Surround Sound vs Dolby Atmos vs Spatial Audio

[struts]

A post by @Shulaf in another thread made me realise that I really didn't understand what Apple's Spatial Audio is or how it relates to Surround Sound and in particular Dolby Atmos, furthermore whether Dione supports Spatial Audio and what on earth SPACE™ is and how that plays into it.  After a bit of digging and some background reading (these two articles are good primers) I think I am starting to get a grip on it but there are some aspects I haven't been able to make sense of.  Hoping folks here with a better understanding can chime in and enlighten me. 

So, as I understand it..

• Surround Sound is where the sound is mixed into multiple channels which fire at you from different directions creating the impression that you are in the middle of the action rather than that everything is taking place in front of you.  Some systems simulate surround sound by reflecting sound off room boundaries like the side and back walls to create that impression.  Dolby Atmos takes this a step further by allowing content creators to define sound sources as "objects" in 3D space which can move about, the Atmos technology then converting this into a mix for the number and placement of the available channels.
  
• Spatial Audio is a technology that is separate from but compatible with surround sound that uses gyroscopes and accelerometers to measure head movement and fix the perceived direction and strength of sounds in space as opposed to fixing them relative to the device that is creating them.  So for instance if you are listening via headphones and you turn your head to the left the channel balance is altered so that a sound that was coming from the left now appears to be coming from straight ahead.  Also, as you move around the system will remix so that you feel like you are moving closer to and further away from various sound sources.  This makes sense to me in a headphone listening context, where the speakers are fixed relative to your head but not relative to real space, and I can understand how it would work with devices that contain gyroscopes and accelerometers that can detect and measure head movement.  
  

What I don't get is:

• What relevance if any does this have in scenarios where the speakers are fixed in space?  When you turn your head or move around your head moves relative to the speakers in reality without needing any dynamic remixing to simulate it.
  
• How can this work technically in devices like Dione that don't contain gyroscopes or accelerometers so can't track head movement or orientation changes?  
  

I think the answers are "none" and "it doesn't", so while it supports Dolby Atmos as far as I can see Dione does not support Spatial Audio even when playing an Airplay 2 stream.  

To add some further spice Devialet talks about "SPACE™ technology": 

SPACE™ technology opens up a new dimension of sound. A patented algorithm upscales any mono or stereo signal into a 5.1.2 signal for an all-enveloping, muli-layered, deeply immersive sound experience, whatever the content you’re enjoying. 

But what on earth does that mean?   Without any metadata how can you make 5.1.2 out of a mono signal?  "Man-guessing"??  I was unable to find any patent filing that might explain this and also notice that while I was writing this post Devialet's website appears to have been updated, "patented" being replaced with "proprietary" in the above quoted text which I copy-and-pasted directly from the page but is now sunk without trace.

If anyone here can shed any light I'd be fascinated to understand if this is technical innovation or simply marketing innovation.

[struts]

Some further digging confirms that Dione is not compatible with Apple's Spatial Audio (list of compatible devices here).  Makes sense per my post above.

Also, it seems that Dione cannot currently be configured as a "home cinema audio" speaker with Airplay 2, which is a prerequisite for supporting the playback of Dolby Atmos content over Airplay (see here).

Here's what you need

• Apple TV 4K
  
• One or two HomePod mini* or HomePod speakers. Other AirPlay 2-compatible speakers are not supported with home cinema audio.
  

* HomePod mini doesn't support Dolby Atmos 5.1 or 7.1 surround sound.

It is not quite clear to me whether this is a technology restriction or commercial lock-out by Apple.  What is clear is that the ability to configure HomePods as home cinema speakers is based on support for HomeKit as well as Airplay 2 and Dione doesn't (yet?) support HomeKit.

So, bottom line as I read it:

• Dione does not support Spatial Audio.
  
• Dione can render Dolby Atmos content from an Apple TV 4K when the two are connected via HDMI but not via Airplay 2.
  
• Dione cannot be combined with Phantoms, HomePods, or any other speakers in a Dolby Atmos surround sound configuration.  
  
• The only speakers that can currently play Dolby Atmos content via Airplay 2 are one or two HomePod mini or HomePod speakers (in which case the Atmos content is presumably downmixed to 1.0.0 or 2.0.0 thereby losing most of its “spatialness”, although I could find no explanation of this on Apple's website)
  
• It is possible to play content simultaneously via Dione and Phantoms or HomePods using Airplay 2's multi-speaker support but in that case the Phantoms/HomePods and the Dione would receive identical stereo signals so it wouldn't be surround sound.
  

Surround sound really does seem to be a can of worms!   Once again, delighted if anyone can shed further light or put me straight if any of this is incorrect.

[ragwo]

@struts
Thank you very much for sorting out the surround sound can of worms!

[alandbush]

To add some further spice Devialet talks about "SPACE™ technology": 

SPACE™ technology opens up a new dimension of sound. A patented algorithm upscales any mono or stereo signal into a 5.1.2 signal for an all-enveloping, muli-layered, deeply immersive sound experience, whatever the content you’re enjoying. 

But what on earth does that mean?   Without any metadata how can you make 5.1.2 out of a mono signal?  "Man-guessing"??  I was unable to find any patent filing that might explain this and also notice that while I was writing this post Devialet's website appears to have been updated, "patented" being replaced with "proprietary" in the above quoted text which I copy-and-pasted directly from the page but is now sunk without trace.

If anyone here can shed any light I'd be fascinated to understand if this is technical innovation or simply marketing innovation.

I suspect, like most marketing speak, the real technical details are omitted.
As you rightly surmise SPACE™ is probably capable of 5.1.2, if the appropriate information is present.

As an example, check out the following description of legacy surround matrix encoders.


Pro Logic II

Using the same matrixed four-channel sound as the original Pro Logic, Pro Logic II can create a 5.1 surround sound mix from a stereo source. Pro Logic II also has another trick up its sleeve: It can separate the surround signal into stereo left and right channels instead of the original Pro Logic’s dual-mono presentation. This processing mode is commonly used when watching non-HD TV channels with a stereo-only audio mix.

Pro Logic IIx

If your video source is presented in 5.1 surround — and your home theater system supports additional speakers — Pro Logic IIx can take that mix and expand it to 6.1 or 7.1. Pro Logic IIx is subdivided into movie, music, and game modes.

Pro Logic IIz

Pro Logic IIz allows the addition of two “front height” speakers that are placed above and between the main stereo speakers. This form of matrix processing aims to add more depth and space to a soundtrack by outputting sounds from a whole new location in the room. Since IIz processing can be engaged with a 7.1 soundtrack, the resulting format could be called 9.1.

Despite the addition of these height channels, Pro Logic IIz does not enable a true 3D placement of sounds. To enable that, you’ll need Dolby Atmos or DTS:X.



BTW - there have been plenty of surround matrix algorithms over the years.  DTS offered NEO and other variations, Lexicon had a highly respected Logic 7. Yamaha, Denton and Marantz had proprietary algorithms.  And of course, there were always the playful effects of Hall, Jazz, Sport et al.

There is a limitation, of sorts, to SPACE™ that you may not have come across.  It requires a PCM digital signal.

[Shulaf]

A post by @Shulaf in another thread made me realise that I really didn't understand what Apple's Spatial Audio is or how it relates to Surround Sound and in particular Dolby Atmos, furthermore whether Dione supports Spatial Audio and what on earth SPACE™ is and how that plays into it.  After a bit of digging and some background reading (these two articles are good primers) I think I am starting to get a grip on it but there are some aspects I haven't been able to make sense of.  Hoping folks here with a better understanding can chime in and enlighten me. 

So, as I understand it..

• Surround Sound is where the sound is mixed into multiple channels which fire at you from different directions creating the impression that you are in the middle of the action rather than that everything is taking place in front of you.  Some systems simulate surround sound by reflecting sound off room boundaries like the side and back walls to create that impression.  Dolby Atmos takes this a step further by allowing content creators to define sound sources as "objects" in 3D space which can move about, the Atmos technology then converting this into a mix for the number and placement of the available channels.
  
• Spatial Audio is a technology that is separate from but compatible with surround sound that uses gyroscopes and accelerometers to measure head movement and fix the perceived direction and strength of sounds in space as opposed to fixing them relative to the device that is creating them.  So for instance if you are listening via headphones and you turn your head to the left the channel balance is altered so that a sound that was coming from the left now appears to be coming from straight ahead.  Also, as you move around the system will remix so that you feel like you are moving closer to and further away from various sound sources.  This makes sense to me in a headphone listening context, where the speakers are fixed relative to your head but not relative to real space, and I can understand how it would work with devices that contain gyroscopes and accelerometers that can detect and measure head movement.  
  

What I don't get is:

• What relevance if any does this have in scenarios where the speakers are fixed in space?  When you turn your head or move around your head moves relative to the speakers in reality without needing any dynamic remixing to simulate it.
  
• How can this work technically in devices like Dione that don't contain gyroscopes or accelerometers so can't track head movement or orientation changes?  
  

I think the answers are "none" and "it doesn't", so while it supports Dolby Atmos as far as I can see Dione does not support Spatial Audio even when playing an Airplay 2 stream.  

To add some further spice Devialet talks about "SPACE™ technology": 

SPACE™ technology opens up a new dimension of sound. A patented algorithm upscales any mono or stereo signal into a 5.1.2 signal for an all-enveloping, muli-layered, deeply immersive sound experience, whatever the content you’re enjoying. 

But what on earth does that mean?   Without any metadata how can you make 5.1.2 out of a mono signal?  "Man-guessing"??  I was unable to find any patent filing that might explain this and also notice that while I was writing this post Devialet's website appears to have been updated, "patented" being replaced with "proprietary" in the above quoted text which I copy-and-pasted directly from the page but is now sunk without trace.

If anyone here can shed any light I'd be fascinated to understand if this is technical innovation or simply marketing innovation.

Great work struts, together we can tackle any lack of knowledge. As we can see the marketing around formats is most of the time larger than the capibilities


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[Drifter]

Dolby Labs developed an algorithm that is able to allow audio producers to record multi channel audio information into a standard audio recording and then encode it into a single stream of audio. In order to decode the multi channel information one requires the use of a decoder. AV receivers (Denon, Yamaha, Marantz etc) have this decoder as part of their circuits. Dolby Labs was started in 1965 in London and their first claim to fame was of course the tape noise reduction system.

Dolby's surround sound system all started with Dolby Pro Logic which allowed for the recording of 5.1 channels and has since evolved to Dolby Atmos which allows up to 9.1.4 channels. Dolby Atmos is object based which basically just means that in addition to the front and surround speakers, over head speakers are added and in the 9.1.4 Atmos terminology the ".4" refers to the number of overhead speakers. As you now have speakers that cover front, back and up, you have a 3 dimensional plane in which sounds can be positioned. This is of course similar to the sound stage that you get out of stereo where instruments are placed between the speakers. Atmos obviously creates a larger sound stage as you have speakers all around you.

So for Dolby Atmos to work the source audio requires that the multi channel info was recorded into the audio stream by the producer. Dolby also has a decoder that is able to take standard two channel audio and, using fancy algorithms, split the two channel audio stream into multi channels. This is called Dolby Surround and it is able to split the audio stream even into over head channels. So you can get the same effects from Dolby Surround as from Dolby Atmos. It is surprisingly effective.

In order to use the various Dolby decoders that Dolby Labs have created, one needs to pay Dolby Labs. It would appear as if the Dione does include the Dolby Atmos decoder. HOWEVER, it does not include the Dolby Surround decoder. The way that I understand Devialet's "SPACE is that they effectively wrote their own version of the Dolby Surround that is able to take a standard two channel signal and splits it into 5.1.2 (which is the number of speakers the Dione has) channels.

This has nothing to do with SPATIAL AUDIO from Apple which is headphone audio reproduction system as Struts correctly explained in his OP. Devialet uses the terms "spatialized" which is where the confusion comes in. It has nothing to do with Apple SPATIAL AUDIO but is simply the word that they chose to describe how "SPACE takes a standard two channel audio stream and "upmixes" it into 5.1.2 multi channel audio - exactly what Dolby Surround does.

The Dione does not support Apple SPATIAL AUDIO as it is for headphones and irrelevant to scenarios using fixed position speakers with a listener whose head is facing the front all the time.

Further, Airplay2 does support the transfer of Dolby Atmos signals over its protocol, so in theory you should be able to get the Dione to decode Atmos from an Apple TV that is not directly connected to the Dione via HDMI but is streamed wirelessly using Airplay2. The movie that you are watching obviously need to have a native Atmos soundtrack for this to work. If it does not have a native Atmos soundtrack, The Dione will apply "SPACE" to "simulate" a native Atmos soundtrack.

Dolby is of course not the only company that has created a form of multi channel audio encoding and decoding. DTS has its own version and we also had multi channel DVD-Audio as well as multi channel SACD which both kind of died quiet deaths. Auro Technology also a system that is called Auro 3D. In addition to these native multi channel capacilities, they have all also created algorithms to split standard two channel audio into multi channels. Dolby has its Surround system, DTS calls their NEO 6 and Auro also does this. Seems like Devialet has now added their name to this list with "SPACE".

I hope this explanation helps ......

[struts]

Dolby Labs developed an algorithm that is able to allow audio producers to record multi channel information into a standard audio recording. In order to decode the multi channel information one requires the use of a decoder. AV receivers (Denon, Yamaha, Marantz etc) have this decoder as part of their circuits. It all started with Dolby Digital with allowed for the recording of 5.1 channels and have since evolved to Dolby Atmos which allows up to 9.1.4 channels. Dolby Atmos is object based which basically just means that in addition to the front and surround speakers, over head speakers are added and in the 9.1.4 Atmos terminology the ".4" refers to the number of overhead speakers.

So for Dolby Digital or Dolby Atmos to work the source audio requires that the multi channel info was recorded into the audio stream by the producer. Dolby also has a decoder that is able to take standard two channel audio and, using fancy algorithms, split the two channel audio stream into multi channels. This is called Dolby Surround and it is able to split the audio stream even into over head channels. So you can get the same effects from Dolby Surround as from Dolby Atmos. It is surprisingly effective.

In order to use the various Dolby decoders that Dolby Labs have created, one needs to pay Dolby Labs. It would appear as if the Dione does include the Dolby Atmos decoder. HOWEVER, it does not include the Dolby Surround decoder. The way that I understand Devialet's "SPACE is that they effectively wrote their own version of the Dolby Surround that is able to take a standard two channel signal and splits it into 5.1.2 (which is the number of speakers the Dione has) channels.

This has nothing to do with SPATIAL AUDIO from Apple which is headphone audio reproduction system as Struts correctly explained in his OP. Devialet uses the terms "spatialized" which is where the confusion comes in. It has nothing to do with Apple SPATIAL AUDIO but is simply the word that they chose to describe how "SPACE takes a standard two channel audio stream and "upmixes" it into 5.1.2 multi channel audio - exactly what Dolby Surround does.

The Dione does not support Apple SPATIAL AUDIO as it is for headphones and irrelevant to scenarios using fixed position speakers with a listener whose head is facing the front all the time.

Further, Airplay2 does support the transfer of Dolby Atmos signals over its protocol, so in theory you should be able to get the Dione to decode Atmos from an Apple TV that is not directly connected to the Dione via HDMI but is streamed wirelessly using Airplay2.

Hi @Drifter

Many thanks for filling in the background on Dolby, certainly is a lot to learn here!

I am still a bit confused as to whether Dolby Surround used metadata embedded in the stereo signal or not.  Reading the Wikipedia entry for Dolby Surround (below), the statement that it decodes Dolby Stereo 4-channel soundtracks kinda implies that it does.  If it doesn't then I can only assume that its effect is fairly limited.  Deriving a centre channel from L and R is not rocket science but deriving directional information from data that contain no directional information is.

Dolby Surround

Dolby Surround is the earliest consumer version of Dolby's surround sound decoding technology. It was introduced to the public in 1982 during the time home video recording formats (such as Betamax and VHS) were introducing Stereo and HiFi capability. The name Dolby Surround described the consumer passive matrix decoding technology; the professional, active-matrix cinema technology bore the name Dolby Stereo. It was capable of decoding Dolby Stereo 4-channel soundtracks to 3 output channels (Left, Right, Surround). The Center channel was fed equally to the Left and Right speakers. The Surround channel was limited to a 100 Hz to 7 kHz frequency bandwidth, as dialog from the center channel could leak into the surround channel - there was as little as 3 dB of separation between LCR and Surround channels.[1

]
The glib and hyperbolic description of SPACE™ clearly states that 5.1.2 information can be derived from "any mono or stereo signal", i.e. no metadata.  If that were true then I would expect Devialet to have patented it and for that patent to be one of their most valuable assets.   It is possible to create anything resembling spatial audio out of a rip of a 78rpm mono recording?  Show me!  There's a big difference between "there's something going on above/behind me" and "defined sound sources moving in 3D space above/behind me".

To your last point, yes, Airplay 2 is quite capable of transporting Atmos signals and indeed it does already (see my second post, above). However the way Apple has implemented Atmos support requires that the Apple TV and the relevant speakers be assigned to the same room in the Home app which requires the speakers to support HomeKit (they need a HomeKit Setup Code to identify them) which Dione currently does not.  As I said above Apple currently seem to be confining Atmos-over-Airplay to one or two HomePods or HomePod minis although it is unclear if that is for technical or commercial reasons.  Also, since there is currently no way of assigning speakers in Airplay 2 to receive different channels of the same track other than as a simple stereo pair the only Atmos modes currently supported are 1.0.0 and 2.0.0.

[Drifter]

I have a full dedicated Atmos 7.1.4 theater room using a Denon AVR6700 as a amp/receiver which is fed by an Apple TV 4K.

Some old movies only have a stereo soundtrack, some of the ones from 90's and 00's have Dolby Digital soundtracks (5.1 or 7.1) and most of the new movies are Atmos. I often watch old movies and it is easier for Dolby Surround to do this "upmixing" if the original movie already has a 5.1 or 7.1 soundtrack. Dolby then only needs to add the overhead channels. It does work very well. Using a straight stereo soundtrack is less effective of course as Dolby needs to decide how it will split 2 channels into 12 channels (7.1.4) but it does add an element of "spatialization" to the sound (using Devialet's wording).

As a 5.1 or 7.1 soundtrack does have channel metadata that the Dolby decoder uses for front, centre and surrounds placement, I would assume that the Dolby Surround decoder knows what type of metadata must be reallocated to the over head channels. Of course a standard stereo signal has no multi channel metadata and in these cases Dolby Surround must use some other type of Voodoo to decide to which speaker to send the sounds. As mentioned, in my experience and in my theater setup this is less effective but there are noises coming from behind and above you.

I am sure Devialet will register their SPACE algorithm as IP. I'm quite keen to get Dione users' impressions of how effective this "spatialization" is, both using a 5.1 signal as well as standard stereo (or mono for that matter) signal.

Lastly, I don't use the Home App so I have no first hand experience. I sometimes stream some Tidal tracks that have Atmos encoding from Roon (hosted on an iMac) to my Denon AVR via Airplay2 and that works. Whether you like the result (multi channel music) is of course a matter of taste. Strange that Apple would restrict that if you if you stream from an Apple TV and HomeKit, but again I have no experience as I don't use that part of their echo system.

[Shulaf]

I have a full dedicated Atmos 7.1.4 theater room using a Denon AVR6700 as a amp/receiver which is fed by an Apple TV 4K.

Some old movies only have a stereo soundtrack, some of the ones from 90's and 00's have Dolby Digital soundtracks (5.1 or 7.1) and most of the new movies are Atmos. I often watch old movies and it is easier for Dolby Surround to do this "upmixing" if the original movie already has a 5.1 or 7.1 soundtrack. Dolby then only needs to add the overhead channels. It does work very well. Using a straight stereo soundtrack is less effective of course as Dolby needs to decide how it will split 2 channels into 12 channels (7.1.4) but it does an element of "spatialization" to the sound (using Devialet's wording).

As a 5.1 or 7.1 soundtrack does have channel metadata that the Dolby decoder uses for front, centre and surrounds placement, I would assume that the Dolby Surround decoder knows what type of metadata must to be reallocated to the over head channels. Of course a standard stereo signal has no multi channel metadata and in these cases Dolby Surround must use some other type of Voodoo to decide to which speaker to send the sounds. As mentioned, in my experience and in my theater setup is less effective but their are noises coming from behind and above you.

I am sure Devialet will register their SPACE algorithm as IP. I'm quite keen to get Dione users' impressions of how effective this "spatialization" is, both using a 5.1 signal as well as standard stereo (or mono for that matter) signal.

Lastly, I don't use the Home App so I have no first hand experience. I sometimes stream some Tidal tracks that have Atmos encoding from Roon (hosted on an iMac) to my Denon AVR via Airplay2 and that works. Whether you like the result (multi channel music) is of course a matter of taste. Strange that Apple would restrict that, but again I have no experience as I don't use that part of their echo system.

Hi Drifter nice setup!

For SACD it is still alive it is a neige format, Marantz actually released a new Sacd player last year the SACD 30n. DVD Audio as you said not relevant anymore and replaced by Blu Ray audio.

For the user experience of the Dione I can tell you in rainy scenes with Dolby movie rain sounds like it’s actually coming from above. For helicopters the sound is flying one side to another.

Let me know if you want me to test something specific. I’m willing to help you investigate.

For the Apple part of Dolby Atmos and Spatial audio I would like to share the following article:

https://support.apple.com/en-us/HT212182


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[Drifter]

I have a full dedicated Atmos 7.1.4 theater room using a Denon AVR6700 as a amp/receiver which is fed by an Apple TV 4K.

Some old movies only have a stereo soundtrack, some of the ones from 90's and 00's have Dolby Digital soundtracks (5.1 or 7.1) and most of the new movies are Atmos. I often watch old movies and it is easier for Dolby Surround to do this "upmixing" if the original movie already has a 5.1 or 7.1 soundtrack. Dolby then only needs to add the overhead channels. It does work very well. Using a straight stereo soundtrack is less effective of course as Dolby needs to decide how it will split 2 channels into 12 channels (7.1.4) but it does an element of "spatialization" to the sound (using Devialet's wording).

As a 5.1 or 7.1 soundtrack does have channel metadata that the Dolby decoder uses for front, centre and surrounds placement, I would assume that the Dolby Surround decoder knows what type of metadata must to be reallocated to the over head channels. Of course a standard stereo signal has no multi channel metadata and in these cases Dolby Surround must use some other type of Voodoo to decide to which speaker to send the sounds. As mentioned, in my experience and in my theater setup is less effective but their are noises coming from behind and above you.

I am sure Devialet will register their SPACE algorithm as IP. I'm quite keen to get Dione users' impressions of how effective this "spatialization" is, both using a 5.1 signal as well as standard stereo (or mono for that matter) signal.

Lastly, I don't use the Home App so I have no first hand experience. I sometimes stream some Tidal tracks that have Atmos encoding from Roon (hosted on an iMac) to my Denon AVR via Airplay2 and that works. Whether you like the result (multi channel music) is of course a matter of taste. Strange that Apple would restrict that, but again I have no experience as I don't use that part of their echo system.

Hi Drifter nice setup!

For SACD it is still alive it is a neige format, Marantz actually released a new Sacd player last year the SACD 30n. DVD Audio as you said not relevant anymore and replaced by Blu Ray audio.

For the user experience of the Dione I can tell you in rainy scenes with Dolby movie rain sounds like it’s actually coming from above. For helicopters the sound is flying one side to another.

Let me know if you want me to test something specific. I’m willing to help you investigate.

For the Apple part of Dolby Atmos and Spatial audio I would like to share the following article:

https://support.apple.com/en-us/HT212182


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It would be brilliant to get some sound impressions for the following 3 scenarios:
- Atmos signal decoded by the Dione using Atmos
- 5.1 signal decoded by the Dione using SPACE
- stereo signal decoded by the Dione using SPACE

It would be be even better if the source material (i.e. movie) is the same just with 3 different audio tracks. You can then use the same scene in the movie and explain how the sound changes between the 3 scenarios.

That would be awesome ....