I know that this post is old but I was looking for something very similar the other day (view my IP cam's RTSP video feed on a simple html page without any fancy ActiveX plugins). Lucky me, I found a solution! It is based on ffmpeg, NodeJS, NGINX (not mandatory but useful) and Node Media Server.
The description in the link is detailed and easy to follow, but I still had some tweaks to deal with before I got it to work (regarding endpoints on the NodeJS server). I made an own question for it and got a good and working answer.