c++ - Writing a virtual webcam?

20
votes

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 ?

2
c++pythonwebcamwia
unrelated advice: "don't say that you are a Python programmer", you're a programmer that prefers (or only knows) Python... yet. - Javier
May be s/he's a core developer of cpython... :-) - 6502
@Javier great advice ! though it may be more of a cultural thing. @6502 just thinking about that made me go crazy. if I were a developer of cpython, wouldn't I be a C programmer? or I could be a python programmer because I program python - aloogobi
See also stackoverflow.com/questions/4214786/… - rogerdpack

2 Answers

26
votes

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.

1
votes

Read this first
https://docs.microsoft.com/en-us/windows/win32/directshow/writing-source-filters

Then you can adopt
https://github.com/roman380/tmhare.mvps.org-vcam

You can work on top of this sample virtual camera.

This implements IAMStreamConfig and IKsPropertySet interfaces
This is built using CSourceStream and CSource class which implements IPin and IBaseFilter