The Fundamentals of Atmos (2 Viewers)

[Carlo_M]

With the same caveat I said earlier admitting I'm not a techie, again from the horse's mouth (this is the webpage from which I got that PDF link):

Dolby Atmos for the Home

Scroll down below the video, and you see the section titled Dolby Atmos for the Home Benefits

Within that section is this:

Reproduces All the Audio Objects in the Original Cinema Mix​

Reproduces up to 128 simultaneous audio objects in a mix for rich, realistic, and breathtaking sound.

 

[Tom McA]

Notice that is specifies how many objects (128, though I had gotten the idea it was 168) the cinema version of Atmos can have, but on the home version it only talks about the number of speakers. That's because they don't want to spell out that the total number of objects home Atmos can have is 16. They also play games with wording "every sound in the mix is represented as an audio object". In Atmos, every channel can be referred to as an "object", even if it is one of the locked, 7.1 (or as many as 7.1.4) bed channels.

OK, here we go again. An "object" is an individual piece of sound. A gunshot. A thunderclap. A clown horn. And every object is mixed with positional metadata. And there can be up to 118 of them at a time. (128 is the total track count, with a default of 10 bed, a.k.a. channel-based, tracks). Objects and channels are not the same thing. The number of object CLUSTERS is most often 16, but many objects can be clustered into those groups based on their most logical positions, and the clustering process during encoding is automatic and dynamic, i.e. an object can hop between clusters if its position goes a different way than its friends. Your verbiage of "they don't want to spell out" and "they play games with wording" implies sinister intent, where there is none. It's just simplifying a complex, yet kinda elegant process.

 

[JohnRice]

With the same caveat I said earlier admitting I'm not a techie, again from the horse's mouth (this is the webpage from which I got that PDF link):

Dolby Atmos for the Home

Scroll down below the video, and you see the section titled Dolby Atmos for the Home Benefits

Within that section is this:

Of course all the original objects are in the home soundtrack. That's the contents of the soundtrack. That doesn't mean they are still 128 discrete elements for the home processor to steer.

Anyway, you guys tell yourselves whatever you want and have a nice day.

 

[Carlo_M]

I think you missed the part where I said I don't have a dog in this race. I didn't even give this topic a thought before I read your initial comment. That got me semi-interested and so I did what I normally do when someone says something I didn't know: I do my own research to see if I can confirm (or not) the new thing I read.

In this case, and admittedly I didn't do a super deep dive as this topic doesn't really overly interest me, the research led me to those comments on official Dolby sites. Now I don't know Dolby's corporate philosophy, so I don't know if there's a vested interest in them misleading (or hiding) that information you mention.

If you have any links to technical articles, reviews, or what not that confirm your comments, please do post them here, I'm always willing to ingest new information (ideally from knowledgeable sources that work with the Atmos software/hardware or the audio industry in general, as many general A/V "YouTube Experts" often contain as much misinformation as information).

As I said, I have no dog in this race and if Dolby is purposely misleading us and there are people with some firsthand experience with the encoding/decoding process that can shed additional light, I'm more than happy to absorb new information. Because prior to this morning I had zero information on, nor given any thought to, any difference between Atmos Theatrical vs. Home.

 

[JohnRice]

I give up…

 

[Carlo_M]

Okay I think I see the underlying part in your post that is generating such passion:

That's because Dolby has been incredibly successful at making people believe there is no difference between cinema Atmos and home Atmos. Notice that they provide specifics of the number of channels and objects and their capabilities in cinema use, but when it comes to home, the verbage gets flowery and vague.

Which ascribes a certain motivation to Dolby for deceit.

I guess my take on it is, I personally have never felt like Dolby has promised me that Atmos at home will be equal to Atmos in the theater. To my (admittedly simple) mind, there has to be an inherent compromise in the soundtrack for home delivery to account for the variance of 2, 4 or 6 overhead speakers. Given how Dolby advertises on their site:

In a Dolby Atmos theater, every speaker — as many as 64 total — is powered independently and gets its own separate audio feed. In effect, each speaker is its own zone. In addition to the overhead speakers, Dolby Atmos typically adds more surround speakers and screen speakers.

I would have zero expectation that the soundtrack being delivered to my x.y.2/4/6 system at home would be identical.

But to get back to the point of deceit by Dolby...I will admit that outside of seeing a Dolby trailer in front of a movie, I am not regularly exposed to Dolby advertising or propaganda in any way. I don't see YouTube or TV ads for it. I don't see paid ads on websites I frequent for it. I've never encountered a "[This Program/Podcast] brought to you by Dolby...where your home audio will sound just like the cinema!" ad. And I consume a lot of media (both social and traditional). So perhaps that's why I'm not as passionate for (or, heck, was even aware of) this issue as you are.

 

[Martin Dew]

Yes. The setup for a commercial theater is completely different, and much more complicated. No automation involved. Everything is mapped, if it's done correctly. Also, commercial Atmos has the capability for (as I recall) 168 objects, vs 16 for home.































So, as Josh also dug into, home Atmos soundtracks have 12 "bed" channels. That is the basic 7.1.4 configuration. Those channels (objects) are not object oriented. They are no different than the 5.1 or 7.1 discrete channels we've had for 30 years. There's just more of them. Then there is the capability for an additional four "object based" channels, which are not tethered to any individual speaker, but can roam independently, such as the "joystick" example in the video. A lot of home Atmos soundtracks actually don't use these object based channels. Instead, the sound engineer just hard codes the entire soundtrack into the 7.1.4 bed channels. In reality, if you have a 7.1.4 or lesser system, it makes zero difference, so it's not a negative at all. The real down side (I see it almost as a scam) is, as Josh pointed out, you expand beyond 7.1.4, any additional (middle) surround and overhead speakers are only sent audio from the four object based channels, which often don't even exist. Now, this can be overcome with additional processing, but that involves synthesizing virtual channels like with Dolby Pro Logic.































Anyway, the takeaway is that anyone wanting to spend the significant $ to expand beyond 7.1.4 really needs to know the serious limitations they will face. Manufacturers do NOT make this clear, since they want to sell you more stuff.































BTW, regarding subwoofers, I've decided to always talk about one subwoofer channel, because there is only one subwoofer channel in soundtracks. You could have 20 subwoofers, but there's still only one subwoofer channel in the soundtrack. I have dual subs, but that doesn't technically means it's 7.2.4, since it's running both subs off one channel from the preamp. I'm just trying to be accurate., Yeah, there are receivers and processors that have independent sub outputs, but the soundtrack still only has one sub channel. There can be more to it, since the subs also play audio that's crossed over from the other channels, but, again, the soundtrack only has one sub channel.































That's a good

Yes. The setup for a commercial theater is completely different, and much more complicated. No automation involved. Everything is mapped, if it's done correctly. Also, commercial Atmos has the capability for (as I recall) 168 objects, vs 16 for home.

So, as Josh also dug into, home Atmos soundtracks have 12 "bed" channels. That is the basic 7.1.4 configuration. Those channels (objects) are not object oriented. They are no different than the 5.1 or 7.1 discrete channels we've had for 30 years. There's just more of them. Then there is the capability for an additional four "object based" channels, which are not tethered to any individual speaker, but can roam independently, such as the "joystick" example in the video. A lot of home Atmos soundtracks actually don't use these object based channels. Instead, the sound engineer just hard codes the entire soundtrack into the 7.1.4 bed channels. In reality, if you have a 7.1.4 or lesser system, it makes zero difference, so it's not a negative at all. The real down side (I see it almost as a scam) is, as Josh pointed out, you expand beyond 7.1.4, any additional (middle) surround and overhead speakers are only sent audio from the four object based channels, which often don't even exist. Now, this can be overcome with additional processing, but that involves synthesizing virtual channels like with Dolby Pro Logic.

Anyway, the takeaway is that anyone wanting to spend the significant $ to expand beyond 7.1.4 really needs to know the serious limitations they will face. Manufacturers do NOT make this clear, since they want to sell you more stuff.

BTW, regarding subwoofers, I've decided to always talk about one subwoofer channel, because there is only one subwoofer channel in soundtracks. You could have 20 subwoofers, but there's still only one subwoofer channel in the soundtrack. I have dual subs, but that doesn't technically means it's 7.2.4, since it's running both subs off one channel from the preamp. I'm just trying to be accurate., Yeah, there are receivers and processors that have independent sub outputs, but the soundtrack still only has one sub channel. There can be more to it, since the subs also play audio that's crossed over from the other channels, but, again, the soundtrack only has one sub channel.

That's a good last point, John.

5.1 and 7.1 used to indicate how many available channels were encoded in the audio software file, like 'Dolby Digital 5.1' or 'Dolby Surround 4.0'.

But since immersive or 3D audio came along, those numbers now appear to represent how many loudspeakers an individual uses in his system, like 7.2 or 9.4.6.

It's irritating because the two ideas are frequently conflated and misunderstood.

 

[JohnRice]

That's a good last point, John.

5.1 and 7.1 used to indicate how many available channels were encoded in the audio software file, like 'Dolby Digital 5.1' or 'Dolby Surround 4.0'.

But since immersive or 3D audio came along, those numbers now appear to represent how many loudspeakers an individual uses in his system, like 7.2 or 9.4.6.

It's irritating because the two ideas are frequently conflated and misunderstood.

What I regret is that the last several posts have done nothing to improve the understanding of home Atmos, and how it actually functions in real-world situations. To genuinely understand, to the best possible, how it works. As I think back on this exchange, I realize nothing has been gained. I doubt anyone understands anything any better. I've been thinking through the complexities since. Such as, when a sound engineer creates an Atmos soundtrack for home, it's not realistic to ignore the fact that not everyone has an Atmos processor. After all, they are typically built on a "7.1 core". It also reinforces my assertion that an Atmos processor is beneficial these days, even when the system isn't an Atmos configuration. At least it is if Atmos soundtracks are going to be played back.

Since this thread has been derailed (in my opinion) it migfht be in order for a new, more specific one.

 

[Doug2000]

I dIsagree that the thread has been derailed or that its done nothing to further the understandings of how Atmos works.

 

[DFurr]

Since I'm not an ordinary home theatre person I need help understanding all this talk of 7.4.1, 7.1.4, etc, etc.
I don't have nor want Dolby Atmos so from my list of speakers which system do I have??
left, center, right, (2) subs, (2) left surrounds, (2) right surrounds, (1) left rear discrete, (1) right rear discrete....rear speakers used for Dolby EX.

What are the numbers for this system?

 

[Edwin-S]

What is the actual crux here? That setting up a home "ATMOS" system is just a waste of money because the overhead speakers are improperly or not used at all?

 

[Edwin-S]

Since I'm not an ordinary home theatre person I need help understanding all this talk of 7.4.1, 7.1.4, etc, etc.
I don't have nor want Dolby Atmos so from my list of speakers which system do I have??
left, center, right, (2) subs, (2) left surrounds, (2) right surrounds, (1) left rear discrete, (1) right rear discrete....rear speakers used for Dolby EX.

What are the numbers for this system?

7.1.4 or 7.4.1 is just semantics to me. They mean the same thing.

7 = 3 front, 2 sides and 2 rears.
.1 or .2 = 1 or 2 subwoofer channels
.4 = 4 height or overhead channels

Edit: Whether they are all used in a home video sound mix is a different story, but 7.4.1 is the number of channels available to steer sound to.

 

[DFurr]

7.1.4 or 7.4.1 is just semantics to me. They mean the same thing.

7 = 3 front, 2 sides and 2 rears.
.1 or .2 = 1 or 2 subwoofer channels
.4 = 4 height or overhead channels

Edit: Whether they are all used in a home video sound mix is a different story, but 7.4.1 is the number of channels available to steer sound to.

So if i hear you correctly my system is a 7.2

 

[Edwin-S]

So if i hear you correctly my system is a 7.2

Yes. If you are not using any height speakers sometimes also called presence speakers.

It is the same as a 5.1 system which would be 3 fronts, sides or 2 rears and 1 subwoofer, just 2 more speakers added.

 

[Edwin-S]

My setup is 7.1. If a person stuck using a consistent nomenclature with three positions then it would be 7.0.1.

 

[DFurr]

My setup is 7.1. If a person stuck using a consistent nomenclature with three positions then it would be 7.0.1.

Just to be sure that I understand, my 2 left surrounds come from one channel as do my 2 right surrounds. My two subs come from separate channels. So is mine 7.1 or 7.2 or 7.0.2?

 

[Edwin-S]

Just to be sure that I understand, my 2 left surrounds come from one channel as do my 2 right surrounds. My two subs come from separate channels. So is mine 7.1 or 7.2 or 7.0.2?

When I refer to a system as 7.2 or 7.0.2, I'm defining it as the number of discreet channels the receiver can provide. I don't go by number of speakers. A 7.2 or 7.0.2 system means 7 channels, each driving a single speaker plus two separate subwoofer channels.

If you are driving two surround speakers with one channel on the left and two speakers on the right with another channel then what you have is a 5.2 system, because you are just splitting the single channel over two speakers. The sound coming from them will be identical since the signal is the same.

 

[DFurr]

When I refer to a system as 7.2 or 7.0.2, I'm defining it as the number of discreet channels the receiver can provide. I don't go by number of speakers. A 7.2 or 7.0.2 system means 7 channels, each driving a single speaker plus two separate subwoofer channels.

If you are driving two surround speakers with one channel on the left and two speakers on the right with another channel then what you have is a 5.2 system, because you are just splitting the single channel over two speakers. The sound coming from them will be identical since the signal is the same.

Understood. So what about my two rear speakers Dolby EX, each on separate channels? (this is my last question, I promise!!)

 

[Edwin-S]

Understood. So what about my two rear speakers Dolby EX, each on separate channels? (this is my last question, I promise!!)

Not including the two subwoofers, do you have 9 speakers in the system?

 

[JohnRice]

Just to be sure that I understand, my 2 left surrounds come from one channel as do my 2 right surrounds. My two subs come from separate channels. So is mine 7.1 or 7.2 or 7.0.2?

You have a nearly traditional 7 channel surround system. You just have two pairs of duplicate side surrounds, but that doesn't really make it 9 channels, as you already pointed out.

When it comes to subwoofers, numbers tend to be thrown around. The bottom line is, there is only one subwoofer channel in surround soundtracks. So, from that perspective there are no multiple sub channels. Of course, the subs also typically receive bass frequencies that are crossed over from the L&R channels. So, they can have some separate bass frequencies from that. But, then again, I'm not sure many soundtracks actually use discrete L&R channel bass, but tend to just send all bass that isn't solely in the sub channel to both the L&R channels, which means you're really just back to a single sub channel, even if you have multiple subs.

All of that is why I've kind of steered away from talking about multiple sub channels. In fact, I have dual subs, but I run them off a single channel, and individually calibrate them to interact properly with each other and the room. You can also do that with a MiniDSP, but it's still starting with one sub channel and adjusting each output to each sub. In reality, what processors/receivers are doing with multiple sub outputs is just calibrating each sub separately, which is a very important thing to do, but they aren't truly creating two different sub channels, at least most of the time, and it probably doesn't make any difference when they have slightly different signals. That's about the best I can explain how I approach the concept.