Orban OPTIMOD 8685, Руководство по эксплуатации

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OPTIMOD SURROUND PROCESSOR INTRODUCTION
1-23
Choosing your Encoder
The state of the art in encoder technology is rapidly changing. At this writing, the
most efficient audio encoder technology available is MPEG4 HE-AACv2, which also
has the advantage of being standards-based. Orban is the first provider of this tech-
nology for streaming audio applications with Opticodec-PC 1010.
Be aware that different encoders are optimized for different bit rates, so you should
match your encoder to your potential audience. An encoder appropriate for a dial-
up rate of 20kb/sec may not be optimum for ISDN, DSL, or E-1/T-1 rates. This makes it
necessary to use more than one algorithm to optimally serve audiences with these
disparate connection speeds.
MPEG-1 Layer 3 has become a de-facto standard for distribution of non-streaming,
high fidelity audio on the Internet, although HE-AACv2, as used in Opticodec-PC, is
far more efficient. Thanks to the Apple iPod®, AAC/MP4/M4A is rapidly becoming
the de-facto standard for downloadable music.
OPTIMOD 8685 is well matched to AAC, HE-AAC, and MP3. It can effectively pre-
process audio intended for playback from either format. If you decide to use MP3,
choose your MP3 encoder wisely, as not all MP3 encoders are created equal — they
provide different levels of quality for a given bitrate.
EAS Transmission
In normal operation, 8685 audio processing may not provide the minimum modula-
tion level required by EAS Emergency Alert System (EAS) standards. It may therefore
be necessary to defeat the 8685’s dynamics processing during the broadcast of EAS
tones and data.
The L
OOK
-A
HEAD
L
IMITER
preset provides an easy way to do this. (You could also use
the
P
ASS
-T
HROUGH
preset.) If you set the level of your EAS message generator ap-
propriately, simply recall the L
OOK
-A
HEAD
L
IMITER
preset, run the test, and then recall
the previous processing preset. (Presets can be recalled via the front panel, PC Re-
mote, the 8685’s Ethernet terminal server, clock-based automation, and GPI.)
If it is impractical to set the level of the EAS message generator to work correctly
with the fixed throughput gain provided in factory
L
OOK
-A
HEAD
L
IMITER
preset, you
can instead edit the
L
OOK
-A
HEAD
L
IMITER
preset’s throughput gain to set the correct
modulation level. To set the gain, adjust the preset’s G
AIN
control, which is available
in Intermediate Modify and Advanced Modify. When you are satisfied, save the re-
sult as a User Preset. See
Customizing the 8685’s Sound on page 3-16
PC Control and Security Passcode
PC software control provides access to OPTIMOD 8685 via network, modem or direct
(null modem cable) connection, with computers running Windows 2000, XP, or Vista.
PC access is permitted only with a valid user-defined passcode.