Overview of spatial audio with Dolby Atmos in Logic Pro for Mac
In Logic Pro for Mac, you can create fully immersive spatial audio mixes using integrated Dolby Atmos tools. Dolby Atmos features are available when Enable Complete Features is selected in Logic Pro > Settings > Advanced.
Dolby Atmos is an object-based format, which is fundamentally different from channel-based formats like stereo or conventional surround formats (5.1, 7.1).
Channel-based format
A standard stereo or surround mix is in a channel-based format. All the tracks in a mix are routed to the stereo or multichannel outputs. For example, in a mix in 5.1 surround, you have six output channels. You listen to your mix over six speakers (one for each channel), and at the end, you bounce your mix to an audio file containing those six audio channels. Playing back a surround mix on any playback device requires a speaker setup with the exact speaker format it was mixed in (in this case, 5.1).
Object-based format
With an object-based format like Dolby Atmos, you don’t route and pan a track in your mix to specific output channels. Instead, on each track (the so-called object tracks), you can freely position and move the signal around in a virtual three-dimensional space. The bed tracks in your Dolby Atmos project are an exception—you route and pan them to a channel-based surround bed like conventional surround tracks.
Dolby Atmos plug-in
The Dolby Atmos plug-in is the heart of a Dolby Atmos mix. It renders the audio output signals of both the bed and object tracks, as well as the object track position and movement automation, in real time. The Dolby Atmos plug-in is automatically inserted on the surround master channel strip when you select Dolby Atmos in your Audio project settings. You use the Dolby Atmos plug-in to monitor your mix in different surround speaker formats, including binaural options intended for mixing and monitoring on headphones.
Speaker agnostic
A Dolby Atmos mix is not restricted to a specific surround speaker system like 5.1, 7.1, or 7.1.4. Because the data for the three-dimensional pan position of each object in a Dolby Atmos mix is stored separately, a playback device that is capable of playing back a Dolby Atmos mix can produce the mix on whatever speaker system is available. For example, if the playback system doesn’t have any overhead speakers, the audio signals that were positioned in the height channels will be folded down to the closest surround channels. This process, called rendering, is essential to the object-based Dolby Atmos format.
Export to ADM BWF file
Instead of bouncing the final Dolby Atmos mix to an audio file with a channel number that reflects that format (for example, 5.1), you export the Dolby Atmos mix to a Dolby Atmos master file, the ADM BWF file. This is an interleaved audio file that contains the audio signals of the individual object tracks (up to 118) plus up to 10 audio channels of the 7.1.2 surround bed that the bed tracks are routed to. The pan information for all objects in your mix is also stored in the file as separate metadata in addition to configuration data.