4
5
6
7
156
TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 09-10/2013
—
4. This graph shows the bandwidth
during the captured transmission. Inter-
estingly, the bandwidth is not constant,
when displayed in millisecond interval.
5. This graph shows the bandwidth of
the same transmission, but as Bits/
second. With just two transponders fed
into the network, a 100MBPS switch
is working at its limit. In fact, we tried
to use a 100MBPS switch and it froze
after a few seconds. A regular operation
was only possible using a 1000MBPS
switch.
6. Using DekTec’s StreamXpert soft-
ware, which already has been tested
in TELE-satellite 11-12/2012, together
with the professional DekTec DTE-3137
receiver, one has much more feed-
back about the IPTV broadcast. Notice
the lower left corner: a graph shows
continuously the occupied network
bandwidth.
7. StreamXpert can show all possi-
ble information about the streamed
transponder, including the programme
clock reference (PCR), required for
correct synchronization of audio and
video. This allows editing the times-
tamps in order to compensate for any
detected errors.
vices.
Note that Multicast is
not only used for IPTV;
it is used whenever the
same data needs to be
sent to multiple com-
puters, such as, when
multiple
computers
need to be installed all
at the same time via a
network. That‘s how IT
professionals, for ex-
ample, in universities or
large company‘s install
an operating system on
hundreds of computers
all at once.
With Unicasting how-
ever, the stream - un-
like Multicasting - is
sent to one specific re-
ceiver. This has the ad-
vantage of not loading
down the network for
all the remaining users
allowing data traffic to
function normally. The
data is routed in the
switch between the in-
puts of the servers and
the users while the re-
maining switch ports
remain free.
The disadvantage is
the fact that for eve-
ry additional user the
stream would have to
be individually retrans-
mitted. In no time at all
the network bandwidth
