RoadRunner
U S E R S G U I D E
39
Decoder Independent
(
DIN
) — Codecs manufactured by MUSICAM
USA and CCS Audio Products contain decoders that are normally
slaved to the encoder format, making separate encoder and decoder
setups unnecessary
. Codecs manufactured by anyone else, including
Telos and Comrex, do not have this decoder/encoder interaction. It is
therefore necessary to run the decoder independently from the
encoder when connecting your
RoadRunner
to other manufacturer’s
codecs
.
It is also necessary to run the decoder independently when
the decoder configuration is not the same as the encoder
configuration. The decoder bit rate, algorithm and line format setup
sequence is available only when decoder independent is selected.
Decoder bit rate
(
DBR
) — For best results, you should select the highest
bit rate available end-to-end and appropriate to your application.
When the decoder is independent from the encoder, it is possible to
select a different bit rate for each direction of transmission as long as
the basic clock rate is the same. For example, you can send audio at 64
kb/s, and receive audio at 128 kb/s, but not at 112 kb/s, since a
different basic rate is used. You cannot mix 56 and 64 kb/s basic rates.
Decoder algorithm
(
DAL
) — A detailed discussion of the available
algorithms is found in an earlier section. When operating
independently, the algorithm used can be different for each direction of
transmission.
Decoder line format
(
DLI
) — At 56 or 64 kb/s with an internal
terminal adapter or when using the G.722 algorithm, you must use a
single line format. Use the 2-line format when using 112 or 128 kb/s bit
rate with an internal terminal adapter. The two line format requires
two connections be made to the far-end codec; that is, both ISDN ‘B’
channels are used. When connected to two far end codecs
simultaneously, you can switch the return audio between the two units
by changing the Line Format from Line 1 to Line 2.
EXAMPLE 2 – ADVANCED SETUP OF ENCODER AND DECODER
In this example, we will set the RoadRunner to send low-delay G.722 to
a far-end codec, but we will set the RoadRunner to receive high-fidelity
MPEG Layer 2 at 128 kb/s from the far end. Other algorithm
combinations can be set up in a similar fashion.
First, configure the encoder as in the previous example:
!
note:
