Where’s My Atmos, and What Is An IAB?
IAB is the Standard; Dolby Atmos Is One Company’s Implementation
Does your cinema theater have an Atmos Immersive Audio rendering system?
Are you playing DCPs labeled “Atmos”?
Then your cinema theater can play a DCP labeled “IAB”
…and that is the label you will see now instead of Atmos.
<Screenshots of TMS listings, one showing Atmos and another showing IAB>
The short explanation is:
There is a set of SMPTE Standards that deal with Immersive Audio, and all media players – Integrated Media Blocks (IMBs) that are inside the projector, or separate external systems (SMSs) – are following that set of SMPTE Standards:
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- All movies that use the standardized method for Immersive Audio will use the term “IAB Compliant“
- IAB Compliant soundtracks will be labeled “IAB” in their Naming Convention Name
- On your Media Player or Theater Management System or Library Management System, the term “IAB” will be used (not Atmos, or DTS:X or AuroMax)
- You may be more familiar with seeing ATMOS or DTS:X or AuroMax on the designation for the movie. In the future, only IAB will be used.
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Now you will only see “IAB” in the Naming Convention listing
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You will not see ATMOS
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You will not see DTS:X
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You will not see AuroMax
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Part 2 – IAB is the Standard; Dolby Atmos Is One Company’s Implementation
Here is the detailed background of that simple phrase.
In the Digital Cinema Book of Abbreviations, most are created by combining the first letter of the words. These are called acronyms – IAB is one more Three Letter Acronym (TLA) in the Cinema technology pool. If you want to talk to techs, you have to know them, just so you can nod your head wisely, then look them up later.
IAB stands for Immersive Audio Bitstream.
Bitstream is a computer term that we should explain first.
Simply explained, in a standard audio system the audio starts from the Media Server, then goes to an Audio Processor.
In a sound system that can play Immersive Audio, the audio system includes a magic box that delivers a 2nd stream of information to the sound system. The box may be magic, but the information it is sending – called a data stream – doesn’t use magic. It follows a standard that was agreed upon by a lot of engineers who understand magic. They made an Immersive Audio (IA) Standard so that every magic “IAB” box will use a very exact system of presenting the information to the Immersive Audio speaker system. That stream of information uses bits of information, so it is called a ‘bitstream’. Since it is a computer, the word “bits” has a special definition. And, of course, it is a crazy computer-style abbreviation.
Computers – in their deep dark places – only understand two choices. Everything in the memory, everything in the processors, and everything in the back and forth communication, is described as a one or a zero – or combinations of ones or zeros. We say that every unit of information is one of these ‘binary’ choices. Binary means exactly that: Two Choices. In computers, each Binary Unit are called a “Bit“. When those bits are put together in a particular order, and sent in a stream from the magic box, that stream of bits is called: …all together now, it is called a Bitstream. …really, it is a kind of magic.
<example of CPL Annotation Text with ATMOS, and another with IAB>
Dolby released the Dolby Atmos sound system in April of 2012 at CinemaCon.
Before the release of Atmos, there was mainly 5.1 and 7.1 sound systems. The 11.1 and 13.1 Auro systems from Barco were released shortly before.
These systems are called: Channel-based. Typically, these systems included the 3 front channels (Left, Center and Right) and the two surround channels (Left Surround and Right Surround). They also included the ‘point 1’ of the 5.1 channel-based system – the Low Frequency Effects (LFE) channel. The 7.1 system added 2 rear surround channels. The Auro system added upper channels.
Just to be clear, even though the LFE channel might have several cabinets of speakers, it is only one channel. This is the same for the side surround channels – each speaker on one wall gets the same channel of sound. Together they are called an “array”.
For example: You might hear a tech say, “…the amplifier for the left surround array.” They would be talking about all the left surround speakers together.
Each of the front speaker cabinets usually have more than one speaker also, usually a high frequency speaker and mid frequency speaker and one or two low frequency speakers. But each set is still just one channel.
And just to emphasize the point: If you look at the amplifier rack, one set of wires go from one amplifier channel to one channel of speakers.
What Did Atmos Add?
The Atmos system introduced a new concept to the auditorium. The name of this new development is called the “Object”.
The Atmos system still includes the 5.1 or 7.1 channels. It calls these the Bed Channels.
The word “bed” has a tradition in the music business. For example, if you hang around a band you will hear them say, “Let’s lay down the bed tracks.” Those are the basic tracks for the rhythm and harmony with the main melody elements of a song. So. Bed Tracks. The basic 5.1 or 7.1 channels of the movie sound.
The Object is different. It is a sound, but it has no particular channel to go to. There is no particular cable for it to go to.
The object has a position in space to go to. Go to 4 meters in front of the screen, 3 meters from the left side and 1 meter from the ceiling. Be very narrow, but very loud.
But that position in space probably doesn’t have a speaker, right?
In fact, with Atmos and the there systems there are a lot of extra speakers. The problem is that in one auditorium might have 8 additional speakers plus the bed channels, and in another auditorium there might be 20 additional speakers. In fact, the total combination of speakers can be 64. So, maybe there is a speaker in that position, …but there probably isn’t.
But it requires magic to do this. Computer magic. And sound magic. That kind of magic that tricks the Human Hearing System.
Computer Magic/Sound Magic
This is simple magic. After a long time of practice, several engineers in different parts of the world noticed that you can trick the hearing system if you could play sound from a combination of speakers.
To explain this, we will go back before all these extra channels, to the time when there was just one speaker, the mono speaker. Then we will proceed to left and right. Then, the magic of Stereo.
Because, for a long time, there was only one speaker behind the cinema screen. After a while, some people put in multiple speakers, but all playing the same sound. That was just the level of the technology of the time. You need more volume, you need more speakers. But the signal was mono. One channel.
Since there was nothing else to compare it to, they probably just called it the Speaker, not the mono speaker. That is similar to the Acoustic Guitar. Before the electric guitar was developed, no one called it the acoustic guitar. It was just the guitar.
When two separate channels became available for the sound, the mixer has some decisions to make. S/he can mix everything to one channel or to the other, or to both.
For example, the sound mixer might put all the sound from one voice, or one instrument of the music into one channel. That might be perfect. For example, if two people are standing on the left side of the screen, it is logical that this sound is all coming from the left speaker. The same is true if people are on the right side of the screen, to put their sound into the right speaker. It would certainly be confusing the other way.
But, if you are sitting on the left side of the screen, you might not hear the sound from the right side. So, many mixes might put all the sound into both speakers.
There is a trick that can be played on the ear though. If the same sound comes from two speakers into the ears at the same time, the sound will seem like it is coming from the center speaker – even if there is no speaker there! This is called a Phantom Center. If you are sitting in the center seat you can hear this most clearly. People on either side can partly hear it, but not as perfectly. And the further from center, the less the phantom center effect is created.
Fortunately, in cinema theaters, there is a center speaker. When a person is walking from the left to right side of the room, the mixer doesn’t have to play tricks to get the sound to seem like it is going from one side of the screen to the other. Using the surround speakers lets the mixer take the sound further right and left around you.
The Immersive Audio standard uses this phantom trick. If the mixer wants the sound of an eagle to be over your head at a certain position, they move a position pointer to that place and the computer creates a magic set of numbers for that sound to be in that place at that time. Remember that bitstream stuff above? Those position and time and the code for that sound and the level of that sound and how wide or narrow – these are all made into bits and they are all flowed into a larger number of bits of the bitstream.
Take some time to draw a picture of all these elements happening for one sound.
Then draw a picture of another and another, all happening at the same time, using paper clips or erasers or whatever is on the desk. Then pick a time before and after for those three elements and put those on another piece of paper. Now, move all of them across the desk and prove that gravity works. That waterfall of paper and clips and batteries and cables is a showing how an Immersive Audio Bitstream works. Yell out, IAB! A stream of bits representing audio that is immersive.
So, that’s it. A bunch of engineers figured out how to convince computers to do magic, creating phantom sounds that can appear anywhere. …and the magic boxes can make the same phantom sound appear using 8 speakers or using 20 speakers. Then they spent millions of money units to make the chips and new variations of those chips, and then the final variation of those chips work efficiently.
But the Movie Studios said, “We only want to distribute one version of the movie, not one for every company who makes a different bitstream.”
And the Cinema Exhibitor said, “We are not going to buy something like this unless it will work with all the companies. No matter what, we have to buy a lot of new amplifiers and a lot of new speakers and hang them and wire them. The magic boxes must be compatible.”
So, dozens of engineers from competing companies got together in meetings of the Society of Motion Pictures and Television Engineers (SMPTE), and had meetings and meetings and agreements and created the Immersive Audio Bitstream – IAB. Hey! That’s the name of this article!
And now, every movie that is released with this standard bitstream will have IAB on the label instead of ATMOS or DTS:X or AuroMax.
IAB
Work-In-Progress – more drawings needed
A Bit More
A little more information about “Bitstream” in case you are interested.
You know that computers are not wise. They don’t know anything. They only know OFF or ON. Not Connected or Connected. Give. Take. This situation. That situation.
We call these opposites “states”. What state is this in. Good state. Bad state. Working. Not working. Letters. Numbers. Not pushed or pushed? We use the word “state” to mean what position or condition is some thing in. Is it OFF or ON? Is it circle or square, in or out, left or right. And most often in the computer world, you see the state as a series of zero or one, zero or one, zero or one. Eight of those zero-or-one is a byte. Two bytes is a word. But the basic thing is that there are two states.
The word ‘binary’ describes this two-state situation. Words starting with ‘bi-‘ usually has something to do with two.
Programmers use two states to create the world inside a computer. Zero – 0 – or One – 1 – are basic tools. Why? Because it all started with a device called the transistor. Back in the 1950’s and 60’s when it was invented, it was a pretty big deal. Nobel prize for the inventors. The transistor changed almost everything. Because the basic physical element of a computer is the transistor, every choice that a computer goes through to do something is based upon two choices. Did a key get hit to input data? Yes. Do I print that key value on the screen? Yes. The first great microprocessor that started us on the road to personal computers came in the mid-70s and had 3,500 transistors. The main computer processor chips now have a billion or more transistors.
00001011 looks a like one thousand eleven. But to a computer it looks like a ‘1’ in the 1’s column and a ‘1’ in the 2’s column, a ‘0’ in the 4’s column, and a ‘1’ in the 8’s column. Added together, to a computer this looks like an eleven.
But each item unit in a line of zeros and ones is a unit in a particular order.