Virtual webcam input as byte stream

Here you go:

• DirectShow Source filter using Dekstop window as source
• Writing a Direct Show Source Filter
• Way to generate video from a bunch of images?
• Writing a virtual webcam?
• Virtual Webcam in C++
• Virtual Webcam Driver

More at MSDN Forums:

• How to render a byte array from socket/application using DirectShow?
• Injecting sample from samplegrabber into a graph

If you prefer to skip programming and to just install a virtual camera that you don't happen to have available, you can install a virtual DirectShow camera backed by an IP camera put on Internet and continue your DirectShow experience from there.