With Atmos, Dolby has reinvented surround sound production, exhibition and distribution. But it’s taken me 6 months to finally “get it”.
Back in November, Dolby flew me and members of the Brain Farm team out to San Francisco for a special screening of the Art of Flight in Dolby’s reference theater. This theater is basically Dolby’s cinema laboratory. It has a 1920s movie house style to it, but behind the acoustically transparent side walls are numerous shelves so they can swap out different speakers in different arrangements for whatever they’re testing at the time. The theater is even isolated from the rest of the building on a completely different concrete base. When Dolby does something, they go all the way. But the first thing I noticed when I walked into the theater, was speakers on the ceiling. What in the world were those for? Then a member of the Dolby team told me about the theater being a lab and they were working on something new. Hmm
A bit later in the visit, I got a few more details in the project, but I honestly didn’t understand what they were telling me. It was such a different way to think about audio and mixing. It sounded like another version of “virtual speakers” and stuff that like that, which I never bought into. Any “virtual surround” I’ve ever heard has sounded thin and phasey to me.
Dolby has announced Atmos and now it makes sense to me. Personally, I wouldn’t understand it now if it hadn’t been explained to me in November.
Now, this blog doesn’t exist to regurgitate what exists out there in cyberspace, and especially press releases. If I can’t add a unique voice to the conversation, I won’t speak up. But I felt the need to say something after reading about Atmos on Dolby’s site, and reading other online sources. I feel like people may not be getting the power of this system, at least from the perspective of someone working behind the scenes. This system greatly simplifies some of the challenges we currently have with surround sound production.
Problem 1 – Mixing for 5 points or 7 points in space
Initially, we had mono. A single speaker behind the screen. Later, stereo Left and Right were added, while retaining this Center speaker for dialog. With Dolby Stereo (or Dolby Surround and Dolby Pro Logic), there were these 3 front channels and one rear channel that’s matrix mixed into the stereo track. Even though a theater had surround speakers going all the way around the room, the entire surround channel was mono. So any information placed in that channel had to be more or less non-directional. If it’s raining in a scene, you could put the rain in the rear channel. If a car passed by during this scene, the car’s audio would not be placed in the rear channel since it had no directionality to it. It would be strange to hear a single car on both sides of you and behind you, and then move to the left front channel. With THX, they specified surround speakers with dipole configurations (2 speaker arrays or 2 tweeters faced away from each other and out of phase). This added to the non-directionality of the channel. Hearing the same rain effect on THX surround speakers was really diffuse and scattered, which I personally thought was really cool. I even built my own THX-spec dipole surround speakers because THX speakers at the time were really expensive.
Then Dolby Digital 5.1 came and changed the single matrix rear channel into 2 discreet full range channels. Now audio mixers could add directionality to the surround channels. This effectively split the theater into left and right sides.
Later we got 6.1 and 7.1, which split the theater again. There was left side, right side and now left rear and right rear. The mixers then had the option to treat the surround channels as either 3 or 4 distinct points in space, or make the channels more diffuse and ambient. But where do you go from here? 9.1? 13.2? This was Dolby’s problem as they figured out their next step.
The main issue here though, is that we’re still just talking about points in space. When you’re in a 7.1 mixing room, there are 7 speakers all pointed at your head. If you turn 2 points off, you don’t necessarily have 5.1, since the speakers have to be moved to compensate for the change in location. For example, in 7.1, you might have 2 speakers to your sides and 2 speakers behind you. If you remove the rear speakers and just go with the sides, there’s now a hole in the sound field behind you. 5.1 mixing is designed for the surround speakers to be angled to your side and behind you (120 degrees off axis), not either/or. So a 7.1 mix then has to be downmixed to 5.1. You can’t simply take away 2 channels when you do the conversion (especially if you’ve treated the sides as directional and the rears as ambient). As a mixer, you’re either working in 7.1 or 5.1. They’re not interchangeable.
Atmos does away with the points in space idea, and introduces 3D space to audio mixing using pan-through arrays. This isn’t a completely foreign concept in audio. With the introduction of stereo, you could place sounds anywhere in the space between the 2 speakers by using different levels of pan. With 5.1 and 7.1, the concept is the same. But you’re still only dealing with points of reproduction. Think more like a planetarium. With 3D space, you don’t think, ‘I’m gonna put this sound in the rear left speaker.’ You instead place the sound behind you in 3D space, and Atmos will determine which speakers play that sound based on the speaker arrangement of the playback system. Whether your playback system has 2 surround speakers, or 64. Yes, a theater can now have 64 distinct speakers (not just 64 speakers playing 8 channels of audio, like with 7.1, but 64 distinct channels), and Atmos will know where to place the sounds even if you didn’t mix on a system with 64 channels. Dolby is calling this Author Once, Optimize Anywhere. Which brings me to…
Problem 2 – Multiple Sets of Mixes and Deliverables
We mixed the Art of Flight in 7.1 at Skywalker Sound with assistance from Dolby (which was awesome, btw). We did the entire mix in 7.1, and then created separate versions in 5.1 and stereo. These mixes couldn’t simply be created from the 7.1 mix without human intervention, or just mixed down. The 7.1 and 5.1 versions of Art of Flight are different. In fact, the side surround channels in the 7.1 version of Flight have a really active music track and handle a lot of spill from the front speakers. This would sound strange in 5.1. In the case of the Blu-Ray, this means we have to put 3 audio tracks on there: TrueHD 7.1, Dolby Digital 5.1 and 2.0 (stereo). The Blu-Ray spec requires that any disc with TrueHD 7.1 have a “core” 5.1 track in there for systems that can’t handle TrueHD.
With file and tape deliverables, it gets even messier. Luckily, we didn’t have to create a HDCAM SR with Dolby E, which would have required a separate encoder. But we did create a few different tapes with the different track layouts for stereo, 5.1 and 7.1. Once again, because the 5.1 and 7.1 mixes are different, you can’t just pull 5 tracks from the 7 tracks on the 7.1 HDCAM SR. You need the HDCAM SR tape with the 5.1 mix on it.
Dolby Atmos solves this deliverables problem by creating only 1 deliverable. Since Atmos can take your mix in 3D space and translate it to any playback system, you only need to make one mix. If your home system is 5.1, Atmos will optimize the mix for that environment. If your theater has 30 speakers, it will optimize for that. This also means only one DCP (finally!). DCPs are cumbersome to make and reducing it down to one file for all systems really simplifies the whole thing. Now you don’t have to send certain theaters certain DCPs.
Problem 3 – Getting People Back Into Theaters
Atmos adds a few new things that are compelling to both theater goers and theater owners. For the audience, Atmos adds overhead surround channels as part of the 3D space. Who knows how this is going to be used, and it’s going to be cool to hear mixers start to take advantage of it. With 3D space and the use of many distinct channels surrounding the audience, it will be less critical where you sit to enjoy good sound imaging. The effects will be rendered properly as the mixer intended, no matter your position in the theater.
Initially, it’s things like this that theater owners hope to use to get people back into the theater, since it’s things you can’t get at home. For theater owners, a big expense is constant upgrades from changing technologies. Just ask the owners that have gone from 35mm film to 2k digital to 3D. Or have invested in Dolby Digital, DTS, THX and Sony’s surround technologies (sometimes all in the same multiplex). With Atmos, Dolby is creating a new platform that will help the theater owners future proof. As you upgrade your theaters to add more channels, the Atmos processor adapts the mix to your new setup. You will always have the best mix for your venue no matter how you set it up. If you have different theaters with different numbers of speakers, as many multiplexes do, you don’t need to get different versions of the movie from the distributor. The same version will work on all Atmos systems no matter their configuration.
Going forward, it will be interesting to see how this technology is adapted for use outside of the theater. Will the Blu-Ray spec be updated to accept Atmos so authors can use 1 file instead of 3? Will we see Atmos surround, complete with overhead speakers, in the home? How will audio mixers modify their spaces to monitor all these possible channels? What will the ideal mixing setup be? When Angus from Dolby first told me about this concept in November, my first question to him was, well how do you mix to that? These are amazing times. And here we all thought the cinematographers were having all the fun!
What do you think? Do you think this is the next step in the evolution of surround sound, or do you think it’s just a gimmick? As a pro, do you see this making your job easier or harder? Join the conversation in the comments.
Here are some great videos from Soundworks Collection on Dolby Atmos. The second one has some great detail on the theories behind the 3D sound space and the single deliverable.
As a side note, while we were visiting Dolby, President and CEO Kevin Yeaman told us that he had just recently finished building a media room/theater at his house and the Art of Flight was his reference disc to wow his friends and family. Now that’s an endorsement!
Update: According to NoFilmSchool.com, Disney/Pixar’s Brave will be the first film released in Dolby Atmos, which has a scheduled release date of June 22nd. I wonder how many Atmos theaters will be ready by then.