Dolby Laboratories DP570 Specifications download pdf (Page 6)

Standards and Practices for Authoring Dolby

Digital and Dolby E Bitstreams

2.3 Metadata

Metadata is additional control information that is carried along with the encoded

audio program and provides essential information about the audio to a Dolby Digital

decoder. Metadata provides many important functions including dynamic range

control for less-than-ideal listening environments, level matching between programs,

downmixing information for the reproduction of multichannel audio through fewer

speaker channels, and other information. Metadata makes Dolby Digital a complete

delivery system for audio, rather than just an audio compression system.

2.4 Integrated Receiver Decoders (IRD) and Set-Top Boxes (STB)

When receiving digital television broadcasts, whether via terrestrial, cable, or satellite

transmission, either an integrated receiver or a set-top box is needed to separate the audio

and video components from the carrier signal. Every STB has a built-in Dolby Digital

decoder that supplies an analog stereo downmix of the program audio (either Lt/Rt or

Lo/Ro, see Section 3.6 for more information). Some STBs may also offer a mono signal

(derived from the Lo/Ro signal) modulated over an RF/antenna output. In addition to

these outputs, a digital output is provided for connection to an external decoder.

2.5 Dolby Digital Surround EX

Dolby Digital Surround EX

is an extension to the Dolby Digital 5.1 format. It was

introduced to the movie-going public with Star Wars: Episode One—The Phantom

Menace. Originally developed for theatres, this format has migrated into consumer

products and media. Surround EX is primarily used for DVD soundtracks, although it

may be incorporated into the broadcast chain at some point in the future.

The format itself is different from that found in a conventional 5.1 home theater

environment. A back surround channel is added, creating a center surround channel

between the left and right surround speaker channels. This additional “center” or back

surround channel is achieved through a matrix encode of the three discrete surround

channels (Ls, Bs, Rs) during the audio mastering process. This creates a stereo-

compatible Lst/Rst (Left Surround Total, Right Surround Total) for the surround

channels. In this way, a DVD released in the Surround EX format is compatible with

all existing home theater configurations.

The metadata stream contains a specific parameter that can be flagged to indicate that

the Dolby Digital audio stream is encoded in Surround EX. This metadata parameter

is informational only, and simply allows those consumer decoders that are capable of

decoding in the Surround EX format to switch automatically into this mode.

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Dolby Laboratories DP570 Specifications Page 6