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Chapter 6 Audio Modules
Note the following limitations:
ATSC Standard A/53 specifies that only 48 kHz sampling may be used, and that ES bit
n
rates must be less than or equal to 384 Kbps for a complete service. It also specifies that
a two-channel dialog-only service must be less than or equal to 192 Kbps. Total audio ES
rate per service must be less than or equal to 51 2 Kbps.
Embedded audio must be 48 kHz sampling and synchronous with the video. See SMPTE
n
272M for definitions.
MPEG AAC and HE AAC can be placed into the output Transport Stream encapsulated in
either of two methods:
ADTS
n
ADTS is an acronym for "Audio Data Transport Stream. " This is the default used if the user
selects MPEG-2 AAC/HE AAC. ADTS is assigned a stream type of 0x0F.
LATM/LOAS
n
LATM is an acronym for "Low Overhead Audio Transport Multiplex. " LOAS is an acronym
for "Low Overhead Audio Stream," and furnishes an outer wrapper for LATM's inner
wrapper of the raw audio Elementary Stream syntax. MPEG-4 AAC and HE AAC
bitstreams are encapsulated as LATM/LOAS and assigned a stream type value of
0x1 1.Encapsulation mode is controlled by selecting "MPEG-2" or "MPEG-4" as required.
Stream Density
IOM-RAC2 supports decoding, leveling, and encoding of 16 streams (with no more than eight
streams of 5.1), for example, eight streams of 5.1 plus eight streams of 2.0 are allowed.
Level Magic™ Dynamic Audio Leveling
Audio leveling is also supported by the IOM-RAC2 audio module.
Dynamic leveling uses the same technology found in Jünger Audio's Level Magic™ hardware
based processors. Level Magic is a trademark of Jünger Audio Studiotechnik GmbH. The
dynamic leveling option requires a firmware license.
AHC-RAC Module
The AHC-RAC module has four BNC connectors, which support AES3 and S/PDIF inputs. The
audio module also includes an RJ45 connector that can be used to supply Dolby serial audio
metadata (this is not an Ethernet connector). The AHC-RAC module uses the first three of the
four BNC connectors for 5.1 applications, or one connector per service for stereo
applications, The 4th BNC connector is unused. Up to five AHC-RAC cards can be installed in
a chassis.
Figure 6–1: AHC-RAC Digital Audio Input Ports
Connecting the AHC-RAC Audio Input Cables
Connect a coaxial cable with BNC connectors from the digital audio port to the audio source:
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Need picture of AHC-RAC
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AHC-RAC Module
Electra 9200, Rev O
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