.. _vlm-share-screen:

#########################################
VLM Example: Share Screen in Real Time
#########################################

This page explains how to setup a ``.vlm`` file that shares the screen in real time. We will do this by recording the screen and streaming it in the local network. 

As a pre-requisite, refer to :ref:`VLM Introduction <vlm-introduction>` to understand how to configure a simple ``.vlm`` file. Further, you may refer to Screen Record to get a deeper understanding of how screen recording is implemented in VLC.  


*************************
Setting up the VLM File
*************************

For this example, we will stream the recording over UDP. To get a basic idea of how streaming over UDP works, refer to Stream over UDP. 

In UDP streaming, we either need to specify the IP address of the receiving device, or we can stream to the multicast IP address (streaming to the multicast address simply means that the content will be pushed to all the devices in the local network). 

We will cover both the scenarios.


.. _vlm-share-screen-multicast:

+++++++++++++++++++++++++++++++++++++
Sharing screen in the Multicast Mode
+++++++++++++++++++++++++++++++++++++

In case you wish to stream to multiple receivers or you don't know the IP address of the receiver, you can use the following vlm code:

.. code-block ::

   new screen_share broadcast enabled
   setup screen_share input "screen://"
   setup screen_share output #transcode{vcodec=mpgv}:udp{mux=ts,dst=239.255.255.250:8090,sap,name=testing}
   setup screen_share option sout-keep
   setup screen_share option screen-fps=100
   setup screen_share option file-caching=1000
   control screen_share play

For the above code:

 + Create a new file in any text editor and copy the code.
 + Save the file with the ``.vlm`` exension (like ``share.vlm``)

======================
Start screen sharing
======================

Now, execute the vlm file by running the following code in the terminal (on the device whose screen you want to share):

.. code-block ::

   $ vlc --vlm-conf=share.vlm

Running the above code will start the recording and streaming.


.. _vlm-receive-screen-record:

====================================
Receive the screen-recording stream
====================================

To receive the recording, simply open the VLC Media Player on the receiving device(s) and follow these steps:

 + Navigate to :menuselection:`View -> Playlist`
 + Click on ``Network Streams (SAP)`` which is in the ``Local Network`` section on the left side.
 + You will see a SAP stream by the name ``testing``, like in the figure below.
 + Double click on it to begin receiving.

.. figure::  /images/advanced/vlm/introduction_SAP.png
   :align:   center

   How the stream looks like in the VLC window.

|


In this case, the recording is pushed to all the devices (including the idle ones), as illustrated by the diagram below:

.. graphviz::

   digraph multicast {
      rankdir=TB;
      node [shape=circle];

      { node [width=0 shape=point label=""]; two, one;
      }
      
      { node [shape=plaintext] "Multicast screen sharing";
      }

      {node [shape=box] "\n  Network  \n  Switch  \n "
      }
      
      
      "\n  Network  \n  Switch  \n " -> "Idle Device\nIP: 192.168.0.104" [label="  However, the stream is also\n  pushed to the idle devices."] 
      "Receiving Device 2\nIP: 192.168.0.103" -> "Idle Device\nIP: 192.168.0.104" [style=invis]
      "Receiving Device 1\nIP: 192.168.0.102" -> "Receiving Device 2\nIP: 192.168.0.103" [style=invis]
      
      one -> two [arrowhead=none]
      one -> "Receiving Device 1\nIP: 192.168.0.102" [label="  The recording is pushed to all the\ndevices, so any device can\nconnect and start receiving."]
      two -> "\n  Network  \n  Switch  \n " [arrowhead=none]
      two -> "Receiving Device 2\nIP: 192.168.0.103" [label="This is very useful when there are\nmany devices in the local network\nthat wish to receive the recording."] 

      "Streaming Device \n IP: 192.168.0.101" -> "\n  Network  \n  Switch  \n "

      "Streaming Device \n IP: 192.168.0.101" -> "Multicast screen sharing" [style=invis]
      "Idle Device\nIP: 192.168.0.104" -> "Multicast screen sharing" [style=invis]

     subgraph devices {
      rank=same;
      "\n  Network  \n  Switch  \n ", "Streaming Device \n IP: 192.168.0.101", "Idle Device\nIP: 192.168.0.104";
      }
      
      subgraph arrow {
      rank=same;
      two, "Receiving Device 2\nIP: 192.168.0.103";
      }

      subgraph arrow2{
        rank=same;
        one, "Receiving Device 1\nIP: 192.168.0.102";
      }

    }

|


.. _vlm-share-screen-unicast:

++++++++++++++++++++++++++++++++++++
Sharing screen in the Unicast Mode
++++++++++++++++++++++++++++++++++++

In case you wish to share the screen to only one device, it might be better to stream it in the unicast mode. 

For unicast streaming, we will modify the IP address in the ``dst`` parameter in the third line of the same VLM file. Assuming that the IP address of the receiving device is ``192.168.0.102`` (replace this with the IP address of the receiving device in your local network), the VLM file would look like:

.. code-block ::

   new screen_share broadcast enabled
   setup screen_share input "screen://"
   setup screen_share output #transcode{vcodec=mpgv}:udp{mux=ts,dst=192.168.0.102:8090,sap,name=streaming}
   setup screen_share option sout-keep
   setup screen_share option screen-fps=100
   setup screen_share option file-caching=1000
   control screen_share play

Rest of the steps (for execulting the vlm file and receiving the stream) remain the same.

Following is how a simplified version of the network might look like: 

.. graphviz::

   digraph unicast {
      rankdir=TB;
      node [shape=circle];

      { node [width=0 shape=point label=""]; two, one;
      }
      
      { node [shape=plaintext] "Unicast screen sharing";
      }
      
      
      "Streaming Device \n IP: 192.168.0.101" -> "Idle Device 2\n IP: 192.168.0.104" [label="As the server does\nnot pushes it to them"] [arrowhead=none] 
      "Idle Device 1\n IP: 192.168.0.103" -> "Idle Device 2\n IP: 192.168.0.104" [style=invis]
      "Receiving Device\n IP: 192.168.0.102" -> "Idle Device 1\n IP: 192.168.0.103" [style=invis]
      
      one -> two [arrowhead=none]
      one -> "Receiving Device\n IP: 192.168.0.102" [label="The server pushes the stream only\nto a specific device on the\nlocal network."]
      two -> "Streaming Device \n IP: 192.168.0.101" [arrowhead=none]
      two -> "Idle Device 1\n IP: 192.168.0.103" [label="       The rest of the devices cannot\nreceive the recording"] [arrowhead=none]

      "Streaming Device \n IP: 192.168.0.101" -> "Unicast screen sharing" [style=invis]
      "Idle Device 2\n IP: 192.168.0.104" -> "Unicast screen sharing" [style=invis]


     subgraph devices {
      rank=same;
      "Streaming Device \n IP: 192.168.0.101", "Idle Device 2\n IP: 192.168.0.104";
      }
      
      subgraph arrow {
      rank=same;
      two, "Idle Device 1\n IP: 192.168.0.103";
      }

      subgraph arrow2{
        rank=same;
        one, "Receiving Device\n IP: 192.168.0.102";
      }

    }