AVT MAGIC AC1, Руководство по аппаратному и программному обеспечению

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PAGE 66
W i n d o w s P C S o f t w a r e
Ancillary Data (ISO/MPEG)
The usage of an ISO/MPEG Audio coding algorithm
1
allows a transmission
of a transparent inband data channel (
Ancillary Data
). The data is included in
the MPEG data stream.
• Under Mode you decide which physical interface ( ON - using Data Inter-
face 1 or ON - Using Data Interface 2 ) is used for the ancillary data.
Please select OFF , if you do not want to transmit ancillary data.
Data Channel 1/2 (J.52)
In addition to the transmission of
Ancillary Data
in the MPEG data stream, a
further transparent data channel ( LSD Low Speed Data ) can be used when the
ITU-T Standard J.52 is used. For transmitting LSD, a channel with fixed band
width is opened in parallel to the Audio signal.
ATTENTION In the following, all available transparent data channels are described. Two
physically independent interfaces can be configured according to your re-
quirements.
Since the implementation of the data channels is not completely defined, they
usually work only between systems from the same manufacturer.
1
The transmission of Ancillary Data is currently only possible with ISO/MPEG Layer III.
NOTE
Please consider that in this way the full bit rate is no longer available for the
Audio signal. The Audio quality is reduced depending on the ancillary data
rate. Special attention should be paid to the fact that the size of the data chan-
nel is dynamic: If data is available, a channel with the needed band width is
opened. If no data is to be transmitted, all available bits are used for the Au-
dio coding.
The maximum data rate can be selected under
Configuration Æ Data Inter-
faces (see CHAPTER 5.7.2.1.2, page 57).
In maximum, 15% of the gross MPEG data rate can be used for ancillary data
(e.g. at 128 kbit/s
Æ maximum ancillary data rate: 19,2 kbit/s)
ATTENTION If you already use an interface for Ancillary Data , you must deactivate the
data interface which is used under Data Channel 1/2 (J.52) by selecting OFF .
NOTE
If you selected 7 kHz as Audio mode, you can use one transparent data chan-
nel for each B channel independently from each other.
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