Table of Contents
Advertisement
Linear Acoustic LA-5180 Metadata Frame Sync/Generator Operation Manual
The SAP program audio can be treated like a standard mono or stereo program with the
table at the end of this section being used as the basis for metadata settings. Note that just
like the main audio program, the bitstream mode metadata parameter is set to Complete
Main as the SAP program contains all of the elements necessary for a complete alternate
language program.
In the U.S., the ATSC system provides two ways to accommodate the Secondary Audio
Program. It can either be sent as a separate audio service, or as a separate virtual channel.
7.4.6
Visual Descriptive
A Visual Descriptive soundtrack is comprised of the main audio program mixed with a
narration track that describes the on-screen action. Although it is possible to create a 5.1
channel Visual Descriptive program, there are usually not enough distribution audio chan-
nels nor emission data rate to handle more than a mono or stereo program. In many ways,
a Visual Descriptive program is similar to an SAP program and can be treated as such. The
primary difference is that the bitstream mode metadata parameter should be set to Assc.
Visual Imp. (Associated Visual Impaired program).
7.5
Summary
All of the flexibility and control afforded by audio systems that utilize metadata absolutely
requires the producer to correctly set the parameters because they affect important aspects
of the audio-and can seriously compromise the final product if set improperly. Although
most metadata parameters are transparent to consumers, certain parameters affect the out-
put of a home decoder, for example when downmixing for a specific speaker configura-
tion, or when the consumer chooses Dynamic Range Control to avoid disturbing family
and neighbors. Monitoring in a calibrated environment with the proper metadata tools and
an understanding of the basic functionality of the system is essential and will go a long way
towards making a successful production.
7.6
Typical Metadata Settings
The table on the next page shows typical settings for several types of audio content. Note
that the dialogue level (dialnorm) setting is not indicated as the true value of this parameter
must be measured using a loudness meter such as the Dolby LM100. Other settings are
generally valid for any program of the type indicated at the head of the column, but note
that it is critical to monitor the effects of these settings.
NOTE: The following table is a guide only; the effects of these settings may or may not
be appropriate for a given program. Monitor carefully to verify.
48
Metadata
Advertisement
Table of Contents
