AVT MAGIC AC1, Руководство по аппаратному и программному обеспечению

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W i n d o w s P C S o f t w a r e
– J.52 : IUT-T Standard, which allows a so-called Capability Exchange
1
and a permanent delay compensation
2
when 2 B channels are used. De-
pending on the implementation, transparent data channels can be also
transmitted. An unsymmetrical Audio transmission (e.g. MPEG with 2
B in transmit direction, 7 kHz in receive direction) is also possible. This
procedure is supported by several manufacturers (e.g. MAYAH Cen-
tauri). For
MAGIC DC7/AC1 this procedure is set by default.
– OFF : No signalling is used. The encoded Audio data is transmitted
without any further framing. With this way of signalling, only one B
channel can be used. The procedure is possible with almost every avail-
able Audio codec on the market.
If
G.722 (7 kHz) is selected as Audio quality (see below), the so-called
SRT procedure ( Statistical Recovered Timing ) is used when no signal-
ling is selected.
– MusicTaxi : This proprietary signalling is used by Audio codecs from
the company Orban (former Dialog4) and has been also implemented
by some other manufacturers for compatibility reasons. 2 B channels
can be transmitted. The Audio transmission is symmetrical, i.e. the
same coding algorithm must be used in transmit and receive direction.
– CCS-L2 : A further proprietary signalling from the company Musicam
USA (in Europe formerly CCS). The procedure supports only a sym-
metrical Audio transmission with ISO/MPEG Layer II with up to 2 B
channels. Therefore, the fee-based option
ISO/MPEG Layer II Upgrade
(order number.: 450305) is required to use this signalling.
• Under Audio Quality TX you select the Audio quality for the transmit di-
rection. Depending on the selected Transmission Type the following set-
tings are available:
– G.722 (7 kHz)
– MPEG (15 kHz)
• The Audio quality in receive direction ( Audio Quality RX ) can only be se-
lected for the transmission type J.52 , since all other procedures only allow
a symmetrical Audio transmission. The following options are available
3
:
– G.722 (7 kHz)
– MPEG (15 kHz)
• The option Bit Inversion allows an inversion of the encoded Audio signal
and is only available when OFF is selected as signalling type.
1
Capability Exchange: At the beginning of the connection, the systems exchange information
about how many B channels are possible, which Audio coding algorithms and specific codec pa-
rameters are available etc. After this exchange, the best possible transmission mode is set auto-
matically. However, you have also the possibility to force a certain procedure, e.g. when you only
need a 7 kHz connection.
2
B channels are routed individually in the ISDN network. When Audio signals are transmitted
with 128 kbit/s, the two B channels have to be set together at the same time at the receiver which
is done by a delay compensation. This procedure is called Inverse Multiplexing. If B channels are
re-routed in the network because of line errors during a connection, an Audio transmission with
a static delay compensation, which was measured at the beginning of the connection, would not
work anylonger. J.52 adapts the delay compensation dynamically and is protected from delay
variations.
NOTE
If you defined only a 1B connection for Connection 1 , you can define addi-
tionally a Telephone or 7 kHz (Auto) connection for the second B channel.
You can also establish connections with two different algorithms to two dif-
ferent partners at the same time.