Dolby Digital Plus

Type of format	Lossy audio format
First released	2004
Developer	Dolby Laboratories
Compression Type	CBR
Bitrate	4.736 Mbps
Channels	7.1
Bits	16-24
Sample	48 KHz
Filename extension	.eac3 ?
Open Format?	?
Free Format?	?
Magic Number	?

Dolby Digital Plus, (also known as Enhanced AC-3) is an extension and successor of Dolby Digital developed by Dolby Laboratories for the transport and storage of multi-channel digital audio. It has a number of improvements over that codec, including support for a wider data rates (4.736 mbit/s), an increased channel count (7.1), and multi-program support (via substreams), as well as additional tools (algorithms) for representing compressed data and counteracting artifacts. 

It uses the same MDCT compression algorithm like Dolby Digital. The DD+ extension bitstream is used on players that support it.

This audio codec is part of the BD specifications and its an optional codec for developers. 

Despite the codec's improvements, it's rarely used for primary audio for movie releases, and now been succeeded by Dolby TrueHD and Dolby Atmos. However, it is often used for foreign language tracks, usually for foreign buyers.

Additionally, Dolby Digital Plus is one of the two codecs used for Secondary Audio, except it is limited to 48 Khz sampling rate, five channels of sound, 256 kbps, and 16-bit resolution.

 The full set of technical specifications for E-AC-3 (and AC-3) are standardized and published in Annex E of ATSC A/52:2012, as well as Annex E of ETSI TS 102 366.

Links

• ATSC Standard: Digital Audio Compression (AC-3, E-AC-3)
• ETSI Digital Audio Compression (AC-3, Enhanced AC-3) Standard
• Audio Engineering Society Convention Paper 6196 - "Introduction to Dolby Digital Plus, an Enhancement to the Dolby Digital Coding System" (Archived)
  
• Wikipedia Page 
• Multimedia WIKI Page
  
• Dolby's website - Dolby Digital Plus
  

Author(s) : Æ Firestone