You can Use Flowplayer for playing the retrieved video:
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
body
{
font-family: Arial;
font-size: 10pt;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<asp:FileUpload ID="FileUpload1" runat="server" />
<asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="btnUpload_Click" />
<hr />
<asp:DataList ID="DataList1" Visible="true" runat="server" AutoGenerateColumns="false"
RepeatColumns="2" CellSpacing="5">
<ItemTemplate>
<u>
<%# Eval("Name") %></u>
<hr />
<a class="player" style="height: 300px; width: 300px; display: block" href='<%# Eval("Id", "FileCS.ashx?Id={0}") %>'>
</a>
</ItemTemplate>
</asp:DataList>
<script src="FlowPlayer/flowplayer-3.2.12.min.js" type="text/javascript"></script>
<script type="text/javascript">
flowplayer("a.player", "FlowPlayer/flowplayer-3.2.16.swf", {
plugins: {
pseudo: { url: "FlowPlayer/flowplayer.pseudostreaming-3.2.12.swf" }
},
clip: { provider: 'pseudo', autoPlay: false},
});
</script>
</form>
</body>
</html>