1046: Type was not found or was not a compile time constraint: DynamicStream.

I'm trying to set up a dynamicstream for the first time but am getting these errors:

1046: Type was not found or was not a compile time constraint: DynamicStream.

1046: Type was not found or was not a compile time constraint: DynamicStreamItem.

Do I need to import something in order to use the DynamicStream class?

My script is:

import fl.video.*;

var nc:NetConnection = new NetConnection();
nc.connect("rtmp://localhost/vod");

var ds:DynamicStream = new DynamicStream(nc);

var dsi:DynamicStreamItem = new DynamicStreamItem();
dsi.addStream ("video500", 500);
dsi.addStream ("video1000", 1000);
dsi.addStream ("video1500", 1500);

ds.play2 (dsi);