I decided not to take that route just yet, as it is not native and would not work from any other client application. Back to the drawing board. My challenge is: combining HDMI video from a usb capture device with PTZ control through Serial Port. and get combined control through preferred NCS. With the help from Duckduckgo, I came up with a few DIY ONVIF Camera solutions, unfortunately none offer PTZ control. There’s a cool Win application worth mentioning that does ONVIF desktop streaming…(DeskCamera) but still no PTZ 
But then I came across RPOS (short for Raspberry Pi Onvif Server) baking off one of my pi’s was a BreeeZe. With my PTZ cam connected to the usb Videograbber and serial port of the Pi I have successfully built an ONVIF PTZ-camera.
ONVIF-DevMan, automatically picks up the ONVIF protocol and can control all aspect of the camera.
Unfortunately NCS can’t, When I select ONVIF source, The discovery feature finds the Pi and I can add it to the “edit video source” box, but I cannot save the config. I don’t know why that is but I thought it might have something to do with the calling of the ONVIF profiles?
On my Pi, I have Soap logging enabled and I notice an entirely different type of response between NCS and the Pi than between ONVIF-DevMan and the Pi.
Who knows why I cannot connect to this ONVIF camera? I have a chinese ptz dome cam, also here I cannot just press save in the ONVIF tab I must also add rtsp in the custom url, but at least then PTZ works on the dome. If I do the same to the Pi, Whhenever I try to control PTZ, the Pi’s SOAP tells me
web request received : /onvif/PTZ
DeviceService - Calltype : info, Data : Handling POST on /onvif/device_service
DeviceService - Calltype : received, Data : <s:Envelope xmlns:s=“http://www.w3.org/2003/05/soap-envelope” xmlns:a=“WS-Addressing 1.0 Namespace”><s:Header>adminhnQSk8GWCY91YLkqd8D8dZoAhxY=NBxYRTcPkIRVX5VNQ5SxLg==2021-02-18T09:50:27.689Z<a:To s:mustUnderstand=“1”>http://192.168.123.234:8081/onvif/device_service</a:To></s:Header><s:Body xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance” xmlns:xsd=“http://www.w3.org/2001/XMLSchema”></s:Body></s:Envelope>
DeviceService - Calltype : error, Data : TypeError: Cannot read property ‘output’ of undefined