Ac-3 Distribution System - Linear Acoustic AERO.one V3 User Manual

Linear Acoustic AERO.one V3 User Guide
3.1

AC-3 Distribution System

Figure 3-1 shows how an AERO.one would be installed in a typical AC-3 distribution system
that might be found at a PBS or FOX station. The Dolby Digital (AC-3) bitstream data rate
is 384 or 448 kbps and is delivered within a standard 19.39 Mbps ATSC transport stream.
This allows a local station to use a commonly available transport stream splicer to insert lo-
cally generated digital television video and audio streams. Alternately, a station could decode
the network audio and video, insert local programming, then re-encode the audio and video
for transmission to consumers (resulting in potentially detrimental side effects on the audio
due to the loss of metadata).
As there is no way to deliver the professional audio metadata in this scenario, it is simply ig-
nored and default values are set in the Dolby Digital encoder for audio coding mode, Dia-
logue Level (dialnorm), and Line and RF Mode DRC presets. The audio is then processed
by the AERO.one so that it matches these metadata defaults. See section 3.3 below for a de-
scription of exactly how to set these parameters.
A built-in Dolby manufactured Dolby Digital (AC-3) encoder will be available as an option
for the AERO.one in the near future. This option will simplify the wiring and configuration
necessary when using an external encoder. It also adds the reliability of a redundant power
supply and the flexibility of HD and SD-SDI I/O. Please contact your salesperson or the
factory for availability.
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Applications