it is possible to stream video with SignalR?

I implemented video streaming on top of SignalR. You can find my example at http://weblogs.asp.net/ricardoperes/archive/2014/04/24/video-streaming-with-asp-net-signalr-and-html5.aspx.

No, SignalR is based on standards (WebSockets, LongPolling, ForeverFrame, etc.) which only stream text based JSON messages. You're probably better off looking into the WebRTC specification. Now, you could bring these two technologies together by sending control messages with SignalR that triggers some JavaScript that changes the WebRTC feed that the browser is currently showing.