Reference

What is E-AC-3 / Dolby Digital Plus?

E-AC-3 is the codec behind Dolby Digital Plus. It extends the Dolby Digital family with more efficient coding, higher data-rate flexibility and support for up to 7.1 discrete channels in common delivery profiles.

E-AC-3 is: a lossy audio codec. Dolby Digital Plus is: the consumer-facing Dolby name commonly associated with it. It can also serve as a delivery carrier for Dolby Atmos metadata.

Technical and delivery characteristics

Property	Dolby Digital Plus / E-AC-3
Channels	Up to 7.1 discrete in common consumer delivery
Compression	Lossy
Supported data rates	Dolby documents 32 kbps to 6 Mbps across mono-to-multichannel uses
Streaming	Designed for scalable broadcast, streaming and downloaded media
Metadata	Dialogue normalization, dynamic-range and downmix controls

Relationship to Dolby Digital

E-AC-3 builds on the Dolby Digital coding family but is not simply the same AC-3 bitstream at a higher bitrate. Dolby designs the ecosystem so compatible products can provide fallback/conversion paths for legacy Dolby Digital equipment.

E-AC-3 and Atmos

Streaming services commonly deliver Dolby Atmos using Dolby Digital Plus with additional Atmos information. That does not make Atmos itself a codec; E-AC-3 remains the delivery codec/bitstream layer.

Where you may find it

E-AC-3 may be carried in MP4/ISOBMFF-family files, MPEG transport streams, Matroska and disc/broadcast workflows. A raw elementary stream may use an .eac3 extension.