eng TELE-audiovision 1305

Entering the
World of IpTv
If you’re interested in checking out
the world of IPTV, you won’t need
any special hardware – a digital
USB receiver and a VLC (Video LAN
Client) is enough for initial experiments.
This great program can not only
play back almost any multimedia
format, it can also, among other
things, stream multimedia data into
the network as well as receive and
display a network stream.
It’s actually very simple to do and
can be tested using just one computer.
The idea behind this is that the
built-in network card can also be accessed
via the IP address 127.0.0.1.
This IP address represents the
so-called Local Host and means that
you can test the client directly on the
same server. For example, you can
test a web server on the same PC if
you enter in “localhost” or 127.0.0.1
in the browser’s address line. The
PC never has to be connected to the
network.
First VLC must be installed. This
multimedia talent can be downloaded
free of charge from its official
website (www.videolan.org). If you
already have an older VLC version
installed, it would be a good idea to
upgrade to the current version for
security reasons.
In order to stream TV, you would,
of course, need a corresponding receiver
on your PC. VLC can be used
with a variety of BDA compatible
tuners; in our case we are using a
DVB-T receiver.
The first hurdle is to get VLC
into reception mode. For starters,
though, you might first want
to try receiving a transponder with
VLC without streaming. For this
you select “Media” in the menu and
then “Open Capture Device”. Under
“Capture Mode” you should select
“TV (digital)” and for the “Delivery
System” you should chose the correct
tuner, in our case it’s DVB-T.
Now the reception parameters
can be entered into the Options. For
our setup the frequency of 754MHz
must be entered in VLC in KHz –
754000KHz! This little detail has
already caused problems for many.
The bandwidth in our case is 8MHz.
The “Play” button starts the TV
playback. If everything worked, then
there’s nothing stopping us from
streaming. If it didn’t work, simply
double-check your entries; sometimes
an extra “0” found its way into
the settings or some other small error
has popped up.
Tip: to switch between the different
transponder channels, you can
click on the right mouse button and
then under “Playback – Program”
you should find the channels.
If you now select “Stream…”
under the “Media” menu heading,
you can reconfigure the TV receiver,
only this time instead of clicking on
“Play” you can click on “Stream”. The
reception parameters in this second
go-around should now be correctly
filled in so that you can click directly
on “Stream”. An Assistant will now
guide you through three steps.
In the first step the reception parameters
are shown all together in a
row. These can be used in configuration
files or as start parameters and
are very helpful for more advanced
applications.
In the second step the receiver is
specified. With Unicast the stream is
sent to only one receiver. First the
protocol is selected – for the first attempts
use the RTP/TS protocol; it is
supported by the most clients. Configure
the IP address with 127.0.0.1.
The port can be set to 5004. Deactivate
the Transcoding option. This
would unnecessarily load down the
PC and, aside from that, we want to
maintain the best possible picture
quality.
In the third and last step the option
“Stream all elementary streams”
should be selected so that the entire
stream from the tuner can be inserted
into the network. This would
make even videotext available on the
TV.
Clicking on the “Stream” button
starts the process. At this point
though, nothing exciting will happen
as yet. The VLC won’t show the
stream locally and nothing can be
seen in the window; only the “Play”
button is replaced with a “Pause”
button. Now open up a second VLC
window and select the entry “Open
Network Stream…” in the “Media”
menu. A new window will open in
which you must enter in exactly this
address: rtp://127.0.0.1:5004. After
confirming the entry, a window will
instantly open for each channel and
the resulting chaos resembles what
you might see in a TV studio. All of
the channels are shown simultaneously
with video and audio in separate
windows.
What happened? The second VLC
window accessed the transport
stream from the first VLC window via
the local host address on port 5004
with the help of the RTP protocol. It
routed the stream correctly to the
second VLC window and showed
each channel in its own window.
If you now were to use a second
computer that would be linked to the
first PC via the network, then you
could pass the transport stream from
one computer to the other via that
network. For this to work you’d need
to enter in the IP address of the second
computer into the first computer
instead of the Local Host IP address
mentioned above. With the second
computer you would enter the IP
address of the first computer – once
again this would be instead of the
Local Host IP address. And that’s it!
The IP address of the computers
can be read in the Windows Network
Assistant or through the command
“ipconfig-all” entered into a DOS
shell that can be accessed by typing
in “cmd” in the Windows Start Menu.
Last but not least, a few tips:
1) Don’t try right away to stream
over the Internet. For that purpose
the stream needs to be transcoded
in order to significantly reduce the
bandwidth.
2) Streaming in your own network
can load it down quite heavily; find
out first if other users need the
network.
3) The Internet offers quite a few
tips and tricks regarding streaming.
The VLC forum is especially occupied
with this subject.
Have fun with your first streaming
experiments!
www.TELE-audiovision.com — 05-06/2013 — TELE-audiovision International — 全球发行量最大的数字电视杂志 123