Chapter 7: Metadata; Metadata Structural Overview - Linear Acoustic MetaMAXLA-5180 Operation Manual

Metamax series audio metadata frame synchronizer and generator

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Linear Acoustic LA-5180 Metadata Frame Sync/Generator Operation Manual

Chapter 7: Metadata

7.1

Audio Metadata, or data about the audio data, comes in two varieties: Consumer and Pro-

fessional. Consumer Metadata (sometimes called Dolby Digital Metadata) describes a sin-

gle audio program that can be from one to 5.1 channels of audio, carries setup information

for the emission encoder (Dolby Digital (AC-3), aacPlus or other), and helps consumer de-

coders optimize their reproduction of multichannel audio. Professional Metadata (some-

times called Dolby E Metadata) carries up to eight consumer metadata programs along

with setup information for mezzanine coders such as the Dolby E and Linear Acoustic e-

squared systems (if they are used). In essence, Consumer Metadata is a subset of Profes-

sional Metadata.

It is very important to note that Consumer Metadata is found only inside an emission bit-

stream. The metadata connectors found broadcast equipment produce and accept only

Professional Metadata. The products then extract the Consumer Metadata for only the

program whose audio they are processing. Here is an example:

A program is being created and it contains 5.1 channels of main audio plus mono SAP and

a mono Visual Descriptive versions. The Professional Metadata is set for a 5.1 + 1 + 1 Pro-

gram Configuration (5.1 plus two mono, or three programs in total). When this metadata

stream is eventually connected to three emission encoders, each one is set to "look" at a

different program. The first encoder would extract and use the Consumer Metadata for

Program 1 (which tells is to configure itself for a 5.1 channel main program), the second

encoder simultaneously extracts and uses the Consumer Metadata for Program 2 (which

tells it to configure itself for a mono SAP program), and the third encoder extracts and uses

the Consumer Metadata for Program 3 (a mono Visual Descriptive program).

Ideally, metadata is first inserted during program creation or mastering (although it can be

added or modified later during distribution), and is carried through transmission. Consum-

er decoders process the decoded audio according to metadata parameters set by the pro-

gram creator. Metadata can provide content producers with unprecedented control over

how original program material is reproduced in the home. A prime example of this is the

separation of loudness and dynamic range, allowing both to be controlled independently

as long as the metadata is set properly.

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