Have you tried our updated RTSP code? With the latest development firmware it’s very fast and lets you achieve the maximum frame rate while being able to connect to the camera remotely via FFPMEG.
As for MQTT. The library is probably fine but if we didn’t put effort into make it non-blocking and it’s still just really a demo you may need to take the python script that has the code in it and edit it to be more performant: openmv/mqtt.py at master · openmv/openmv · GitHub
For an example of how to write better socket code see our rtsp.py code: openmv/rtsp.py at master · openmv/openmv · GitHub
You’ll notice that in the RTSP code I aggressively handle all types of errors, recreate sockets, have low timeouts, and etc. The code only handles one connection at a time. It could be expanded to handle multiple. But, it runs smoothly now.