IP Cameras are using Real Time Streaming Protocol (RTSP) to transport the media (video and audio) from the camera to the server. Unfortunatelly the RTSP URLs are different among camera manufacturers.
Following table helps you to find the proper RTSP URL for the major brands:
ONVIF Camera Discovery Tool
ONVIF (the Open Network Video Interface Forum) is a global and open industry standard that provide a standardized intarface to IP Cameras. Using this protocol you can discover the capabilities of your camera.
If you do not find the proper URL of your stream ONVIF Discovery Tool can help you to discover the RTSP streams of your camera.