eng TELE-audiovision 1411

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Of course this did not keep up us from
giving the encoder a quick try right
away. We simply connected an Xbox
360 to the CW-4412 via HDMI and distributed
the encoded stream via multiplex
on our local network. Did it work?
Just like that? It actually did, and we
could flawlessly receive and process
the stream with the TSReader and VLC
applications. Our first conclusion: Using
the CW-4412 is child’s play and selfexplanatory.
Encouraged by this initial success we
went about experimenting with different
bit rate settings in order to evaluate
their impact on the video quality.
Then we proceeded with feeding a
number of different signals to the CW-
4412, ranging from analog camcorder
to rarely used HDMI resolutions, only
to find out that the encoder willingly
accepted and processed anything we
threw at it. To honest, this device was a
challenge for the TELE-audiovision test
team, not the other way round. It simply
works flawlessly, does exactly what
you want it to do and, in addition, is extremely
easy to operate. Others might
have decided to cut short the test and
go for a coffee – but not us!
We looked at all features and options
and fed any type of source signal we
could find or create. The range of settings
for creating an MPEG-4 stream
that meets bespoke requirements is impressive;
there’s simply no better word
for it. What’s more, the CW-4412 reacts
to all commands and adjustments
with breath-taking speed. You change
a parameter and the next second the
created MPEG-4 stream reflects that
change. This gives technician the option
of making adjustments on-the-fly,
and all that viewers will notice is a very
short signal interruption.
CBR & VBR
Depending on area of application and
available bandwidth, the CW-4412 can
create an encoded stream with either
constant bit rate (CBR) or variable bit
rate (VBR). With CBR the encoder will
compress the signal more or less highly
in order to constantly reach the pre-defined
target bit rate. This means a sequence
with little changes in the video
will be subject to hardly any compression,
while sudden changes in the video
(such as movements or new objects)
will require high compression in order
not to exceed the target bit rate.
What are the benefits and drawbacks
of CBR? For one thing, it is much easier
to calculate the required bandwidth or
overall bit rate of a transponder if it carries
CBR signals, for obvious reasons.
In addition, virtually all receivers can
handle CBR signals. But where there’s
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www.TELE-audiovision.com — 11-12/2014 — TELE-audiovision International — 全 球 发 行 量 最 大 的 数 字 电 视 杂 志
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