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I googled your "night owl dvr" and found the manual. That said I could not find an SDK for the box. (quick search). Typically here when I do not know the URL of an IP camera I have used Firefox; then properties of the video link. I then grab that link and put it in a new Firefox browser window to validate that the link works. Depending on security setting it may prompt you to enter a login name and password. Here I have security settings related to whether or not you need to log in to see streaming video, access to video stream with no configuration options, admin user access so for and so on.
Most of the time though the link should work. First test the link inside the network with a device on the same subnet. When outside of your home network say with a PDA phone you may need to open up specific ports on your firewall to access the video streams depending on the manner of how your "night owl dvr" is configured for streaming. Typically though for RTSP streaming its multiple ports. The whole can get a bit "willy nilly"; such that the vendors provide specific clients to access their DVRs. These clients can be for a variety of different OS's; whether they are mobile or desktop. There are standards typically related to the codecs of streaming. What you see though is sometimes whoever is writing the OS may put the application on the OS directory in a different spot calling a different name and many times its whatever as long as it works. This too sometimes causes issues with the specific URL link making it propietary per NVR/DVR device.