Stream video to HTML5 Aplication from OpenCV

Question

I have a device that uses GStreamer to stream RTSP h264 video over a multicast network; Now I would like to create a desktop application that could receive, process, and show that video. Because of ease of use (graphics/ animation), I decided that using HTML/CSS/JS to create that application would be best, but to keep some C++ functionalities (communication with device, and video processing) I looked for some library that could handle "both worlds", I choose Ultralight (best one I found), but I don't know how to send video to that kind of application? Previously I used OpenCV and SFML to show my video, but that might not be the best way to create GUI with.

So my question is how to receive RTSP H264 video stream (multicast) in such an application?

Maybe that's possible using OpenCV and Ultralight, but I have not found that functionality there. I want to work with that video in C++ and OpenCV on the client-side a little and then show it in a pretty application.