Dolby Atmos Mixing In Pro Tools
Welcome to Part 1 of our 4-part Learning Series, where we demystify Dolby Atmos Mixing and the Internal Pro Tools Renderer by taking you through the fundamentals of converting a stereo session into one that can utilize the power of Dolby Atmos. Written by Avid Master Instructor Andy Hagerman, this article series is a must for anyone wanting to mix in Dolby Atmos.
We strongly advise Professional Audio Engineers to attend the 6-day (24 hours), official AVID Pro Tools | Dolby Atmos Certification with the Avid Masters to cover advanced mixing applications, hundreds of pages of documentation and techniques. The Avid Masters author the curriculum for Pro tools Certification worldwide, inlcuding Eric Kuehnl and Frank D. Cook who have contributed more than 20 years of Avid's Pro Tools Certification Textbooks to ALP College/ University Learning Partners around the world.
Dolby Atmos Mixing is transforming the audio industry -” it’s not only the fastest-growing playback format on the scene, but it provides very useful workflow features for producers and creatives.
In this series of four articles, we’re going to demystify Dolby Atmos mixing, starting with a discussion of the fundamental structure underpinning this new audio standard. In the following articles, we’ll progress through a basic workflow of converting a traditional stereo mix into an immersive Atmos experience. If you’ve been on the fence, now’s the time for you to give Dolby Atmos mixing a try, and the good news is that it’s easier than you think.
Understanding Dolby Atmos
One of the biggest challenges that we as mix engineers face is "mix translation". For those not familiar with the term, this refers to how a mix sounds in the real world as opposed to in the finely-tuned acoustics of a studio environment. A mix that sounds perfectly fine in an expensive studio might sound much different in a theater. Worse yet, because of differences in sizes and speaker layouts, even different theaters might sound significantly different from each other.
While it’s true that Dolby Atmos mixing brings all kinds of advantages to our mixing workflows, I believe that the initial goal of Dolby Atmos was to make mixes sound as good as they possibly could in a wider variety of playback scenarios. They do this through an ingenious new way of thinking about audio -” as beds or objects…
Beds
The first challenge when it comes to Dolby Atmos is to understand a new set of terms. We’ll start out with the term "Bed".
Understanding beds is a good place to start, since it’s the kind of mixing that you’ve been doing all along. Let’s start with a stereo example: When you pan a signal hard left, it’s coming out of the left channel, and when you slam it hard right, the sound jumps to the right speaker. Easy right?
Whenever you pan any signal in that stereo field anything other than hard left or right, you’re directing your DAW to route some of the signal to the left channel and some to the right. The amount of signal sent to the various channels will determine the perceived position of the audio (and if the levels are equal between the left and right channels, the signal will be perceived as being between those speakers, something referred to as a "phantom center".)
Below you can see the stereo meters of a signal that is being panned to the right speaker.
With traditional surround mixing, we’re working in the same channel-based way. Below is how a 5.1 panned signal would look in the output meters:
Whether you’re mixing in stereo or surround, with traditional mixing your panning would control the channels that were outputting signals. For the purposes of our discussion, we’ll refer to this as "channel-based" mixing. Depending on where the speakers were positioned in the listener’s playback space, their experience may be significantly different from the intention of the mixing engineer.
Channel-based mixing is one component of Dolby Atmos -” in the world of Atmos, we refer to these as beds. The default bed size for a Dolby Atmos mix is 7.1.2 (left, center, right, left side, right side, left rear surround, right rear surround, left top middle, right top middle, and LFE), and is indicated in the Dolby Atmos Renderer window (which we’ll dive deeper into in the next article) by an outlined box.
You’ll see that as we pan a signal that is assigned to a bed, the different channels of the bed activate. This is similar to what you’ve already experienced with traditional mixing.
Beds are traditionally used for tracks whose positioning isn’t critical, or that aren’t extensively moved in your mix. For example, ambiences and music beds are typically assigned to beds.
A Dolby Atmos mix can include multiple beds of various channel configurations. For the purpose of this series of articles, we’ll stick with the default bed configuration, which is a single 7.1.2 bed.
The order of channels in a Dolby Atmos bed is different from the Pro Tools meters. The channels (from left to right) are Left, Right, Center, LFE, Left Side, Right Side, Left Rear Surround, Right Rear Surround, Left Top Middle, and Right Top Middle.
Objects
When mixing in Dolby Atmos, if a track isn’t assigned to a channel-based bed, it’s assigned to an Object. Objects are arguably where Dolby Atmos shines brightest and it is here where the folks at Dolby Labs have most directly addressed the problem of mix translation.
When you’re mixing in a non-Atmos way, or when you’re working with beds, your panning will directly determine the allocation of signals to individual channels. If, in the listening environment, the speakers were misplaced or missing, your mix would suffer. Objects, on the other hand aren’t channel-based, but how is this possible?
The answer is metadata -” extra information that is added to a file. In the case of a Dolby Atmos Object, metadata is determines the position of that sound in a three-dimensional space (in terms left>right, front>back, and height). In any given listening environment, objects will use the available speakers to provide the best possible listening experience in that space.
For example, let’s say that in a home listening environment you’ve got a speaker in the front center, specifically so that you can hear dialog clearly. If your dialog is assigned to an object, and if it’s panned to that center position, you’ll hear it out of that speaker, no problem. On the other hand, if your room doesn’t have a center speaker, that same Dolby Atmos object, being position-based, will use the available speakers to provide a "phantom" center. Objects translate the producer’s intent to the best extent possible.
Here's how an object is represented in Pro Tools’ Dolby Atmos Renderer window. In this example, the track you see here is assigned to an object (object #11, to be precise), and as the signal moves in the listening space, while you don’t see any activity on any of the channels. you do see a small sphere in the theatrical view, which indicates the position of the audio signal.
Renders | Re-Renders
As mixing engineers, we’re often asked to create multiple mixes in different channel formats (for example, a stereo mix, a 5.1 version, a 7.1 version, and so on). In the past, this has been a time-consuming headache, but Dolby Atmos makes it easy. In future articles of this series, we’ll go through the steps of exporting your Dolby Atmos mix, so this is a bit of a sneak peek at the process:
Here you can see a Bounce Mix dialog box for a Dolby Atmos Mix:
Here’s where a bit of terminology comes into play: When you create Dolby Atmos mixdown, you’re rendering your mix into a proprietary Dolby file (called a Dolby ADM BWF file). You’ll see that in this specific example, we’re rendering 1 bed and 47 objects.
One of the fantastic aspects of Dolby Atmos is that you can -” at the same time that you create your ADM file -” create any number of traditional surround format mixes. Dolby calls these re-renders. In this example, we’re creating a binaural mix, a stereo mix, and 5.1 and 7.1.4 surround mixes, all with a single click of a button. And because we’re working with object-based audio, each mix will preserve the accuracy of your mix, to the extent possible for each format.
Binaural mixes and stereo mixes, though both comprise two channels, are quite different. A binaural mix simulates the position of sonic elements in a three-dimensional space and is intended to be listened to using headphones. A stereo mix does not implement this kind of psychoacoustic sleight of hand, and can be enjoyed on either speakers or headphones.
If you’ve been hesitant about trying your hand at Dolby Atmos, now’s a perfect time to start exploring this exciting new format. And now that you understand the logic behind beds, objects, renders, and re-renders, you’re ready to confidently take the next steps.
In the series, you’ll learn the following:
- Part 2: Setting Up Your Pro Tools Session: In this article, we’ll start with standard stereo tracks, and then build a Dolby Atmos session, ready for immersive mixing.
- Part 3: Dolby Atmos Panning: Taking a moment to understand the Dolby Atmos panner window is time well spent. When you’re done with this article, you’ll be able to position your sounds with confidence!
- Part 4: Exporting Dolby Atmos: Bouncing your mix is always a make-or-break moment, and that’s especially true when working in Dolby Atmos. In this final article, you’ll bounce your Dolby Atmos session in a number of ways.
Once you’ve mastered the basics, trust me: You’ll be hungry for more. Promedia Training offers a wide range of courses, including official Dolby Atmos certification courses, that can take your creative work to the next level. The teachers at Promedia are first-rate, and can show you valuable tips and tricks, whether you’re a beginner or seasoned professional.
That’s it for now, see you next time!
Author: Andy Hagerman
Avid Master Pro Tools Instructor
AVID Pro Tools | Dolby Atmos Certification
Andrew Hagerman has been a professional musician and teacher for the majority of his nearly 60 years. Beginning his musical life at the early age of eight as a tubist and bassist, Andy continued his studies at the prestigious Northwestern University in Chicago, Illinois. During his time there, MIDI and computer music were in their infancy, and Andy recognized the usefulness of these new technologies in aiding the creative process. He had the unique opportunity to learn these tools as they were being created and refined, and his quest for the best in audio and music technology ultimately led him to use and teach Avid’s Pro Tools