AC-4 is Dolby's next-generation codec, built for next-generation broadcast and streaming and adopted by ATSC 3.0 and DVB. Unlike AC-3, it is object-based from the ground up, carrying immersive Dolby Atmos efficiently enough for terrestrial TV and mobile. It bakes in features the older codecs bolt on: dialogue enhancement that lets viewers raise speech over the mix, robust loudness and dynamic-range metadata, and a compact immersive mode (AC-4 IMS) for low bitrates. AC-4 is far more efficient than E-AC-3 at the same quality, but its newer footprint means decoder support is still expanding compared with the ubiquitous AC-3/E-AC-3 base.
The book · Volume 4 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From PCM and Codecs to Loudness, Accessibility, and Real-Time Voice Processing
AC-4 is the codec next-generation broadcast is built around, and supporting it means handling new decoders, dialogue features and device gaps. Volume 4 covers AC-4 in detail within audio codecs: Dolby and broadcast codecs, channels and layouts, loudness and LUFS, and accessibility features such as dialogue enhancement. Written by Nikolay Sapunov, CEO at Fora Soft.
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