Inserting Ads Based on Sort Criteria

  • Article

You can use the role attribute to filter content in a playlist so that advertisements can be inserted at specific locations. The following example code illustrates how to load a playlist and programmatically insert an ad after every second song. Assume that the publishing point uses the following playlist.

<?wsx version="1.0"?>
<smil>
    <media src="c:\wmpub\wmroot\Song_1.wma" role="song" />
    <media src="c:\wmpub\wmroot\Song_2.wma" role="song" />
    <media src="c:\wmpub\wmroot\Presentation_Intro.wmv" role="intro" />
    <media src="http://encoder_name:80" role="presentation" />
    <media src="c:\wmpub\wmroot\Song_3.wma" role="song" />
    <media src="c:\wmpub\wmroot\Song_4.wma" role="song" />
</smil>

To add an advertisement after every second song, use code similar to the following.

Visual Basic .NET Example

Imports Microsoft.WindowsMediaServices.Interop
Imports interop_msxml

Private Sub InsertAds()

  ' Declare variables.
  Dim Server As WMSServer
  Dim Playlist As IWMSPlaylist
  Dim Ad_Elements() As IXMLDOMElement
  Dim Root_Node As IXMLDOMElement
  Dim New_Element As IXMLDOMElement
  Dim NodeList As IXMLDOMNodeList
  Dim Attr As IXMLDOMNode
  Dim Song_Child As IXMLDOMNode
  Dim Next_Child As IXMLDOMNode
  Dim lIndex As Long
  Dim lSongCounter As Long
  Dim lAdNumber As Long

  Try
    ' Create the WMSServer object.
    Server = CreateObject("wmsserver.server")

    ' Load an existing playlist.
    Playlist = Server.CreatePlaylist
    Playlist.load("c:\wmpub\wmroot\playlist.wsx")

    ' Find the root node. The root node of a server-side
    ' playlist must be the smil element.
    Root_Node = Playlist.documentElement

    ' Retrieve a list of the media elements in the smil
    ' time container. In this example, all child elements of
    ' the root node are media elements.
    NodeList = Root_Node.getElementsByTagName("media")

    ' Create a media element for the playlist and identify
    ' it as an advertisement by setting the role attribute
    ' to "Advertisement". This enables logging plug-ins to log 
    ' information about the ads.
    ReDim Ad_Elements(0)
    Ad_Elements(0) = Playlist.createElement("media")
    Ad_Elements(0).setAttribute("role", "Advertisement")
    Ad_Elements(0).setAttribute("src", "c:\wmpub\wmroot\Ad_1.wmv")
    Ad_Elements(0).setAttribute("id", "media_advertisement")

    ' Initialize variables to count the number of songs and ads.
    lSongCounter = 0
    lAdNumber = 1

    ' Iterate through the list to find the songs. In this example,
    ' a song is identified by a role attribute equal to "song".
    For lIndex = 0 To NodeList.length - 1

      ' Retrieve the role attribute for each media element
      ' and check to see whether it equals "song".
      Attr = NodeList.item(lIndex).attributes.getNamedItem("role")
      If Attr.nodeValue = "song" Then
        lSongCounter = lSongCounter + 1
      End If

      ' Insert an ad after two songs.
      If (lSongCounter <> 0) And (lSongCounter Mod 2 = 0) Then

        ' Clone Ad_Elements(0) to add the same advertisement
        ' each time.
        ReDim Preserve Ad_Elements(lAdNumber)
        Ad_Elements(lAdNumber) = Ad_Elements(0).cloneNode(False)

        ' Retrieve the media element associated with the role attribute.
        Song_Child = NodeList.item(lIndex)

        ' Find the next child node.
        If Not Song_Child Is Root_Node.lastChild Then
          Next_Child = Song_Child.nextSibling
        End If

        ' Insert the ad in front of the next child node. If the song 
        ' is the last media element in the playlist, then append the ad.
        If Not Song_Child Is Root_Node.lastChild Then
          New_Element = Root_Node.insertBefore(Ad_Elements(lAdNumber), _
                                               Next_Child)
        Else
          New_Element = Root_Node.appendChild(Ad_Elements(lAdNumber))
        End If

        lAdNumber = lAdNumber + 1
        lSongCounter = 0

      End If

    Next

    ' Save the playlist.
    Playlist.save("c:\wmpub\wmroot\ModifiedPlaylist.wsx")

  Catch Err As Exception
    ' TODO: Exception handler goes here.

  Finally
    ' TODO: Clean-up code goes here.

  End Try

End Sub

C# Example

using Microsoft.WindowsMediaServices.Interop;
using interop_msxml;

// Declare variables.
WMSServer Server;
IXMLDOMDocument Playlist;
IXMLDOMElement[] Ad_Elements = new IXMLDOMElement[256];
IXMLDOMElement Root_Node;
IXMLDOMElement New_Element;
IXMLDOMNodeList NodeList;
IXMLDOMNode Attr;
IXMLDOMNode Song_Child;
IXMLDOMNode Next_Child;
int iIndex;
long lSongCounter;
long lAdNumber;

try
{
  // Create the WMSServer object.
  Server = new WMSServerClass();

  // Load an existing playlist.
  Playlist = Server.CreatePlaylist();
  Playlist.load("c:\\wmpub\\wmroot\\Playlist.wsx");

  // Find the root node. The root node of a server-side
  // playlist must be the smil element.
  Root_Node = Playlist.documentElement;

  // Retrieve a list of the media elements in the smil
  // time container. In this example, all child elements of
  // the root node are media elements.
  NodeList = Root_Node.getElementsByTagName("media");

  // Create a media element for the playlist and identify
  // it as an advertisement by setting the role attribute
  // to "Advertisement". This enables logging plug-ins to log 
  // information about the ads.
  Ad_Elements[0] = Playlist.createElement("media");
  Ad_Elements[0].setAttribute("role", "Advertisement");
  Ad_Elements[0].setAttribute("src",  "c:\\wmpub\\wmroot\\Ad_1.wmv");
  Ad_Elements[0].setAttribute("id", "media_advertisement");

  // Initialize variables to count the number of songs and ads. 
  lSongCounter = 0;
  lAdNumber = 1;

  // Iterate through the list to find the songs. In this example 
  // a song is identified by a role attribute equal to "song".
  for (iIndex=0; iIndex<NodeList.length; iIndex++)
  {
    // Retrieve the role attribute for each media element
    // and check to see whether it equals "song".
    Attr =  NodeList[iIndex].attributes.getNamedItem("role");
    if (Attr.nodeValue.ToString() == "song")
    {
      lSongCounter = lSongCounter + 1;
    }
  
    // Insert an ad after two songs.
    if ((lSongCounter != 0) && (lSongCounter % 2 ==  0))
    {
      // Clone Ad_Elements(0) to add the same advertisement
      // each time.
      Ad_Elements[lAdNumber] =  (IXMLDOMElement)Ad_Elements[0].cloneNode(false);

      // Retrieve the media element associated with the role attribute.
      Song_Child = NodeList[iIndex];

      // Find the next child node.
      if (Root_Node.lastChild != Song_Child)
      {
        Next_Child =  Song_Child.nextSibling;

        // Insert the ad in front of the next child node. If the song 
        // is the last media element in the playlist, append the ad.
        if (Root_Node.lastChild !=  Song_Child)
        {
          New_Element=(IXMLDOMElement)Root_Node.insertBefore(Ad_Elements[lAdNumber], Next_Child);
        }
      }
      else
      {
        New_Element=(IXMLDOMElement)Root_Node.appendChild(Ad_Elements[lAdNumber]);
      }
              
      lAdNumber = lAdNumber++;
      lSongCounter = 0;
    }
  }

  // Save the playlist.
  Playlist.save("c:\\wmpub\\wmroot\\ModifiedPlaylist.wsx");
}

catch (Exception exc)
{
  // TODO: Exception handler goes here.
}

finally
{
  // TODO: Clean-up code goes here.
}

This example code creates the following playlist.

<?wsx version="1.0" ?>
<smil>
    <media role="song" src="c:\wmpub\wmroot\Song_1.wma"/>
    <media role="song" src="c:\wmpub\wmroot\Song_2.wma"/>
    <media role="Advertisement" src="c:\wmpub\wmroot\Ad_1.wmv" 
                                id="media_advertisement"/>
    <media role="intro" src="c:\wmpub\wmroot\Presentation_Intro.wmv"/>
    <media role="presentation" src="http://encoder_name:80"/>
    <media role="song" src="c:\wmpub\wmroot\Song_3.wma"/>
    <media role="song" src="c:\wmpub\wmroot\Song_4.wma"/>
    <media role="Advertisement" src="c:\wmpub\wmroot\Ad_1.wmv" 
                                id="media_advertisement"/>
</smil>

See Also (General)

See Also (Visual Basic .NET)

See Also (C#)

See Also (C++)