[LionIT]

How to listen to the stereo downmix of an ATMOS album with headphones? I ask because of the superiority of ATMOS releases compared to the stereo releases (e.g. The Cure's last album).
I don't need binaural effects, but just to enjoy music in best quality and avoid loudness war.
Thanks!

If you stream through smartphone there are Amazon Music, Apple Music and Tidal that offer Atmos tracks in binaural format, so the ideal for headphones directly connected (wired or Bluetooth).
If you need to use a DAC + headphones amplifier the most immediate solution at the moment is to use Apple Music on Mac, with Dolby Atmos option set to Always On.
When you use a smartphone as a source for USB DAC, it is not entirely clear which format is being played, so you are not very sure that you have Atmos.

 

[Ongii]

Thank you @LionIT !
Just a couple of questions for the details:

- If I listen via smartphone:
...this has to support Atmos I suppose? Mine (Nothing Phone 2) does not.
...also with standard headphones?

- For DAC + Headphones amp: only with a "real" Mac, or would an iPAD be sufficient?

And finally: what if I attach an headphone amp to the Zone2 of my ATMOS-capable (streamer: Shield) AVR? I suppose I would get there the downmix. Am I right?
Thanks again

 

[LionIT]

Thank you @LionIT !
Just a couple of questions for the details:

- If I listen via smartphone:
...this has to support Atmos I suppose? Mine (Nothing Phone 2) does not.
...also with standard headphones?

Amazon Music comes with integrated Atmos decoder. I also believe the other apps, but check online.

- For DAC + Headphones amp: only with a "real" Mac, or would an iPAD be sufficient?

I don't know how exactly it works on iPad, sorry.

And finally: what if I attach an headphone amp to the Zone2 of my ATMOS-capable (streamer: Shield) AVR? I suppose I would get there the downmix. Am I right?
Thanks again

Million dollar question... You will never have absolute certainty of the format you are playing. It could be Atmos 2.0 downmix and not the binaural which is suitable for headphones.

 

[DVDdoug]

DISCLAIMER - I don't have Atmos.

Dolby ATMOS with headphones does not exist, it is a lie, physically impossible,

I agree with what you are saying but Dolby has a "broader" definition for Atmos. They don't say it's ALWAYS multi-channel or that you can always pinpoint the location of the sound. They say something about an "immersive" experience.

I've never heard head-tracking headphones but in theory they could work. Although... I'm in the majority of listeners who can't even get a realistic stereo soundstage with headphones so I doubt they would work perfectly for me.

I tried the old Dolby Headphone once with a Dolby test DVD. Some people were saying you could get surround. I never perceived the sound coming from behind. (And Dolby never made that claim.)

I'm not really a headphone guy and to me headphones are simply a "different experience". I don't expect them to sound like speakers in a room.