Audio compression and spatial sound platform — Dolby Digital for multichannel, Dolby Atmos for object-based 3D sound. Cinema standard since the '90s.
You can immediately tell when Dolby is playing in the cinema: the mix is spot on. The sound doesn't just come from two channels, but from six, eight, or more – and since Atmos, also from above. Dolby is less a single technology than an ecosystem of compression, decoding, and spatial design that has shaped the standard for professional film sound mixing since the 1990s.
Dolby Digital – that's the classic. 5.1 channel sound (Left, Center, Right, Surround Left, Surround Right, Subwoofer) is compressed with the AC-3 codec and stored on 35mm film or DCP. The crucial advantage on set and in editing: lossless spatial definition via discrete channels. You no longer mix for stereo and hope for the best – you know exactly which speaker receives which information. An ambient sound can live entirely in the surround channel, while dialogue sits front and center. This gives you controllability that is impossible with stereo.
Dolby Atmos flips the paradigm. Instead of discrete channels, you now work with object-based audio: you define a sound as a three-dimensional object in space with X, Y, Z coordinates and size. The system scales automatically – whether your mix plays in a large Atmos cinema with 64 speakers or in a smaller 7.1.4 setup, the objects reposition themselves spatially correctly. In editing, this means: you don't work for a fixed speaker configuration, but for space itself. A helicopter flies across the scene – in the Atmos mix, you define the flight path once, and the playback takes care of the implementation.
Practically on set: you'll typically be dealing with Dolby specifications if your project is intended for cinema. The sound mixer needs to know that certain frequency ranges are adjusted in the mix – Dolby systems have tone mapping that normalizes spectra. In editing, your sound editor works with the requirements: Atmos means additional work (object automation, height channel definition) but offers spatial freedom that Linear PCM stereo or Dolby Digital 5.1 cannot provide. For streaming, there's also Dolby Digital Plus (E-AC-3), which is more compressed for home distribution.
In short: Dolby is not optional if you're doing professional film sound mixing. It defines how your sound travels – from the mix to the viewer's ear.