September 2019 - Immersive Audio Rollout Looms

The rise of immersive audio for cinema has entered an exciting new chapter of final testing and preparations for rolling out the format widely some five years after SMPTE’s TC-25CSS Cinema Sound Systems Working Group on Interoperability of Immersive Sound Systems in Digital Cinema first formed to standardize the delivery of immersive audio. Brian Vessa, Sony Pictures’ Executive Director of Audio Mastering, has been a big part of this evolution as the Founding Chair of the TC-25CSS committee and chair of the IMF Audio Essence Drafting Group in SMPTE’s TC-35PM Media Packaging and Interchange Technology Committee.

Vessa points out that the audio standards community has been “a bunch of busy beavers” in recent years, making sure that all the necessary standards got published, particularly the ST 2098 suite of immersive audio standards announced by SMPTE in the last year, and various related documents. These include ST 2098-1, which  Vessa calls the “parent document” for defining immersive audio metadata; 2098-2, which he calls the “main document”—the Immersive Audio Bitstream (IAB) specification; and 2098-5, which defines digital cinema immersive audio channels and soundfield groups—“basically, all the immersive audio channels and the current loudspeaker configurations for immersive audio,” he explains.

Along the way, he adds, SMPTE’s Digital Cinema technology committee, TC-21DC, worked in parallel with TC-25CSS to standardize the protocols necessary for making sure that immersive audio devices could interoperably communicate with Digital Cinema Packages (DCP’s).

“A number of associated documents were also recently created that specify how a IAB DCP that contains immersive audio should get made,” he says. “One document explains the MXF track file [ST 429-18] that IAB fits in; another the DCP operational constraints [ST 429-19]; the immersive audio KDM [Key Delivery Message, ST 430-1 addendum]; and the creation of a Digital Sync Signal and Aux Data Transfer Protocol [ST 430-14].”