DOLBY ATMOS IS JUST THE START. NEXT-GEN AUDIO FORMAT AC-4 WILL OFFER FAR MORE…
So it seems that Dolby Atmos is only the beginning. Dolby has a new next-gen audio format waiting in the wings, which evolves the concept of object-based audio for broadcasters. AC-4 builds on the core idea behind Atmos, but offers an even more versatile toolset.
With AC-4, broadcasters can flag specific objects during the encoding phase, which an AC-4 decoder in a TV will understand. For example, dialogue, often criticised for being indistinct, can be raised without affecting any other element in the soundfield. Specific effects, such as birdsong or gunshots, can be tagged. While AC-4 can handle 126 objects, that number would never be transmitted at the same time. Most TV broadcasts are expected to consist of around 12 objects at a time, plus a conventional 5.1 sound mix.
With AC-4, viewers can fine-tune their listening experience. Imagine watching a sporting event where you can choose between multiple commentaries, or simply remove the commentary altogether. Crucially, AC-4 compression is twice as efficient as Dolby Digital Plus. Where traditional 5.1 requires between 384kbps to 448kbps, Dolby Digital Plus utilises 192kbps to 224kbps. However, AC-4 delivers the same quality for 5.1 at about 96kbps.
So when will you see (or rather hear) AC-4? Dolby suggests the first commercial services could kick in as early as 2019 on all major TV manufacturers.
We had an early preview of Dolby AC-4 with some encoded football footage. Unlike a conventional broadcast, we could select from multiple languages, as well as Home and Away commentaries. Switching between those is instant. Without a next-gen audio codec like AC-4, this kind of audio interaction would not be possible over broadcast.
Soon we could be enjoying live Dolby Atmos audio, with an unprecedented level of personalisation. You ain’t heard nothing yet.