AC-3, marketed as Dolby Digital, is the 1991 surround codec that brought 5.1 to cinema, DVD, and ATSC broadcast television. It carries up to six channels (five full-range plus LFE), typically at 384-448 kbps on disc, and introduced the metadata-driven loudness control — dialnorm — that the broadcast world relied on for decades. Though E-AC-3 has replaced it for streaming and AC-4 and MPEG-H are taking over next-generation broadcast, AC-3 is far from gone: it remains a baseline in legacy delivery, set-top boxes, optical media, and HDMI/S-PDIF passthrough, so decoders must still support it everywhere.
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-3 still arrives in broadcast feeds and older libraries, and its dialnorm metadata changes how loud your output plays if you ignore it. Volume 4 covers audio codecs in detail, with channels and layouts, loudness and LUFS, so you can decode, normalize and re-encode AC-3 sources without level jumps or broken surround. Written by Nikolay Sapunov, CEO at Fora Soft.
Ingesting AC-3 broadcast audio and getting level jumps after transcoding?
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