11
DOLBY Encoded Signals
DOLBY Signal Indication
Illumination of the blue
DOLBY LED
underneath a channel pair indicates that a DOLBY encoded signal has been
detected on that channel pair.
What is a DOLBY Encoded Signal?
A DOLBY encoded signal is a bitstream that contains multi-channel audio data compressed to fit in a single AES/EBU
bitstream (one channel pair). A DOLBY bitstream can also be present in a pair of embedded audio channels in SDI
video. Unlike with regular uncompressed digital audio (PCM), this bitstream must be decoded into its discrete channels
before it can be monitored as audio. Up to 8 discrete channels may be decoded from a DOLBY signal.
The
ARDM-552 DOLBY Module
must be installed in the AR-DM1 audio monitor in order to decode DOLBY signals from
any input module. If this module is not present, the AR-DM1 will indicate DOLBY signal presence with the aforementioned
blue LED, but will not be able to decode the bitstream into discrete channels.
Decoding and Monitoring DOLBY Signals
■
Introduction
If your AR-DM1 has been configured with the optional
ARDM-552 DOLBY Module
, you will be able to decode and
monitor a DOLBY signal on any channel pair. Two varieties of DOLBY signals can be decoded: DOLBY DIGITAL (AC-
3), and DOLBY E.
What is DOLBY DIGITAL?
DOLBY DIGITAL, also known as AC-3, is an encoded bitstream that carries up to 6 discrete channels of audio.
DOLBY DIGITAL is typically used to transmit a multi-channel audio program to consumers on a DVD or through
DTV.
What is DOLBY E?
DOLBY E is an encoded bitstream that carries up to 8 discrete channels of audio. DOLBY E has several technical
advantages over DOLBY DIGITAL, which make it ideal for distributing multi-channel audio within a production
environment using an existing AES/EBU pair of audio channels.
■
Entering DOLBY Decoding Mode
Once a DOLBY signal is detected, use the following steps to enter DOLBY decoding mode:
1.
Press the
PAIR
button to enter the Pair monitor mode.
2.
Use the
LEFT
,
RIGHT
, and
9-16
buttons to select the channel pair containing the DOLBY bitstream.
3.
Press the
DOLBY
button to enter DOLBY decoding mode. Once this mode is entered, channel presence for 8
channels of decoded audio from the selected bitstream will appear on LEDs 1-8 or 16-9, depending upon the
source channel of the bitstream.
4.
DOLBY decoding mode can be exited by pressing the
DOLBY
button again.
5.
Pressing the
DOLBY
button will have no effect without the
ARDM-552 DOLBY Module
installed, or if no
DOLBY bitstream is present.
■
Downmixing DOLBY Decoded Audio
As with non-encoded multi-channel audio, DOLBY decoded audio channels can be monitored in Single, Pair, or
Downmix modes. In Downmix mode, however, several additional downmix configurations are available, depending on
the program format as described in the metadata of the DOLBY bitstream. See the
DOLBY Downmix Configurations
table on
page 12
for a table of available downmix configurations
