Using IP Cameras
Webcam or IP camera?
First of all we need to understand the difference between a regular webcam (most likely connected to your computer through USB) and a real IP camera (also called a Network camera), which is connected through a network. This connection can be either by cable or wireless through WIFI. A properly installed USB-connected webcam will show up as a separate named source in the Camera modules, in which case you should select this and not choose IP Camera as the source.
About IP cameras
When it comes to real IP cameras there a lot of brands and models available on the market, and which one is right for you of course depends a lot on how you will use it and what demands you have. There are both fixed cameras and remote controlled PTZ (Pan, Tilt, Zoom) cameras available.
The performance and quality of IP cameras differs a lot depending on what model you choose. You should also keep in mind that these type of cameras are usually designed primarily for security applications (CCTV), where other specifications and functions might be of higher value. For example, although today you can find many models of high resolution (megapixel) cameras, most of them are intended for capturing and analyzing a series of still frames and actually they have a rather poor frame rate. Depending on your application, for video production you will likely want a camera that at least can generate a steady 25 or 30 frames per second and for demanding use (fast motion) even more. A low frame rate will result in stuttering video.
RTSP or MJPEG?
Modern IP cameras usually support both MJPEG, streamed over HTTP, as well as H.264 streamed over the RTSP-protocol. The IP Decoder module supports streams using the RTSP or RTMP protocols. If your camera only supports MJPEG you should instead use the "IP Camera" setting in the Camera I module. Keep in mind that the Camera I module does not support audio extraction from its source, so if you need audio from your camera make sure it supports RTSP. Performance wise, using H.264 over RTSP is generally the better choice in order to get maximum quality and frame rate without the need for massive bandwidth.
Read VidBlaster's Help for more information about these modules. Make sure to use the IP camera's video stream URL, not its web page. Search the forum for several threads about IP cameras.