Finding the appropriate RTSP URL for some cameras can be very tricky. Not all cameras support a RTSP feed, especially the proprietary “cloud” cameras such as Nest DropCam, Amazon CloudCam, Ring Doorbell, WyzeCam (and many more).
Many older camera only support MJPEG streams and no not support H.264 streaming. The Alexa devices such as the Echo Show, Echo Spot, Fire TV and Fire Tablets do not support MJPEG streaming at this time, only H.264.
First, look in the product manual/online documentation for your camera or NVR system to see if the manufacturer clearly lists the RTSP url and port number.
If you are unable to locate anything in the product documentation, then try searching Google with a search term like “Foscam R2 RTSP URL” (replace the camera manufacturer and model with yours) you may find websites or users forums where that question has been asked and answered before.
The following site may be helpful in locating the RTSP URLs for your camera.
Click on the link for your camera manufacturer and then search the page for your camera model. A number of URLs may be listed for each camera model, but only URLs listed with the type “FFMPEG” or “VLC” are possibly compatible. Types “JPEG” and “MJPEG” are not compatible.
You can also check the user forums for your manufacture or contact the manufacturers customer support and ask if the product supports a RTSP H.264 encoded video stream.