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>3.1. VLS structure</H1
><P
>&#13;From a user's point of view, VLS can be divided into
four kinds of components
:</P
><P
></P
><UL
><LI
><P
>&#13;a <EM
>manager</EM
>
,</P
></LI
><LI
><P
>&#13;<EM
>inputs
</EM
>,</P
></LI
><LI
><P
><EM
>&#13;converters
</EM
>,</P
></LI
><LI
><P
>&#13;
et des <EM
>sorties</EM
>
.</P
></LI
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><P
><B
>Figure 3-1.
VLS structure
</B
></P
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SRC="images/archi-vls.jpg"></P
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><A
NAME="AEN397"
></A
>3.1.1. Input</H2
><P
>&#13;The role of an <EM
>input</EM
> is to
read MPEG streams from a given source (file, DVD, DVB card, device,
...), and feed the right <EM
>converters</EM
> with these
streams. An input may be able to read several streams, which are called
<EM
>programs</EM
>. There are several kinds of inputs
:</P
><P
></P
><UL
><LI
><P
>&#13;the <EM
>local</EM
> input, which can read
videos from files or DVDs
,</P
></LI
><LI
><P
>&#13;
the <EM
>video</EM
> input, which
can read videos from MPEG encoding cards devices
,</P
></LI
><LI
><P
>&#13;the <EM
>dvb</EM
> input, which
can read videos from DVB cards,
l'entr<74>e <EM
>dvb</EM
>, qui peut
lire depuis des cartes DVB,</P
></LI
><LI
><P
>&#13;the <EM
>v4l</EM
> input, which
can read from acquisition cards supported by the Video4Linux
drivers
.</P
></LI
></UL
><P
>&#13;You can use several inputs and play several programs
at the same time
.</P
></DIV
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><A
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></A
>3.1.2. Converter</H2
><P
>&#13;The role of a <EM
>converter</EM
> is to
receive a stream from an input, and convert it into the MPEG-TS format.
VLS is able to convert PS streams (from DVDs, for instance) into TS
streams (ps2ts converter). Of course, it can also read TS streams, and
fix them by handling stream discontinuities (ts2ts converter)
.</P
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><A
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></A
>3.1.3. Channel</H2
><P
>&#13;
A <EM
>channel</EM
> receives a stream from a
converter, and send it to a given destination (network, file, ...).
If you want, you can call a "channel" an "output": it is the
same thing !). Currently, two kinds of channels are supported:
<EM
>network</EM
> and <EM
>file</EM
>. Note that,
at the moment, VLS can support only one output per
stream, so you cannot play a stream on the network and write it into
a file at the same time. The network output is highly configurable:
you can choose which network interface you want to use, and specify
source and destination IP addresses
.</P
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><A
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></A
>3.1.4. Manager</H2
><P
>&#13;The <EM
>manager</EM
> controls
the way streams are sent. Through an <EM
>administration
interface</EM
>, you can tell the manager to start, stop,
suspend, resume, forward or rewind the different programs. You
can also get a list of all programs available in the Program
Table. The manager gets this table from the VLS configuration file
(<TT
CLASS="filename"
>vls.cfg</TT
>), so it cannot be changed once VLS has
been started. At the moment, you cannot ask the manager whether a given
stream is being broadcasted, but you will get an error message if you
try to stop a stream that was not broadcasted
.</P
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