....
<telerik:RadPageView runat="server" ID="RadPageView3">
<asp:FormView runat="server" ID="FormView2" DataKeyNames="PROYECTO" DataSourceID="SqlDataSource1" OnDataBound="FormView1_DataBound">
<ItemTemplate>
<telerik:RadMediaPlayer ID="RadMediaPlayer1" StartVolume="50" runat="server" Width="700px" BackColor="Black" Source='<%#Eval("VIDTEASER")%>' Poster='<%#"portadas/"+Eval("PROYECTO") + ".jpg"%>'
Height="394px">
</telerik:RadMediaPlayer>
<%# Eval("VIDTEASER") %>
</ItemTemplate>
</asp:FormView>
</telerik:RadPageView>
</telerik:RadMultiPage>
Play Without Video a link from Youtube!, sound ist ok and Fullscreen ist Ok