Telos Zephyr, User Manual

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Section 7 AUDIO CODING PRINCIPLES
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LIII JSTEREO (Joint Stereo) mode takes advantage of the redundancy which usually
is present in stereo program material. The encoder switches from discrete L/R to
matrixed L+R/L- R dynamically. When in L+R/L- R mode bits are allocated
dynamically to these two bit- streams allowing maximum advantage be taken
advantage of redundancy between the two channels.
Mono vs MONO128 vs Dual vs JSTEREO in Layer II
With one transmission path,
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LII MONO provides mono capability.
With two transmission paths,
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LII MONO128 provides the best Layer II quality by combining both transmission
paths to achieve a higher bitrate. This mode require a 5 DSP (Stereo) Zephyr
configuration and 2 data paths.
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LII DUAL mode is simply two simultaneous mono channels.
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LII JSTEREO mode uses the “intensity coding” method in order to provide
maximum quality for stereo program material and compensates for any delay
between the two transmission paths.
Sampling Rate
This option sets the sample rate for the transmitted and received coded audio.
Input/output is independent and is set in the AES menus. The Layer III mode may be
operated at either 48 kHz or 32 kHz sample rate. 48 kHz offers lower delay and 20 kHz
IMPORTANT!
The Layer III decoder in L3 STEREO mode requires that both
channels be connected and operating in order for the decoder
to function. Until both channels are present, the decoder will
not output anything, even if the Xmt mode at the other end is
not stereo. Any data drop outs would cause interruption in both
audio channels.
If your application requires the ability for the two channels to
come and go independently, such as when they are from
independent sites, you must use G.722. That is the only
decode mode which supports fully independent operation.
HOT TIP!
In LIII JSTEREO mode, when the program is completely
mono, the full bitrate of the two transmission channels are
combined, resulting in the best quality mono signal with the
Zephyr. This could be used for particularly critical mono
material. The identical signal must be fed to both inputs,
preferably by splitting the signal just before it enters the
Zephyr; the system automatically takes care to properly assign
the bits and no special mode is required.