Writing a virtual webcam?

Question

I need to create a virtual webcam that poses as a webcam, but takes as input a set of images that it plays. I have seen solutions like ManyCam, and Fake Webcam, but they all seem to one limitation or the other (resolution, max file size, fps etc.) I am working on Windows XP SP3.

I understand that I have to write a WIA interface for this task, but being a Python programmer, I have never written drivers or interfaces to devices. What are the main tasks in writing this interface ? What would the flow look like ?

Answer 1

You need to write DirectShow filter which is a COM server that implements an IPin, IAMStreamConfig and IKsPropertySet interfaces. For the IPin part you'd better to start by inheriting the CSourceStream class, for that you need to get the Windows SDK, having the SDK installed there would be a DirectShow Base Classes sources in samples\multimedia\directshow folder, there you'll find the CSourceStream (among many others). DllRegisterServer function of the COM server should register your filter within CLSID_VideoInputDeviceCategory category using filter mapper.

After building the COM-server, you register it with regsvr32 tool, and your virtual webcam should appear in the web cam lists.

Also check the samples\multimedia\directshow\filters\ball sample that can be improved and used as a starting point for your task.