Im running the command such as following and this command broadcasts the video to ethernet port. But here is my question that how I can add overlay onto video where overlay values are stored in shared memory and may change any time.
gst-launch-1.0 -v videotestsrc ! video/xraw,format=NV16, width=1920, height=1080, framerate=30/1 ! omxh264enc ! queue ! rtph264pay config-interval=10 ! udpsink host=192.168.1.5 port=5004
Should I run another thread to do it?
It looks like the compositor or videomixer plugin is what you are looking for. I've never used them myself so I can't be much help, but there's a nearly complete list of plugins here.